AMAZING facts about our cells !!!!!!
There are approx 200 different "types" in our bodies ! Between 50 -70 Billion cells die in our body everyday ! 120 days is the average life span for a red blood cell Approx 2 Kg of our cells are Bacteria alone ! |
CELLS Life is both wonderful and majestic. Yet for all of its majesty, all organisms are composed of the fundamental unit of life, the cell. The cell is the simplest unit of matter that is alive. This standard is looking at the processes that happen at the cellular level and how factors such as availability of resources and the activity of enzymes can affect the cell. The basics.. Living organisms are composed of one or more cells Cells are the smallest unit of life All cells come from pre-existing cells Some interesting but not overly useful stuff...... The cell theory has amassed tremendous credibility through the use of the microscope in the following: Robert Hooke- studied cork and found little tiny compartments that he called cells Antonie van Leeuwenhoek- observed the first living cells, called them 'animalcules' meaning little animals. I'm a little bit disappointing that this name didn't stick. Schleiden- stated that plants are made of 'independent, separate beings' called cells Schwann- made a similar statement to Schleiden about animals Cell definition: The cell is the basic structural and functional unit of life. Every cell consists of a cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids. |
Check out the cells below and see what differences you can make between a Plant and Animal Cell
Watch the You Tube video below to learn more about the "parts" of a cell and what function they have !!
Check out the above site on Organelle Functions...its very Kul !!! (click on the button to take you there...)
Watch the videos below to have a good recap/revision of Junior Plants and the process of Photosynthesis - any questions from the two videos below???
Place them on the "question board" below...
Place them on the "question board" below...
pHOTOSYNTHESIS !
Is "undoubtedly the most important single metabolic innovation in the history of life on the planet" !!!
Photo = light Synthesis = to make
SO.......Plants are able to produce Glucose molecules from carbon dioxide and water using light energy and the presence of chlorophyll !!!
This process is ENZYME controlled every step of the way !!
Photosynthesis is defined as.....the enzyme controlled chemical process that that occurs in Chloroplasts where plants use light energy to fix carbon dioxide and water in the production of GLUCOSE and OXYGEN.(in the presence of Chlorophyll)
The Glucose is stored as STARCH
Where does this innovative cellular process occur?.....specialised organelles called CHLOROPLASTS.
Photo = light Synthesis = to make
SO.......Plants are able to produce Glucose molecules from carbon dioxide and water using light energy and the presence of chlorophyll !!!
This process is ENZYME controlled every step of the way !!
Photosynthesis is defined as.....the enzyme controlled chemical process that that occurs in Chloroplasts where plants use light energy to fix carbon dioxide and water in the production of GLUCOSE and OXYGEN.(in the presence of Chlorophyll)
The Glucose is stored as STARCH
Where does this innovative cellular process occur?.....specialised organelles called CHLOROPLASTS.
Actvity 1: Please watch this video and then respond to the following question below.
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Chloroplast structure:
The structure of the Chloroplast directly relates to the process of Photosynthesis.
it is essential that you can draw and recognise all the internal structures inside the Chloroplast AND link this to its function
The structure of the Chloroplast directly relates to the process of Photosynthesis.
it is essential that you can draw and recognise all the internal structures inside the Chloroplast AND link this to its function
Stroma = the transparent Liquid part
Grana = stacks of the Thylakoid discs
Thylakoids = Discs that contain the Chloropyll (and other proteins/enzymes) embedded in their membrane
Lamellae = membrane structures that interconnect the grana stacks
Grana = stacks of the Thylakoid discs
Thylakoids = Discs that contain the Chloropyll (and other proteins/enzymes) embedded in their membrane
Lamellae = membrane structures that interconnect the grana stacks
Chloroplasts:
Chloroplast Structure: - often described as “ rod shaped” See diagram in books
- Stroma = liquid part
- Grana = Stacks of the thylakoid discs
- Thylakoids=discs that contain the Chlorophyll (& enzymes) in their membranes
- Lamellae = membrane structures - (extension of Thylakoids) that connect the grana together.
Chloroplast features: see notes on button link above
- A Chloroplast under the electron Microscope - spend some time on this diagram so you can confidently recognise the Stroma and Grana - you may just get a picture like this in externals !!
Just a wee reminder of the Photosynthesis equation - Brace yourself.....you need to write it balanced at Level 2
Leaf adaptations and Internal leaf structure: both must link back to the process of Photosynthesis !!
External Leaf Structure - just a wee reminder !
External Leaf Structure - just a wee reminder !
Summary of adaptations and External Leaf structure
Internal Leaf Structure:
Internal Leaf structure and function:
Cuticle: A waxy layer that prevent water loss by evaporation. The cuticle is transparent and very thin to allow maximum light penetration.
