B2.1 Supplyimg The Cell

Question 1

What is diffusion?

Answer 1

The net movement of particles from a region of high concentration to a region of low concentration, down the concentration gradient

Question 2

When does diffusion stop?

Answer 2

Until the concentration is the same everywhere and the gradient is 0

Question 3

Is diffusion passive or active? Why?

Answer 3

Diffusion is passive because energy is not transferred

Question 4

Give some examples of where diffusion occurs in the body

Answer 4

Glucose and oxygen for respiration diffuse into cells

Carbon dioxide diffuses out of respiring cells as it is poisonous

Question 5

How does diffusion occur with cells?

Answer 5

The particles pass through the cell membrane to an area of low concentration

Question 6

What factors affect the rate of diffusion and explain why

Answer 6

The shorter the distance particles need to move the faster the rate because it takes less time for the particles to travel

The steeper the concentration gradient, the greater the net movement of particles, eg CO2 concentration in a plant is low to increase the rate of diffusion

The larger the surface area the quicker the rate of diffusion because there is more space for particles to move, eg the small intestine is folded to increase surface area contact with blood stream

Question 7

What is osmosis?

Answer 7

A special type of diffusion of water through a semi permeable membrane from an area of high water potential(lowest concentration of solute) to an area of low water potential

Question 8

What is water potential?

Answer 8

The concentration of free water molecules. The more solute dissolved there is the lower the water potential

Highest water potential is 0

Question 9

Why does osmosis occur?

Answer 9

So that water levels in cells stay constant

Question 10

How does a selectively permeable membrane work?

Answer 10

Small holes called pores are small enough for water to pass through but not big enough for larger molecules to pass through

Question 11

What happens to plant cells and animal cells when water potential is higher outside cell?

Answer 11

The plant cell takes up water and becomes turgid because pressure increases

Animal cells take in water, swell up and burst. This is called lysis

Question 12

What happens if water potential is lower outside cells?

Answer 12

Plant cells lose water and their turgor pressure falls until they become flaccid. The cell collapses and becomes plasmolysed

Animal cells lose water and become crenated(crinkled)

Question 13

What is active transport?

Answer 13

The movement of substances from an area of low concentration to an area of high concentration against the concentration gradient. It is active so energy is transferred

Question 14

Why do cells that use active transport have a lot of mitochondria?

Answer 14

They need to respire to produce large quantities of ATP so the more mitochondrion the higher the rate of active transport

Question 15

What are carrier proteins?

Answer 15

A protein that is across the width of the cell membrane. A particular molecule binds to the specific protein and then changes shape/rotates to move it into cells

Question 16

What are some examples of active transport?

Answer 16

In digestion - there is more glucose in the blood than intestine

Plants and root cells - there is a lower concentration of nitrate ions and minerals in the soil so active transport is used to move it into cells

Question 17

What is mitosis and what is the purpose of it?

Answer 17

Mitosis is the process in which cells divide to produce 2 identical daughter cells which are clones. It is used to replace worn out, damaged or dead cells and used for growth in children and everything

Question 18

Describe the process of dna replication

Answer 18

The dna molecule unzips so that the bases on each stand are exposed
Free nucleotides in the nucleus line up using complementary base pairing
Dna bases are formed and 2 identical molecules of DNA are produced

Question 19

Describe the steps in mitosis

Answer 19

Interphase - DNA replication
Prophase -
Metaphase - chromosomes align in the centre of the cell attached with spindle fibres
Anaphase - chromosomes separate and move to opposite pop,es
Telophase - 2 nuclei Reform at 2 ends of cell
Cytokenisis - subcellular structures divide and 2 daughter cells are formed

Question 20

What is cell differentiation?

Answer 20

When cells become specialised to form a particular job and is more adapted to its function

Question 21

Adaptations of a sperm cell

Answer 21

Flagellum - to propel the cell and has a lot of mitochondrion

Lots of mitochondria - for respiration to occur so that the flagella has energy to move

Acrosome - an Enzyme to break down the outer layer of the egg cell and transfer genetic material

Question 22

Fat cell adaptations

Answer 22

Fat cells are specialised to store fat(energy) for use when food is short. They also provide insulation and protection.

They are adapted by having small cytoplasm so that they can expand

Question 23

Red blood cell adaptations

Answer 23

Biconcave Disc shape - increases surface area to volume ration to speed up the rate of diffusion of oxygen and CO2

Haemoglobin- Protein that binds to oxygen to make oxyhemoglobin

No nucleus - more space for haemoglobin

Question 24

Ciliated cells purpose and adaptations

Answer 24

Present in the airway to produce sticky mucus to trap bacteria and dirt

Cilia(hairs) to trap dirt and bacteria and sweep mucus away to the back of the throat

Question 25

Palisade cells adaptations

Answer 25

Full of chloroplast

Shape to allow packing and maximising absorption of sunlight

Question 26

What are stem cells and function?

Answer 26

Stem cells are undifferentiated cells which differentiate to any type of specialised cells

Question 27

Where are stem cells found and how do adult ones differ from embryonic

Answer 27

Embryonic stem cells are found in embryos and they have the ability to differentiate into any cell type

Adult stem cells are found in body tissues like bone marrow and can differentiate into some cells but not all, eg stem cells in the marrow differentiate into blood cells

Question 28

What are adult stem cell used for?

Answer 28

A repair mechanism to regenerate tissue and heal injuries

Question 29

Where are stem cells found in plants?

Answer 29

They are found in meristems in shoot tips

They have different structures like no chloroplast and thin walls

Question 30

Why can’t differentiated plant cells not divide through mitosis?

Answer 30

Cell walls are too thick