Topic 2 - Cells and Control ✅

Biology GCSE Edexcel Topic 2 Cells and Control Flashcards

What is the cell cycle

A sequence of growth and division that happens in cells

What is mitosis

The process by which a single cell divides into two identical daughter cells

What are the stages of mitosis

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis

Describe interphase

• DNA in each cell is copied

• makes x-shapes, each containing a chromosome and its copy

Describe prophase

• The membrane around the nucleus breaks down

• Spindle fibres form

Describe metaphase

• The chromosomes line up in the middle of the cell

• Spindle fibres attach

Describe anaphase

• Each of the chromosome X-shapes splits to form two single chromosomes

• The single chromosomes move away from each other

Describe telophase

• The single chromosomes arrive at opposite ends of the cell

• The membranes around each nucleus start to form again

Describe cytokineses

• The cytoplasm of the cell is separated

• Cell membrane divides the cell into two daughter cells

Describe the importance of mitosis in growth and repair

• Mitosis generates new cells that are genetically identical to each other.

• Mitosis helps organisms grow in size and repair damaged tissue

Describe the importance of mitosis in asexual reproduction

• Mitosis is important in asexual reproduction as there is only one parent

• This means it is fast

• It produces genetically identical offspring, meaning you can reproduce desirable traits

Describe mitosis in terms of cells

• the production of two daughter cells, each with identical sets of chromosomes, in the nucleus of the parent cell

• This results in the formation of two genetically identical diploid body cells

What is cancer

Cancer is the result of changes in cells that lead to uncontrolled cell division

Describe growth in animals

• Animals grow by cell division and differentiation

• Differentiation is when cells change to become specialised, making them more efficient

Describe growth in plants

• Plants grow by cell division, elongation and differentiation

• At the tip of the roots is the meristem, where cells divide by mitosis

• Then the cells get bigger at the zone of elongation

• Behind the zone of elongation is where the cells differentiate to form specialised cells 

Explain the importance of cell differentiation in the development of specialised cells

• Differentiation produces specialised cells, adapted to carrying out specific functions.

• This means that multicellular organisms can work more efficiently

What are percentile graphs

• Data is collected and divided into percentiles

• If the graph is about height and you are in the 25th percentile, it means 75% of people are taller than you

What are stem cells

Cells that divide repeatedly over time to produce cells that then differentiate

What is the function of embryonic stem cells

Embryonic stem cells can differentiate to form all specialised cells in your body

What is the function of stem cells in animals

To replace cells that are injured or diseased, because these cells cannot divide

What is the function of stem cells in the meristems of plants

• The function of stem cells in the meristem is to allow the plant to grow correctly throughout its life

• Stem cells in meristem may be used to grow plants with desirable features or to grow rare species that are going extinct

Risks (4) of using stem cells in medicine

• If the growing stem cells are contaminated with a virus, an infection can be transferred to the individual

• Religious or ethical objections - some may see it as interfering with the natural process of reproduction

• Body may not accept the stem cells

• The process of differentiation is not fully understood - it is hard to control stem cells to form the cells we desire

Benefits (2) of using stem cells in medicine

• Can be used to replace damaged or diseased body parts

• Unwanted embryos from fertility clinics, that would otherwise be discarded, can be used

Structure of cerebral cortex

• Two hemispheres

• Made of mainly neurones

Function of cerebral cortex

Used for:

• Most of our senses

• Language

• Memory

• Behaviour

• Consciousness

Structure of cerebellum

• In two halves

• Made mainly of neurones

Function of cerebellum

Controls:

• Balance

• Posture

• Fine muscle movements

Structure of medulla oblongata

• Central link between brain and spinal cord

• Made mainly of neurones

Function of medulla oblongata

Controls breathing rate and heart rate

Function of the cornea

Cornea is a clear covering that refracts light into the eye

Function of the lens

Transmits and focuses light into the retina by refraction

Function of the iris

Controls the amount of light entering the eye

Describe cataracts

• Protein builds up in the lens

• Makes it cloudy

• Means light can't pass through properly, so your vision becomes blurry

Describe long sightedness and how it is caused

• When you can't see close objects

• Caused when your eyeball is too short or your lens is too flat

• Meaning lens doesn't refract enough and light focuses behind the retina

 

