3.2.1 Cell structure

Question 1

What is a plant cell wall made of?

Answer 1

Cellulose

Question 2

What is the function of a mitochondrion?

Answer 2

Mitochondria produce ATP through aerobic respiration.

Question 3

What is the function of a ribosome?

Answer 3

Ribosomes synthesise proteins.

Question 4

In multicellular organisms, what is a tissue?

Answer 4

A group of cells working together to perform a particular function.

Question 5

Plant cells have a vacuole, but animal cells do not. Give two functions of a plant cell vacuole.
[2 marks]

Answer 5

• Helps maintain pressure inside the cell / keeps the cell rigid.
• Isolates unwanted chemicals inside the cell.

Question 6

Suggest how ciliated cells are adapted to their function in terms of the organelles they contain. Explain your answer.
[2 marks]

Answer 6

• Ciliated epithelial cells have lots of mitochondria…

- …because they need lots of energy.

Question 7

Pancreatic cells make and secrete hormones into the blood. From production to secretion, list, in order, four organelles involved in making hormones.
[4 marks]

Answer 7

• ribosomes
• rough endoplasmic reticulum
• Golgi apparatus
• Golgi vesicle
• cell-surface membrane

Question 8

What is a plasmid?

Answer 8

A small loop of DNA that isn’t part of the main circular DNA molecule.

Question 9

What is a flagellum?

Answer 9

A long, hair-like structure that rotates to make the prokaryotic cell move.

Question 10

What is the protein coat around the core of a virus called?

Answer 10

Capsid

Question 11

Cholera is a disease caused by the prokaryotic organism Vibrio cholerae.
Name the polymer that makes up the cell wall of Vibrio cholerae.
[1 mark]

Answer 11

Murein

Question 12

Cholera is a disease caused by the prokaryotic organism Vibrio cholerae.
Outline the process by which Vibrio cholerae replicates.
[3 marks]

Answer 12

• Vibrio cholerae replicates its circular DNA and its plasmids.
• The cell gets bigger and the DNA moves to opposite poles.
• New cell walls begin to form.
• The cytoplasm divides to make two daughter cells.
• This process is called binary fission.

Question 13

Cholera is a disease caused by the prokaryotic organism Vibrio cholerae.
There are different strains of Vibrio cholerae. One strain has a capsule. Another does not. Suggest how having a capsule might benefit Vibrio cholerae.
[1 mark]

Answer 13

Having a capsule may help to protect Vibrio cholerae from attack by the immune system cells of the people it infects.

Question 14

What is meant by a microscope’s magnification?

Answer 14

Magnification is how much bigger the image is than the specimen.

Question 15

What is meant by a microscope’s resolution?

Answer 15

Resolution is how well a microscope distinguishes between two points that are close together.

Question 16

Explain the difference between optical (light) microscopes and electron microscope.

Answer 16

Optical microscopes:

• use a light beam
• can distinguish between objects greater than 0.2 micrometres

Electron microscopes:

• use beam of electrons
• can distinguish between objects as close as 0.1 nanometres

Question 17

Explain the difference between TEMs and SEMs.

Answer 17

• Transmission electron microscope (TEMs) show the internal structure of organelles (2D).
• Scanning electron microscope (SEMs) show the surface of the specimen (3D).

Question 18

Explain why a homogenised cell solution should be kept ice-cold and isotonic.
[2 marks]

Answer 18

• It should be kept ice-cold to reduce the activity of enzymes that break down organelles.
• It should be kept isotonic to prevent damage to the organelles through osmosis.

Question 19

Describe how you would use cell fractionation techniques to obtain a sample of chloroplasts from leaf tissue.
[3 marks]

Answer 19

• Macerate/homogenise/blend/break tissues/cells (in solution).
• Place into a centrifuge…
• …and spin at different/increasing speeds until chloroplasts fraction obtained.