2020 alevel bio paper 1

The action of the carrier protein X in Figure 1 is linked to a membrane-bound ATP hydrolase enzyme. Explain the function of this ATP hydrolase (2)

• ATP hydrolase splits into ADP and Pi which releases energy

• Solutes can be transported against its concentration gradient

Describe how amino acids join to form a polypeptide so there is always NH2 at

one end and COOH at the other end. You may use a diagram in your answer.

• one amine group joins to cook group to form a peptide bond

• Free amine group at one end, free coop group at the other

At Q on Figure 3 there is a small increase in pressure and in rate of blood flow in the

aorta.

Explain how this happens and its importance.

• aorta has elastic tissue for recoil which smooths blood flow

Describe a method this student could use to prepare colour standards and use them to give data for the total anthocyanin extracted.

• use known concentration of blueberry

• Prepare dilution series

• Compare results with colour standards to give a score

Cyclin D stimulates the phosphorylation of DNA polymerase, which activates the

DNA polymerase.

Describe how an enzyme can be phosphorylated.

• phosphate attaches to enzyme

• This causes hydrolysis of ATP

Particulate matter is solid particles and liquid particles suspended in air. Polluted air

contains more particulate matter than clean air.

A high concentration of particulate matter results in the death of some

alveolar epithelium cells. If alveolar epithelium cells die inside the human body they are replaced by non-specialised, thickened tissue.

Explain why death of alveolar epithelium cells reduces gas exchange in human lungs.

• reduced surface area

• Long diffusion pathway so less oxygen diffuses into the blood for diffusion

• Rate of gas exchange is reduced

A tick is a small animal that bites humans and feeds on their blood. This results in proteins from the tick saliva entering the human body. Scientists have suggested one hypothesis for the allergic reaction to alpha-gal in red meat. They think that an earlier immune response to a tick bite can cause a person to have an allergic reaction to alpha-gal in red meat.

Suggest how one antibody can be specific to tick protein and to alpha-gal

• antibody is complimentary to protein and alpha gal

• They bind to form an antigen antibody complex

Complete Table 2 to show three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell

• prokaryotic dna is circle whist eukaryotic is linear

• Eukaryotic dna is attached to histones whilst prokaryotic dna is not

• -eukaryotic dna has intros whilst dna in prokaryotic has no introns

Scientists investigated the genetic diversity between several species of sweet potato.

They studied non-coding multiple repeats of base sequences.

Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome.

• no coding- dna that don’t code for an amino acid

• They’re positioned between genes