Topic 2 - Cells and Controll

The regular sequence of growth and division that cells undergo
It is also described as the life cycle of cells

interphase, mitosis, cytokinesis

cells grow, organelles are replicated, DNA synthesiseplication,

● Double helix 'unzips' exposing two strands
● DNA bases align next to complementary bases on
the DNA strands
● Complementary base pairs join
● Two identical DNA molecules formed

A linear DNA molecule tightly coiled around proteins

The DNA in the arm of each of the chromosome is replicated

An increase in the number or size of cells. More cells produced from mitosis.

75% of boys of that age have a height equal to or greater than this value. Or 25% of boys of that age have a height which is equal to or less than that value.

It is possible to track growth of the child and see if it changes significantly from the percentile the child is following over time. This may indicate a problem with the child's growth.

Differentiation allows unspecialised cells to change into specialised cells which perform specific functions in the body.

The cells in the meristem divide rapidly by mitosis. They can elongate (get longer in length) and differentiate into the specialised cells of the plant.

Thick walls with lignin to withstand water pressure, no cytoplasm so lots of space for water, pores in the sides of the vessel to allow water and mineral ions to leave the vessel.

(final value - starting value)/ starting value x 100%

As the cells divide and differentiate, they will need many new proteins to make more cell structures which are provided by the ribosomes.

Used for growth and repair and replacement of damaged cells ,asexual reproduction

A diploid cell has two sets of chromosomes (46 in humans) and a haploid cell has half the usual number of chromosomes, one set (23 in humans).

The cell grows and makes new sub-cellular structures such as mitochondria. At the end of interphase, the DNA replicates.

The two daughter cells are genetically identical.

prophase, metaphase,anaphase, telophase

The membrane of the nucleus breaks down and the spindle fibres appear. The chromosomes are visible in the nucleus.

The chromosomes line up in the middle of the cell. The spindle fibres attach to the chromosomes. The chromosomes are made up of two sister chromatids attached at the middle. M IS FOR MEET IN MIDDLE

The chromatids are pulled apart by the spindle fibres, and the chromosomes move to opposite sides of the cell. A IS FOR APART

A membrane forms around the chromosomes to make the nucleus.

IS NOT PART OF MITOSIS Cytokinesis, A new membrane, and in plants a cell wall, forms between the two new cells to separate them

Because the two offspring produced are genetically identical- have the same chromosomes as the parent

In asexual reproduction, the offspring are genetically identical to the parent (clones) so cells must divide by mitosis in order for this to take place.

The cells no longer divide in a controlled way and can divide rapidly forming tumours that cause damage to the body.

Sperm cells are haploid, so only have half the number of chromosomes. Mitosis results in an exact copy of a diploid cell, so cannot produce sperm cells.

the disease caused by an uncontrolled division of abnormal cells in a part of the body.

● Slower growth than normal (below the bottom line)
● Faster growth than normal (above the top line)
● Abnormal growth (irregular growth patterns)

● Cell division occurs in all body cells. It occurs at a slower rate in adults that in younger animals as growth stops and cell division is only required for replacement and repair.
● Most cells differentiate at an early stage and become specialised. Some adult stem cells retain their ability to differentiate.

● Cell division can only occur in meristematic tissue. The rate of cell division remains the same throughout a plant's life.
● Meristematic stem cells can differentiate into any cell type for as long as the plant lives
● Cell elongation occurs in all cells. Cells expand and enlarge enabling growth of the plant.

Stem cells can divide over and over again and produce cells which differentiate into specialised cells.

The process by which a cell changes to become specialised for its job - some genes are switched on or off.

In the growing root and shoots of the plant. Meristem cells.

Embryonic stem cells can produce any type of specialised cell. Adult stem cells can only produce a limited number of specialised cells, usually part of the tissue where they are located.

These are adult stem cells. They can differentiate to produce cells of the blood and are necessary to replace the cells that make up the blood tissue.

Stem cells can differentiate into some or all cell types, could replace damaged cells, such as cells of the heart tissue following a heart attack.

The stem cells may not divide as expected and could continue to divide and form a cancer. The cells may be rejected by the patient because they are recognised as foreign by the immune system. Potential side effects. Hard to find a suitable donor for stem cells

Enable the growth and development of tissues in human embryos

Replacement of dead cells

In the roots and shoots of plants

Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during the life of a plant

● Stem cells collected
● Stem cells stimulated to differentiate into specific
cell types e.g. heart muscle cells
● Specialised cells transplanted into the patient
● Used to treat damage or disease e.g. heart disease

The embryos used to take stem cells are destroyed and seen as a potential waste of human life

May lead to the reproductive cloning of humans

They can differenciate into any cell types and replace and repair tissues and faulty cells.

Mainly made of neurones
It is wrinkled
Has 2 hemispheres

Controlls Personalty, senses, language, memory,behavior and consiousness

Controls how much light enters the eye

Mainly made up of neurones
Has neurones that connect to the back of the spinal chord

Controlls reflexes
Controlls breathing and heart rate

Controlls balence and posture
Co ordinates the timing and fine controll of muscle activity making sue movements are smooth

Contains Nerves - Long neurones with blood vessels

Carries information betwee the brain and the rest of the body

The brain and spianal chord (Central Nervous System)
All the nerves outside the brain and spinal chord (Periphral Nervous System)

Stimulus : A change in the Environment
Receptor : Detects the stimulus
(Electrical impulse transfered to the brain via the sensory neurone)
Co-ordinator: Brain and Spinal Chord controll responce
(Transfered to the effector via the Motor neurone)
Effector: The part of the body responds to the stimulus
Responce : The action in responce to the stimulus

1) Pain receptors sence stimulus
2)An electrical impusle is generated and travels down the sensory neuron in the arm
3)The impule passes from a sensory neurone to a relay neuron in the spinal chord
4) The impolse is passed from the relay neuron to the motor neurone at the synapse
5) The impulse travels down the axon of the motor neurone to the effector
6) The hand is moved away from the object causing pain

The pathway is shorter than if the impulses went to the brain to be processed

This is because they do not need to transfer impulses over long distances

1) The electrical impulse arrives at the end of the neurone. The gap between the two neurones is called the synapse
2) The vesicle containing neurotransmitters merges with the cell membrane
3)The neurotransmitter diffuses accross the synapse
4)The neurotransmitter bindes to a receptor on the post synaptic neurone
5) THe impulse is generated in the next neurone/ travels down the axon

REFER TO TABLE IN BOOK

It contains a layer receptor cells called cones that are sensitive to coloured light and cones to detect high intencity light and seeing colours

The transparent front part of the eye which covers the iris and the pupil ad converges the light

Musicles in the iris controls how much light enters the eye. Also is the colured part of the eye

Part of the eye that further converges the light to focus on the eye

Impulses generated by cones are sent by the opic nerve to the brain

Controls how much light enters the eye

1) light is reflected of an object
2) lens changes shape to focus light on retina
3) Rods and Cones dectect light
4) Electrical impulse via the optic nerve to the brain

Have some cones that do not dectect some wavelengths of light and so have diffuculty in seeing some colour

It cannot be cured or corrected

when the eyeball is too long or the lens is doing too much bending. The light converges in front of the retina

with a diverging lens that spreds out rays before they reach the eye

The light rays converge behind the retina. This is because the eyeball is too small or the cornea is too flat or the lens cannot bend the light enough

A converging lens to bend the light before it reaches the eye

Cloudy protein building up in the lens, blocking light from hitting the retina

Artificial lens that is flexible clear and transparant

Reshapes the cornea to bend light better