Describe short sightedness and its causes

• When you can't see distant objects

• Caused by the eyeball being too long or the lens too curved (too convex)

• Means the lens refracts a lot

• Light focuses in front of the retina

How can cataracts be corrected

Replace cloudy lens with an artificial plastic one

How can long-sightedness be corrected

Use contact lenses with a convex lens

How can short sightedness be corrected

Use contact lenses with a concave lens

Describe colour blindness

• When you can't distinguish between certain colours

• Caused by your red and green cone cells either not working or a lack thereof

What are cone cells in the retina

• Cells found in the retina that are sensitive to bright light,

• and which detect different colours

What are rod cells

 cells found in the retina that are sensitive to dim light

Why is difficult to access brain tissue in the skull

• It is very invasive to cut the skull open and examine the brain

How does CT scanning work

• CT scanning uses X-rays to create detailed cross-sectional images of the brain.

  • It can provide information about the structure of the brain and identify abnormalities, such as tumours or bleeding.

How does PET scanning work

• A radioactive tracer is injected into the blood

• Areas where the tracer builds up (areas with greater blood flow) will be highlighted on a scan

• This is useful for identifying tumours, as these use more blood than normal tissue

Explain some of the limitations in treating damage and disease in the brain

• The brain is complex and delicate

• It can be easily damaged

• We do not fully understand what part of the brain does what

• When cancerous tumours form in the brain, they can get buried deep in the brain or spinal cord, making them difficult to remove

What are neurones

• Nerve cells adapted to quickly transmit nerve impulses

• They are functional units of the nervous system

What is the function of the axon

• Carries impulses away from the cell body

• Enables the transmission of nerve impulses over long distances

Function of dendrons and dendrites

• Carry impulses towards the cell body

• Dendrites provide a large surface area to receive impulses

Role of the myelin sheath

• Electrically insulating layer

• Surrounds the axon and increases the speed of impulses

Function of the sensory neurone

Carries impulses from the receptors to the central nervous system

Structure of a sensory neurone

• Long dendron carries impulses from receptors to the cell body

• Cell body found part way along the neurone

• Short axon carries impulses from the cell body to the CNS

Function of motor neurone

Carries impulses from the central nervous system to effectors

Structure of motor neurone

• Short dendrites carry impulses from the CNS to the cell body

• Cell body found at one end of the neurone

• Long axon carries impulses from the cell body to the effectors

Function of relay neurone

• Carries impulses from sensory neurones to motor neurones

• Within the CNS

Structure of relay neurone

• Short dendrites carry impulses from sensory neurones to the cell body

• Short axon carries impulses from the cell body to motor neurones

How does the central nervous system coordinate a response to a stimulus

• Stimulus

• Sensory receptor detects stimulus

• Sensory receptor sends impulses along sensory neurone to CNS

• CNS coordinates response

• CNS sends information to effector along motor neurone

• Effector produces a response to the stimulus

What is a synapse

• A small gap between neurones

• Nerve impulses are transmitted across it

How are nerve impulses transmitted across a synapse

• Nerve impulse reaches presynaptic neurone

• This triggers the release of neurotransmitters

• Neurotransmitters diffuse across the synapse

• They bind to receptors on the postsynaptic neurone

• This stimulates an impulse in the postsynaptic neurone

Why do synapses slow down the transmission of nerve impulses

It takes time for the neurotransmitters to diffuse across the synapse and bind to receptors on the postsynaptic neurone

What is a reflex

• An automatic response to a stimulus by the body

• It is involuntary

• It is a protective mechanism

Describe the reflex arc

Stimulus -> sensory receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response