B2.1

Question 1

What is diffusion?

Answer 1

Net overall movement of gas particles from a region of high concentration to a region of low concentration across
Moves down a concentration gradient
Continues until the concentration gradient is zero

Question 2

Where does diffusion occur in the body?

Answer 2

All cells need glucose and oxygen for respiration so the boood transports these around your body
They diffuse into the cells that need them

Question 3

What factors affect rate of diffusion?

Answer 3

Distance - takes particles less time to travel a shorter distance so rate of diffusion increases
Concentration gradient - steeper concentration gradient, the greater the net movement
Surface area - increase SA allows more space for diffusion so more particles can move in a period of time

Question 4

What is osmosis?

Answer 4

Net movement of water molecules across a selectively permeable membrane down a water potential gradient

Question 5

What happens to plant cells with different WP gradient?

Answer 5

Cell becomes turgid if water enters it as it has a lower WP
Cell remains same if it has the same WP
Cell become flaccid if it loses water and eventually becomes a plasmolyse cell after cell contents collapse away

Question 6

Where does osmosis occur in animal cells?

Answer 6

Cell placed in a solution that is more dilute will swell and may burst, called lysis
Cell placed in more concentrated solution will lose water, and crenates

Question 7

What is active transport?

Answer 7

Allows cells to move substances from an area of low to high concentration
As the particles move against their concentration gradient energy must be transferred

Question 8

What are the 3 key features of active transport?

Answer 8

1) particles are transported against a concentration gradient
2) ATP is required
3) process makes use of carrier proteins in the cell membrane

Question 9

What are carrier proteins?

Answer 9

They span across the width of the cell membrane
A particular molecule that the cell requires will bind to the carrier protein
Energy is transferred from an energy transfer to the protein so it can change shape of rotate
The molecule is then transported to the cell and rotates or changes shape again

Question 10

What is mitosis?

Answer 10

The process in which body cells to divide to produce two genetically identical daughter cells

Question 11

Why does mitosis occur?

Answer 11

Replace worn out cells, repair damaged tissue and enable organism to increase in size

Question 12

What are the 4 stages of the cell cycle?

Answer 12

DNA replication
Movement of chromosomes
Cytokinesis
Growth of the daughter cell

Question 13

How is DNA replicated?

Answer 13

The chromosomes need to be copied so:
- the DNA molecule unzips forming two separate strands
- free nucleotides in the nucleus line up against each of the strand with their complementary bases
- this forms DNA base pairings
- when the whole strand is complete there is an identical copy of the DNA

Question 14

How do the chromosomes move?

Answer 14

• chromosome line up across the centre of the cell
• the two identical copies of each chromosome are pulled apart by cell fibres to opposite ends of the cell
• each end now contains a full set of identical chromosomes
• to new nuclei are formed

Question 15

What is cytokinesis?

Answer 15

The cell membrane pinches inwards to separate the now two daughter cells
The daughter cells will then grow independently and follow the cell cycle

Question 16

What is cell differentiation?

Answer 16

The cells become specialised to perform particular jobs
The structure changes so it is better adapted to perform its function

Question 17

How are sperm specialised?

Answer 17

To transfer genetic material from the male to the ovum. Its adaptions include:
- flagellum (tail) which propels the sperm to the ovum
- lots of mitochondria for respiration so ATP can be produced for the flagellum to move
- acrosome, stores digestive enzymes which break down the outer layers of the ovum to allow the sperm to transfer and incorporate its genetic material

Question 18

How are fat cells specialised?

Answer 18

To store fat
Enables an animal to survive when food is short, provides insulation and a protective layer around organisms such as the heart
- have a small layer of cytoplasm surrounding a fat reservoir

Question 19

How is a red blood cell specialised?

Answer 19

Transport oxygen around the body:
- biconcave disc, increases SA to volume ratio speeds up diffusion of oxygen into the cell and CO2 out of it
- packed with haemoglobin, binds to oxygen to form oxyhaemoglobin
- no nucleus, more space for haemoglobin

Question 20

How are ciliated cells specialised?

Answer 20

The cilia sweeps mucus from lungs produced by goblet cells and any bacteria is swallowed and killed in the tomach

Question 21

How are palisade cells specialised?

Answer 21

Carry out photosynthesis
Near the surface of the leaves and full of chloroplasts

Question 22

What are stem cells?

Answer 22

Undifferentiated cells that divide by mitosis and form cells that differentiate and become specialised
Can develop into any type of specialised cell
Used during development, growth, repair

Question 23

What are the two types of stem cells?

Answer 23

Embryonic - found in embryos, divide by mitosis to produce all the cells needed to make an organism. Can differentiate into all cell types
Adult - found in various body tissues (brain,bone marrow, skin, liver). Can differentiate into some different types of cells but not as many. There are blood stem cells in the bone marrow

Question 24

Where are stem cells in plants?

Answer 24

The meristems and shoot tips continue to grow throughout a plants life

Question 25

Where are stem cells found?

Answer 25

Plant meristems
Have very thin walls, small vacuoles and no chloroplasts
- can make stem thicker