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GCSE Biology > B1 - Cell Biology > Flashcards

B1 - Cell Biology Flashcards

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1
Q

What are prokaryotes?

A

Usually single-celled organisms- no nuclei or organelles.

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2
Q

Describe 3 features of prokaryotic cells

A

1) No nucleus; DNA is stored in the cytoplasm. 2) No organelles separated by a membrane (e.g. mitochondria). 3) Smaller than eukaryotic cells

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3
Q

What are eukaryotic organisms?

A

Organisms usually, multicellular, which contain eukaryotic cells

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4
Q

Where are eukaryotic cells usually found?

A

In multicellular organisms

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5
Q

Describe 2 features of eukaryotic cells.

A

1) Always have a nucleus 2) Always have organelles separated by a membrane (e.g. mitochondria).

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6
Q

What is smaller: animal/plant or bacterial cell?

A

Bacterial cell

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7
Q

What are the 2 types of DNA found in bacterial cells?

A

1) Circular strand of DNA which floats freely in the cytoplasm. 2) Plasmids- small rings of DNA.

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8
Q

1) What are embryonic stem cells?

2) Where can they be found?

A

1) Unspecialised cells which can develop into any type of cell. This is because all their genes are switched on
2) They can be taken from embryos that are a few days old.

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9
Q

1) What are adult/mature stem cells? 2) Where can they be found?

A

1) Stem cells found in adults. Because not all the genes are switched on, they cannot differentiate into any type of cell. For example, bone marrow stem cells can become red blood cells but not gametes.
2) Can be found in the brain, heart and bone marrow.

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10
Q

What is the main function of mature stem cells in the body?

A

Repairing and replacing cells.

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11
Q

What is differentiation/specialisation?

A

The process by which a cell gains different subcellular structures, which enable it to become specialised for its function.

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12
Q

What could embryonic stem cells be used for?

A

-Replacing defunct cells in sick people, e.g. nerve cells for people paralysed by spinal injuries, or insulin producing cells for diabetics, etc. -Developing replacement organs/tissues to implant in people who need them. -Therapeutic cloning.

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13
Q

What is therapeutic cloning?

A

A process which produces an embryo with the same genes as the patient. This means that the stem cells produced by the embryo are not rejected by the patient’s body during medical treatment.

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14
Q

What are adult stem cells used for?

A

To cure disease, e.g. transferring bone marrow stem cells from a healthy person to replace faulty blood cells in a sick person.

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15
Q

Why are some people against stem cell research?

A

Why are some people against stem cell research?

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16
Q

Why are some people advocates of stem cell research?

A

1) Some argue that the cells used are ones from unwanted embryos in fertility clinics which would be destroyed anyway, so they may as well be used for progress in curing disease.
2) Others think that curing patients who already exist and are suffering is more important than the rights of embryos.

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17
Q

What are the pros of using stem cells to cure disease?

A

1) Improves lifestyles of people with diseases which can be treated with stem cells
2) Would bring an end to side effects from other treatments.

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18
Q

What are the cons of using stem cells to cure disease?

A

1) Can be very expensive.
2) Not a fully developed technology; long term effects unknown.
3) Can only work in specific cases, e.g. stem cells could attack body cells because they think they’re foreign.
4) Could lead to misuse.

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19
Q

Unspecialised stem cells in plants are grouped together in tissues called ___

A

meristems

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20
Q

Where in plants is meristem tissue found?

A

The tips of shoots and in the roots

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21
Q

What makes stem cells in meristem tissue in plants different from stem cells in most animals?

A

Animal stem cells can only differentiate into certain types of cell. Cells in the meristem tissues can differentiate into any type of plant cell, throughout the plant’s entire life. This allows the plant to continue to grow.

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22
Q

How can we use stem cells from meristems?

A

Cloning plants quickly and economically, thus:

1) Protecting rare species from extinction.
2) Cloning plants with desired features for farmers, e.g. disease resistance.

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23
Q

What are chromosomes?

A

Coiled up lengths of DNA molecules

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24
Q

How many chromosomes are in a human body cell?

A

46 / 23 pairs

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25
Q

Body cells normally have 2 copies of each chromosome- why?

A

One from the mother, one from the father

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26
Q

What do genes control?

A

The development of different characteristics

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27
Q

For what are sperm cells specialised?

A

Reproduction

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28
Q

How are sperm cells specialised for reproduction?