Upper Epidermis: A protective layer of cells that produces the cuticle. The epidermis is is also transparent and very thin to allow maximum light penetration.
Palisade Mesophyll: Rod shaped cells that contain large numbers of chloroplasts for photosynthesis. These cells are located close to the leaf surface to maximise light absorption. They are upright, elongated and tightly packed together in order to increase the surface area for light absorption. Chloroplasts are found near the palisade cell surface to maximise light absorption and to reduce the distance that carbon dioxide and oxygen have to diffuse (to / from the chloroplast stoma)
Spongy Mesophyll: These cells are smaller than those of the palisade mesophyll and are found in the lower part of the leaf. They also contain chloroplasts, but not quite as many. These cells have large air spaces between them that allow carbon dioxide and oxygen to diffuse between them. The air spaces also gives these cells a large surface area to maximise the diffusion of carbon dioxide into the cell and oxygen out of the cell.
Vein: Plant veins consists of xylem (vessels that carry water) and phloem (vessels that carry dissolved nutrients such as sugar). These vessels play an essential role in transporting water to the chloroplasts in the mesophyll tissues for photosynthesis. They also transport the sugar produced by photosynthesis away from these cells to the rest of the plant tissues to be used as an energy source or stored.
Lower Epidermis: A protective layer of cells. The lower epidermis produces a waxy cuticle too in some plant species. The lower epidermis contains pores called stomata that allow carbon dioxide and oxygen to move in and out of the plant respectively.
Stomata: Tiny pores (small holes) surrounded by a pair of sausage shaped guard cells. These cells can change shape in order to close the pore. In very hot conditions water inside the leaf evaporates and the water vapour can escape through the stomata. Closing them prevent reduces water loss, but also limits the diffusion of carbon dioxide and oxygen in and out of the leaf.
Upper Epidermis: A protective layer of cells that produces the cuticle. The epidermis is is also transparent and very thin to allow maximum light penetration.
Palisade Mesophyll: Rod shaped cells that contain large numbers of chloroplasts for photosynthesis. These cells are located close to the leaf surface to maximise light absorption. They are upright, elongated and tightly packed together in order to increase the surface area for light absorption. Chloroplasts are found near the palisade cell surface to maximise light absorption and to reduce the distance that carbon dioxide and oxygen have to diffuse (to / from the chloroplast stoma)
Spongy Mesophyll: These cells are smaller than those of the palisade mesophyll and are found in the lower part of the leaf. They also contain chloroplasts, but not quite as many. These cells have large air spaces between them that allow carbon dioxide and oxygen to diffuse between them. The air spaces also gives these cells a large surface area to maximise the diffusion of carbon dioxide into the cell and oxygen out of the cell.
Vein: Plant veins consists of xylem (vessels that carry water) and phloem (vessels that carry dissolved nutrients such as sugar). These vessels play an essential role in transporting water to the chloroplasts in the mesophyll tissues for photosynthesis. They also transport the sugar produced by photosynthesis away from these cells to the rest of the plant tissues to be used as an energy source or stored.
Lower Epidermis: A protective layer of cells. The lower epidermis produces a waxy cuticle too in some plant species. The lower epidermis contains pores called stomata that allow carbon dioxide and oxygen to move in and out of the plant respectively.
Stomata: Tiny pores (small holes) surrounded by a pair of sausage shaped guard cells. These cells can change shape in order to close the pore. In very hot conditions water inside the leaf evaporates and the water vapour can escape through the stomata. Closing them prevent reduces water loss, but also limits the diffusion of carbon dioxide and oxygen in and out of the leaf.
STAGES of PHOTOSYNTHESIS !
How does Photosynthesis work??
There are 2 phases- 1.the Light Phase/reaction
2. the Dark Phase or Carbon Fixation Light independent
The Light Phase: (The photo part) - Light dependent
Water → Oxygen + Hydrogen + ATP
The light Independent Phase: (the dark phase)
Also known as - The Calvin Cycle or Carbon fixation: (the synthesis part)
Hydrogen + Carbon Dioxide → Glucose
How does Photosynthesis work??
There are 2 phases- 1.the Light Phase/reaction
2. the Dark Phase or Carbon Fixation Light independent
The Light Phase: (The photo part) - Light dependent
- Takes place when the chlorophyll in the Thylakoid membranes (of the grana) absorbs light Energy.
- The light rays excite the chlorophyll molecules and their electrons- these get released.
- Their Energy is used: to make ATP AND split the Water molecule (Photolysis) - splitting by light - occurs in the Grana.
- The H2O molecule is split into H and 02 gas - O2 gets released (O2 is not needed for rest of process so effectively released as a waste product) Yay… we use this !
- The H is picked up and carried by a special carrier molecule -NADPH to the second stage of the process and into the Stroma.
