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GCSE Biology [AQA] > B1 - Cell Biology > Flashcards

B1 - Cell Biology Flashcards

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1
Q

Do prokaryotic cells have membrane bound organelles?

A

. Have no nucleus
. No membrane bound organelles
. Contain ribosomes only

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2
Q

What do eukaryotic cells contain?

A

. Have a nucleus which contains DNA
. Contain membrane bound organelles

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3
Q

Which cells are larger - eukaryotic or prokaryotic?

A

Eukaryotic

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4
Q

Cells are measured using the unit of …

A

Micrometers (ųm)

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5
Q

The human eye can only see … ųm sized objects?

A

50

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6
Q

1 micrometer (ųm) = …..

A

1 thousandth of 1 millimetre

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7
Q

Put in order (smallest to largest) - chromosome, nucleus, gene, cell, and DNA.

A

. Gene
. Chromosome
. DNA
. Nucleus
. Cell

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8
Q

In bacteria cells, what is the function of the pilus?

A

. Pilus - small hairs around the bacteria cell
. Help bacteria cells stick to one another or to surfaces

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9
Q

In bacteria cells, what is the function of the slime capsule?

A

Protects bacterium from white blood cells and helps groups of bacteria stick together.

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10
Q

In bacteria cells, what is the function of the flagellum?

A

. Flagella - tail on the bacteria cell
. Aids movement of the bacteria through fluids by rotation

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11
Q

What are plasmids?

A

Small loops of extra dna

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12
Q

Are yeast cells eukaryotic or prokaryotic?

A

Eukaryotic

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13
Q

What is the function of mitochondria?

A

Provide energy - site of respiration

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14
Q

What is the function of ribosomes?

A

Protein synthesis

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15
Q

What is the function of cytoplasm?

A

Site of chemical reactions - contains enzymes

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16
Q

What is the function of the cell membrane?

A

Control what enters and exits the cell

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17
Q

What are chromosomes?

A

Coiled up lengths of DNA molecules.

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18
Q

What is the function of a nucleus?

A

Contains generic material that controls the activities of the cell

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19
Q

What is the function of a cell wall?

A

Supports and strengthens plant cell - made of cellulose

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20
Q

What is the function of a permanent vacuole?

A

Contains cell sap (a weak solution of sugar and salts)

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21
Q

What is the function of chloroplasts?

A

Site of photosynthesis
Contains chlorophyll to absorbs light

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22
Q

What is magnification?

A

How much an image has been enlarged compared to the actual size of the object

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23
Q

What is the equation for magnification?

A

Magnification = image size ÷ real size

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24
Q

What is resolution?

A

The ability to distinguish between two objects that are very close together

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25
Q

What does a light microscope do?

Why do you need iodine solution to use a light microscope?

A

It uses light to make cells visible.

Iodine solution is a stain used to highlight objects in a cell by adding colour to them.

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26
Q

What does an electron microscope do?

A

Fires electrons at dead samples to form an image.

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27
Q

What are the differences between a light microscope and an electron microscope?

A

Light microscope:
Lower resolution
Lower magnification
Cheaper

Electron microscope:
Higher resolution
Higher magnification
Expensive

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28
Q

How do you prepare a slide (a strip of clear glass or plastic) when using a light microscope?

A
  1. Add a drop of water
  2. Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers.
  3. Using the tweezers, place the epidermal tissue into the water on the slide.
  4. Add a drop of iodine solution
  5. Get a cover slip (a square of thin, transparent plastic or glass) and stand it upright in the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen.
    Try not to get any air bubbles because they will obstruct your view of the specimen.
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29
Q

How do you use a light microscope to look at the slide you’ve prepared?

