Back to AI Flashcard MakerBiology /OCR Biology A - 2.1.5 - Biological Membranes Part 3
Active transport
Movement of substances from low to high conc. across a cell membrane, using ATP and protein carriers (against a conc. gradient)
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Key Terms
Term
Definition
Active transport
Movement of substances from low to high conc. across a cell membrane, using ATP and protein carriers (against a conc. gradient)
What do carrier proteins combine reversibly with
Specific solute molecules or ions. They also have a region that binds to and allows the hydrolysis of a molecule of ATP to release energy
Sodium potassium pump
Carrier proteins binds 3 Na+ ions and 1 ATP | ATP is hydrolysed to release energy and the carrier protein changes shape
Tonicity
How much solute is in the solution
Hypotonic
Less solute | Higher water potential
Hypertonic
More solute | Lower water potential
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| Term | Definition |
|---|---|
Active transport | Movement of substances from low to high conc. across a cell membrane, using ATP and protein carriers (against a conc. gradient) |
What do carrier proteins combine reversibly with | Specific solute molecules or ions. They also have a region that binds to and allows the hydrolysis of a molecule of ATP to release energy |
Sodium potassium pump | Carrier proteins binds 3 Na+ ions and 1 ATP | ATP is hydrolysed to release energy and the carrier protein changes shape |
Tonicity | How much solute is in the solution |
Hypotonic | Less solute | Higher water potential |
Hypertonic | More solute | Lower water potential |
Highest water potential | 0 kPa | Pure water - no solute dissolved |
Endocytosis | Taking in large particles into the cell using vesicles and ATP Csm invaginates when it comes into contact w/ substance Enfolds membrane til it fuses --> forms vesicle Vesicle pinches off and moves into cytoplasm to necessary organelle |
Phagocytosis | Endocytosis carries out by phagocytic cells |
Pinocytosis | Taking in liquid into the cell |
Passive transport | Diffusion Facilitated diffusion Osmosis |
Bulk transport | Movement of molecules through a membrane by the action of vesicles |
Thickness of plasma membrane | 7.5 nm |
How factors affect the rate of diffusion | (Temp x SA x Conc. diff)/(diffusion distance x size of particle) |
Receptor mediated endocytosis | Transports LDLs and viruses into the cell only | Requires ATP |
Investigating cell membrane permeability | Cut 5 equally sized beetroots w/ a cork borer Rinse and dry - to remove all pigment Add beetroots to diff test tubes w/ 5cm^3 of water Add each tt to a diff water bath w/ diff temp for same amount of time Remove beetroot and using a pipette transfer remaining sol. to cuvette until 3/4 full Use blue filter and measure abs High abs, more pigment released, more permeable |
Investigating water potential of plant cells | Prepare sucrose sol. of diff conc. Use cork borer to get identically sized potato cylinders Measure mass w/ mass balance Place each cylinder is diff conc. solution for same amount of time Calculate % change in mass Plot conc. on x and % change on y to find when conc. was isotonic |
Examples of model cells | Agar jelly Visking tubing Gelatine cubes These have a similar cytoplasm to our cells |
Investigating diffusion using model cells (conc.) | Prepare agar jelly / indicator and alkali (pink) Prepare tt w/ diff conc. of acid Cut equal sized cubes from agar jelly and place into tt Use stopwatch and record time taken to go colourless Higher conc. of acid = less time to go colourless Repeat at least 3x and calculate mean |
Why do we do repeats | Calculate mean | Reduce effect of random error |
Precision | Having all your values close to EACH OTHER |
Accuracy | Having all your values close to the TRUE VALUE |
Why does facilitated diffusion not use ATP | Molecules have their own kinetic energy | Uses gradient |
Which type of fatty acid tail contributes most to fluidity | Unsaturated |
Intrinsic proteins | Channel proteins Carrier proteins Glycoproteins |
Extrinsic proteins | Present in one side of bilayer Hydrophilic R groups on outer surface Can be present in either layer and some move between layers |
Process of active transport | Molecule binds to receptor in channel of carrier protein Binding of phosphate causes proteins to change shape - opening up to the inside Molecule released to inside of cell Phosphate released and recombines w/ ADP Carrier protein returns to orig shape |
Processes requiring ATP as an immediate source of energy | Active transport Exocytosis Endocytosis |