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Biology > B1- Cell Biology > Flashcards

B1- Cell Biology Flashcards

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1
Q

What cells are eukaryotic?

A

Animals and plants

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2
Q

What cells are prokaryotic?

A

Bacteria, single cell organisms

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3
Q

What type of cell is complex?

A

Eukaryotic

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4
Q

Organelle definition:

A

Things inside cells e.g nucleus

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5
Q

What organelles are in an animal cell?

A
  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
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6
Q

Define nucleus:

A

Contains genetic material that controls the activities of the cell

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7
Q

Define Cytoplasm:

A

Gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions happen.

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8
Q

Define mitochondria:

A

These are where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work.

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9
Q

Define Ribosomes:

A

These are where proteins are made in the cell.

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10
Q

Define cell wall:

A

Made of cellulose. It supports the cell and strengthens it.

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11
Q

Define vacuole:

A

Contains cell sap,a week solution the cell and strengthens it.

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12
Q

Define chloroplasts:

A

These are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll, which absorbs the green light needed for photosynthesis.

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13
Q

What are the organelles of a plant cell?

A
  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Plasmids (sometimes)
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14
Q

What organelles does a eukaryoctic cell have that a bacteria doesn’t?

A
  • Chloroplasts
  • Mitochondria
  • Nucleus
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15
Q

What does a bacteria cell have instead of a nucleus?

A

Single circular strand of DNA

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16
Q

Define plasmids:

A

Small ring of DNA

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17
Q

What do microscopes let us do?

A

Let us see thing that we can’t see with the naked eye

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18
Q

What do light microscopes use?

A

light and lenses

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19
Q

What do electron microscopes use instead of light?

A

Electrons

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20
Q

Do electron microscopes have a higher or lower magnification than light microscopes?

A

Higher

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21
Q

Do electron microscopes have a higher resolution than a light one?

A

Yes

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22
Q

What does resolution mean?

A

The ability to distinguish

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23
Q

What is the equation for magnification?

A

magnification=image size/real size

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24
Q

1.7 x 10^-2

A

0.017

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25
Q

Examples of a specimen

A

plant or animal cells

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26
Q

How are some cells different to others?

A

In structure and function

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27
Q

Define differentiation

A

The process by which a cell changes to become specialised for its job

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28
Q

What happens as cells change?

A
  • They develop different subcellular structures

- Turns into different types of cells ( this allows them to carry out specific functions)

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29
Q

When does most differentiation occur in an organism?

A

When the organism develops

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30
Q

In animal cells is the ability to develop lost at an early or late stage ( before or after they become specialised)?

A

Early (before)

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31
Q

Do plant cells ever lose their ability to differentiation?

A

No

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32
Q

What are cells that differentiate in mature animals mainly for?

A

Repairing and replacing cells e.g skin or red blood cells.

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33
Q

What are undifferentiated cells called?

A

Stem cells

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34
Q

What are sperm cells specialised for?

A

reproduction

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35
Q

What is the function of a sperm cell?

A

To get the male DNA to the female DNA

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36
Q

What is the point of a tail and a streamline head in a sperm cell?

A

To help it swim

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37
Q

Why to sperm cells have a lot of mitochondria?

A

To provide a lot of energy

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38
Q

Why do sperm cells also carry enzymes in its head?

A

To digest through the egg cell membrane

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39
Q

What are nerve cells specialised for?

A

Rapid signalling

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40
Q

What is the function of a nerve cell

A

To carry electrical signals from one part of the body to another

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41
Q

Why are nerve cells long?

A

To cover more distance

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42
Q

What do nerve cells have at the end of them?

A

branched connections

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43
Q

What are branched connections on a nerve cell used for?

A

To connect other nerve cells and form a network throughout the body

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44
Q

What are muscle cells specialised for?

A

Contraction

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45
Q

Are muscle cells long or short?

A

Long

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46
Q

Why are muscle cells long?

A

So they have space to contract

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47
Q

Why do muscle cells have lots of mitochondria?

A

To generate energy to contract

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48
Q

What are root hair cells specialised for?

A

Absorbing water and minerals

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49
Q

What cells are on the surface area of plant cells?

A

Root hair cells

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50
Q

What are phloem and xylem cells specialised for?

A

Transporting substances

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51
Q

What do phloem and xylem cells form?

A

Phloem and xylem tubes

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52
Q

What do phloem and xylem tubes transport?

