Topic 2- Cells And Control

Question 1

What is meant by the cell cycle for a multi cellular organism?

Answer 1

Very living cell needs to be able to grow and repair itself in order to stay alive. In organisms that are made of many cells (multicellular organisms) the process of growth and and repair require new cells. These are produced in a process called the cell cycle.

Question 2

Stages of interphase and mitosis are?

Answer 2

• the diploid cell has two sets of chromosomes (chromosomes that are the same are showed in pairs.) this in interphase.
• each chromosome is copied and the copy remains attached forming an X shape.
• the copies of the chromosomes separate and each daughter cell ends up with the same number of of chromosomes as the parent cell.

Question 3

What is formed during the cell cycle?

Answer 3

Two identical daughter cells are formed from the daughter cell.

Question 4

What is the difference between haploid and diploid nucleus cells?

Answer 4

The nuclei of a human body contains two copies of each 23 types of chromosomes making 46 in all. Cells with two copies of each chromosome (two sets) are diploid. Gametes (sex cells) contain one company of each type of chromosome and are haploid.

Question 5

How many stages are there in the cell cycle?

Answer 5

2, interphase and mitosis.

Question 6

What happens during interphase?

Answer 6

This is the first phase in which the cell makes extra sub-cellular cell parts (e.g mitochondria) DNA replication also occurs, to make copies of all chromosomes. These copies of chromosomes stay attached to each other so the look like Xs.

Question 7

What stage happens after interphase and what occurs during this?

Answer 7

Mitosis is the second stage which is also known as cell division. The cell splits to form two daughter cells, which are not hide tidal to the parent cell. Mitosis occurs in a series of continuous stages.

Question 8

What makes the lover different from other organs in the body and how does this benefit transplants?

Answer 8

Damaged human organs cannot regrow apart form the liver. Liver transplants are often done using part of a liver because the transported piece of liver grows by mitosis to form a full sized liver. The liver pieces can therefore be taken from live donors because livers grow back.

Question 9

What are the stages of mitosis?

Answer 9

Prophase: the nucleus starts to break down and spindle fibres appear.

Metaphase: by the end of metaphase the chromosomes are lined up on the spindle fibres across the middle of the cell.

Anaphase: the chromosome copies are separated and moved to either end of the cell on the spindle fibres.

Telophase: a membrane forms around around each set of chromosomes to form a nuclei.

Cytokinesis: a cell surface membrane forms to separate the two cells during this phase. Cell walls form on plant cells.

Question 10

What is asexual reproduction?

Answer 10

Some organisms can reproduce using one parent. Asexual reproduction produces offspring that are clones, which means their cells have the same chromosomes as their parents. (They are genetically identical)

Question 11

What organisms use asexual reproduction?

Answer 11

Strawberry plants reproduce asexually using stems to grow along the ground called runners. While potatoes use tubers.

Some animals such as aphids can reproduce this way.

Question 12

What is one difference between asexual and sexual reproduction?

Answer 12

Asexual reproduction is much faster that sexual reproduction because organisms do not need others for reproduction. However sexual reproduction produces variations and asexual does not.

Question 13

How can mitosis cause growth of cancer cells?

Answer 13

Normal cells only divide when they need to. Changes in a cell can however sometimes turn them into cancer cells which means they undergo uncontrollable cell division. The rapid cell division produces growing lumps of cells called tumours that can damage the body and result in death.

Question 14

What is growth?

Answer 14

It is an increase in size as a result of an increase in number of cells. The number of cells increases due to cell division by mitosis. Growth can be recorded by taking measurements over time, such as length or mass.

Question 15

How are baby’s measured?

Answer 15

Using percentile graphs that are made to measure a large amount of baby’s.

The curved line on the graph shows the rate of growth of a baby who stays at exactly the same percentile within their population. Most babies don’t grow at the same rate all the time so plotting their mass helps to identify weather they are growing normally. The baby should remain near the percentile curve as it grows older.

Question 16

How is a red blood cell specialised?

Answer 16

A red blood cell has no nucleus allowing more space for red haemoglobin molecules (which carry oxygen). It also has a large surface area allowing oxygen to diffuse in and out more quickly.

