Topic 2 - Cells and Control

Question 1

What is mitosis?

Answer 1

a type of cell division that results in the production of two daughter cells each having identical sets of chromosomes in the nucleus to the parent cell. Resulting in the formation of two genetically identical diploid body cells.

Question 2

What is mitosis for?

Answer 2

Growth, repair and asexual reproduction

Question 3

What is the order of the process in the cell cycle?

Answer 3

1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase
6. Cytokinesis

Question 4

What happens in Interphase?

Answer 4

Cell prepares for division; DNA replicates, new organelles are manufactured and cell grows; chromosomes present as granular material (chromatin)

Question 5

What happens in early Prophase?

Answer 5

Chromosomes spiralise and condense and become visible as threads; centrioles move to opposite poles of the cell and spindle fibres begin to form

Question 6

What happens in late Prophase?

Answer 6

Chromosomes spiralise and condense further and can now be seen to consist of two sister chromatids joined at the centromere

Question 7

What happens in Metaphase?

Answer 7

Nuclear membrane has disintegrated and spindle fibres have grown across the cell; chromosomes line up independently along the equator of the spindle attaching to the fibres via their centromeres

Question 8

What happens in early Anaphase?

Answer 8

As the cell enters anaphase, the centromeres divide into two separating the sister chromatids of each chromosome

Question 9

What happens in Anaphase?

Answer 9

Spindle activity pulls the chromatids apart and the separated chromatids move to opposite poles of the cell

Question 10

What happens in Telophase?

Answer 10

The chromatids are now described as chromosomes and they begin to uncoil. The spindle fibres disintegrate and the cell begins to constrict along its central axis. A nuclear membrane begins to form around each set of chromosomes

Question 11

What happens in Cytokinesis?

Answer 11

As the membrane continues to constrict, the cytoplasm becomes divided forming two genetically identical daughter cells. Each cell now possesses and exact copy of each chromosome that was present in the nucleus of the original cell

Question 12

How do chromosomes contain genetic information?

Answer 12

Most cells in your body have a nucleus. The nucleus contains your genetic material in the form of chromosomes. Chromosomes are coiled up lengths of DNA molecules.

Question 13

Whats meant by diploid?

Answer 13

Body cells normally have two copies of each chromosome- which makes them diploid cells. One chromosome from father and one from mother

Question 14

What happens in the cell cycle?

Answer 14

Body cells in multicellular organisms divide to produce new cells during a process called the cell cycle. The stage of the cell cycle when the cell divides is called mitosis. Multicellular organisms use mitosis to grow or to replace damaged cells or to reproduce (asexual reproduction)

Question 15

How can you calculate the number of cells they’ll be after multiple divisions of a cell by mitosis?

Answer 15

Number of cells = 2n (n= the number of divisions by mitosis)

Question 16

What is the importance of mitosis on growth?

Answer 16

Multicellular organisms grow by producing extra cells which are genetically identical to the parent cells, so they can perform the same functions

Question 17

What is the importance of mitosis on asexual reproduction?

Answer 17

Specialised parts of plants can produce new organisms that are genetically identical to the parent

Question 18

What is the importance of mitosis on repair?

Answer 18

Damaged cells need to be replaced by ones which are genetically identical to the parent cells, so they can perform the same functions

Question 19

What is cancer a result of?

Answer 19

The rate at which cells divide by mitosis is controlled by the chemical genes in an organism’s DNA. If there’s a change in one of the genes that controls cell division, the cell may start dividing uncontrollably. This can result in a mass of abnormal cells called a tumour. If the tumour invades and destroys surrounding tissue it id called cancer

Question 20

Whats growth?

Answer 20

An increase in size or mass

Question 21

What is cell differentiation?

Answer 21

The process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently

Question 22

What is cell division?

Answer 22

Process by mitosis. The division of a cell into two daughter cells with the same genetic material

Question 23

What is cell Elongation?

Answer 23

Plants also grow by cell elongation. This is where a plant cell expands, making the cell bigger and so making the plant grow

Question 24

What happens in growth with animals?

Answer 24

All growth in animals happens by cell division. Animals tend to grow while they’re young and then they reach full growth and stop growing. When you’re young, cells divide at a fast rate but once you’re an adult, most cell division is for repair - the cells divide to replace old or damaged cells. This also means cell differentiation is lost at an early stage

Question 25

What happens in growth with plants?

Answer 25

In plants, growth in height is mainly due to cell elongation - cell division usually just happens in the tips of the roots and shoots in areas called meristems. But plants often grow continuously. So, plants continue to differentiate to develop new parts

Question 26

What are percentile charts?

Answer 26

Percentile charts are used to monitor growth. Growth charts are used to assess a child’s growth over time, so that an overall pattern in development can be seen and any problems highlighted (obesity, malnutrition, dwarfism)

Question 27

How do you read of a percentile chart?

Answer 27

If your child follows the 75th percentile, that means that they are bigger than 75% children and smaller than 25%

Question 28

What are stem cells?

Answer 28

Undifferentiated cells are called stem cells. Depending on what genes they’re given, stem cells can divide by mitosis to become new cells, which then differentiate.

Question 29

What are embryonic stem cells?

