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Edexcel GCSE Biology > SB2 - Cells and Controls ✓ > Flashcards

SB2 - Cells and Controls ✓ Flashcards

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1
Q

SB2a - When a regular human body cell divides, what is this process called, and how does it occur?

A

Mitosis

  • Prophase
    • The nucleus starts to break up and spindle fibres appear.
  • Metaphase
    • The chromosomes are lined up on the spindle fibre across the middle of the cell
  • Anaphase
    • The chromosome copies are separated and moved to either side of the cell
  • Telophase
    • A membrane forms around each set of chromosomes to from a nuclei
  • Cytokeniesis
    • Cell surface membrane forms separating the two cells (Implants, a cell wall is also formed)
  • Interphase
    • Copies of the chromosomes are formed in the nucleus
  • The cycle repeats
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2
Q

SB2a - What are the products of mitosis called?

A

Daughter Cells

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3
Q

SB2a - What type of organisms do not require mitosis to occur?

A

Unicellular organisms

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4
Q

SB2a - How many types of chromosones are in a human cell and what is it called when these are alone or paired up?

A
  • 23 types of chromosomes.
  • When they are paired up to have 46 chromosomes this is a diploid cell and a haploid cell only has 23 chromosomes.
  • Gametes are haploid cells while all other cells in a human are diploid.
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5
Q

SB2a - How are tumors formed?

A
  • When cells mutate, they can become cancer cells.
  • This means that they will divide even when they don’t require to divide.
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6
Q

SB2a - Why does asexual reproduction require mitosis?

A
  • As asexual reproduction only needs one parent, the offspring will have the same DNA as the parent.
  • As the offspring are clones and their chromosomes are identical, their cells are formed by mitosis.
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7
Q

SB2b - Define growth.

A

The increase in size as a result of an increase in size of or numbers (due to cell division) of cells.

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8
Q

SB2b - How is the growth of a baby monitored and how does this work?

A

Using a percentile growth curve:

  • This graph has many lines showing you how a babies conditions compare to the average.
  • The healthiest position would be at 50% as half of the population is above or below you.
  • Being above 98% or below 2% is reason for concern as only 2% of the population is above or below you.
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9
Q

SB2b - What is cell differentiaiton?

A

When a less specialised cell is changed to become a specialised one.

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10
Q

SB2b - How are red blood cells specialised for their purpose?

A
  • Biconcave shape means more surface area for oxygen diffusion.
  • No nucleus means more space for red haemoglobin molecules and carry more oxygen
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11
Q

SB2c - What are the meristems?

A
  • A group of cells near the end of each shoot that allow plants to continue growing throughout their lives.
  • They divide rapidly and the cells are elongated and differentiated.
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12
Q

SB2c - How are root hair cells specialised for their function?

A
  • Root hair cells have hair to increase their surface area to allow them to absorb water more effectively.
  • They also don’t contain chloroplasts (as they are underground and can’t photosynthesise)
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13
Q

SB2c - How are xylem cells specialised for their function?

A
  • They have thick walls containing lignin.
  • This causes the cells to die
  • As the cells die, the end walls connecting them break away, meaning the cells form a long tube
  • Along with the fact that they have no internal structure at all (nucleus, chloroplasts etc.) this makes it easier to transport water and minerals.
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14
Q

SB2c - What are the zones of differentiation elongation and cell division?

A
  • D: Where cells are specialised
  • E: Where cells are elongated (vertically extended)
  • CD: Where rapid mitosis occurs (Meristems)
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15
Q

SB2d - What is an embryonic stem cell?

A

A cell in an early stage embryo that is not specialised and can differentiate to form any type of specialised cell.

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16
Q

SB2d - Where can adult stem cells be found and how are they different to embryonic stem cells?

A

Adult stem cells can be found in most tissues including bone marrow but can only differentiate to cells in the tissue around them .

17
Q

SB2d - How can stem cells be used to treat lukemia?

A
  • A patient’s bone marrow is destroyed using radiation
  • Adult stem cells are inserted into the patient
  • The stem cells will differentiate specialise and divide to form new blood cells and bone marrow
18
Q

SB2d - What are the problems with using stem cells in medicine?

A
  • If stem cells continue to divide, it can cause a cancerous tumour to form
  • Stem cells of one person can be rejected by the immune system of another
19
Q

SB2d - Why don’t plants have adult stem cells?

A

Their cells remain able to differentiate freely throughout their lives.

20
Q

SB2e - What type of cells is the brain mostly made up of?

A

Neurones

21
Q

SB2e - What are the three major structures of the brain, and what are each of their functions?

A
  • Cerebral cortex: Main functions and control such as memories language etc.
  • Cerebellum: Controls balance and movement
  • Medulla oblongata: Controls heart and breathing rate
22
Q

SB2e - How did Phineas Gage’s accident prove what the cerebral coretex is used for?

