Biology mock (start of 2020) - topics to improve

Question 1

Describe features of eukaryotic DNA

Answer 1

• DNA in double membrane-bound nucleus
• DNA wound round histone proteins
• Normally multiple linear chromosomes
• No plasmids (but circular DNA does occur in mitochondria and chloroplasts, short and not associated with proteins similar to prokaryotic DNA)

Question 2

Describe features of prokaryotic DNA

Answer 2

• DNA free in the cytoplasm
• Naked
• Single circular chromosome
• May contain smaller loops of DNA (plasmids)

Question 3

Which two monosaccharides make up lactose?

Answer 3

Galactose and glucose

Question 4

Which two monosaccharides make up maltose?

Answer 4

Two alpha glucose

Question 5

Which two monosaccharides make up sucrose?

Answer 5

Fructose and glucose

Question 6

Draw and label a DNA nucleotide

Answer 6

Deoxyribose (pentose sugar - 5 carbons)
Nitrogenous base - on 2nd C (right)
Phosphate group - on 5th carbon (left)

Question 7

Give two features of DNA + explain how each one is important in the semi-conservative replication of DNA

Answer 7

• Hydrogen bonds are easily broken between the two strands
• There are two strands that make up DNA so both can act as templates
• DNA has complementary base pairs

Question 8

What is the outer layer of a prokaryotic cell called?

Answer 8

A capsule (NOT capsid - capsid is a structure of a virus)

Question 9

Describe the test for lipids

Answer 9

Emulsion test:

• Add ethanol AND water to your sample in a test tube
• Shake gently
• Positive test is that if white emulsion is formed

Question 10

Which structure of a plant cell has stacked membranes arranged in parallel and contains DNA

Answer 10

Chloroplast

Question 11

Which cell organelle is not surrounded by two membranes?

Answer 11

Golgi apparatus

Question 12

Explain why two proteins have the same number and type of amino acids but different tertiary structures

Answer 12

• Amino acids may not be in the same order/sequence

- When the chain twists bonds can be formed in different places

Question 13

Explain why you only use the first 5mm from the tip of the onion root

Answer 13

The very end of the root will undergo mitosis but the rest will not have any cells undergoing mitosis

Question 14

Why should you press down firmly on the cover slip for the root tips experiment?

Answer 14

To squish cells/root tips so that the light is able to travel through. This will allow you to see the root tips more clearly

Question 15

Describe + explain what the student should have done when counting cells to make sure that the mitotic index he obtained for this root tip was accurate

Answer 15

• Compare his value of mitotic index with his peers that also did the experiment
• Only counted whole cells
• Look at another area to count cells undergoing mitosis using the microscope

Question 16

Why is C to D on the graph flattening? (graph axis - x is external conc. of molecule and y is rate of uptake by epithelial cells)

Answer 16

All carrier proteins have been used up/are limiting

Question 17

Describe how the secondary structure of a polypeptide is produced by bonds between amino acids

Answer 17

• Hydrogen bonds form to keep the twisted polypeptide chain in place
• Forming a beta-pleated sheet/alpha helix

Question 18

Name the different stages of mitosis in order

Answer 18

Interphase
Prophase
Metaphase
Anaphase
Telophase ( + cytokinesis)

Question 19

Describe the interphase

Answer 19

• The cell grows and the DNA replicates itself
• The chromosomes are not visible
• Not strictly part of mitosis

Question 20

Describe the prophase

Answer 20

• Chromosomes condense + become visible
• Centrioles move to opposite ends/poles of the cell
• Spindle apparatus form spindle fibres (part of the spindle apparatus) at the centrioles

Question 21

Describe the metaphase

Answer 21

• The nuclear envelope breaks down

- Chromosomes align along the equator/centre of the cell pulled by spindle apparatus

Question 22

Describe the anaphase

Answer 22

• Centromeres split, allowing chromatids to separate

- Chromatids move towards the poles, pulled by the spindle fibres

Question 23

Describe the telophase

Answer 23

• Spindle fibres disperse
• Nuclear envelope reforms
• Chromosomes decondense

Question 24

Describe cytokinesis

Answer 24

A ring of protein filaments form around the equator of the cell, which then tightens + splits the cell into two