A

1) Large nucleus - contains genetic information
2) Long tail + streamlined head to swim to egg
3) Mid-section full of mitochondria to transfer energy for movement when respiring
4) Acrosome (layer round head) contains digestive enzymes to break down egg’s membrane

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29
Q

For what are muscle cells specialised?

A

Contraction: including moving the skeleton and squeezing food through the digestive system.

30
Q

How are muscle cells specialised for contraction?

A

1) Long for space to contract
2) Contain lots of mitochondria for respiration to generate energy for contraction
3) Store glycogen - can be broken down into glucose - used in respiration to generate energy for contraction

31
Q

For what are nerve cells specialised?

A

Rapid signalling of electrical impulses.

32
Q

How are nerve cells specialised for rapid signalling?

A

1) Long axon to carry information over long distances
2) Numerous dendrites (branched connections) pass information to neighbouring cells
3) Synapses adapted to pass impulses between neurones using neurotransmitters

33
Q

For what are root hair cells specialised?

A

Absorption of water and mineral ions.

34
Q

How are root hair cells specialised for absorption?

A

1) Large SA:V to increase rate of absorption
2) Large vacuole to maintain water potential
3) Lots of mitochondria respire to transfer energy for active transport of mineral ions

35
Q

For what are xylem cells specialised?

A

1) Transpiration, i.e. the transportation of water and dissolved minerals from the roots to leaves
2) Providing structural support to the plant.

36
Q

How are xylem cells specialised for the transportation of water?

A

1) Dead cells form long, hollow tubes up which water can travel with little resistance
2) Pits in cell wall allow water to move horizontally to another cell
3) Lignin build up in a spiral in the cell wall, increasing strength to withstand water pressure

37
Q

For what are phloem cells specialised?

A

Translocation, i.e. transporting cell sap / food (dissolved sugars).

38
Q

How are phloem cells adapted for the transportation of food substances

A

1) Cell walls between cells break down, forming sieve plates which allow food to move freely
2) Few organelles (kept alive by companion cells with lots of mitochondria)

39
Q

For what are red blood cells specialised?

A

Carrying oxygen from the lungs to cells

40
Q

How are red blood cells adapted for carrying oxygen?

A

1) Biconcave disc shape gives large SA for absorbing oxygen
2) No nucleus- more room for oxygen
3) Contain haemoglobin, a red pigment, which binds to oxygen in the lungs to form oxyhaemoglobin (reverse reaction happens in body cells)

41
Q

For what are white blood cells specialised?

A

Fighting infection

42
Q

How are white blood cells specialised for fighting infection?

A

1) Some engulf pathogens: phagocytosis
2) Others produce antibodies and antitoxins
3) Nucleus

43
Q

Why is there reference to 23 pairs of chromosomes, rather than just 46 single chromosomes?

A

Body cells have two copies of each chromosome, called a homologous pair (a maternal and paternal chromosome).

44
Q

What is the cell cycle?

A

The process by which a parent cell grows, then divides to form 2 genetically identical daughter cells.

45
Q

What is the importance of the cell cycle?

A

It is used for the growth and repair of cells.

46
Q

What are the names of the three phases of the cell cycle?

A

1) Growth
2) Mitosis
3) Division

47
Q

What happens in the growth phase of the cell cycle?

A

1) Starts with one parent cell
2) DNA replicates - no. chromosomes doubles
3) Number of organelles increases.

48
Q

What happens in the mitosis phase of the cell cycle?

A

1) Pairs of chromosomes line up at the middle of the cell 2) They are then pulled apart to opposite ends of the cell
3) Membranes form around each set of chromosomes, creating 2 nuclei.

49
Q

What happens in the cell division phase of the cell cycle?

A

1) The cytoplasm and cell membrane divide

2) This produces 2 genetically identical daughter cells

50
Q

How do prokaryotic cells reproduce?

A

Binary fission

51
Q

Describe the process of binary fission.

A

1) Circular DNA + plasmids reproduce
2) Cell grows + circular DNA strands move to opposite poles of the cell
3) Cytoplasm starts to divide + new cell walls form
4) Cytoplasm divides; 2 daughter cells produced.

52
Q

How do electron microscopes compare to light microscopes?

A
  • Electron microscopes: more expensive, better resolution, larger magnification
  • Light: less expensive, used in schools.
53
Q

Magnification =

A

image size ÷ real size

54
Q

Image size =

A

magnification x real size

55
Q

Real size =

A

image size ÷ magnification

56
Q

Define diffusion.