A

Food & water

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53
Q

Where do the long phloem and xylem cells join to form the tubes?

A

End to end

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54
Q

Are xylem tubes hollow in the center?

A

yes

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55
Q

Do phloem cells have a lot of subcellular structures and why?

A

No,so stuff can travel through them

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56
Q

Why do cells have to able to divide?

A

In order to grow and survive

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57
Q

Do most cells in your body have a nucleus?

A

Yes

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58
Q

Does cytoplasm contain genetic material in the form of chromosomes?

A

No, it is the nucleus

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59
Q

True or false: Chromosomes are coiled up lengths of DNA molecules.

A

True

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60
Q

Do each chromosome carry a small number of genes?

A

No, it is a large number

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61
Q

What do different genes control?

A

The development of different characteristics e.g hair

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62
Q

How many copies do body cells normally have and why?

A
  1. One from the mother and one from the Father.
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63
Q

True or false?

Body cells in multicellular organisms divide to produce new cells as part of stages called the cell cycle.

A

True

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64
Q

What is the stage of the cycle called when the cells divide?

A

Mitosis

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65
Q

What do multicellular organisms mitosis to do?

A

Grow ad replace cells that have been damaged

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66
Q

What does the end of the cell cycle result in?

A

Two identical cells to the original cell with the same number of chromosomes

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67
Q

In a cell that is not dividing how is the DNA spread out?

A

Long strips

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68
Q

What does the cell have to do before it divides?

A

Grow and increase the amount sub cellular structures such as mitochondria and ribosomes

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69
Q

What does the cells do before they divide

A

It duplicates its DNA so there’s one copy for each new cell

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70
Q

Each ‘arm’ of the chromosome isn’t a duplicate of the rest. True/False

A

False it is an exact duplicate

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71
Q

When everything inside the cell and DNA has been copied what is the cell ready for?

A

Mitosis

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72
Q

What does the chromosomes line up and cell fibers at the middle of the cell?

A

Pull the apart

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73
Q

The two arms of each chromosome go to opposite ends of the cell. True/False

A

True

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74
Q

Where do membranes form?

A

Around each of the sets of chromosomes

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75
Q

How are the nuclei of the new cells made

A

Membranes form around chromosomes

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76
Q

What happens in the last stage of mitosis?

A

The cytoplasm and cell membrane divide

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77
Q

What is the term called for the cell that is produced in the last stage of mitosis?

A

Daughter cells

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78
Q

the daughter cell contains the exact same DNA as each other and the parent cell. True/False

A

True

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79
Q

What is the term for how prokaryotic cells reproduce?

A

Binary fission

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80
Q

How many does the cell split into in binary fission?

A

2

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81
Q

In binary fission what do the circular DNA and plasplasmid(s) do

A

Replicate

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82
Q

What do the circular DNA do when the cell gets bigger in binary fission?

A

Move to opposite ‘poles’ (ends) of the cell

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83
Q

What is the 3rd step of binary fission?

A

The cytoplasm begins to divide and new cell walls begin to form

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84
Q

What happens when the cytoplasm divides

A

Two daughter cells are produced

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85
Q

How many copies does each daughter cells have of circular DNA (binary fission)?

A

1

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86
Q

Each daughter cell has a variable amount of plasmid(s) (binary fission). True/false

A

True

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87
Q

Is bacteria fast at dividing (in the correct conditions)

A

Yes

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88
Q

What will happen to the bacteria cells if the condition are not ideal?

A

They will stop dividing and die

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89
Q

Do embryonic or adult stem cells have the ability to turn into any type of cell?

A

Embryonic

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90
Q

What is differentiation?

A

The process of where a cell becomes specialised for a certain job

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91
Q

What are undifferentiated cells called?

A

Stem cells

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92
Q

Can stem cells divide to make more stem cells?

A

Yes

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93
Q

undifferentiated cells can differentiate into different types of cell depending on the instruction given: True/false

A

True

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94
Q

Where are stem cells found?

A

In early human embryos

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95
Q

Why are embryonic stem cells exciting to doctors and medical researchers?

A

Because they have the potential to turn into any kind of cell

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96
Q

Where have all different cells in the human body have come from?

A

Few embryonic stem cells.

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97
Q

Where is one place adult stem cells are found?

A

Bone marrow

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98
Q

Can adult stem cells turn into any type of cell?