Water → Oxygen + Hydrogen + ATP
The light Independent Phase: (the dark phase)
Also known as - The Calvin Cycle or Carbon fixation: (the synthesis part)
- Occurs in the Stroma (liquid part)
- CO2 is captured and fixed into a molecule in the stroma
- The ATP and NADPH are used to provide the energy to put H and CO2 through a series of enzyme controlled steps to incorporate them into a substance called G-3-P (glyceraldehyde 3-Phosphate) - this is then used to make Glucose
- Any excess Glucose is stored as starch
- ATP produced in the light phase is used to “run” this 2nd stage and produce G--3P - Glucose
Hydrogen + Carbon Dioxide → Glucose
Cellular RESPIRATION !!
Click here for a recap of information on the Mitochondria - the POWER HOUSE of the cell.
Extra bits......
The HEAT generated as a by product of Respiration is used to maintain body temperature in warm-blooded animals (birds and animals)
CELLULAR RESPIRATION:
It occurs in all living cells all the time!
Cellular respiration is the process by which the biochemical energy of "food" /Glucose molecules is broken down and released in the form of ATP = (re-charging ATP).
Very simply - breaking down Glucose to produce ATP !
ATP - adenosine Triphosphate - is the so called "Energy Molecule" recognised by all cells and is used to fuel all chemical reactions.
During Aerobic respiration - one single Glucose molecule will produce/recharge 38 ATP molecules !!
-it involves a series a complex Enzyme controlled reactions.
The purpose of aerobic respiration is to release energy from food. It is needed for metabolism, growth, movement etc.
Respiration equation:(need to learn this)
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP).
Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used as an example to examine the reactions and pathways involved.
It occurs in special organelles called MITOCHONDRIA !
ALL living things Respire, day and night !
Where in the cell does it happen ?
In the Cytosol AND in the Mitochondria ..(the Cytosol is part of the cytoplasm not contained in membrane bound organelles)
ATP is used to fuel:
- Active transport of substances across membranes
-The synthesis of other molecules like amino acids and proteins
- Muscle contractions
-Nerve cells conducting messages/impulses
-Plant Cells forming cell walls
Respiration can be Aerobic or Anaerobic In Animals -Aerobic Respiration occurs in most body cells - it requires oxygen for the complete breakdown of Glucose molecule. Anaerobic Respiration - in animals - occurs when oxygen is in short supply typically in prolonged exercise and only occurs in muscles.
STAGES of Respiration - here are 3 stages of this Chemical Process:
1. Glycolysis
2. The Krebs Cycle
3. The Electron Transport Chain
Key players in the Cellular Respiration process:
ATP and ADP
S0 ATP........
Adenosine triphosphate (ATP)
Is a small energy carrier molecule that can be used by all the different cell organelles and is required in virtually every cellular process.
ATP carries this "energy" in a chemical bond between the second and third phosphate- called a high E bond.
When ATP is used in cellular process (by enzymes), this bond is broken releasing the energy stored in the bond.
The resulting products, Adenosine diphosphate (ADP) and a phosphate ion can be recycled / recharged through the process of respiration which converts them back to their high energy form (ATP).
(so the Energy from Glucose metabolism adds a hihg E phosphate bond to the ADP to make ATP.
ADP - is the “empty" E carrier whose role is to go back to the cytoplasm and Mitochondria so to be re-charged!
An active cell requires millions of ATP molecules each second.
A working muscle - recycles its ATP at a rate of 10 million molecules per second.
NADH2
Carries the H atoms from the matrix into the Electron Transport Chain onto the cristae of the Mitochondria.
Acetyl Co Enzyme A
Pyruvate loses a C to CO2 forming an acetyl group - this cannot exist alone - so is carried/held by Co-Enzyme A into the Matrix.
Co - enzyme forms an important link between the Cytoplasm and Matrix.
Extra bits......
The HEAT generated as a by product of Respiration is used to maintain body temperature in warm-blooded animals (birds and animals)
Other snippets on Mitochondria:
- The number of Mitochondria in a cell varies widely by organism and tissue type. There are many more in Animal cells than Plant cells. Some cells may have a singly mitochondria whilst some have up to several thousand. The higher the ENERGY demands/requirements - the greater the number of Mitochondria. Eg: muscle cells/glands have high numbers of Mitochondria with many folds/cristae !!
- They can reproduce themselves - have their own DNA and protein building machinery.
- They may also be involved in controlling the concentrations of Calcium within cells
ANAEROBIC RESIRATION:
Occurs in the absence of oxygen -only Glycolysis takes place - only 2 molecules of ATP are produced from each Glucose molecule.
In animals this occurs when oxygen is in short supply in prolonged exercise and only occurs in muscles. The Pyruvate formed in Glycolysis is broken down into Lactic Acid - this causes Muscle Fatigue. The muscles need to stop working - to allow replenished supplies of Oxygen to continue the efficient breakdown of the Lactic Acid into Carbon dioxide and water.