Question 17

How is a fat cell specialised?

Answer 17

The cytoplasm of a fat cell is filled with large fat droplets. The fat is stored until the body needs energy.

Question 18

How are neurones (nerve cells) specialised?

Answer 18

Nerve cells have a long fibre that carries electrical impulses around the body and many connection to other neurones.

Question 19

How are muscle cells specialised?

Answer 19

They contain special contractile proteins that can shorten the cell.

Question 20

What is the fund going of a meristem in a plant?

Answer 20

A group of cells near the end of each shoot and root allows plants to continue growing throughout their lives. These groups of cells are called meristems. The cells in meristems divide rapidly by mitosis. Many of the cells produced then increase in length (elongation) and differentiate into specialised cells that have different functions.

Question 21

How do specialised cells help plants?

Answer 21

The many kinds of specialised cells in a plant allow the plant to carry out many different processes effectively.

Question 22

What are two types of specialised cells in a plant?

Answer 22

Xylem cells: contain nor organelles expect mitochondria and are effectively dead which allows more space for water to flow through.

Root hair cell: large surface area to absorb water.

Question 23

How is the growth of a plant measured?

Answer 23

There are many different ways of measuring the growth of a plant including height, leaf surface area and mass. Percentages changes are often worked out for these values and can be calculated using:

Final value - staring value/starting value x 100

Question 24

What are stem cells?

Answer 24

Cells that can divide repeatedly over a long period of time to produce cells that then differentiate are called stem cells.

Question 25

Where do stem cells occur in plants?

Answer 25

In a plant these cells are found in meristems and are sometimes cakes meristem cells.
Plant stem cells are usually able to produce any kind of specialised cell through out their the life of the plant. This does not occur in most animals though, especially vertabrates.

Question 26

What is an embryonic stem cell and wh are the so special?

Answer 26

Animals start life as a fertilised egg cell, which then divide to form an embryo. The cells of an early stage of an embryo are EMBRYONIC STEM CELLS that can produce any type of specialised cell. As the cell continues to divide, the embryo starts to develop different areas that will become the different organs. These stem cells then become more limited in the types of specialised cell they can produce.

Question 27

What is an adult stem cell?

Answer 27

By the time a young animal is fully developed, the stem cells can usually only produce the type of specialised cell that is in the tissue around them. These are called ADULT STEM CELLS.
The adult stem cell in human tissue allow the tissues to grow and replace old or damaged cells.

Question 28

Where are blood cells found?

Answer 28

In marrow in the middle of long bones such as the (femur) they continue to divide throughout their life to produce new blood cells.

Question 29

Why are stem cells important?

Answer 29

They offer a way of treating many different diseases by damaged cells. At the moments scientists are studying other ways to use adult and embryonic stem cells to treat diseases such as type 1 diabetes or to replace damaged cells. This is done by stimulating stem cells to make them produce the specialised cell that are needed and then injecting them into the paces needed.

Question 30

When does embryonic cells start to differentiate in to neurones in the brain?

Answer 30

Once an embryo is 3 weeks old the stem cell in the brain area start to differentiate to produce neurones which makes up most of the brain. An adult brain has about 8.6 billion neurones which interconnect with one another and other parts of the body to process information and control the body.

Question 31

What is the cerebral cortex?

Answer 31

Makes up 80% of the brain. It is used for most of our senses, language, memory, behaviour and consciousness (our inner thoughts and feelings) it is divided into 2 cerebral hemispheres, each with slightly different functions. The right hemisphere communicates with the left side of the body and vice verse.

Question 32

What does the cerebellum do and where is it located?

Answer 32

At the base of the Brian. It is divided into two halves and controls balance and posture. It also coordinated fine timings and fine control of muscles activity, making sure the movements are smooth. Many musicians have developed changes in the cerebellum, including an increase in size.

Question 33

What is the Medulla Oblongata, what is its job and where is it located?