A

No

99
Q

Name one cell adult stem cells can turn into?

A

Blood cells

100
Q

Stem cells from embryos and bone marrow can’t be grown in a lab and produce clones.:True/False

A

False, they can

101
Q

Can medicine use adult stem cells to cure diseases?

A

Yes, they currently do.

102
Q

Can embryonic stem cells be used to replace faulty cells?

A

Yes

103
Q

What is therapeutic cloning?

A

A nucleus of a cell is inserted into a fertilised egg who’s nucleus has been removed

104
Q

What is a risk of using stem cells in medicine?

A

Stem cells that grow in a lab can become contaminated and and then make the patient sicker

105
Q

Why are some people against stem cell research ?

A

They believe that it is wrong to experiment with

human embryos because they have the potential to human life

106
Q

Why do some people think that we should still use human embryos despite he potential of human life?

A

Because they feel that curing existing patients is more important than the rights of embryos

107
Q

What is a reason that using human embryos isn’t taking a life away?

A

The embryos usually experimented on are unwanted ones from fertility clinics that wouldn’t normally be used anyway. However campaigners for the rights of embryos want this banned too.

108
Q

Stem cell research is allowed?

A

It is banned in some countries but is allowed in the UK(with strict guide lines)

109
Q

Where are stem cells found in plants?

A

Meristems

110
Q

How much of a plants life can cell tissue in the meristems turn into any type of plant cell?

A

The plants entire life.

111
Q

Plants stem cells can be used to produce clones of whole plants cheaply and easy:True/False

A

True

112
Q

What is a benefit of using stem cells of plants?

A
  • You can grow rare species of plants to prevent them from being wiped out
  • You ca grow identical plant with a desired feature e.g resistance to a disease
113
Q

What is diffusion?

A

The spreading out of particles from an area of higher concentration to an area of lower concentration

114
Q

What states does diffusion happen?

A

Gas and liquids

115
Q

Why can’t diffusion happen in solids?

A

The particles aren’t free to move randomly

116
Q

What is the simplest type of diffusion?

A

When two gasses diffuse through each other

117
Q

The smaller the concentration gradient the faster the diffusion rate:True/False

A

False. The bigger the concentration gradient the faster the diffusion rate

118
Q

How will temperature impact the rate of diffusion and why?

A

A higher premature will increase the rate because the particles have more energy to move around faster

119
Q

What does a cell membrane do?

A

Hold a cell together and let stuff in and out too

120
Q

How do dissolved substances get in and out of the cell?

A

Diffusion

121
Q

What is the only type of molecules that can pass through the cell membrane?

A

Small ones

122
Q

With diffusion through a cell membrane the particles move from an area of higher concentration to lower concentration but they sill have random movement but what is the overall effect called?

A

Net movement

123
Q

How does the surface area of a of the membrane effect the diffusion rate?

A

The bigger the surface area the faster the rate of diffusion because more particles move through at once

124
Q

What is osmosis?

A

The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration

125
Q

What is a partially permeable membrane?

A

A membrane with small holes in it

126
Q

What is an example of something that can fit through the holes in a partially permeable membrane.

A

Water

127
Q

What is an example of something that can’t fit through the holes in a partially permeable membrane

A

sucrose

128
Q

Does water pass through both ways through osmosis and why?

A

Yes, water particles move randomly

129
Q

Is there a net flow with osmosis?

A

Yes

130
Q

Because of net flow would a strong sugar solution get more or less diluted?

A

More

131
Q

Is osmosis a type of diffusion?

A

Yes

132
Q

What is passive movement?

A

The movement of water particles from an area of higher water concentration to an area of lower concentration

133
Q

What is active transport?

A

When a substance needs to be absorbed against the concentration gradient

134
Q

What type of cells take in minerals and water?

A

Root hair cell

135
Q

How many hairs are on each branch of a root hair cell?

A

Millions

136
Q

How big are the hairs on root hair cells?

A

Microscopic

137
Q

What is the point of a root hair cell having a big surface area?

A

Absorbing more water and mineral ions from cell

138
Q

What are mineral ions used for with plants?

A

Healthy growth

139
Q

What concentration of minerals usually higher in root hair cells or the soil?

A

Root hair cells

140
Q

Can root hair cells use diffusion to take up minerals from the soil?

A

No

141
Q

Why should minerals cells move out of the root hairs?