Occurs in the absence of oxygen -only Glycolysis takes place - only 2 molecules of ATP are produced from each Glucose molecule.
In animals this occurs when oxygen is in short supply in prolonged exercise and only occurs in muscles. The Pyruvate formed in Glycolysis is broken down into Lactic Acid - this causes Muscle Fatigue. The muscles need to stop working - to allow replenished supplies of Oxygen to continue the efficient breakdown of the Lactic Acid into Carbon dioxide and water.
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ENZYMES:
Both Photosynthesis and Respiration is controlled every step of the way by special biological catalysts called
Enzymes:
They increase the rate of chemical reactions.(without them metabolism would take place too slowly for life to exist)
They are PROTEINS that speed up the RATE at which these reactions can occur. They act as Biological Catalysts controlling the rate of chemical reactions in ALL living things - they act using a model called the Induced Fit Model.
1..Enzyme basics.....click here..
Learn more by clicking here on Enzymes !!
2.How do enzymes work ??
Click here to find out about the Lock and Key and Induced Fit models !
Enzymes temporarily combine with the chemicals involved in a reaction. These chemicals are called the substrate. The combination is called the enzyme- substrate complex. When the enzyme and substrate combine, the substrate is changed to a different chemical called the product. The enzyme is not consumed or altered by the reaction.
Lock and Key Model:
The part of the enzyme where the substrate binds is called the active site. Enzymes are highly specific and will only bind one type of substrate. It was originally suggested that this was because an enzyme and substrate both possess specific complementary geometric shapes that fit exactly into one another. This is often referred to as "the lock and key" model. An enzyme only fits one particular kind of substrate in the same way that a lock only fits one particular kind of key.
Induced Fit Model
The lock and key model was later revised slightly. Since enzymes are rather flexible structures, the active site is continually reshaped by interactions with the substrate. As a result, the substrate does not simply bind to a rigid active site; the part of the protein which makes up the active site is moulded around the substrate for an even more precise fit. This very slight change in shape (conformation) is what allows the enzyme to carry out its catalytic function.
FACTORS that affect ENZYME ACTION....click here for this info
Co-factors and Inhibitors - how do they affect Enzyme action ????...click here for info and examples ..
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ANOTHER important Cell Process ......The "Transportation of Materials" into and out of the cell.
See HERE on the Introductory & KEY stuff on the Cell/Plasma Membrane
WHO is the key player....The CELL MEMBRANE !!
This regulates and controls what comes into and out of the cell (selective permeability) and provides protection from the surrounding environment.
The movement of materials into and out of the cell is essential for:
See HERE on the Introductory & KEY stuff on the Cell/Plasma Membrane
WHO is the key player....The CELL MEMBRANE !!
This regulates and controls what comes into and out of the cell (selective permeability) and provides protection from the surrounding environment.
The movement of materials into and out of the cell is essential for:
- the uptake of nutrients
- the elimination of wastes
- the exchange of oxygen and carbon dioxide for cellular respiration
- cell signalling
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The movement of materials across the cell membrane is highly regulated. This regulation is possible because the membrane isselectively permeable -not all substances are capable of moving across it. Some smaller hydrophobic (non-polar / fat soluble) molecules are able to diffuse directly through the membrane. Many charged molecules (ions) are unable to diffuse through the lipid layers of the membrane, while other molecules may simply be too large. The transport of most substances is mediated by specialised carrier proteins embedded in the membrane. These proteins not only regulate what crosses the membrane, but also when substances are able to cross the membrane. For instance during vigorous exercise more glucose must be released into the blood-stream and absorbed by our muscle cells.
Cell membranes are a double layered sheet called a Phospho lipid Bi-layer - Lipid is anther name for fat and phospho -refers to phosphate groups that is attached to it - each phospholipid molecule is arranged with the Hydophilic head (water loving) facing out and and the Hydrophobic tails (water fearing) facing inwards. This keeps the inside water in and outside water out. This arrangement also prevents the phospholipid molecules packing too tightly together and keeps the membrane flexible !
The key molecules imbedded include:
Glycoproteins which transport specific molecules – escort substances into/out of the cell
Glycolipids which act as receptors – they detect and can grab hold of molecules needed by the cell
This model is also sometimes referred to as the Fluid Mosaic model- refer to your notes
The movement of materials such as oxygen, carbon dioxide, glucose, mineral ions nutrients across a cell membrane maybe Passive or Active Transport.