A
  1. Clip the slide onto the stage
  2. Select the lowest-powered objective lens (the one that produces the lowest magnification)
  3. Use the coarse adjustment knob to move the stage up, just below the objective lens
  4. Look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly in focus.
  5. Adjust the focus with the fine adjustment knob, until you get a clear image.
  6. If you need to see the slide with a greater magnification, swap to a higher-powered objective lens and refocus.
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30
Q

What is the function of muscle cells?

A

Contract and relax to move the body

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31
Q

How are muscle cells adapted?

A

. Lots of mitochondria for respiration (muscle contraction requires energy)
. Protein filaments that slide past each other (allows cell to contract and relax)

32
Q

What is the function of sperm cells?

A

To fertilise an egg cell

33
Q

How are sperm cells adapted?

A

. Lots of mitochondria for respiration (energy to move towards egg)
. Streamlined shape to swim
. Head contains enzymes to digest outer coat of egg cell

34
Q

What is a specialised cell?

A

A cell adapted for its function.

It may have a particular shape or more organelles to enable it to do its job effectively.

35
Q

What is the function of root hair cells?

A

To absorb water and mineral ions from the soil

36
Q

How are root hair cells adapted?

A
  • Long thin shape - large surface area to maximise absorption
  • Large vacuole - helps take up water
37
Q

What is the function of xylem cells?

A

Carry water and dissolved mineral ions from the roots up to the leaves.

38
Q

How are xylem cells adapted?

A

. No cytoplasm or organelles - less resistance to flow of water
. No end walls - provide continuous tube
. Walls coated with lignin (waterproof substance) - carry water upwards

39
Q

What is the function of a phloem cell?

A

Carry sugars around a plant

40
Q

What are the two types of phloem cells?

A

. Sieve tubes
. Companion cell

41
Q

What is the function of neurones?

A

Carry electrical impulses around the body, allowing animals to respond to their surroundings.

42
Q

How are neurones adapted?

A

. Dendrites (branched endings) - allow neurones to connect to each other
. Long axon (nerve fibre) - carries electrical impulse great distances around body
. Myelin sheath warped around axon - insulates axon

43
Q

What is the function of a red blood cell?

A

Transport oxygen to body cells so they can respire

44
Q

How are red blood cells adapted?

A

. No nucleus
. Biconcave shape
. Haemoglobin

45
Q

What is the cell cycle?

A

A series of stages in which body cells in multicellular organisms divide to produce new cells.

46
Q

What is mitosis?

A

The stage of the cell cycle, when the cell divides.

47
Q

What is the purpose of mitosis?

A

. Growth and repair
. Replace worn out cells

48
Q

What is the process of mitosis?

A
  1. Parent cell replicates it’s DNA
  2. The membrane breaks down
  3. Chromosomes line up in the centre of the cell
  4. One set of chromosomes is pulled at each end of the cell
  5. Nucleus divides
  6. 2 daughter cells identical to original are produced
49
Q

Bacteria do not have chromosomes, so do not replicate by mitosis. Instead they use a method called … ?

A

Binary fission

50
Q

What is a stem cell?

A

An unspecialised cell which is capable of becoming any type of cell.

51
Q

Once an animal cell specialises can it re-differentiate?
Can plant cells re-differentiate?

A

Animal cells are fixed and can only produce copies of themselves by mitosis.

Plant cells can re-differentiate and these cells are found in tissues called meristems.

52
Q

What are embryonic stem cells?

A

Cells that came from blastocysts (embryos that are 3 to 5 days old)

  • Pluripotent (can become any type of cell in the body)
53
Q

What are adult stem cells?

A

Come from some adult tissues (eg- bone marrow)

  • Can only become a few types of specialised cells
54
Q

What can stem cells be used for?

A

Treating illnesses and injuries

55
Q

What is a clone?

A

An organism genetically identical to its parent.

(meaning its cells have the exact same DNA)

56
Q

What would happen if you receive cells grown from stem cells that don’t have the same genes as your body cells?

A

Your immune system would recognise the cells are foreign, leading to them to be rejected and die.

57
Q

What is the process of therapeutic cloning?

