Biology B3 Ocr Gateway

Front 1

Why do liver and muscle cells have large numbers of mitochondria?

Back 1

Respiration provides energy for cell possesses. Cells that need lots of energy contain mitochondria.

Liver cells - which carry out lots of energy demanding metabolic reactions.

Muscle cells - which need energy to contract (and cause movement)

Front 2

Give two ways in which bacterial cells differ from animal and plant cells.

Back 2

Bacterial cells are smaller and simpler. Bacteria cells don't have chloroplasts or mitochondria. They don't have a true nucleus, instead they have a single strand of DNA.

Front 3

What are the four bases of DNA?

Back 3

A, C, G AND T

Front 4

What evidence did Watson and crick use to build a model of DNA?

Back 4

They used evidence from other scientists to help them understand the structure of the molecule. This includes ...

- X ray data showing that DNA is a double helix formed from two chains wound together.

- other data showing that the bases occurred in pairs.

Front 5

Explain how DNA replicates itself?

Back 5

DNA copies itself every time a cell divides, so that each new cell still has the full amount of DNA. In order to copy itself, the DNA double helix first 'unzips' - to form two single strands.

Front 6

Name the molecule used to carry the code from DNA to the ribosomes.

Back 6

mRNA

Front 7

DNA controls the production of what?

Back 7

Proteins in a cell

Front 8

Proteins are made up of chains of molecules called what?

Back 8

Amino acids

Front 9

Where are proteins made and by what?

Back 9

Proteins are made in the cytoplasm by tiny structures called ribosomes.

Front 10

Where is DNA found?

Back 10

DNA is found in the nucleus and can't move out of it because it is too big.

Front 11

Why are some genes "switched off" ?

Back 11

They are switched off because the proteins they code for aren't produced.

Front 12

What is cytoplasm?

Back 12

A cytoplasm is a gel like substance where most of the cell's chemical reactions take place

Front 13

What is mitochondria?

Back 13

Mitochondria is where most of the reactions involved in respiration take place.

Front 14

What are ribosomes?

Back 14

Ribosomes are where proteins are synthesised

Front 15

What is the cell membrane?

Back 15

The cells membrane holds together the cells and controls what goes in and out

Front 16

What are chloroplasts?

Back 16

Chloroplasts is where photosynthesis happens

Front 17

What is a vacuole ?

Back 17

A vacuole is a relatively large structure that contains cell sap, a weak solution of sugar and salts

Front 18

Proteins have many functions, what are the four main examples?

Back 18

1. Enzymes - control cell reactions

2. Carrier molecules - used to transport smaller molecules e.g. haemoglobin

3. Hormones - used to carry messages around the body e.g. insulin

4. Structural proteins - are physically strong e.g. collagen is a structural protein that strengthens connective tissues.

Front 19

What do enzymes act as?

Back 19

They act as a biological catalyst

Front 20

What is a catalyst ?

Back 20

A catalyst is a substance that speeds up a reaction, without being changed or used up in the reaction itself

Front 21

For an enzyme to work, what do you need?

Back 21

The substrate has to fit into the active site. If the substrate's shape doesn't match the active site's shape, then the reaction won't be catalysed.

Front 22

Enzymes are really picky and only work with what?

Back 22

One substrate

Front 23

Why is this process called the "lock and key" mechanism?

Back 23

It is called that because the substrate fits into the enzyme just like a key fits into a lock.

Front 24

What is a mutation ?

Back 24

A mutation is a change in the DNA base sequence

Front 25

What would happen if a mutation happens within a gene ?

Back 25

It could stop the production of the protein the gene normally codes for- or it might mean a different protein is produced instead.

Front 26

What would happen if a mutation occurs in the reproductive cells?

Back 26

The offspring might develop abnormally or die

Front 27

What would happen if the mutation occurs in the body cells ?

Back 27

The mutant cells can sometimes start to multiply in an uncontrolled way and invade other body parts. This is cancer.

Front 28

Some mutations are beneficial, give examples.

Back 28

A different protein might be produced and the new protein could be an improvement.

Front 29

Mutations can happen other than your chromosomes not copying itself properly, what are they ?

Back 29

1. If you're exposed to ionising radiation, including X rays and ultraviolet light.

2. certain chemicals. Such chemicals like mutagens.

Front 30

If the mutations produce cancer then the chemicals are often called what ?

