3.2.1.2 Organelle Structure and Function

Question 1

What is the nuclear membrane?

Answer 1

Double membrane that controls entry/exit of materials to and from the nucleus.

Question 2

What are nuclear pores?

Answer 2

Holes in the nuclear membrane that allow mRNA and ribosomes to exit.

Question 3

What is the nucleoplasm?

Answer 3

Jelly-like material that makes up the bulk of a nucleus.

Question 4

What is the nucleolus?

Answer 4

Small spherical region in a nucleus that contains ribosomal RNA (rRNA) and manufactures ribosomes.

Question 5

What is chromatin?

Answer 5

An uncondensed complex of DNA and protein.

Question 6

What does chromatin condense into prior to cell division?

Answer 6

Chromosomes

Question 7

What is the function of a mitochondrion?

Answer 7

The site of cellular respiration.

Question 8

In which eukaryotic cell would you not find a nucleus and why?

Answer 8

Red blood cells

To give more room to carry oxygen

Question 9

Which cells contain many mitochondria?

Answer 9

Metabolically active cells such as:
Muscle cells
Intestinal epithelial cells
Sperm cells

Question 10

How are mitochondria adapted to carry out their function?

Answer 10

1. Cristae - extensions of inner membrane provide large surface area for respiration reactions to take place.
2. Matrix - inner space contains ribosomes, and DNA so that respiratory enzymes can be quickly produced when needed.

Question 11

What is the function of a chloroplast?

Answer 11

To carry out photosynthesis

Carbon dioxide + Water –> Glucose + Oxygen.

Question 12

Which plant cells do not contain chloroplasts and why?

Answer 12

Root hair cells - no sunlight underground.

Question 13

What is the chloroplast envelope?

Answer 13

A partially permeable double membrane that surrounds a chloroplast.

Question 14

What are thylakoids?

Answer 14

Flattened sacs found within a chloroplast that contain chlorophyll.

Question 15

What is chlorophyll?

Answer 15

The green pigment found inside the thylakoids of chloroplasts that captures light energy.

Question 16

What are grana?

Answer 16

Stacks of thylakoids.

The place where the 1st stage of photosynthesis takes place (light absorption).

Question 17

What is the stroma of a chloroplast?

Answer 17

The fluid filled space within a chloroplast.

Where the 2nd stage of photosynthesis takes place (sugar synthesis).

Question 18

How are chloroplasts adapted to carry out their function?

Answer 18

1. Granal membranes provide a large surface area for photosynthesis reactions to take place.
2. Stroma contains enzymes for 2nd step of photosynthesis to take place (sugar synthesis).
3. Contain DNA and ribosomes so can quickly produce enzymes required for photosynthesis when needed.

Question 19

What is meant by lamellae?

Answer 19

Folded membranes

Question 20

The flattened sacs and hollow tubes of endoplasmic reticulum and golgi apparatus are called…

Answer 20

cisternae

Question 21

The rough and smooth endoplasmic reticulum, Golgi apparatus and secretory vesicles are all part of the…

Answer 21

endomembrane system (i.e. protein transport out of cell)

Question 22

Why is the rough endoplasmic reticulum described as rough?

Answer 22

It is ‘studded’ with ribosomes.

Question 23

How does the structure of the rough endoplasmic reticulum relate to its function?

Answer 23

1. Folds provide a large surface area for protein synthesis.
2. Cisternae provide a pathway for transport of proteins.
3. Can form vesicles to allow proteins to exit.

Question 24

What happens at the ‘cis face’ of the Golgi apparatus?

Answer 24

Incoming vesicles containing proteins, lipids and carbohydrates are received.

Question 25

What happens at the ‘trans face’ of the Golgi apparatus?

Answer 25

Modified/labelled proteins, lipids or carbohydrates are TRANSferred out of the Golgi apparatus in secretory vesicles.

Question 26

What is the function of the Golgi apparatus?

Answer 26

1. Adds carbohydrates to proteins to form glycoproteins.
2. Forms lysosomes.
3. Transports and modifies stored lipids.
4. Produces secretory enzymes e.g. in pancreatic or epithelial cells.
5. Secretes carbohydrates for cell walls.

Question 27

Describe the process of lysosome action on an engulfed bacterium.

Answer 27

1. Hydrolytic enzyme enters cis face of Golgi apparatus.
2. Lysosome containing hydrolytic enzyme (lysozyme) exits trans face of Golgi apparatus.
3. Lysosome merges with vesicle containing engulfed bacterium and digests bacterium.
4. Soluble debris absorbed into cell. Insoluble debris is egested from cell.

Question 28

What is the function of the smooth endoplasmic reticulum?

Answer 28

1. Synthesise, store and transportation of lipids.
2. Synthesise, store and transportation of carbohydrates.
3. Detoxification of harmful substances.

Question 29

What is the function of a cell wall?

Answer 29

1. Prevents a plant cell bursting due to osmosis.
2. Give plant cells mechanical strength.
3. Structure allows water to pass through it via osmosis.

Question 30

What is the function of a vacuole?

Answer 30

1. Makes plant cells turgid (firm)
2. Contains sugars/amino acids which act as a temporary food store.
3. Contains coloured pigments which attract pollinating insects e.g. petals.

Question 31

Where are 80S ribosomes found?

Answer 31

Eukaryotic cells

Question 32

Where are 70S ribosomes found?

Answer 32

Prokaryotic cells
Mitochondria
Chloroplasts

Question 33

Which are bigger: 70S or 80S ribosomes?

Answer 33

80S (25nm as opposed to 20nm 70S)

Question 34

Ribosomes are made from 2 parts. What are these parts called?

Answer 34

Large subunit

Small subunit