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GCSE Biology OCR 21st Century (Triple) (9-1) > B4 - Using food and controlling growth > Flashcards

B4 - Using food and controlling growth Flashcards

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1
Q

What is respiration?

A

A process that releases energy in the
form of ATP from the breakdown of
glucose

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2
Q

What is ATP?

A

It is a short term energy store in all cells
and is described as the universal energy
carrier.

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3
Q

Why does respiration occur continuously

in living cells?

A

ATP is required for many essential
processes in living cells e.g. movement,
homeostasis and active transport.

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4
Q

What type of reaction is respiration?

A

It is an exothermic reaction that releases

energy in the form of heat.

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5
Q

Where do plants get the glucose

required for respiration?

A

They produce their own glucose during

photosynthesis.

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6
Q

Where do animals get the glucose

required for respiration?

A

From the breakdown of carbohydrates

that they have ingested

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7
Q

What is aerobic respiration?

A

Respiration in the presence of oxygen
that forms ATP from the breakdown of
glucose

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8
Q

Write the word equation for aerobic

respiration

A

glucose + oxygen → carbon dioxide + water (+ATP)

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9
Q

Write the symbol equation for aerobic

respiration

A

C6H12O6 + 6O2 → 6CO2 + 6H2O (+ATP)

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10
Q

What does aerobic respiration require?

A

Glucose, C6H12O6
Or another respiratory substance e.g. lipids, proteins

Oxygen gas, O2

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11
Q

What does aerobic respiration produce?

A

Carbon dioxide gas, CO2
Water, H2O
ATP

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12
Q

Where does aerobic respiration take

place in eukaryotic cells?

A

In the cytoplasm and mitochondria

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13
Q

Where does aerobic respiration take

place in prokaryotic cells?

A

In the cytoplasm

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14
Q

What is anaerobic respiration?

A

Respiration that takes place without
oxygen and forms ATP from the
breakdown of glucose

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15
Q

When may anaerobic respiration take

place in human cells?

A

During vigorous exercise

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16
Q

When may anaerobic respiration take

place in plant cells?

A

If the soil becomes waterlogged

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17
Q

When may anaerobic respiration take

place in bacteria?

A

When bacteria enter puncture wounds

little oxygen available

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18
Q

Where does anaerobic respiration take

place?

A

It takes place in the cytoplasm of

eukaryotic and prokaryotic cells.

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19
Q

What does anaerobic respiration

require?

A

Glucose, C6H12O6

Or another respiratory substance e.g. lipids, proteins

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20
Q

Write the word equation for anaerobic

respiration in muscle cells

A

glucose → lactic acid (+ ATP)

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21
Q

Why may anaerobic respiration in

muscle cells eventually stop?

A

Lactic acid build-up inhibits anaerobic

respiration

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22
Q

What are the symptoms of lactic acid

build-up?

A

Cramp and fatigue

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23
Q

Write the word equation for anaerobic

respiration in yeast cells

A

glucose → ethanol + carbon dioxide

+ATP

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24
Q

What is the problem associated with

ethanol build-up in yeast cells?

A

Ethanol is toxic to yeast cells

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25
Q

Is aerobic or anaerobic respiration more

efficient? Explain why

A

Aerobic respiration is more efficient as it
produces 32 molecules of ATP in
comparison to anaerobic respiration
which produces 2 molecules of ATP.

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26
Q

Why does anaerobic respiration release

less energy than aerobic respiration?

A

Glucose is only partially broken down in

anaerobic respiration.

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27
Q

What is magnification?

A

The number of times bigger an image
appears compared to the size of the
specimen

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28
Q

How can the total magnification of an

image be calculated from lens powers?

A

total magifcation = eyepiece lens magnification X objective lens magnification

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29
Q

How can the magnification of an image

be calculated?

A

magnification = size of image / size of specimen

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30
Q

What is resolution?

A

The smallest distance between two

distinct objects that can be distinguished

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31
Q

How does a light microscope work?

A

A light microscope passes a beam of light
through a specimen. The light then travels
through the eyepiece lens, allowing the
specimen to be observed.

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32
Q

What are the advantages of light

microscopes? (4)

A

● Inexpensive
● Easy to use
● Portable
● Observe both dead and living specimens

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33
Q

What is the disadvantage of light

microscopes?

A

Limited resolution

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34
Q

How does an electron microscope work?

A

It uses a beam of electrons focused
using magnets. The electrons hit a
fluorescent screen which emits visible
light, producing an image.

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35
Q

Name the two types of electron

microscopes

A

Transmission electron microscope (TEM)

Scanning electron microscope (SEM)

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36
Q

What is the advantage of electron

microscopes?

A

Greater magnification and resolution

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37
Q

Why do electron microscopes have a

greater magnification and resolution?

A

They use a beam of electrons which has
a shorter wavelength than photons of
light

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38
Q

How have electron microscopes enabled
scientists to develop their understanding

of cells?

A

● Allow small sub-cellular structures (e.g. mitochondria,
ribosomes) to be observed in detail

● Enable scientists to develop more accurate
explanations about how cell structure relates to function

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39
Q

What are the disadvantages of electron

microscopes?

