Topic 2 - Exam Questions

Question 1

Answer 1

~ Both contain nucleotides.

~ DNA nucleotide contains deoxyribose sugar, ATP contains ribose.

~ DNA nucleotide contains one phosphate, where as ATP three phosphates.

Question 2

Describe what happens to lysosomes once their contents have been digested (2 Marks)

Answer 2

~ Lysosomes fuses with the cell membrane.

~ Contents of lysosome is released from the cell, via exocytosis.

Question 3

Explain why the phospholipids are arranged in two layers in a cell surface membrane (3 Marks)

Answer 3

~ Hydrophobic regions are away from the water.

~ Hydrophilic regions are towards the water.

~ Needed to separate tissue fluid from the cytoplasm.

Question 4

Compare and contrast the structures of a phospholipid and a triglyceride (3 Marks)

Answer 4

~ Both contain glycerol, fatty acids and ester bonds.

~ Phospholipids contain a phosphate group, triglycerides don’t.

~ Triglycerides contain 3 fatty acid chains, phospholipids contain 2 fatty acid chains.

Question 5

Answer 5

~ People with emphysema, have a smaller SA:V.

~ Therefore need a larger concentration gradient, to maintain the rate of diffusion.

Question 6

Explain why thicker mucus is produced if the functioning of the CFTR channel protein is impaired (2 Marks)

Answer 6

~ Chloride ions cannot leave the cell.

~ Water moves out of mucus via osmosis.

Question 7

Describe the role of the CFTR protein in ensuring that the mucus produced in the lungs have the right consistency (3 Marks)

Answer 7

~ Chloride ions leave cells, through the CFTR channel protein.

~ Increasing the solute concentration in the mucus.

~ Water moves out the cell by osmosis and into the mucus.

Question 8

Explain why cystic fibrosis affects the rate of oxygen uptake in the lungs (3 Marks)

Answer 8

~ Thick, sticky mucus produced.

~ Mucus cannot be moved by the cilia.

~ Restricting airflow through the bronchioles.

Question 9

Basal membrane and apical membrane

Answer 9

Basal Cell Membrane:

~ Chloride ions move via AT, against the concentration gradient, using energy from ATP.

Apical Cell Membrane:

~ Chloride ions move by facilitated diffusion, through an open CFTR channel, down the concentration gradient.

Question 10

Answer 10

~ There is a higher concentration of ions in the mucus than the tissue fluid.

~ Water would therefore move via osmosis.

~ As it moves from a higher concentration, to a lower concentration in the mucus.

Question 11

State THREE functions of the phospholipid bilayer (3 Marks)

Answer 11

~ Creates an enclosed space, separating the internal and the external environment.

~ Forms a partially permeable membrane.

~ Provides fluidity to the membrane.

Question 12

Explain TWO features of DNA that help stabilise its structure (2 Marks)

Answer 12

~ Hydrogen bonds between the base pairs.

~ Which provides strength.

Question 13

A sample of DNA contained 23% thymine.

Calculate the percentage of Adenine & Guanine (2 Marks)

Answer 13

~ Adenine 23%, due to complementary base pairs.

~ 23 + 23 = 46. -> 100 - 46 = 54.

~ 54 / 2 = 27%.

Question 14

Describe TWO advantages to DNA having a double helix (2 Marks)

Answer 14

~ Gives stability to the molecule.

~ Protects bases from digestive enzymes.

Question 15

Answer 15

~ A = Sugar phosphate backbone.

~ B = Nucleotide.

~ D = Nitrogenous base.

Question 16

Describe how the primary structure of leptin enables it to be soluble in water (3 Marks)

Answer 16

~ Sequence of AA, bonded by peptide bonds, in a polypeptide chain.

~ Hydrophilic R groups on the outside and hydrophobic R groups on the inside.

~ Forming H bonds with proteins.