Answer 29

Stem cells are found in early human embryos. These embryonic stem cells have the potential to divide and produce any kind of cell at all. This means stem cells are really important for the growth and development of organisms

Question 30

What are adult stem cells?

Answer 30

Adults also have stem cells which are only found in certain places, like bone marrow. These aren’t as versatile as embryonic stem cells - they can’t produce any cell type at all, only certain ones. In animals stem cells are used to replace damaged cells - (make to skin/blood cells)

Question 31

Whats the function of meristem in plants?

Answer 31

In plants, the only cells that divide by mitosis are found in plant tissues called meristems. Meristem tissue is found in the areas of a plant that are growing. Meristems produce unspecialised cells that are able to divide and form any cell type in the plant. But unlike human stem cells, these cells can divide and differentiate to generate any type of cell for as long as the plant lives. The unspecialised cells go on to form specialised tissues like xylem an phloem

Question 32

What are benefits of using stem cells in medicine?

Answer 32

• Medical benefits (therapeutic cloning+regenerative medicine)
• Potential for discovering treatments are cures to a variety of diseases
• Help treat illnesses
• Help scientists learn about human growth and cell development
• Will be able to test potential drugs/medicines without the use of animals/human testers
• The stem cells can be stimulated to differentiate into specialised cells
• Could create specialised cells to replace those damaged by disease or injury

Question 33

What are the risks of using stem cells in medicine?

Answer 33

• Tumour development ( stem cells divide very quickly. If scientists are unable to control the rate at which the transplanted cells divide inside a patient, a tumour may develop)
• Disease transmission (viruses live inside cells. If donor stem cells are infected with a virus and this isn’t picked up, the virus could be passed on to the recipient and so make them sicker)
• Rejection - If the transplanted cells aren’t grown using the patient’s own stem cells, the patient’s body may recognise the cells as foreign and trigger an immune response to try and get rid of them. Makes the patient susceptible to diseases
• Ethical issues (potential human life being taken away)

Question 34

What happens in the nervous system?

Answer 34

1- The nervous system is made up of neurones which go to all parts of the body.
2- The body has lots of sensory receptors. Different receptors detect different stimuli.
3- When a stimulus is detected by receptors, the information is converted to an impulse and sent along sensory neurones to the CNS.
4- The CNS coordinates the response. Impulses travel through the CNS along relay neurones.
5- The CNS sends information to an effector along a motor neurone. The effector then responds accordingly

Question 35

What is a stimulus?

Answer 35

A change in the environment which we are reacting to

Question 36

What are receptors?

Answer 36

Cells which respond to a stimulus

Question 37

What is a sense organ?

Answer 37

They contain the receptors, body parts

Question 38

What is an impulse?

Answer 38

A signal that goes down a neurone

Question 39

What is a neurone?

Answer 39

A nerve cell

Question 40

What is a nerve?

Answer 40

A bundle of nerve cells

Question 41

What is an effector?

Answer 41

Things that cause effects, muscles and glands

Question 42

Whats the CNS?

Answer 42

Central Nervous System, brain and spine

Question 43

Whats the sensory neurone?

Answer 43

Cell that goes towards the CNS

Question 44

Whats the motor neurone?

Answer 44

Cell that goes away from the CNS

Question 45

How are neurones adapted to transmitting information rapidly as electrical impulses?

Answer 45

All neurones have a cell body, the cell body has extensions that connect to other neurones - dendrites and dendrons carry nerve impulses towards the cell body and axons carry nerve impulses away from the cell body.
Some axons are surrounded by a myelin sheath- this acts as an electrical insulator, speeding up the electrical impulse.
Neurones can be very long which also speeds up the impulse (connecting with another neurone slows the impulse down, so one long neurone is much quicker than lots of short ones joined together).

Question 46

Whats a synapse?

Answer 46

Synapses connect neurones. The connection between two neurones is called a synapse. The nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap. The neurotransmitters then set off a new electrical signal in the next neurone. The transmission of a nervous impulse is very fast, but it is slowed down a bit at the synapse because the diffusion of neurotransmitters across the gap takes time

Question 47

Whats a reflex/reflex arc?

Answer 47

An automatic, rapid response to stimuli - they can reduce the chances of being injured. The passage of information in a reflex is called a reflex arc. The neurones in reflex arcs go through the spinal cord or through an unconscious part of the brain.

Question 48

How do reflexes prevent injury?

Answer 48

When a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS. When the impulses reach a synapse between the sensory and the relay neurone, they trigger neurotransmitters to be released. These cause impulses to be sent along the relay neurone.
When the impulses reach a synapse between the relay neurone and a motor neurone, neurotransmitters are released and cause impulses to be sent along the motor neurone. The impulses then travel along the motor neurone to the effector. The muscle then contracts and moves the body part.

Question 49

Why are reflexes quicker than normal responses?

Answer 49

Because you don’t have to spend time thinking about the response

Question 50

How do reflexes help protect the eye?

Answer 50

Light receptors in the eye detect very bright light and send a message along a sensory neurone to the brain. The message then travels along a relay neurone to a motor neurone, which tells circular muscles in the iris to contract, making the pupil smaller