A
  • Phineas gage had a metal rod stuck inside his brain
  • It was through his cerebral cortex
  • He was still able to walk, but his personality changed
  • This shows that this part of the cerebral cortex controls emotions and personality but not movement or breathing/heart rate
23
Q

SB2e - Why may musicians have larger/more developed cerebellums?

A

So can develop and have more control over their fine movements and timing coordination

24
Q

SB2e - The medulla oblongata controls reflexes. What does this mean about its connections?

A

It connects the brain to the rest of the CNS

25
Q

SB2f - During brain surgery, what may be don to investigate roles of the brain?

A

Probing with electricity (electrodes) means that doctors can control the activity of different parts of the brain

26
Q

SB2f - How does a CT scan work?

A
  • A CT scan involves an x-ray beam moving in a circle around the head.
  • It produces images that are slices of the brain.
  • Computers can layer and build these up to produce an image
27
Q

SB2f - How does a PET scan work?

A
  • Radioactive glucose is injected into the body.
  • More active cells take in more glucose.
  • The PET scan scans for where the most radioactivity is coming from showing the levels of activity in the brain.
28
Q

SB2f - Why is spinal cord damage so dangerous?

A
  • Damage to the spinal cord can sever the connection between your brain and the rest of your body.
  • This can loose to the loss of control of limbs such as quadripalegia.
29
Q

SB2f - Why does chemotherapy not always work for brain tumors?

A
  • Chemotherapy involves sending chemical substances through blood to actively kill tumours
  • The brain has a natural filter called the blood-brain barrier which blocks out foreign substances in the brain
  • Additionally, chemotherapy can harm healthy cells
30
Q

SB2g - What makes up the nervous system?

A
  • The CNS (Central nervous system):
    • The brain
    • The spinal cord
  • Nerves
31
Q

SB2g - How does your body communicate?

A

Using electrical signals called impulses

32
Q

SB2g - What are sense organs?

A

Organs that contain receptor cells which will cause the body to have a response to a stimulus. e.g. eyes, ears etc.

33
Q

SB2g - Describe the sturcture of a sensory neuron.

A
  • Dendrites receive the electrical impulses from the receptor
  • This is passed on through the dendron and the axon
  • Axon terminals at the other end allow the electrical impulse to be passed on
  • The cell body containing the nucleus is between the dendron and axon
  • The cell is covered in fatty layer called the myelin sheath
  • This insulates the cell meaning there are no electrical jumps to other cells speeding up neurotransmission
34
Q

SB2h - Describe the structure of the eye.

A
  • There is a clear covering called the cornea covering the eye which refracts most of the light
  • Below this are the iris and the pupil
  • CIllary muscles alter the shape of the eye (constricting or dialating it)
  • A lens to fine tune the light refraction
  • At the back is the retina containing rods (detect light levels) and cones (detect colour. Don’t function well in dim light)
  • This is passed onto optic nerves which pass electrical impulses to the brain
  • Refracted light should meet at the retina
35
Q

SB2h - What is myopia and hyperopia?

A

Myopia is short sightedness (Can see close):

  • This is when light focuses too early (before the retina)
  • The eyeball is too long.
  • This can be fixed with a diverging lens.

Hyperopia is long sightedness (Can see far):

  • This is when light hasn’t focused by the time it reaches the retina.
  • The eyeball is too short.
  • This can be fixed with a converging lens
36
Q

SB2h - What is a cataract?

A
  • Protein build up in the lens can cause it to become cloudy, clouding your vision.
  • This can be corrected by replacing the lens with a plastic one
37
Q

SB2h - What is colour-blindness?

A
  • When the cone cells in your eye don’t properly detect colour
  • The most common form of this is red-green colour blindness
  • This cannot be corrected
38
Q

SB2i - Describe the reaction process (not reflex arc).

A
  • The receptor cells in your sensory organs respond to a stimulus
  • They send a neurotransmission which using neurones, travels to your brain
  • Your brain decides what action to take and sends a neurotransmission using neurones to send a message to an effector e.g. muscle contracting
39
Q

SB2i - Describe the roles synapses play in the reflex arc. (include the three types of neurones)

A
  • The receptor passes on an impulse to the sensory neurone
  • The sensory neurone reaches a ‘junction’ called a synapse. It contains a tiny gap
  • Once it reaches here, a chemical (neurotransmitter) is released passing on the impulse to the relay neurone in the spinal cord
  • The relay neurone reaches another synapse where it releases more neurotransmitters to pass it on to a motor neurone
  • The motor neurone reaches the effector where it causes a response to take place (e.g. muscle contracting)

Edexcel GCSE Biology (11 decks)

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