Click HERE for the intro NOTES on Passive and Active Transport
PASSIVE Transport :
- Substances are moved down their concentration gradient, from an area of high to low concentration
- Does NOT require cellular energy in the form of ATP
- May involve specialised proteins that facilitate the movement of materials across the membrane
- types we need to be familiar with are: Diffusion, Facilitated Diffusion and Osmosis
DIFFUSION:
Click here for the key notes on the process of DIFFUSION
This is the NET movement of molecules from an area of HIGH concentration to an area of LOW concentration.
It occurs because molecules have a natural tendency to exist in equal concentrations ie: as a single concentration.
The word diffusion is actually derived from the Latin word, "diffundere", which means "to spread out" (if a substance is “spreading out”, it is moving from an area of high concentration to an area of low concentration).
The difference between the two areas either side of the Plasma membrane is called the Concentration Gradient. If there is a large difference in concentration = a steep concentration gradient = a steep line = diffusion is faster. If the difference is not so great = concentration gradient is not so steep = diffusion rate is slower.
Molecules that move by simple Diffusion are:
Lipids -many lipids can pass through because they have similar composition to the membrane
CO2 and O2
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Facilitated Diffusion:
This the movement of molecules from an area of High concentration to an area of Low concentration with the aid of a specific protein carrier. (It is a passive process.) The molecules may be too large and cannot pass through the cell membrane by simple diffusion so are "facilitated" across by a specific carrier protein.
Because the cell membrane is impermeable to most electrically charged molecules and water-soluble substances such as Glucose and Amino Acids - these require assistance - the special carrier proteins embedded in cell membranes provide channels for these molecules to pass through.
Carrier proteins are VERY SPECIFIC ie: carry only one type of molecule.
Glucose diffusion into cells can be facilitated by the hormone Insulin (a protein which activates transport channels)
Some proteins can facilitate the movement across a membrane faster than is possible by their concentration gradients
It is also very handy to know of specific examples of Proteins that can facilitate the transport of key molecules such as oxygen - refer to link above on notes Re: Cytochrome P450
Eg: Cytochrome P450 can transport O2 up to 1.8 times faster than it does by simple diffusion.
Watch this animation below:
Cell size and Diffusion:
HOW does "Cell size" affect the rate of diffusion for cellular transport and its efficiency??
HOW does "Cell size" affect the rate of diffusion for cellular transport and its efficiency??
OSMOSIS:
Is a special type of Diffusion BUT is all about WATER only !!!!
- it is the movement of WATER particles from an area of HIGH concentration(so low solute) to an area of LOW water (so high solute) across the semi-permeable membrane.
Why is OSMOSIS so important ??? See here for more details and THEORY on OSMOSIS
Terms you need to be happy using in terms of Osmosis are:
A hypotonic solution causes water to move into the cell. Animal cells do not have a tough cellulose wall and if water continues to move into the cell pressure builds until ultimately the cell bursts (cell lysis)
Osmoregulation is the control of water inside a cell or organism. Depending on whether a cell is a plant or animal cell and depending on what type environment it is in will depend on the way it can "osmoregulate".
Water potential is a measure of the tendency of water molecules to move from one place to another. (see notes)
You need to be comfortable describing and sketching the following scenarios for Plants and Animals:
Plants:
Have a cell wall ie: this is a rigid wall surrounding the membrane - so this changes the effects of osmoregulation - when a plant cell is fill with water - its cell membrane has pressure on it cell wall - this is termed "turgor pressure" and the cell is said to be "turgid" .
In isotonic - Plants are also termed Flaccid
In Hypertonic solutions - Plant cells lose water - plant cells become Plasmolysed - as water drains from the vacuole and the membrane pulls away from the cell wall and the turgor pressure drops
ie: wilts
In Hypotonic solutions - Plant cells gain water - plant cells become firm as water fills the vacuole and the cell membrane pushes against the cell wall - so cells are said to be Turgid. The cell wall stops the plant cells from bursting.
Animals:
Have no cell wall
Is a special type of Diffusion BUT is all about WATER only !!!!
- it is the movement of WATER particles from an area of HIGH concentration(so low solute) to an area of LOW water (so high solute) across the semi-permeable membrane.
Why is OSMOSIS so important ??? See here for more details and THEORY on OSMOSIS
Terms you need to be happy using in terms of Osmosis are:
- A weak or dilute solution (low solute concentration )is a Hypotonic solution
- A strong or concentrated solution (high concentration of solute) is a Hypertonic solution.
- Two solutions with the same concentration (ie: same concentrations of water & solute) are isotonic solutions.
A hypotonic solution causes water to move into the cell. Animal cells do not have a tough cellulose wall and if water continues to move into the cell pressure builds until ultimately the cell bursts (cell lysis)
Osmoregulation is the control of water inside a cell or organism. Depending on whether a cell is a plant or animal cell and depending on what type environment it is in will depend on the way it can "osmoregulate".