Answer 33

This controls your heart rate and breathing rate. It is also responsible for reflexes such as vomiting, sneezing and swallowing.
The mass of neurones that makes it up connect the brain to the spinal cord. The spinal cord is about the width of a finger and consists of many nerves (bundle of neurones). These carry information between the brain and the rest of the body.

Question 34

How can the functions of the brain be investigated on an alive human?

Answer 34

During brain surgery electrodes can apply electrical currents to the brain. It the patients are awake they can be asked to describe what they feel. The current may also make a patient do something or stop an action occurring. This allows functions of brain parts to be investigated.

Question 35

How does scanning help scientists study the brain?

Answer 35

Scaling allows scientists to look deeper into the brain than surgery does. It also allows the study of a health individual without the risk of damaging the brain.

Question 36

What is CT scan and how can it help the study of the brain?

Answer 36

A CT scan shows the shapes of structures in the brain. An X-ray beam moves in a circle around the head and detectors measure the absorption of the X-rays. A computer uses this information to build up a view of the inside of a body as a series of ‘slices’ difference in the shapes link to differences int he way people think and act, suggesting the functions of this parts.

Question 37

Wh can people not feel brain surgery?

Answer 37

Patients cannot feel brain surgery because the brain has no ‘pain receptors’.

Question 38

What does a PET scan do and how can this help brain research?

Answer 38

A PET scan shows brain activity. The patient is injected with radioactive glucose. More active cells take in more glucose than less active ones (for respiration). The radioactive atoms cause gamma rays, which the scanner detects. More gamma rays come from parts containing more active cells.

Question 39

What happens when damage is done to your spinal chord?

Answer 39

This reduces the flow of information between the brain and parts of the body. We’ve damage in the lower spinal cord can abuse loss of feeling in and use of legs. Damage to the neck can cause quadriplegia (loss of use of both arms and legs)

Question 40

Why can’t neurones be repaired by stem cells or mitosis?

Answer 40

There are no adult stem cells that can differentiate into neurones int he spinal cord and so no new neurones cannot be made to repair damage. Wires can be used to electrically stimulate nerves and muscles below the damage but patients do not regain full movement or feeling. However, treatments using stem cell injections are being developed.

Question 41

What are the affects of a brain tumour in the brain and on the body?

Answer 41

Cancer cells often divide rapidly to form a tumour. A brain tumour may squash parts of the brain or stop them from working.

Question 42

How can tumours be treated and what affect does this have on the body?

Answer 42

Tumours can be cut out or the cell can be killed using radiotherapy (high energy x ray beams) and chemotherapy (injecting drugs that kill actively dividing cells) all these methods can damage the body and brain.

Question 43

Why might chemotherapy not work?

Answer 43

It may not work due to the blood-brain barrier - a natural filter that only allows certain substances to get from the blood to the brain (mainly due to cells in the capillary walls in the brain fitting together very closely)

Question 44

How do scientists study how the brain works in labs?

Answer 44

They have managed to grow brain tissue in their labs by using stem cells techniques in some university’s.

Question 45

What is your nervous system and what forms it?

Answer 45

The brain and spinal cord from the central nervous system (CNS) which controls your body. Nerves make up the rest of your nervous system. This organ system allows all parts of your body to communicate using electrical signals or impulses.

Question 46

What is a stimulus and how is this linked to sense organs?

Answer 46

Anything your body is sensitive to, including changes inside your body and your surrounding is called a stimulus. 
Sense organs (such as eyes, ears and skin) contain receptor cells that detect stimuli. For example skin contains receptor cells that detect the stimulus of temperature change.

Question 47

How do receptor cells detect stimuli?

Answer 47

Receptor cells create impulses, which usually travel to the brain. The brain then processes this information and can send impulses to other parts of the body to cause something to happen (a response).

Question 48

What is neurotransmission?

Answer 48

The travelling or transmission of impulses and happens in neurones. Neurones have a cell body and long extensions to carry impulses.

Question 49

What different types of neurones are there?

Answer 49

Sensory neurones: it function is to carry impulses from the rector cell towards the CNS. A receptor cell impulse passes into a tiny branch called a dendrite. It is then transmitted along the dendron and the axon. A series of axon terminals allow impulses to be transmitted to other neurones.

