Structure and function of organelles

Question 1

Where are eukaryotic cells found?

Answer 1

Plant and animal cells

Question 2

What are the functions of the nucleus?

Answer 2

• produces mRNA for protein synthesis
• retains genetic information in the form of DNA or chromosomes

Question 3

What do the nuclear pores do?

Answer 3

They allow the passage of large molecules, such as mRNA, and ribosomes.

Question 4

What does the nucleolus do?

Answer 4

It is the site for the formation of rRNA to make ribosomes.

Question 5

What is the function of the mitochondria?

Answer 5

Site of ATP synthesis

Question 6

What does the small circle of DNA do?

Answer 6

It enables mitochondria to make some of their own proteins and self-replicate

Question 7

What is the function of the Cristae?

Answer 7

They provide a large surface area for the attatchment of enzymes involved in respiration

Question 8

What is the relevance of the shape of a mitochondria?

Answer 8

Being cylindrical gives a larger surface area than a sphere of the same volume
This also reduces the distance of diffusion between the edge and the centre (respiration is more efficient)

Question 9

What is the function of the stroma?

Answer 9

It is fluid filled and contains some of the products of photosynthesis, including lipid droplets and starch grains.

Question 10

What are the functions of the 70s ribosomes and circular DNA?

Answer 10

They enable them to make some of their own proteins and self-replicate

Question 11

How is stacking thylakoids into a Granum good?

Answer 11

Produces a large surface area, efficient for trapping light energy

Question 12

What are the two types of ER?

Answer 12

Smooth ER and Rough ER

Question 13

What is the structure of the ER?

Answer 13

1) Flattened sacs
2) Fluid- filled spaces between them, called cisternae.
3) Continuous with nuclear membrane

Question 14

What is the function of the rough ER?

Answer 14

Has ribosomes on the outer surface - synthesis and transport of proteins.

Found in cells making amylase in salivary glands

Question 15

What is the function of the smooth ER?

Answer 15

It is associates with the synthesis and transport of lipids.

Found in cells with large quantities of fat, carbs and proteins e.g liver

Question 16

What is the structure of the Golgi body?

Answer 16

Vesicles containing polypeptides pinch off from the RER and fuse with the stack of flattened stacks which constitute the Golgi body.

Question 17

What are the functions of the Golgi body?

Answer 17

*Packaging proteins
*Secreting carbohydrates
*Transporting and storing lipids
*Forming lysosomes containing digestive enzymes for exocytosis
*Building more complex molecules

Question 18

What is the structure of a lysosomes?

Answer 18

Temporary vacuoles surrounded by a single membrane.

Question 19

What is the function of the lysosomes?

Answer 19

They isolate potentially harmful digestive enzymes from the remainder of the cell - release these when the cell needs to recycle worn out organelles
Their enzymes can digest bacteria engulfed by phagocytosis

Question 20

What is the structure of a vacuole?

Answer 20

A fluid- filled sac bounded by a single membrane, the tonoplast.

Question 21

What is the function of the vacuole?

Answer 21

• Support soft plant tissues
• Contains cell sap which stores chemicals such as glucose, amino acids and minerals

Question 22

How is the cell wall involved in transport?

Answer 22

Gaps between cellulose fibres make the wall permeable
Space outside the cell where solution moves is the apoplast
The apoplast pathway is the main way that water crosses plant roots

Question 23

How is the cell wall involved in mechanical strength?

Answer 23

The structure of cellulose microfibrils and their arrangement makes the cell wall strong
When the vacuole is full of solution the contents of the cell is pushed against the cell wall - turgid

Question 24

How is the cell wall involved in communication between cells?

Answer 24

Cell walls have pits where plasmodemata (strands of cytoplasm) pass, these run between cells.
The network of cytoplasm is called the symplast - the symplast pathway is important in water transport

Question 25

What structures are found in an animal cell?

Cell Wall, Chloroplasts, Plasmodemata, Vacuole, Centrioles, Energy store

Answer 25

Animal Cell:
Cell Wall - Absent
Chloroplasts - Absent
Plasmodemata - Absent
Vacuole - Present (small, temporary)
Centrioles - Present
Energy store - Glycogen

Question 26

What structures are found in a plant cell?

Cell Wall, Chloroplasts, Plasmodemata, Vacuole, Centrioles, Energy store

Answer 26

Cell Wall - Present
Chloroplasts - Present in cells above ground
Plasmodemata - Present
Vacuole - Present (large, permenant, central)
Centrioles - Absent
Energy Store - Starch

Question 27

What is the function of a chloroplast?

Answer 27

To trap light used for photosynthesis

Question 28

What is the function of a ribosome?

Answer 28

They are important in protein synthesis and the site of translation where mRNA is used to assemble a polypeptide chain.

Question 29

What is the function of chromatin?

Answer 29

During cell division it condensed into chromosomes