A

● Expensive
● Large so less portable
● Require training to use
● Only dead specimens can be observed

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40
Q

How do you convert from m to mm?

A

× 1000 (× 103

)

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41
Q

How do you convert from m to μm?

A

× 1 000 000 (× 106)

42
Q

How do you convert from m to nm?

A

× 1 000 000 000 (× 109

)

43
Q

How do you convert from m to pm?

A

× 1 000 000 000 000 (× 1012)

44
Q

What is the cell cycle?

A

● A series of events that take place in a cell
involving cell growth, DNA replication and
cell division

● It is described as the lifecycle of a cell

45
Q

State the two stages of the cell cycle

A

Stage 1 - interphase

Stage 2 - mitosis

46
Q

What is interphase?

A

The longest stage of the cell cycle that
involves cell growth, the synthesis of
new organelles and DNA replication

47
Q

What does DNA replication involve?

A

● Double helix ‘unzips’ exposing two strands
● DNA bases align next to complementary bases on
the DNA strands
● Complementary base pairs join
● Two identical DNA molecules formed

48
Q

What is mitosis?

A

A form of cell division that produces two
genetically identical ‘daughter’ cells with
the same number of chromosomes

49
Q

Why is mitosis important in organisms?

A

Mitosis is important for:

● Asexual reproduction
● Growth
● Repair of damaged cells
● Cell replacement

50
Q

Describe the stages of mitosis

A

● Chromosomes line up along the cell equator
● Spindle fibres pull the two arms of each chromosome to
opposite poles of the cell
● Nucleus of the cell divides
● A new membrane forms around each set of chromosomes
● Cell divides producing two identical daughter cells

51
Q

A cell divides by mitosis once every 2
minutes. Calculate the number of
identical cells present after 10 minutes.

A

10 ÷ 2 = 5

5 cell divisions have taken place

2^5= 32 cells

52
Q

What is cancer?

A

● Non-communicable disease

● Uncontrolled cell division (due to damaged DNA) results
in the formation of a primary tumour
● Tumour cells break off and spread to other tissues
forming secondary tumours

53
Q

What is a non-communicable disease?

A

A disease that is not spread between

organisms

54
Q

What is sexual reproduction?

A

● Type of reproduction
● Involves the production of gametes by meiosis
● A gamete from each parent fuses to form a zygote

● Genetic information from each gamete is mixed so the
resulting zygote is genetically different from each parent

55
Q

What are gametes?

A

● Sex cells (sperm cells, egg cells)

● Contain half the chromosome number

56
Q

What is meiosis?

A

A form of cell division involved in the
formation of gametes where chromosome
number is halved. It involves two divisions.

57
Q

What must occur prior to meiosis?

A

Interphase

58
Q

What happens during the first stage of

meiosis?

A

The pair of chromosomes are separated
and move to opposite poles of the cell.
Chromosome number is halved.

59
Q

What happens during the second stage

of meiosis?

A

The arms of each chromosome are
separated and move to opposite poles of
the cell. Four genetically different
gametes are produced.

60
Q

Why is meiosis important for sexual

reproduction? (2)

A

● It increases genetic variation
● It ensures that the resultant zygote has
a full set of chromosomes

61
Q

What are stem cells?

A

Cells that are unspecialised and capable
of differentiating into a range of different
cell types

62
Q

What is meant by ‘differentiation’?

A

● A process in which stem cells become specialised
(have a specific function)
● Some genes switch on or off, determining cell
type

63
Q

Why is cell differentiation important?

A

It enables the formation of specialised
tissues with specific functions e.g.
muscle tissue.

64
Q

What are embryonic stem cells?

A

Stem cells found in very early embryos
that are unspecialised and capable of
differentiating into any cell type

65
Q

When do embryonic stem cells begin to

differentiate?

A

After the eight cell stage

66
Q

What is the function of embryonic stem

cells?

A

They enable the growth and
development of tissues in human
embryos.

67
Q

What are adult stem cells?

A

Stem cells that can differentiate into a
limited range of cell types e.g. bone
marrow stem cells

68
Q

What is the primary function of adult

stem cells?

A

Replacement of dead cells e.g.
replacement of red blood cells which
only live for 120 days

69
Q

Where are stem cells found in plants?

A

Meristems

70
Q

Where is meristem tissue found?

A

In regions of the plant where cells are
continuously dividing e.g. root tips, shoot
tips

71
Q

What are meristematic stem cells?

A

Stem cells found in meristems that are
unspecialised and capable of
differentiating into any cell type during
the life of a plant

72
Q

What are plant tropisms?

A

The growth response of a plant to a

stimulus

73
Q

What is positive tropism?

A

The growth of a plant towards a stimulus

74
Q

What is negative tropism?

A

The growth of a plant away from a

stimulus

75
Q

What are the two main types of plant

tropism?

A

Phototropism

Gravitropism

76
Q

Define phototropism

A

A plant’s growth response to light

77
Q

Define gravitropism

A

A plant’s growth response to gravity

78
Q

What are auxins?