Water potential is a measure of the tendency of water molecules to move from one place to another. (see notes)
You need to be comfortable describing and sketching the following scenarios for Plants and Animals:
Plants:
Have a cell wall ie: this is a rigid wall surrounding the membrane - so this changes the effects of osmoregulation - when a plant cell is fill with water - its cell membrane has pressure on it cell wall - this is termed "turgor pressure" and the cell is said to be "turgid" .
In isotonic - Plants are also termed Flaccid
In Hypertonic solutions - Plant cells lose water - plant cells become Plasmolysed - as water drains from the vacuole and the membrane pulls away from the cell wall and the turgor pressure drops
ie: wilts
In Hypotonic solutions - Plant cells gain water - plant cells become firm as water fills the vacuole and the cell membrane pushes against the cell wall - so cells are said to be Turgid. The cell wall stops the plant cells from bursting.
Animals:
Have no cell wall
- In isotonic - no change
- In Hypertonic solutions they shrival up - Dehydrated
- In Hpotonic solutions - they expand, burst (lyse) following excessive net gain of water
The "Tonicity" of Cells....What does this really mean ??? See here for some notes to help with this and what it means for cells !!
WHAT factors will affect the RATE at which Diffusion will occur:
- Size of particles – small particles will diffuse FASTER that large ones
- Temperature – Particles diffuse faster at HIGH temperatures than they do at LOW temperatures because the warmer a particle is the more Kinetic Energy it has.
- STATE – gas particles diffuse FASTER than particles in a liquid.
*** Be prepared to transfer this information into the context of any question on Diffusion....especially the idea of temperature !!!
ACTIVE TRANSPORT
Main ideas behind this:
Key Ideas:
See here for more info /theory on this cool process..............
Main ideas behind this:
Key Ideas:
- Active transport is an active process that requires energy (ATP).
- Active transport moves molecules against their concentration gradient
- Active transport relies on specialised proteins embedded within the membrane
See here for more info /theory on this cool process..............
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The Cell Cycle
The stages in the cell cycle, are interphase (G1, S, G2, mitosis and cytokenisis) You do not need to know the names!
Interphase: Divided into 3 phases; Gap Phase 1 (Cell grows larger), Synthesis (Genome is replicated, Gap Phase 2 (seperates the newly replicated genome.
Mitosis: Include four stages (prophase, metaphase, anaphase, telophase). Spindle fibers attach to the chromosomes and pull sister chromatids apart. It seperates two daughter genomes.
Cytokinesis: Division of the cytoplasm to form two new cells.
Interphase is an active period in the life of a cell during which many metabolic reactions occur such as protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplast.
The stages in the cell cycle, are interphase (G1, S, G2, mitosis and cytokenisis) You do not need to know the names!
Interphase: Divided into 3 phases; Gap Phase 1 (Cell grows larger), Synthesis (Genome is replicated, Gap Phase 2 (seperates the newly replicated genome.
Mitosis: Include four stages (prophase, metaphase, anaphase, telophase). Spindle fibers attach to the chromosomes and pull sister chromatids apart. It seperates two daughter genomes.
Cytokinesis: Division of the cytoplasm to form two new cells.
Interphase is an active period in the life of a cell during which many metabolic reactions occur such as protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplast.
DNA - Deoxyribonucleic acid...the structure is the same in all living things .....
DNA REPLICATION:
The purpose of DNA replication is to produce two identical copies of a DNA molecule. This is essential for cell division during growth or repair of damaged tissues. DNA replication ensures that each new cell receives its own copy of the DNA.
DNA replication is where the DNA in the cell makes an exact copy of itself prior to cell division so that there is a full set of genetic information available in each cell after division has occurred.
Why is it called semi conservative?
Semi-conservative replication is so named because each molecule of DNA that is created - contains one newly synthesised strand and one old/original parental strand - ie has a "conserved" strand.
The semi-conservative nature of DNA replication is possible because of the base pairing rules.
(You may answer with the etymology of the words; semi = partial, conservative = keeping.)
The purpose of DNA replication is to produce two identical copies of a DNA molecule. This is essential for cell division during growth or repair of damaged tissues. DNA replication ensures that each new cell receives its own copy of the DNA.
DNA replication is where the DNA in the cell makes an exact copy of itself prior to cell division so that there is a full set of genetic information available in each cell after division has occurred.
Why is it called semi conservative?
Semi-conservative replication is so named because each molecule of DNA that is created - contains one newly synthesised strand and one old/original parental strand - ie has a "conserved" strand.
The semi-conservative nature of DNA replication is possible because of the base pairing rules.
(You may answer with the etymology of the words; semi = partial, conservative = keeping.)
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Process of replication
This replication process occurs in a series of steps controlled by Enzymes
Because the DNA molecule is anti-parallel and DNA is always built from a 5'---3' direction the nucleotides can only ever be added onto the 3'end of the polynucleotide chain.
