Biology Practice Questions Topic 2A and 2B

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What is a prokaryotic cell and give an example of an organism? What is a eukaryotic cell and give an example of an organism?
Prokaryotic cells are smaller and simpler. Bacteria are prokaryotic cells. Eukaryotic cells are complex. Animal and plant cells are an example of this.
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Describe the structure and function of the: mitochondria and chloroplast
Mitochondria-double membrane (inner=cristae) with matrix, where ATP produced. Chloroplast-double membrane and thlakoid membrane inside which make grana (lamella connects these), stroma (fluid). Photosynthesis occurs in stroma+grana.
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Describe the structure and function of the: golgi, ribosome and lysosome.
Golgi-processes+packages lipids and proteins, has vesicles that store lipids+proteins and transports them. Ribosome-no membrane, where proteins made. Lysosome-membrane bound, contains lysozymes (digestive enzymes) to break down broken/damaged cell.
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Describe the structure and function of the RER, SER and vacuole.
RER-membrane with ribosomes, folds and processes proteins. SER- membrane, no ribosomes, synthesises and process lipids. Vacuole-membrane bound (tonoplast), contains cell sap. Helps to maintain pressure and keep cell rigid.
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Compare eukaryotic and prokaryotic cells.
Eukaryotic nucleus- prokaryotic no nucleus. Eukaryotic membrane bound organelles-prokaryotic no. Euk. larger ribosomes-prok. smaller. Euk. cell wall cellulose-prok. cell wall murein. Euk. no capsule-prok. capsule.
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Define plasmid, capsule and flagella (all in prokaryotic).
Plasmids are small loops of DNA containing genes. Capsule protects bacteria from other cells and helps groups of bacteria to stick together. Flagella rotates to help the prokaryotic cell move.
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Describe the structure of a virus and how it replicates.
Virus have a protein coat (caspid) which surrounds genetic material (DNA or RNA). Caspid has attachment proteins coming off. These bind to complementary receptor proteins (specificity) on the host cell then inject their genetic material = take over.
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Describe how prokaryotic cells replicate.
Use binary fission. Circular DNA+ plasmid replicate - loop DNA only once, plasmids lots of time. Cell gets bigger, DNA loops move to opposite poles. Cytoplasm divides and new cell wall forms. 2 daughter cells, each with one circular DNA+plasmids.
8 of 30
Give some advantages and disadvantages to light and electron microscopes.
Light microscopes- poor resolution (long wavelength light) 2D image, electron microscope high magnification+resolution (electrons short wavelength). Electron - specimen stained=artefacts, in vacuum =dead, thin. Light-thick, living specimen, no stain.
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Define magnification and resolution.
Magnification is how much big the image is than the specimen. Resolution is how well a microscope distinguishes between two points that are close together.
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Give the formula for magnification.
Magnification = Image size/size of real object
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Describe and name TEM and SEM
Transmission electron microscope = beam electrons focussed on specimen, pass through, denser areas absorb more electrons (darker on photograph). Scanning electron microscope = beam of electrons fired at specimen, bounce off creating 3D image.
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Describe the process of cell fractionation.
1)Cell homogenised (break plasma membrane, release organelles). 2) Placed in isotonic buffer solution. 3) Filtered (separate large debris/complete cells). 4) Put in test tube, centrifuged at low speed, pellet removed, supernatant spun again.
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Give the order organelles will be separated from centrifugation in.
First the nucleus as it is the largest, then chloroplast (only in plants) and mitochondria (same size), lysosomes and ER and lastly ribosomes (smallest).
14 of 30
Describe the steps and give reasons on how to squash root cells.
Cut root tip, put in ethanoic acid (freeze mitosis). Heat HCl in water bath. Wash root tip in distilled water (mounted needle), put in HCl. Wash again, take root. Squash (break membrane), add stain to view organelles. Cover+squash (thin so light pas)
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Explain the purpose of key structures in the cell membrane and how they function.(3) Answer on two questions cards.
Phospholipids form a bilayer which doesn't allow water soluble substances to pass through only lipid-soluble. Cholesterol binds to the hydrophobic tails restricting movement making the membrane less fluid and more rigid (good for cells not supported)
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Answer continued.... Receptor proteins (extrinsic) on cell surface allow cell to detect chemicals and respond. Carrier proteins (intrinsic) transport molecules that bind to the binding site causing the protein to change shape and release the molecule
