[Unit 3.4] | Eukaryotic Cell Structure

Question 1

Describe the components & structure of the nucleus.

Answer 1

• Nuclear envelope:
» Double membrane that surrounds the nucleus.
» Controls the entry & exit of materials in and out of the nucleus.

• Nuclear pores: Allows large molecules to enter and exit the nucleus.

• Nucleoplasm: Granular, jelly-like substance that makes up the bulk of the nucleus.

• Chromosomes: Contain linear, protein-bound DNA

• Nucleolus: Manufactures rRNA & assembles ribosomes.

Question 2

What are the functions of DNA? (3)

Answer 2

• Control center (through the production of mRNA and tRNA)

• Retains cell genetic material in DNA

• Produces rRNA & ribosomes

Question 3

Describe the components & structure of the mitochondrion.

Answer 3

• Double membrane that controls the entry and exit of substances.

• Cristae: Extensions of the inner membrane, providing a large surface area for enzymes & proteins involved in respiration

• Matrix: Space within the mitochondria that contains enzymes, proteins, lipids, ribosomes and DNA (for producing more proteins).

Question 4

What is the function of the mitochondrion?

Answer 4

• Aerobic respiration to produce ATP (from substrates like glucose).

Question 5

Describe the components & structure of the chloroplast.

Answer 5

• Envelope: Double membrane that is highly selective about what can enter & exit the organelle.

• Grana:
» Stacks of discs (thylakoids) that contain chlorophyll
» Where the light absorption stage of photosynthesis occurs.

• Stroma:
» Fluid-filled matrix where the synthesis of sugars occurs.
» Contains starch grains

Question 6

What is the function of the chloroplast?

Answer 6

• Site of photosynthesis.

• Contains DNA, ribosomes and enzymes needed for photosynthesis.

Question 7

How does the function/structure of the SER compare to that of the RER?

Answer 7

• SER: Produces, stores & transports lipids & carbohydrates.

• RER: Contains ribosomes to produce, store & transport proteins.

Question 8

What are the functions of the golgi apparatus? (5)

Answer 8

• Modify proteins: add carbohydrates to form glycoproteins.

• Produce secretory enzymes

• Secrete carbohydrates

• Transport, modify & store lipids (Transported in Golgi Vesicles)

• Form lysosomes

Question 9

What are the functions of lysosomes? (4)

Answer 9

• Hydrolyse material ingested by phagocytes

• Release enzymes to destroy material around the cell

• Digest worn-out organelles

• Break down dead cells

Question 10

What is the difference between an 80s and a 70s ribosome?

Answer 10

• 80s: Eukaryotic. 25nm diameter
• 70s: Prokaryotic, smaller

Question 11

Describe the structure & function of a ribosome.

Answer 11

• Consists of a large and small subunit which both contain proteins & rRNA.

• Site of protein synthesis

Question 13

What is the role of the cell wall and how does it differ in plants/fungi?

Answer 13

• Provides rigidity to the cell.

• Made of cellulose in plants vs chitin in fungi

Question 15

What are the functions of a vacuole? (2)

Answer 15

• Make cells turgid

• Provide sugars and amino acids as a temporary food store