Topic 2 - Cells (SL)

Question 0

What is the function of a plasma membrane?

Answer 0

Controls entry and exit of substances (active transport)

Question 1

What is the function of a cell wall?

Answer 1

Protective outer layer to stop damage and bursting if internal pressure is too high

Question 2

What is the function of the cytoplasm?

Answer 2

Contains enzymes that catalyse the reactions of metabolism and contains DNA in the nucleoid

Question 3

What is the function of pili?

Answer 3

Hair like structures a projecting from the cell wall that can be ratcheted in and out; when connected to another bacterial cell they can pull cells together

Question 4

What is the function of flagella?

Answer 4

Solid protein structures with a corkscrew shape that rotate and cause locomotion

Question 5

What is the function of ribosomes?

Answer 5

Synthesise proteins by translating mRNA. Some stay in the cell and some are secreted

Question 6

What is the function of the nucleoid?

Answer 6

Region of cytoplasm containing naked DNA

Question 7

What is the function of lysosomes?

Answer 7

Store digestive enzymes

Question 8

What is the function of the Golgi apparatus?

Answer 8

Processes proteins before secretion

Question 9

What is the function of the nucleus?

Answer 9

Stores the genetic material

Question 10

What is the function of mitochondria?

Answer 10

Carries out aerobic respiration

Question 11

What is the function of the rough endoplasmic reticulum (rough ER)?

Answer 11

Synthesises proteins for secretion from the cell

Question 12

FUNCTIONS OF MEMBRANE PROTEINS

Hormone binding sites

Answer 12

Site exposed on outside of membrane allowing a specific hormone to bind. A signal is transmitted to the inside of the cell

Question 13

FUNCTIONS OF MEMBRANE PROTEINS

Enzymes

Answer 13

Catalyse reactions inside or outside the cell depending on the location of the active site

Question 14

FUNCTIONS OF MEMBRANE PROTEINS

Channels for passive transport

Answer 14

Each channel allows one specific substance to pass through

Question 15

FUNCTIONS OF MEMBRANE PROTEINS

Pumps for active transport

Answer 15

Pumps release energy from ATP and use it to remove specific substances across the membrane

Question 16

What is diffusion?

Answer 16

Diffusion is the passive movement of molecules from a region of higher concentration to a region of lower concentration, as a result of the random motion of particles

Question 17

What is simple diffusion?

Answer 17

Substances move between the phospholipid molecules in the membrane

Question 18

What is facilitated diffusion?

Answer 18

Channel proteins cause particles to move from a region of higher concentration to a region of lower concentration

Question 19

What is osmosis?

Answer 19

Osmosis is the passive movement of water molecules from a region of lower solute concentration to a region of higher concentration, across a partially permeable membrane

Question 20

Describe the process of active transport

Answer 20

1. Particle enters the pump from the side with lower concentration
2. Particle binds to a specific site
3. Energy from ATP is used to change the shape of the pump
4. Particle is released on the side with higher concentration and the pump returns to its original shape

Question 21

Describe the process of endocytosis

Answer 21

1. Part of the plasma membrane is pulled inwards
2. A droplet of fluid becomes enclosed when a vesicle pinched off
3. Vesicles can then move through the cytoplasm carrying their contents

Question 22

Describe the process of exocytosis

Answer 22

1. Vesicles fuse with the plasma membrane
2. The contents of the vesicle are expelled
3. The membrane then flattens out again

Question 23

Roles of the plant cell wall

Answer 23

• Maintain the cell’s shape
• Allow high pressure to build up inside without bursting - this prevents excessive water uptake by osmosis and makes the cell almost rigid to support the plant

Question 24

Roles of glycoproteins

Answer 24

- Support single layers of thin cells which might otherwise tear - Cell to cell adhesion

Question 25

Describe the cell cycle in eukaryotes

Answer 25

Interphase ➡️ Mitosis OR G1, S phase, G2 ➡️ Prophase, Metaphase, Anaphase, Telophase

Question 26

What is cytokinesis?

Answer 26

The process of dividing the cytoplasm to form two cells

Question 27

1.) Early prophase

Answer 27

Chromosomes become shorter and fatter by supercoiling | Spindle microtubules grow

Question 28

2. Late prophase

Answer 28

Each chromosome consists of two identical chromatids formed by DNA replication in interphase and held together by a centromere Spindle microtubules extend from each pole to the equator

Question 29

3. Metaphase

Answer 29

The nuclear membrane has broken down and chromosome have moved to the equator Spindle microtubules from both poles are attached to each centromere on opposite sides

Question 30

4. Anaphase

Answer 30

The centromeres divide and the chromatids become chromosomes | Spindle microtubules pull the genetically identical chromosomes to opposite poles

Question 31

5. Early telophase

Answer 31

All chromosomes have reached the poles and nuclear membranes form around them Spindle microtubules break down

Question 32

6. Late telophase

Answer 32

Chromosomes uncoil and are no longer individually visible | The cell divides (cytokinesis) to form two cells with genetically identical nuclei

Question 33

Uses of mitosis

Answer 33

Growth Embryonic development Repair of damaged tissues Asexual reproduction