Cells and Control

What is the cell cycle?

The series of stages a cell goes through as it grows, copies its DNA and divides.

What happens during interphase?

The cell grows, increases its number of organelles and replicates its DNA.

What happens during prophase?

Chromosomes condense and become visible, the nuclear membrane breaks down and spindle fibres begin to form.

What happens during metaphase?

Chromosomes line up along the equator of the cell.

What happens during anaphase?

Spindle fibres pull the sister chromatids apart to opposite ends of the cell.

What happens during telophase?

New nuclear membranes form around each set of chromosomes.

What is cytokinesis?

The division of the cytoplasm to form two separate daughter cells.

What is mitosis?

A type of cell division that produces two genetically identical daughter cells.

Why is mitosis important in growth?

It increases the number of cells in an organism.

Why is mitosis important in repair?

It produces new cells to replace damaged or dead cells.

How is mitosis involved in asexual reproduction?

It produces genetically identical offspring from a single parent.

What are daughter cells?

The cells produced when a parent cell divides.

What does diploid mean?

A cell containing two sets of chromosomes, one set from each parent.

How many chromosomes are in a human diploid body cell?

46 chromosomes arranged in 23 pairs.

What is produced by mitosis?

Two genetically identical diploid daughter cells.

Why are daughter cells produced by mitosis genetically identical?

Because the DNA is replicated before division and each daughter cell receives an identical set of chromosomes.

What is cancer?

A disease caused by changes in cells that result in uncontrolled cell division.

How does growth occur in animals?

Through cell division and cell differentiation.

How does growth occur in plants?

Through cell division, cell elongation and cell differentiation.

What is cell differentiation?

The process by which an unspecialised cell develops structures and functions that make it specialised.

Why is cell differentiation important?

It allows cells to become specialised for particular functions, allowing tissues and organs to develop.

What is a specialised cell?

A cell adapted to perform a particular function.

What is a stem cell?

An unspecialised cell that can divide and develop into different types of specialised cells.

What are embryonic stem cells?

Stem cells from early embryos that can differentiate into many different types of body cell.

What is the function of embryonic stem cells?

They can develop into different specialised cell types during the development of an organism.

Where are stem cells found in adult animals?

In certain tissues, such as bone marrow.

What can animal stem cells do?

They can divide and differentiate into a limited range of specialised cells.

What are meristems?

Regions of actively dividing unspecialised cells found in plants, particularly at the tips of roots and shoots.

What can meristem cells develop into?

Different types of specialised plant cells.

What are percentile charts used for?

To compare an individual's growth or development with the expected range for a population.

What does a percentile tell you?

It shows how an individual's measurement compares with measurements from a population of the same age or sex.

Why are percentile charts useful for monitoring growth?

They can identify unusual growth patterns or changes that may require investigation.

What is one potential medical benefit of stem cells?

They could replace damaged or diseased cells and tissues.

Give an example of a condition that could potentially be treated using stem cells.

Some blood disorders and conditions involving damaged tissues.

What is a potential ethical risk of using embryonic stem cells?

Obtaining embryonic stem cells involves using embryos, which raises ethical concerns.

What is another medical risk associated with stem-cell treatment?

Cells may divide uncontrollably or differentiate incorrectly, potentially causing tumours or other problems.

Why can stem-cell treatment cause immune system problems?

Cells from another person may be recognised as foreign and attacked by the immune system.

Why are stem cells potentially useful in medicine?

They can produce new specialised cells that could replace damaged cells.

What are the three main brain structures required by the specification?

The cerebral hemispheres, cerebellum and medulla oblongata.

What is the function of the cerebral hemispheres?

They are involved in conscious activities such as intelligence, memory, reasoning, personality and voluntary movement.

What is the function of the cerebellum?

It coordinates muscle movement, balance and posture.

What is the function of the medulla oblongata?

It controls involuntary functions such as breathing and heart rate.

Why is it difficult to investigate brain tissue directly?

The brain is enclosed inside the skull, making it difficult and dangerous to access without surgery.

How can CT scans be used to investigate the brain?

CT scans produce detailed images of the brain and can identify abnormalities such as tumours or areas of damage.

What does CT stand for?

Computed tomography.

How can PET scans be used to investigate brain function?

PET scans show areas of the brain that are more metabolically active, allowing scientists to investigate which areas are active during particular tasks.

What does PET stand for?

Positron emission tomography.

Why are CT and PET scans useful for studying the brain?

They allow the brain to be investigated without directly accessing the brain tissue.

Why can damage to the brain be difficult to treat?

Brain tissue is highly complex and specialised, and damaged neurones often cannot easily be replaced.

Why can spinal injuries be difficult to treat?