A

The process by which particles from an area of high concentration move down a concentration gradient to an area of lower concentration.

57
Q

What factors increase the rate of diffusion across a partially permeable membrane?

A
  • Surface area
  • Moisture (gases dissolve first so diffuse faster)
  • Thinner membrane
  • Temperature
  • Higher concentration gradient
58
Q

Define active transport.

A

The process by which substances are absorbed against a concentration gradient.

59
Q

Define active transport.

A

The process by which substances are absorbed against a concentration gradient.

60
Q

Give two examples of active transport.

A

1) Water and mineral ions can’t diffuse into plant root hair cells because their concentration is higher inside the cells than in the soil, so they are absorbed via active transport. 2) When there is a lower concentration of glucose and amino acids in the gut than in the blood, they can’t diffuse into the blood. Active transport is needed so that glucose can be transported to cells for respiration.

61
Q

How are exchange surfaces in multicellular organisms adapted for efficient exchange of substances?

A

1) Thin membranes
2) Large SA:V 3) Animals: lots of blood vessels
4) Animals: gas exchange surfaces ventilated

62
Q

How are the alveoli adapted to maximise gas exchange?

A

1) Large SA
2) Moist lining quickens diffusion
3) Walls 1 cell thick
4) Good blood supply

63
Q

What is the inside of the small intestine covered in?

A

Villi

64
Q

Explain how the structure of villi is related to their function.

A

Function = increase rate of absorption of the products of digestion into the blood

1) They increase the SA of the small intestine
2) They have a single layer of surface cells to reduce the distance across which diffusion occurs
3) They have a good blood supply for the uptake of substances

65
Q

How is the underneath of a leaf adapted for maximum diffusion of gases?

A

1) Covered in stomata

2) Flattened shape of leaf increases SA 3) Air spaces between cells inside leaf increase inner SA

66
Q

What is the gas exchange surface in fish?

A

The gills

67
Q

How is the structure of gills adapted for maximum gas exchange?

A

Gills are composed of thin filaments, creating a large SA for gas exchange. Each filament is covered in tiny structures called lamellae, further increasing the SA. The lamellae quicken diffusion by having lots of blood capillaries and a thin surface layer of cells. A large concentration gradient is maintained between the water and blood, so rate of diffusion into blood is maximised.

68
Q

Describe how you would use a light microscope to view onion cells. Include how you would prepare a slide. (6)

A

To prepare a slide:

1) Put a drop of water on a clean slide.
2) Use tweezers to place a small piece of onion epidermal tissue into the water.
3) Add a drop of iodine solution.
4) Place a cover slip on top, tilting and lowering it to make sure it traps no air bubbles.

To use the microscope:

1) Clip the slide onto the stage.
2) Select the lowest powered objective lens.
3) Use the coarse adjustment knob to move the stage to just below the lens, then look down the eyepiece and move the stage downwards until it’s roughly in focus.
4) Use the fine adjustment knob to focus the image.

69
Q

Describe how you would prepare an uncontaminated bacterial culture, using an aseptic technique

A

Bacteria are grown in a culture medium (containing nutrients).

Using agar jelly:

1) Pour agar nutrient broth solution (heated beforehand to sterilise it) into a sterilised Petri dish and allow it to cool and set.
2) Sterilise an inoculating loop by passing it through a flame, then transfer the bacteria to the agar plate.
3) Lightly tape on the lid of the Petri dish (to prevent entry of microorganisms - but fully taping it would allow toxic anaerobic bacteria to grow).
4) Store the dish upside down to prevent drops of condensation falling onto the agar surface.
5) Store at 25°C to reduce the chances of harmful bacteria growing

70
Q

Describe how you would investigate the effect of antibiotics on bacterial growth.

A

1) Clean your work surface with disinfectant.
2) Sterilise an inoculating loop by passing it through a flame.
3) Open a sterile agar plate and hold it near a flame (to kill bacteria in the air around it).
4) Use the loop to evenly spread the bacteria over the plate.
5) Place sterile, antibiotic-soaked filter paper discs onto the plate. Use one control disc, soaked in sterile water.
6) Incubate the plate upside down, at 25°C, for 48 hours.
7) The more effective the antibiotic against the bacterium, the larger the inhibition zone that forms around the disc.

GCSE Biology (7 decks)

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