Cells - Cell Structure

Question 1

U. marinum cells ingest bacteria and digest them in the cytoplasm.
Describe the role of one named organelle in digesting these bacteria.

3 MARKS

Answer 1

1. Lysosomes;
2. Fuse with vesicles
3. (Releases) hydrolytic enzymes;

Question 2

Describe the structure and function of the nucleus. (3 marks)

Answer 2

1. Surrounded by a nuclear envelope (double membrane) which contains nuclear pores to allow the movement of molecules (1)
2. Contains chromatin (DNA + proteins) which condenses into chromosomes during cell division (1)
3. Contains the nucleolus, which is responsible for ribosome production (1)

Question 3

What are the key differences between prokaryotic and eukaryotic cells? (4 marks)

Answer 3

• Prokaryotic cells lack membrane-bound organelles, while eukaryotic cells contain them (e.g., nucleus, mitochondria) (1)
• prokaryotic cells have smaller (70S) ribosomes, whereas eukaryotic cells have larger (80S) ribosomes (1)
• DNA in prokaryotic cells is circular and free in the cytoplasm, whereas in eukaryotic cells, it is linear and contained within a nucleus (1)
• Prokaryotic cells may have a cell wall made of peptidoglycan, while eukaryotic plant cells have a cell wall made of cellulose (1)

Question 4

Describe the structure of a mitochondrion and explain how it is adapted to its function. (4 marks)

Answer 4

• Has a double membrane; the inner membrane is highly folded into cristae, increasing surface area for ATP synthesis (1)
• Contains mitochondrial matrix, where enzymes for respiration are located (1)
• Has its own circular DNA and 70S ribosomes, allowing it to make some of its own proteins (1)
• Site of aerobic respiration, producing ATP for cellular processes (1)

Question 5

What is the difference between the rough and smooth endoplasmic reticulum? (2 marks)

Answer 5

• Rough ER has ribosomes on its surface and is involved in protein synthesis and folding
• Smooth ER has no ribosomes and is involved in lipid and carbohydrate metabolism (1)

Question 6

What is the function of the Golgi apparatus? (3 marks)

Answer 6

• Modifies, sorts, and packages proteins and lipids from the rough ER (1)
• Produces lysosomes (1)
• Transports materials in vesicles (1

Question 7

Compare and contrast the structure of a virus and a prokaryotic cell. (4 marks)

Answer 7

• Viruses are acellular, while prokaryotic cells are living cells (1)
• Viruses contain genetic material (DNA or RNA) within a protein coat (capsid), whereas prokaryotic cells have DNA in the cytoplasm (1)
• Viruses lack organelles such as ribosomes, while prokaryotic cells have 70S ribosomes (1)
• Viruses require a host cell to reproduce, while prokaryotic cells can replicate independently via binary fission (1)

Question 8

Give two structures found in all prokaryotic cells and in all eukaryotic cells

Answer 8

1. Cell(-surface) membrane;
2. Ribosomes;
3. Cytoplasm;
4. DNA;

Question 9

Describe how a sample of chloroplasts could be isolated from leaves.

Answer 9

1. Blend the cells in a blender to break the cell membrane and filter to remove large debris
2. Put in a isotonic prevent damage to organelle via osmosis, Cold: Reduces enzyme activity that might break down organelles and Buffered: Maintains constant pH to prevent enzyme denaturation solution
3. place in a centrifuge and spin and remove necleus
4. spin at a higher speed until the cholorplast settles

Question 10

Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.

4 marks

Answer 10

1. DNA in nucleus is code (for protein);
2. Ribosomes/rough endoplasmic reticulum produce (protein);
3. Mitochondria produce ATP (for protein synthesis);
4. Golgi apparatus package/modify;
5. Vesicles transport
6. (Vesicles) fuse with cell(-surface) membrane;

Question 11

Name an organelle found in both a chloroplast and a prokaryotic cell.

Answer 11

ribosome

Question 12

Name the process by which prokaryotic cells divide.

Answer 12

Binary Fission

Question 13

Contrast how an optical microscope and a transmission electron
microscope work and contrast the limitations of their use when studying cells.

6 marks

Answer 13

1. TEM use electrons and optical use light;
2. TEM allows a greater resolution;
3. (So with TEM) smaller organelles can be observed
4. TEM view only dead specimens and optical (can) view live specimens;
5. TEM does not show colour and optical (can);
6. TEM requires thinner specimens;
7. TEM requires a more complex/time consuming preparation;