A
  1. A few of the patient’s cells are taken to provide a source of their DNA
  2. This DNA is inserted into an empty egg cell that has had its nucleus removed
  3. The egg cell with the patient’s DNA develops into an embryo that provides stem cells for treatment

The stem cells are not rejected by the patient’s immune system because they have the same DNA

58
Q

What are the problems with therapeutic cloning?

A

. Low success rate
. Kills the embryo
. Could be used to clone a human being

59
Q

What is diffusion?

A

Net movement of molecules down a concentration gradient, to reach an equilibrium - (high concentration to low concentration).

60
Q

How does concentration gradient affect the rate of diffusion?

A

The steeper the gradient (more of a difference) the faster diffusion will be.

61
Q

How does temperature affect the rate of diffusion?

A

Warmer molecules have more kinetic energy, so they move around faster.

This means that, as temperature increases the rate of diffusion increases.

62
Q

How does the size of molecules affect the rate of diffusion?

A

Smaller molecules diffuse faster.

63
Q

How does the surface area of the cell membrane affect the rate of diffusion?

A

Faster diffusion

64
Q

How does stirring affect the rate of diffusion?

A

Increases the movement of molecules so diffusion is faster.

65
Q

What is osmosis?

A

Movement of water molecules from an area of high concentration to a low concentration, across a partially permeable membrane.

66
Q

What is active transport?

A

Molecules move against the concentration gradient; from an area of low concentration to high concentration.

67
Q

How do root hair cells use active transport?

A

Root hair cells use active transport to move mineral ions against the concentration gradient into cells.

68
Q

How does the small intestine use active transport?

A

The cells of the small intestine move sugar molecules against the concentration gradient into the blood.

69
Q

Where does the energy for active transport come from?

A

Aerobic respiration

70
Q

Why does active transport require energy?

A

For carrier proteins in the mitochondria to move.

71
Q

Why do multicellular organisms need exchange surfaces?

A

Multicellular organisms need exchange surfaces for efficient by diffusion.

This is because they have a smaller surface area compared to their volume.
Meaning not enough substances can diffuse from their outside surface to supply their entire volume.

72
Q

How are villi adapted for exchanging substances?

A

The inside of the small intestine is covered in millions of villi, which provide a much larger surface area. The increased surface area helps digested food to be absorbed more quickly into the blood.

  • A single layer of surface cells
  • A very good blood supply to assist quick absorption
73
Q

How do alveoli help gas exchange happen in the lungs?

A

The job of the lungs is to transfer oxygen to the blood and to remove waste carbon dioxide from it.

Lungs have millions of alveoli:

  • large surface area
  • moist lining for quicker dissolving of gases
  • very thin walls
  • good blood supply
74
Q

How is the structure of leaves adapted to maximise gas exchange?

A

The underneath of the leaf is covered in stomata for oxygen and water vapour to diffuse out of.

The guard cells close the stomata to stop the plant losing water faster than it can be replaced by the roots.

Flattened shape of the leaf increases surface area.

The walls of the cells inside the leaf form another gas exchange surface.

The air spaces inside the leaf increases surface area so carbon dioxide is likelier to get into the cells.

75
Q

How are the gills of a fish adapted to maximise gas exchange?

A

Water (containing oxygen) enters the fish through its mouth and passes through the gills. The concentration of oxygen in water is always higher than in the blood.

  • Each gill is made of lots of thin plates called gill filaments, which increase the surface area for gas exchange
  • The gill filaments are covered in lots of tiny structures called lamellae, which further increases the surface area
  • The Lamellae have lots of blood capillaries to speed up diffusion
  • They also have a thin surface layer of cells to minimise the distance that the gases have to diffuse
  • Blood in the Lamellae flows in the one direction and and water flows over in the opposite direction, which maintains a large concentration gradient between the water and the blood

GCSE Biology [AQA] (7 decks)

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