Channel proteins (intrinsic) form water-filled tubes allowing water soluble ions to diffuse across. Protein is specific to that ion.
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Describe the process used to test permeability of cell membranes (give reasons).
Collect specimen (cut to size), place in distilled water (so any excess colour from cut moves out), put test tube of water in bath (varying temps), bring up to temp, put root in. Leave, then shake to disperse colour. Use colorimeter.
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Define hypertonic, hypotonic and isotonic.
Hypertonic = low water potential, more solute. Hypotonic = more water potential, less solute. Isotonic = same water potential as the specimen.
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How is facilitated diffusion different to diffusion and why is it needed?
Facilitated diffusion=proteins allow molecules (carrier proteins) and ions (channel proteins) to cross the cell membrane. Large molecules (too slow), ions (cannot pass hydrophobic tail) and water-soluble molecules (cannot move through bilayer).
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What does diffusion and facilitated diffusion depend on?
Diffusion depends on concentration gradient (larger=faster), thickness (smaller=faster), surface area (larger=faster). Rate FD depends on concentration gradient and number of channel proteins (more=faster).
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Define active transport.
Active transport is moving molecules against their concentration gradient from a low to high concentration using ATP (energy) from respiration. It is faster than FD due to ATP.
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Describe how active transport works.
The molecule or ion binds to the receptor site on carrier protein. ATP binds to protein and breaks down into ADP and Pi=carrier changes shape. Molecule/ion released then phosphate released=protein goes back to normal. ATP reforms in condensation.
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Give the three factors affecting rate of active transport.
Speed of carrier proteins (faster=faster rate), number of carrier proteins (more=faster), rate of respiration and therefore amount of ATP produced (more=more energy).
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What organelle will cells have more of if they carry out more active transport?
Mitochondria as mitochondria release ATP from aerobic respiration.
25 of 30
Explain how the small intestine is adapted for absorption.
It is long for a larger surface area and it gives more time for absorption. The epithelium is lined with villi and microvilli to further increase surface area. One cell thick=short diffusion pathway. Lots of mitochondria to provide ATP for energy.
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Define co-transport.
A type of active transport, that transports monosaccharides from the epithelium to the capillaries. It does not transport disaccharides and polysaccharides as they are too large.
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Describe how sodium, potassium and glucose move through the small intestine.
1) Sodium ions are transported out of epithelial cells by sodium-potassium pump (carrier protein) which uses active transport (so needs ATP) to create a concentration gradient. Sodium moves out, potassium moves into the epithelial cell.
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2) This causes sodium ions to diffuse from the the lumen into the epithelial cell using a sodium-glucose transporter. Sodium moves down the concentration gradient but glucose moves up it so the sodium pulls (co) it across so no ATP is required.
3) This causes the concentration of glucose to increase inside the epithelial cell so they move from a high to low concentration through a carrier protein by facilitated diffusion into the capillary. Sodium ions continue moving out by ATP.
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Summarise this process from the lumen to the blood capillary in the small intestine.
Sodium= sodium-potassium pump, moves out of epithelial into blood by AT leaving low conc. in epithelial. Sodium in lumen pulls glucose through into epithelial cell by co-transport. Glucose high conc. in epithelial so diffuses by FD into capillary.
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Other cards in this set

Card 2

Front

Describe the structure and function of the: mitochondria and chloroplast

Back

Mitochondria-double membrane (inner=cristae) with matrix, where ATP produced. Chloroplast-double membrane and thlakoid membrane inside which make grana (lamella connects these), stroma (fluid). Photosynthesis occurs in stroma+grana.

Card 3

Front

Describe the structure and function of the: golgi, ribosome and lysosome.

Back

Preview of the front of card 3

Card 4

Front

Describe the structure and function of the RER, SER and vacuole.

Back

Preview of the front of card 4

Card 5

Front

Compare eukaryotic and prokaryotic cells.

Back

Preview of the front of card 5
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Priya2610

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Very very useful!

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