T2 - Cells and Control Flashcards Preview

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Flashcards in T2 - Cells and Control Deck (73):
1

Chromosomes

Coiled up lengths of DNA molecules

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Diploid cell

Cells which have 2 copies of each chromosome (1 chromosome from mother and father)

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What is made when a cell is divided by mitosis?

2 cells identical to the original cell - the nucleus of each has the same number of chromosomes as the original

4

Why do multicellular organisms use mitosis?

To grow, replace damaged cells, reproduction (asexual)

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Interphase (mitosis)

DNA is spread out in long strings so before it divides, the cell has to grow and increase the amount of subcellular structures (eg ribosomes and mitochondria) Then, it duplicates its DNA and forms X shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other

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Prophase (mitosis)

1st phase:
The chromosomes condense, getting shorter and fatter. The membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm

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Metaphase (mitosis)

2nd phase:
The chromosomes line up in the middle of the cell

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Anaphase (mitosis)

3rd phase:
Cell fibres pull the chromosomes apart, the 2 arms of each chromosome go to opposite ends of the cell

9

Telophase (mitosis)

4th phase:
Membranes form around each of the sets of chromosomes, these become the nuclei of the 2 new cells

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Cytokinesis

Before telophase ends, the cytoplasm and cell membrane divide to form 2 separate cells

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Cell differentiation

The process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently

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Cell division

By mitosis

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Cell elongation

Where a plant cell expands, making the cell bigger and so making the plant grow

14

All growth in animals happens by....

Cell division

15

In plants, growth in height is mainly due to....

Cell elongation

16

What is the rate at which cells divide by mitosis controlled by?

Chemical instructions (genes) in an organisms DNA

17

What might happen if there’s a change in one of the genes that controls cell division? What could it cause?

Cells might start to divide uncontrollably - can result in a mass of abnormal cells (tumour), if the tumour invades and destroys surrounding tissue, it’s cancerous :(

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Stem cells

Undifferentiated cells (not specialised)

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Where are stem cells found?

Early human embryos

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What are stem cells important for and why?

Growth and development because they have the potential to divide and produce any kind of cell

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What are stem cells used for in animals?

To replace damaged cells (eg make new skin or blood)

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Meristems

Plant tissues which contain the only cells that divide by mitosis. Found on the tips of roots and shoots

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What do meristems form? How is this different to humans?

Unspecialised cells which can grow and form any type of cell. But, unlike human cells they can divide and differentiate to generate any type of cell for as long and the plant lives

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What are the 3 risks for using stem cells in medicine?

Tumour development - cells can divide quickly if not controlled
Disease transmission - if a virus from inside the stem cell isn’t detected, it could make the patient sicker
Rejection - the patient’s body could recognise they are foreign cells and trigger immune response

25

Neurons

Nerve cells - make up the spinal cord

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Central nervous system (CNS)

Made up of the brain and spinal cord. The spinal cord relays information between the brain and the rest of the body

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What’s the brain made up of?

Billions of interconnected neurones

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Cerebrum

The largest part of the brain, divided into 2 halves. Responsible for movement, intelligence, memory, language and vision. Right hemisphere controls the muscles on the left hand side (and vice versa)

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Cerebral hemispheres

2 halves of the largest part of the brain (cerebrum)

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Cerebellum

Part of the brain which is responsible for muscle coordination and balance

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Medulla oblongata

Controls unconscious activities like breathing and heart rate

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What are the 2 scanners used to investigate the brain?

CT and PET

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CT scanning

Uses x-rays to produce an image
Shows the main structures in the brain but not the functions
If it shows a diseased / damaged brain structure, the function of that part can be worked out

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PET scanning

Use radioactive chemicals to show active parts of the brain
Very detailed, show structure and function
Can show if areas are unusually inactive or active, useful for studying disorders that change the brain’s activity

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Why can treating problems in the CNS be tricky?

Hard to repair damage
Not easy to access
Treatment could lead to permanent damage

36

Sensory receptors

Groups of cells that can detect a change in the environment

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Stimulus

Change in the environment

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Effector

Muscle or gland

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What’s the process from when a stimulus is detected, to when the effector responds?