Question 50

How are dendrons and axons developed to suite their purposes?

Answer 50

Dendrons and axons are frequently long to allow fast neurotransmission over long distances. There is also a fatty layer around surrounding these parts called myelin sheath. This is electrical insulates a neurone from neighbouring neurones stopping the signal losing energy. It also makes an impulse ‘jump’ along the cell between the gaps in the myelin and so speed up neurotransmission.

Question 51

Where are the eyes cell receptors found?

Answer 51

The eye is a sense organ that contains receptor cells found in a layer called the retina.

Question 52

What are cone cells?

Answer 52

Cones are receptor cells that are sensitive to the colour of light. Some cones detect red light while others detect green and blue. Cones generate impulses in sensory neurones, which lead into the brain through the optic nerve. The information from all cones is processed into full colour vision at the back of the cerebral hemisphere.

Question 53

What are rod cells?

Answer 53

Rods are receptor cells that detect differences in light intensity, not colour. Rods work well in dim light where as cones also work in bright light, which is why your colour vision is poor in dim light.

Question 54

What is the pupil?

Answer 54

The pupil is the dark in the middle of the eyes and is where light enters. The amount of light entering the eye is controlled by muscles in the iris, which can constrict the pupil (decrease its diameter) or dilate it (make it bigger) bright light can damage to receptor cells in the retina.

Question 55

How do we see light?

Answer 55

Light rays entering the eye need to be focused onto a point in the retina to produce a clear image. Most forcing is done by the cornea, which bends and refracts light to bring them together. The lens then fine tunes the focusing. Ciliary muscles make the lens fatter to focus light from near objects and thinner to focus light from distant objects.

Question 56

What do people with short sight see and what causes it?

Answer 56

For short -sighted people distant objects appear blurred. This is because the rays of light form distant objects are focused in front of the retina. There are two possible reasons for this:
-the eyeball is too long
-cornea is too curved and bends the rays more than it should.
This can be fixed by a wearing a diverging lens.

Question 57

How is long sightedness cause and what do they see?

Answer 57

The long sighted eyeball is too short, so the image is focused behind the retina.

This can be fixed by wearing a converging lens.

Question 58

What can fix being long or short sighted?

Answer 58

Contact lenses or lenses in glasses or a laser can be used to cut away some of the cornea and reshape it.

Question 59

What is cataract?

Answer 59

Some times protein builds up inside the lens and makes it cloudy. This is cataract full vision can be restored by replacing the clouded lens with a plastic one.

Question 60

What is colour blindness?

Answer 60

People with this have some cones that do not work properly and so have difficulty in seeing some colours. The most common form is red-green colour blindness, in which the cones detect green light are faulty, asking it difficult to tell the difference between reds, greens and browns. This cannot be corrected.

Question 61

What are effectors?

Answer 61

When the brain coordinates ma response to a stimuli, impulses are sent to effectors and these carry out actions. Effectors include muscles and glands (e.g sweat glands)

Question 62

What different types of neurones are there?

Answer 62

Motor neurones: carry impulses to effectors.
Relay neurones: are short neurones that are found in the spinal cord, where they link motor and sensory neurones.
There also make up a lot of the nerve tissue in the brain. Neither of these types of neurones have a dendron and the dendrites are on the cell body.

Question 63

What is a synapse and what happens here?

Answer 63

One neurone meets another at a synapse, which contain a tiny gap. When an impulse reaches an axon terminal a neurotransmitter substance is released into the gap. This is detected by the next neurone, which generates a new impulse. Synapses slow down neurotransmission. They are however useful because neurotransmitters and only released from axon terminals and so impulses only flow in one direction.

Question 64

What happens during the reflex arc?

Answer 64

If you touch a hot object you need to pull your finger away quickly to stop it burning you. You don’t want to have to waste your time thinking about this and so a reflex is used. Reflex actions are responses that are automatic, extremely quick and protect the body. They use the neurone pathway called reflex arcs, which bypass parts of the brain involved in processing information and so are quicker than the responses that need processing.