Exam Questions Flashcards
Outline how vesicles are moved from one organelle to another (2)
- Cytoskeleton provides pathway.
- Vesicle moves along microfilaments/microtubules.
- Requires ATP.
Describe the structure of a plasma membrane (3)
- Phospholipid bilayer, with heads facing outwards and tails facing inwards.
- Glycolipids and glycoproteins scattered throughout.
- Cholesterol between phospholipids.
Describe the effect of high temperature on the structure of (yeast) cell membranes (4)
- High temperature increases the KE of the phospholipids.
- Phospholipids move around more, creating gaps in the membrane.
- Bilayer becomes more fluid.
- Channel/carrier proteins denature. Increases permeability.
State two functions of membranes within cells (2).
- Form vesicles to transport substances inside cell.
- Compartmentalise (organelles and cytoplasm.)
What is the role of cholesterol in cell membrane? (2)
- Cholesterol molecules fit within bilayer.
- Stabilise membrane by regulating fluidity.
What is meant by cell signalling? (1)
Communication between cells.
Explain how cell surface membranes contribute to the process of cell signalling. (4)
- Release of signal molecule by exocytosis.
- Glycoproteins/glycolipids act as receptors that are specific to certain signal molecule.
- Signal molecule and receptor are complementary.
- Attachment of signal molecule causes change inside cell.
- Cell surface membrane allows entry of some signal molecules.
How can some proteins (e.g. COPI) ensure a vesicle is transported to the correct target organelle? (2)
- Receptor only found on target organelles.
- Shape of receptor and protein are complementary.
Describe how extracellular enzymes are released from cell. (2)
- Exocytosis
- Vesicles transport enzymes to cell membrane.
- Vesicles fuse to cell membrane.
- Enzymes released from cell.
State two examples of active transport (2)
- Mineral ions into root hair cells.
- H ions out of companion cells.
Describe how an enzyme breaks down a substrate (5)
- Substrate complementary to active site.
- Substrate fits into active site on enzyme.
- Destabilises bonds in substrate.
- Forms enzyme-substrate complex.
- Amino acids leave active site.
Student repeated investigation twice.
How would this have improved investigation? (2)
Improved reliability.
As allows for calculation of mean.
What do triglycerides, phospholipids and cholesterol all have in common?
All are insoluble.
Describe the tertiary level of protein structure (2)
- Overall 3D shape of protein (folding driven by interactions between R groups).
- Hydrophobic interactions, ionic bonding, hydrogen bonding, and disulfide linkages.
What level of protein structure involves subunits?
Quarternary. (Two or more polypeptide chains)
Describe the formation of a hydrogen bond between two molecules of water and explain why water can form these bonds (3)
- Between O and H of adjacent molecules.
- Between d+ H and d- O.
- Water is polar.
Why is the ability of water to act as a solvent important for the survival of organisms? (3)
- Medium for metabolic reactions.
- Can transport substances dissolved in blood.
- Able to dilute toxic substances.
Describe structure of collagen molecule (6)
- Peptide bonds between amino acids in polypeptide.
- Polypeptide chains wrap together to form triple helix.
- Every third amino acid is glycine.
- Hydrogen bonds between polypeptide chains.
- Lots of triple helices form fibrils.
- Molecules staggered so no weak spots.
Why are fibrous proteins insoluble?
Have large proportions of amino acids with hydrophobic R-groups.
What role does collagen play in the body?
In tendons/ligaments as strong.
Describe the structure and role of keratin.
- In hair/nails.
- Fibrous protein.
- Consists of long stranded molecules.
- Contains lots of cystine, so forms strong disulphide bonds.
Describe the structure and role of elastin.
- In skin/arteries.
- Fibrous protein.
- Elastic fibres stretch when blood pulses through artery, then recoil between pulses.
- Long strands containing hydrophobic regions, so insoluble.
Uses of cholesterol (3)
- Stability of membrane.
- Used in liver to produce bile.
- Used to make vitamin D - bones.
