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Yr 12 Biology A Level > Exam Questions > Flashcards

Exam Questions Flashcards

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1
Q

Outline how vesicles are moved from one organelle to another (2)

A
  • Cytoskeleton provides pathway.
  • Vesicle moves along microfilaments/microtubules.
  • Requires ATP.
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2
Q

Describe the structure of a plasma membrane (3)

A
  • Phospholipid bilayer, with heads facing outwards and tails facing inwards.
  • Glycolipids and glycoproteins scattered throughout.
  • Cholesterol between phospholipids.
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3
Q

Describe the effect of high temperature on the structure of (yeast) cell membranes (4)

A
  • 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.
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4
Q

State two functions of membranes within cells (2).

A
  • Form vesicles to transport substances inside cell.

- Compartmentalise (organelles and cytoplasm.)

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5
Q

What is the role of cholesterol in cell membrane? (2)

A
  • Cholesterol molecules fit within bilayer.

- Stabilise membrane by regulating fluidity.

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6
Q

What is meant by cell signalling? (1)

A

Communication between cells.

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7
Q

Explain how cell surface membranes contribute to the process of cell signalling. (4)

A
  • 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.
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8
Q

How can some proteins (e.g. COPI) ensure a vesicle is transported to the correct target organelle? (2)

A
  • Receptor only found on target organelles.

- Shape of receptor and protein are complementary.

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9
Q

Describe how extracellular enzymes are released from cell. (2)

A
  • Exocytosis
  • Vesicles transport enzymes to cell membrane.
  • Vesicles fuse to cell membrane.
  • Enzymes released from cell.
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10
Q

State two examples of active transport (2)

A
  • Mineral ions into root hair cells.

- H ions out of companion cells.

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11
Q

Describe how an enzyme breaks down a substrate (5)

A
  • 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.
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12
Q

Student repeated investigation twice.

How would this have improved investigation? (2)

A

Improved reliability.

As allows for calculation of mean.

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13
Q

What do triglycerides, phospholipids and cholesterol all have in common?

A

All are insoluble.

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14
Q

Describe the tertiary level of protein structure (2)

A
  • Overall 3D shape of protein (folding driven by interactions between R groups).
  • Hydrophobic interactions, ionic bonding, hydrogen bonding, and disulfide linkages.
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15
Q

What level of protein structure involves subunits?

A

Quarternary. (Two or more polypeptide chains)

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16
Q

Describe the formation of a hydrogen bond between two molecules of water and explain why water can form these bonds (3)

A
  • Between O and H of adjacent molecules.
  • Between d+ H and d- O.
  • Water is polar.
17
Q

Why is the ability of water to act as a solvent important for the survival of organisms? (3)

A
  • Medium for metabolic reactions.
  • Can transport substances dissolved in blood.
  • Able to dilute toxic substances.
18
Q

Describe structure of collagen molecule (6)

A
  • 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.
19
Q

Why are fibrous proteins insoluble?

A

Have large proportions of amino acids with hydrophobic R-groups.

20
Q

What role does collagen play in the body?

A

In tendons/ligaments as strong.

21
Q

Describe the structure and role of keratin.

A
  • In hair/nails.
  • Fibrous protein.
  • Consists of long stranded molecules.
  • Contains lots of cystine, so forms strong disulphide bonds.
22
Q

Describe the structure and role of elastin.

A
  • In skin/arteries.
  • Fibrous protein.
  • Elastic fibres stretch when blood pulses through artery, then recoil between pulses.
  • Long strands containing hydrophobic regions, so insoluble.
23
Q

Uses of cholesterol (3)

A
  • Stability of membrane.
  • Used in liver to produce bile.
  • Used to make vitamin D - bones.

Yr 12 Biology A Level (15 decks)

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