Stimulus is detected by receptors
Information is converted to a nervous (electrical) impulse
Sent along sensory neurones to the CNS
CNS coordinates response (decides what to do) and sends impulses which travel through the CNS along relay neurones
CNS sends information to the effector along a motor neurone
Effector responds

40

Reaction time

Time it takes you to respond to a stimulus

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All neurones have a.... with a....

Cell body with a nucleus

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What do neurones’ cell body’s have?

Extensions that connect to other neurones

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Dendrites and dendrons

Carry nerve impulses toward the cell body

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Axons

Carry nerve impulses away from the cell body

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Myelin sheath

Surround axons. Acts as an electric insulator, speeding up the electrical impulses

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Sensory neurone

One long dendron located in the middle of the neurone (carries nerve impulses from receptor cells to the cell body) and one short axon (carries nerve impulses from call body to CNS)

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Motor neurone

Many short dendrites (carry nerve impulses from CNS to cell body) and one long axon (carries nerve impulses from cell body to effector cells)

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Relay neurone

Many short dendrites (carry nerve impulses from the sensory neurones to the cell body) and an axon (carries nerve impulses from cell body to motor neurones)

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Synapse

The connection between 2 neurones

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Neurotransmitters

Chemicals which transfer nerve signals. They set off a new electrical signal in the next neurone

51

Describe the speed of the transmission of nervous impulses

Very fast but slows down a bit at the synapse because the diffusion of neurotransmitters across the gay takes time

52

Reflexes

Automatic, rapid responses to stimuli - can reduce chances of being injured

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Reflex arc

The passage of information in a reflex (from receptor to effector)

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The neurones in reflex arcs go through the.... or through an....

Spinal cord or an unconscious part of the brain

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Describe the process from when a stimulus is detected to the reflex action

Stimulus is detected by receptors
Impulses sent along a sensory neurone to a relay neurone in the CNS
When impulses reach a synapse between the sensory and relay neurone, they trigger neurotransmitters to be released
These cause impulses to be sent along the motor neurone
Impulses travel along the motor neurone to the effector which reacts

56

How can reflexes protect the eye?

Light receptors in the eye detect v bright light and send a message along a sensory neurone to the brain. The message then travels Along a relay neurone, which tells circular muscles in the iris to contract, making the pupil smaller

57

Cornea

Refracts (bends) light into the eye

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Iris

Controls how much light enters the pupil

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Lens

Refracts light, focusing it onto the retina

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Retina

Light sensitive part. Covered in receptor cells (rods and cones) which detect light

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Rods

More sensitive in dim light, can’t sense colour

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Cones

Sensitive to different colours but not so good in dim light

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Optic nerve

Information from light is converted into electrical impulses. The optic nerve carries these impulses from the receptors to the brain

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What happens to the eye when looking at distant objects?

The ciliary muscle relaxes which allows the suspensory ligaments to pull tight. This pulls the lens into a less rounded shape so light is refracted less

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What happens to the eye when looking at close objects?

The ciliary muscle contracts which slackens the suspensory ligaments. The lens becomes a more rounded shape so light is refracted more

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Long sighted people are unable to focus on.... objects

Near

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What is going on with the eye when people are long sighted?

Lens is the wrong shape and doesn’t bend the light enough or the eyeball is too short
Light from near objects is brought into focus behind the retina
Can use glasses or contacts with a convex lens to correct it

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Short sighted people are unable to focus on.... objects

Distant

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What is going on with the eye when people are short sighted?

Lens is wrong shape and bends light too much or the eyeball is too long
Light from distant objects is brought into focus in front of the retina
Can use glasses or contact lens with a concave lens to correct it

70

Most common form of colour blindness can’t tell the difference between.... and...
What causes this?

Red and green - caused when red or green cones aren’t working properly

71

Cataract

Cloudy patch on the lens which stops light being able to enter the eye normally

72

What are people with a cataract likely to experience?

Blurred vision
Less vivid colours
Difficulty seeing bright light

73

How can a cataract be treated?

Replacing the faulty lens with an artificial one