Cell structure

Question 1

Why are different organelles important?

Answer 1

Provide distinct environments and conditions for different cellular reactions

Question 2

Nucleus

Answer 2

Contains genetic information in the form of genes

Question 3

Nuclear envelope

Answer 3

DNA is contained within a double membrane to prevent damage in the cytoplasm

Question 4

Nuclear pores

Answer 4

In the nuclear envelope- allows substances to move in and out of the nucleus since DNA is too large to leave the cell

Question 5

How is DNA organised in the nucleus

Answer 5

DNA wraps around histones- forming chromatins- which coil and condense to form chromosomes

Question 6

Nucleolus

Answer 6

Is an area within the nucleus responsible for producing ribosomes. Contains proteins and RNA.

Question 7

Mitochondria

Answer 7

Is the site of respiration within a cell.
Inner membrane- cristae.
Fluid interior- matrix

Question 8

Vesicles

Answer 8

Membranous sacs that are responsible for storage and transport within the cell

Question 9

Lysosome

Answer 9

A specialised type of vesicle which have enzymes that break down waste material in cells (eg old organelles/ pathogens)

Question 10

Cytoskeleton

Answer 10

Network of fibres helping maintain the shape and stability of the cell/ cell movement/ movement of organelles
Microtubules- scaffold like structure, act as tracks for movement of organelles, make up spindle fibres
Microfilaments- cell movement, cell contraction during cytokinesis
Intermediate fibres- mechanical strength

Question 11

Centriole

Answer 11

Component of the cytoskeleton, assembly and organisation of spindle fibres

Question 12

Flagella

Answer 12

Enable cell mobility, sensory organelle to detect chemical changes in the cell environment

Question 13

Cilia

Answer 13

Hair like structure that beat to cause fluids/objects adjacent to the cell to move

Question 14

Endoplasmic reticulum

Answer 14

Network of membranes connected to the outer membrane of the nucleus
Smooth ER- lipid/carbohydrate synthesis and storage
Rough ER- has ribosomes bound to surface, synthesis and transport of proteins

Question 15

Ribosomes

Answer 15

The site of protein synthesis. Made up of equal amounts of protein and rRNA

Question 16

Golgi apparatus

Answer 16

Modifying proteins then packaging them into vesicles

Question 17

Describe the process of protein production

Answer 17

• DNA sequence of a gene is copied onto mRNA
• mRNA leaves the nucleus via the nuclear pore and attaches to a ribosome on the surface of RER
• Ribosome produces the protein and is enters the RER
• Proteins are packaged into vesicles and travel to the golgi apparatus via microtubules
• Vesicles fuse into the golgi, where they are further modified
• Proteins are packaged into vesicles again and leave the golgi
• Vesicles fuse with the cell surface membrane and release proteins via exocytosis

Question 18

P- Cell wall

Answer 18

Surrounds the cell surface membrane
Made of cellulose
Gives the plant cell shape and rigidity because the contents of the cell push against the wall
Freely permeable
Prevents the cell from bursting
Acts as a defense mechanism, protecting the contents of the cell against invading pathogens.

Question 19

P- Vacuole

Answer 19

Membrane lined sacs in the cytoplasm containing cell sap

Important in the maintenance of turgor (contents of the cell push against the cell wall to maintain rigidity)

Question 20

P- Chloroplast

Answer 20

Responsible for photosynthesis

Can make their own proteins

Question 21

What is the difference between prokaryotic and eukaryotic cells?

Answer 21

• Ribosomes in P cells are smaller than in E (70s and 80s)
• P cells have a cell wall made of murein/ peptidoglycan, plant cell walls are made of cellulose
• DNA in E cells exists in chromosomes in the nucleus and is wrapped around histones, P cells have DNA lying free in the cytoplasm and is only one molecule
• E cells have membrane bound organelles
• P cells reproduce via binary fission