SO......Replication of the leading strand is continuous and can be copied directly, but replication of the lagging strand is fragmented into sections called Okazaki fragments and then DNZ Ligase bonds these sections together.
More on the leading and Lagging strand:
The Leading & Lagging Strand
DNA polymerase can only synthesise DNA in a 5' → 3' direction (because nucleotides can only be added to the 3' OH). One strand can be synthesised continuously as DNA Polymerase can simply follow-on behind DNA helicase as it unwinds the two strands. This is known as the leading strand.
The other stand, known as the lagging strand must be synthesised in short bursts. On this strand DNA Polymerase moves away from the replication fork.
As soon as DNA Polymerase has finished copying one section another section has already been unwound by DNA Helicase and is waiting to be copied. Thus the lagging stand is synthesised in sections called Okazaki fragments (after the scientist who discovered them). Enzyme Ligase joins these fragments together ensuring the lagging strand becomes one continuous strand.
Click here for some notes if you would like them......
This replication process occurs in a series of steps controlled by Enzymes
- The two parent strands on the double helix molecule are separated..are unwound - by the enzyme Helicase
- Helicase breaks the weak H bonds between the base pairs and therefore exposing the base pairs.
- Each original parent strand acts as a template/pattern to be copied from to form the new strand.
- Nucleotides from within the nucleus join up following the complementary base-pairing rule A-T and C-G .These are delivered to the newly synthesised strand by DNA Polymerase
- Two new polynucleotide chains are then formed.
Because the DNA molecule is anti-parallel and DNA is always built from a 5'---3' direction the nucleotides can only ever be added onto the 3'end of the polynucleotide chain.
SO......Replication of the leading strand is continuous and can be copied directly, but replication of the lagging strand is fragmented into sections called Okazaki fragments and then DNZ Ligase bonds these sections together.
More on the leading and Lagging strand:
The Leading & Lagging Strand
DNA polymerase can only synthesise DNA in a 5' → 3' direction (because nucleotides can only be added to the 3' OH). One strand can be synthesised continuously as DNA Polymerase can simply follow-on behind DNA helicase as it unwinds the two strands. This is known as the leading strand.
The other stand, known as the lagging strand must be synthesised in short bursts. On this strand DNA Polymerase moves away from the replication fork.
As soon as DNA Polymerase has finished copying one section another section has already been unwound by DNA Helicase and is waiting to be copied. Thus the lagging stand is synthesised in sections called Okazaki fragments (after the scientist who discovered them). Enzyme Ligase joins these fragments together ensuring the lagging strand becomes one continuous strand.
Click here for some notes if you would like them......
THIS IS EXTENSION WORK: - (not required for standard Level 2 NCEA)
The 5 prime and 3 prime ends to DNA
Because the two strands are anti-parallel biologists found it necessary to some how label the two strands accordingly. Eventually it became common practise to refer to one end of each strand as the 3' (three prime) end and the other end of each strand as the 5' (five prime) end.
This symmetry also gives DNA direction. (because we know Polymerase works in a 5'-3' direction)
This is actually based on the sugar molecules within each strand. The carbon atoms in the sugar molecule of each strand can be numbered starting with the carbon that is bound to the base and going clockwise from there. You will find that at one end of each strand the 5th carbon is bound to the phosphate at the end of the strand. At the other end the 3rd carbon has an OH group at the end of the strand. DNA nucleotides can only be added to this end and the phosphate of a free nucleotide will form a bond with this OH group.
The 5 prime and 3 prime ends to DNA
Because the two strands are anti-parallel biologists found it necessary to some how label the two strands accordingly. Eventually it became common practise to refer to one end of each strand as the 3' (three prime) end and the other end of each strand as the 5' (five prime) end.
This symmetry also gives DNA direction. (because we know Polymerase works in a 5'-3' direction)
This is actually based on the sugar molecules within each strand. The carbon atoms in the sugar molecule of each strand can be numbered starting with the carbon that is bound to the base and going clockwise from there. You will find that at one end of each strand the 5th carbon is bound to the phosphate at the end of the strand. At the other end the 3rd carbon has an OH group at the end of the strand. DNA nucleotides can only be added to this end and the phosphate of a free nucleotide will form a bond with this OH group.
MITOSIS:
Check this out...
Check this out...
mitosis.docx
MITOSIS - A type of cell division for growth, repair, replacement.
Cells divide in the process of Mitosis allowing growth to occur and worn-out or damaged cells to be replaced. Mitosis produces two new daughter cells that are genetically identical to each other - so that they can continue to carry out essential life processes.
Click HERE for key notes on Mitosis
mitosis.docx
click here for Mrs B's notes
MITOSIS - A type of cell division for growth, repair, replacement.