Back 30

Carcinogens

Front 31

What are the advantages of being multicellular?

Back 31

1. You are bigger- this means you can travel further and get your nutrients in a variety of different ways.

2. Cell differentiation- you have different cells doing different jobs.

3. You are more complex- they have specialised organs, different shapes and behaviour.

Front 32

What does the nervous system do ?

Back 32

A system to communicate between different cells

Front 33

What does the circulatory system do ?

Back 33

A system to supply cells with nutrients they need

Front 34

What does the respiratory system do ?

Back 34

A system that controls the exchange of substances with the environment

Front 35

What is mitosis?

Back 35

Mitosis is when a cell reproduces itself by splitting to form two identical offspring

Front 36

When does mitosis happen?

Back 36

When your body wants identical cells- eg. When you want to grow.

Front 37

What happens before before mitosis starts ?

Back 37

The DNA in the cell is replicated.

Front 38

What happens in the start of mitosis?

Back 38

The DNA coils into double armed chromosomes. These arms are exact copies of each other.

Front 39

What happens after the DNA coils?

Back 39

The chromosomes line up at the centre of the cell, and then divide as cell fibres pull them apart. The two arms of each chromosomes go to opposite poles of one cell.

Front 40

What happens after the chromosomes are pulled apart?

Back 40

The cytoplasm divides and you get two new cells

Front 41

What does mitosis make new cells for?

Back 41

Growth and repair

Front 42

What is meiosis ?

Back 42

It is another type of cell division- it creates gametes

Front 43

Where are gametes formed and what by ?

Back 43

They are formed by meiosis in the ovaries and testes

Front 44

What are gametes?

Back 44

They are the sex cells - eggs and sperm

Front 45

The body cells of mammals are diploid? What does diploid mean ?

Back 45

It means that each of the organisms body cells gad two copies of each chromosome in its nucleus

Front 46

What do red blood cells transport?

Back 46

Oxygen from the lungs to all the cells in the body

Front 47

Describe the structure of a red blood cell

Back 47

1. It is small and has a biconcave shape to give it a large surface area to volume ratio for absorbing oxygen.

2. Red blood cells do not have a nucleus- this frees up space for more haemoglobin, so they can carry more oxygen.

3. Red blood cells are flexible- they can easily pass through capillaries.

Front 48

What is a plasma?

Back 48

A plasma is a pale yellow liquid which carries just about everything that needs to be transported around your body.

Front 49

What does the plasma carry?

Back 49

1. red blood cells, white blood cells, and platelets.

2. water

3. digested food products like glucose and amino acid

4. carbon dioxide

5. urea

6. hormones- chemical messengers

7. Antibodies- proteins involved in the body's immune system

Front 50

What are the three different types of blood vessels?

Back 50

1. Arteries

2. Capillaries

3. Veins

Front 51

What do arteries carry?

Back 51

blood under pressure

Front 52

What does a artery look like?

Back 52

The walls are thick compared to the size of the hole down the middle (the lumen). They contain thick layers of muscle to make them strong.

Front 53

What do capillaries carry ?

Back 53

They carry the blood really close to every cell in the body to exchange substances with them.

Front 54

Describe a capillary

Back 54

They are really small and branch of arteries. They have permeable walls, so substances can diffuse in and out. They supply food and oxygen and take away wastes like carbon dioxide. Their walls are only one cell thick. This increases the rate of diffusion by decreasing the distance over which it occurs.

Front 55

What do veins transport?

Back 55

Veins take blood back to the heart.

Front 56

Describe a vein

Back 56

Capillaries eventually join up to form veins. The blood is at lower pressure in the veins so the walls don't need to be as thick as artery walls. They have a bigger lumen than arteries to help blood flow despite the lower pressure. They also have valves to keep the blood flowing in the right direction.

Front 57

Mammals have a double circulatory system- what is the first system?

Back 57

The first system connects the heart to the lungs. Deoxygenated blood is pumped to the lungs to take in oxygen. The blood the returns to the heart.

Front 58

Mammals have a double circulatory system- what is the second system?

Back 58

The second system connects the heart to the rest of the body. The oxygenated blood in the heart is pumped around the body. It gives up its oxygen, and then the deoxygenated blood returns to the heart to be pumped out to the lungs.

Front 59

Give an example of a animal that doesn't have a double circulatory system

Back 59

fish