Damage to the spinal cord can prevent electrical impulses travelling between the brain and the rest of the body.

Why can brain tumours be difficult to treat?

Surgery may damage important areas of the brain, while treatments such as radiotherapy can also damage healthy tissue.

Why is surgery on the brain particularly risky?

Different areas of the brain control essential functions, so damaging healthy brain tissue can cause serious effects.

What is the function of the nervous system?

To detect stimuli, process information and coordinate rapid responses.

What is a sensory receptor?

A specialised cell or group of cells that detects a stimulus and converts it into an electrical impulse.

What is a sensory neurone?

A neurone that carries electrical impulses from sensory receptors to the CNS.

What is the CNS?

The central nervous system, consisting of the brain and spinal cord.

What is a relay neurone?

A neurone in the CNS that connects sensory neurones to motor neurones.

What is a motor neurone?

A neurone that carries electrical impulses from the CNS to an effector.

What is an effector?

A muscle or gland that produces a response.

What is an axon?

A long fibre that carries electrical impulses away from the cell body of a neurone.

What is a dendron?

A fibre that carries electrical impulses towards the cell body of a neurone.

What is the myelin sheath?

A fatty insulating layer around some axons that increases the speed of electrical impulse transmission.

What is a synapse?

A junction between two neurones where neurotransmitters transfer the signal.

Why can't an electrical impulse directly cross a synapse?

There is a small gap between the neurones.

What happens at a synapse?

An electrical impulse causes neurotransmitters to be released. They diffuse across the synaptic gap and bind to receptors on the next neurone, triggering another electrical impulse.

What are neurotransmitters?

Chemical substances released by neurones that transmit signals across synapses.

Why does transmission across a synapse occur in one direction?

Neurotransmitters are released from the first neurone and receptors are located on the next neurone.

What is a reflex action?

A rapid, automatic response to a stimulus that does not require conscious thought.

What is a reflex arc?

The pathway followed by an electrical impulse during a reflex action.

What is the pathway of a reflex arc?

Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.

Why are reflex actions important?

They provide rapid responses that help protect the body from harm.

Why are reflex actions faster than conscious responses?

They are processed through a short pathway involving the spinal cord rather than requiring conscious processing by the brain.

What is the function of the eye?

It detects light stimuli and allows organisms to see.

What is the cornea?

The transparent outer layer of the eye that refracts light as it enters.

What is the lens?

A transparent structure that refracts light and focuses it onto the retina.

What is the iris?

A ring of muscle that controls the size of the pupil and therefore the amount of light entering the eye.

What is the retina?

The light-sensitive layer at the back of the eye containing rod and cone cells.

What are rod cells?

Light-sensitive cells that work well in dim light but do not detect colour.

What are cone cells?

Light-sensitive cells that detect different colours and work best in bright light.

What causes short-sightedness (myopia)?

The eyeball is too long or the lens is too powerful, causing light to focus in front of the retina.

How is short-sightedness corrected?

Using a concave lens to diverge the incoming light so it focuses on the retina.

What causes long-sightedness (hyperopia)?

The eyeball is too short or the lens is too weak, causing light to focus behind the retina.

How is long-sightedness corrected?

Using a convex lens to converge the incoming light so it focuses on the retina.

What is a cataract?

A condition where the lens becomes cloudy, reducing the amount of light reaching the retina.

How are cataracts treated?

The cloudy lens can be surgically removed and replaced with an artificial lens.

What is colour blindness?

A condition where some types of cone cells do not work correctly, making it difficult to distinguish certain colours.

Why can't colour blindness usually be corrected with glasses?

It results from the absence or malfunction of cone cells rather than a focusing problem.

What is an estimate?

An approximate value rather than an exact measurement or calculation.

When should estimates be used?

When an exact value is unnecessary, impossible to obtain or when checking whether an answer is sensible.

How do you calculate percentage gain?

Percentage gain = (increase ÷ original value) × 100.

How do you calculate percentage loss?

Percentage loss = (decrease ÷ original value) × 100.

What is a correlation?

A relationship between two variables.

What does positive correlation mean?

As one variable increases, the other tends to increase.

What does negative correlation mean?

As one variable increases, the other tends to decrease.

What does no correlation mean?

There is no clear relationship between the two variables.

What is a scatter diagram used for?

To investigate the correlation between two variables.

What does it mean if points on a scatter diagram are close to a line of best fit?

There is a stronger correlation between the variables.

What does it mean if points are widely scattered?

There is a weaker correlation.

What should you be able to do with graphs, charts and tables?

Extract, interpret and compare information from them.

What does it mean to translate information between numerical and graphical forms?

Converting data between numbers or tables and graphs or charts.