Cells divide in the process of Mitosis allowing growth to occur and worn-out or damaged cells to be replaced. Mitosis produces two new daughter cells that are genetically identical to each other - so that they can continue to carry out essential life processes.
Click HERE for key notes on Mitosis
mitosis.docx
click here for Mrs B's notes
The following can slow down mitosis: temperature, pH, presence of mutagens such as alcohol or radiation, availability of raw materials/essential nturients in the cell.
Mitosis is usually higher during periods of growth and repair during infancy / childhood / early development in animals AND following the breaking of dormancy, and during seasonal growth in plants following damage to the organism when repair of tissue is necessary.
Mitosis occurs at a higher rate in areas where most growth or replacement of cells is occurring, such as:
Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase)
Prophase: The spindle microtubules are extended from each pole to the equator.
Metaphase: Chromatids move to the equator and the spindle microtubules from each pole attach to each centromere on opposite sides.
Anaphase: spindle microtubules pull sister chromatids apart making the centromeres to split. This brings the sister chromatids apart, splitting them into chromosomes. Each identical chromosome is pulled to opposite poles.
Telophase: Spindle microtubules break down, while chromosomes uncoil and therefore are no longer individually visible. The nuclear membrane now reforms.
The cell then is divided by cytokinesis to form two daughter cells with identical genetic nuclei.
Mitosis is usually higher during periods of growth and repair during infancy / childhood / early development in animals AND following the breaking of dormancy, and during seasonal growth in plants following damage to the organism when repair of tissue is necessary.
Mitosis occurs at a higher rate in areas where most growth or replacement of cells is occurring, such as:
- root / shoot tips - are the growing point for a plant - so Mitosis rapid here especially during spring or when seedlings are young/seeds are germinating, buds, flowers are forming etc
- hair follicles - constantly gowing
- bone marrow - constantly active in forming new red blood cells to replace those damaged or worn out from transporting Oxygen around the body
- skin cells - are constantly active in forming new cells to replace the daily loss from the epidermis
- mucous membranes etc.
Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase)
Prophase: The spindle microtubules are extended from each pole to the equator.
Metaphase: Chromatids move to the equator and the spindle microtubules from each pole attach to each centromere on opposite sides.
Anaphase: spindle microtubules pull sister chromatids apart making the centromeres to split. This brings the sister chromatids apart, splitting them into chromosomes. Each identical chromosome is pulled to opposite poles.
Telophase: Spindle microtubules break down, while chromosomes uncoil and therefore are no longer individually visible. The nuclear membrane now reforms.
The cell then is divided by cytokinesis to form two daughter cells with identical genetic nuclei.
THE CELL CYCLE
This involves both the production of new cells AND the growth of these cells.
Multicellular organisms rely on cellular division to generate new cells needed for growth and repair.
The cycle of events that lead up to DNA Replication and division (mitosis) is called the cell cycle.
Interphase: 90% of the time the Cell is in Interphase – This is a very active period – many metabolic processes and cell reactions take place during this phase the cell prepares for division by accumulating nutrients, duplicating cell contents, copying DNA, Protein Synthesis, and growing.
This phase can be divided into three phases
G (gap phases)- cells monitor the environment, cell synthesis of RNA and Proteins to induce growth. When conditions are right the cell enters the S phase..
S (synthesis) phase –DNA synthesis (making) and replication of DNA
G2 Cells continue to grow RNA synthesis/protein synthesis and prepare for Mitosis
Mitosis: the chromosome copies separate, the nucleus divides and the cell divides. This produces two cells called daughter cells. Each daughter cell is genetically identical to the parent cell and to one another.
Cytokinesis This is the process by which daughter cells separate. The cell contents are divided, and the two new daughter cells are formed.
This involves both the production of new cells AND the growth of these cells.
Multicellular organisms rely on cellular division to generate new cells needed for growth and repair.
The cycle of events that lead up to DNA Replication and division (mitosis) is called the cell cycle.
Interphase: 90% of the time the Cell is in Interphase – This is a very active period – many metabolic processes and cell reactions take place during this phase the cell prepares for division by accumulating nutrients, duplicating cell contents, copying DNA, Protein Synthesis, and growing.
This phase can be divided into three phases
G (gap phases)- cells monitor the environment, cell synthesis of RNA and Proteins to induce growth. When conditions are right the cell enters the S phase..
S (synthesis) phase –DNA synthesis (making) and replication of DNA
G2 Cells continue to grow RNA synthesis/protein synthesis and prepare for Mitosis
Mitosis: the chromosome copies separate, the nucleus divides and the cell divides. This produces two cells called daughter cells. Each daughter cell is genetically identical to the parent cell and to one another.
Cytokinesis This is the process by which daughter cells separate. The cell contents are divided, and the two new daughter cells are formed.
.Click here for more info on this if needed..
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