A

● A group of plant hormones involved in plant
tropisms

● Control growth in plant roots and shoot tips

79
Q

Compare the effect of auxins in plant

shoots and roots

A

Auxins stimulate growth in plant shoots

Auxins inhibit growth in plant roots

80
Q

Where are auxins produced?

A

Root and shoot tips

81
Q

How do auxins move through a plant?

A

They diffuse through the plant in solution

82
Q

Are plant shoots positively or negatively
phototropic? How does this affect shoot

growth?

A

● Positively phototropic

● Plant shoots grow towards the light

83
Q

Explain why plant shoots are positively

phototropic

A

● Shoot tip exposed to light
● On the shaded side of the root, auxin accumulates
● Elongation of cells on the shaded side
● Shoot tip bends towards the light

84
Q

Are plant shoots positively or negatively
gravitropic? How does this affect shoot

growth?

A

● Negatively gravitropic
● Plant shoots grow upwards, away from
gravity

85
Q

Explain why plant shoots are negatively

gravitropic

A

● Shoot placed horizontally
● Due to gravity, auxin accumulates on the lower side of
the shoot
● Elongation of cells on the lower side
● Shoot bends upwards growing away from gravity

86
Q

Are plant roots positively or negatively
phototropic? How does this affect root

growth?

A

● Negatively phototropic

● Plant roots grow away from the light

87
Q

Explain why plant roots are negatively

phototropic

A

● Root exposed to light
● On the shaded side of the root, auxin accumulates
● Inhibition of cell growth on the shaded side
● Root grows away from the light

88
Q

Are plant roots positively or negatively
gravitropic? How does this affect root

growth?

A

● Positively gravitropic
● Plant roots grow downwards, towards
gravity

89
Q

Explain why plant roots are positively

gravitropic

A

● Root placed horizontally
● Due to gravity, auxin accumulates on the lower side of
the root
● Inhibition of cell growth on the lower side
● Root bends downwards growing towards gravity

90
Q

Explain how plant tropisms increase the

chance of survival

A

● They enable plants to respond to their environment
● Shoot growth towards the light maximises light absorption
● Root growth downwards increases the uptake of water
and minerals from the soil and enables anchorage of the
plant body to the ground

91
Q

Describe the role of auxins in

commercial plant cultivation

A

● Rooting powders contain auxins
● Auxins stimulate the growth of roots in cuttings
● Enables rapid plant cloning

92
Q

What are gibberellins?

A

Plant hormones that control germination

and flowering

93
Q

How do gibberellins trigger germination?

A

In the presence of water, gibberellins
break seed dormancy, initiating
germination.

94
Q

What is ‘bolting’ in plants?

A

● In response to a period of low temperatures or limited
water availability
● Flowering and seed production increase in a final bid
for a plant to reproduce before death
● Triggered by gibberellins

95
Q

Why are gibberellins important in

commercial plant cultivation?

A

● Applied to seeds to make them germinate at times of the year when
they naturally wouldn’t
● Makes sure all seeds germinate at the same time
● Initiate flowering in plants at any time of the year
● Enable flowering under conditions in which plants would normally not
● Can increase fruit size

96
Q

What effect does ethene have on plants?

A

● Causes dead leaves to drop off a plant by
triggering the expansion and bursting of cells in
leaf stalks

● Stimulates enzymes that control fruit ripening

97
Q

Why is ethene important in commercial

plant cultivation?

A

● Used to remove the dead leaves from plants, aiding
the collection of fruits and seeds

● Enables fruits to be picked while they are unripe and
less easily damaged. They can be stimulated to ripen
during transportation to shops.

98
Q

How can stem cells be used in

medicine?

A

● Stem cells collected
● Stem cells stimulated to differentiate into specific
cell types e.g. heart muscle cells
● Specialised cells transplanted into the patient
● Used to treat damage or disease e.g. heart disease

99
Q

Where can embryonic stem cells be

collected from?

A

● Donor stem cells removed from
embryos grown in vitro
● Patient’s own stem cells removed from
the umbilical blood before birth

100
Q

What are the benefits of using stem cells

in medicine?

A

● Treat damage or disease e.g. heart disease, type 1 diabetes
● Treat diseases that would otherwise be untreatable
● Used in scientific research
● Growing organs for transplants

101
Q

What are the risks of stem cell use in

medicine?

A

● Transplanted stem cells could cause tumours
● Finding suitable stem cell donors is a difficult task
● Stem cells may be rejected by the body (immunosuppressants taken)
● Potential side effects
● Long term risks of using stem cells are unknown
● Stem cells may become contaminated during preparation and when
transplanted, transmit infections to the patient, making them sicker

102
Q

What are the ethical issues related to the

use of stem cells in medicine?

A

● The embryos used to provide stem cells are
destroyed which is seen as unethical and a waste
of potential human life

● May lead to the reproductive cloning of humans

GCSE Biology OCR 21st Century (Triple) (9-1) (6 decks)

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