A

If they follow the rule of diffusion

142
Q

What method is used to minerals move out of root hair cells?

A

Active transport

143
Q

Where does active transport get the energy to use?

A

From respiration

144
Q

What is an example of how active transport used in the human body?

A

Taking glucose from the gut and from kidney tubels

145
Q

What changes how quickly stuff moves from an organism and its environment?

A

Surface area to volume ratio

146
Q

What do organisms exchange substances with?

A

Their environment

147
Q

What process do cells use to take in substances and get rid of waste products?

A

Diffusion

148
Q

What process is it when oxygen and carbon dioxide are transferred between cells and their environment?

A

Gas exchange

149
Q

What is urea?

A

A waste product produces from the breakdown of proteins

150
Q

In humans what diffuses cells into blood plasma for removal from the body by kidneys ?

A

Urea

151
Q

Do multi cellular organisms need exchange surfaces?

A

Yes

152
Q

How do gasses or dissolved substances get in or out of a singular cell organism?

A

Diffused across the cell membrane

153
Q

How are exchange surfaces adapted to maximise effectiveness

A

-They have a thin membrane
, so substances only have a short distance to diffuse.
-They have large surface area so lots of substance can diffuse at once
-Exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly.
Gas exchange surfaces in animals (e.g alveoli) are often ventilated too- air moves in and out

154
Q

What is the job of the lungs?

A

To transfer oxygen to the blood and to remove waste carbon dioxide from it

155
Q

What are the millions of little air sacks called in the lungs?

A

Alveoli

156
Q

Where does gas exchange take place within the lungs?

A

Alveoli

157
Q

What are the alveoli specialised to do?

A

Maximise the diffusion of oxygen and carbon dioxide

158
Q

What features does the alveoli have to maximise diffusion?

A
  • An enormous surface area( about 75 m^2 in humans)
  • A moist lining for dissolving gases
  • Very thin walls
  • A good blood supply
159
Q

Where does carbon dioxide in a leaf diffuse into?

A

Air spaces within the leaf then into cells where photosynthesis happens

160
Q

The underneath of the leaf is used as an exchange surface:True/False

A

True

161
Q

What is the stomata?

A

Biddly little holes on the bottom of the leaf which carbon dioxide diffuses through

162
Q

What two things diffuse in and out of the stomata?

A

Water vapour and oxygen

163
Q

What controls the size of the stomata?

A

Guard cells

164
Q

When would the guard cells close the stomata?

A

If it is losing water faster then it is being replaced y the roots?

165
Q

What is a good reason for the flattened shape of the leaf?

A

It increases the area of this exchange surface so that it’s more efficient`

166
Q

What do the walls of the cells inside the leaf form?

A

Another exchange surface

167
Q

How are exchange surfaces adapted to maximise effectiveness?

A
  • They have a thin membrane, so substances only have a short distance to diffuse
  • They have a large surface area so lots of substances can diffuse at once
  • Exchange surfaces in animals have lots of blood vessels,to get stuff into and out of the blood quickly
  • Gas exchange surfaces in animals (e.g alveoli) are often ventilated too - air moves in and out
168
Q

What are the two types of cells?

A

● Eukaryotic (plant and animal)

● Prokaryotic (bacteria)

169
Q

What are the differences between eukaryotic and

prokaryotic cells?

A

Prokaryotic cells are much smaller than
eukaryotic cells.
Eukaryotic cells contain membrane
bound-organelles and a nucleus containing
genetic material, while prokaryotes do not.

170
Q

What is the prokaryotic cell wall composed of?

A

Peptidoglycan

171
Q

How is genetic information stored in a prokaryotic

cell?

A

Found free within the cytoplasm as:
● Chromosomal DNA (single large loop of circular DNA)
● Plasmid DNA

172
Q

What are plasmids?

A

● Small, circular loops of DNA found free in the
cytoplasm and separate from the main DNA.
● Carry genes that provide genetic advantages
e.g. antibiotic resistance.

173
Q

What is order of magnitude?

A

A power to the base 10 used to quantify

and compare size.

174
Q

What is a micrometre (µm)?

A

1 × 10-6 metres

175
Q

What is a nanometre (nm)?

A

1 x 10-9 metres

176
Q

What is the difference in order of magnitude between
a human hair (length = 100 µm) and the HIV virus
(length = 100 nm)?

A

100 µm = 10-4 m
100 nm = 10-7 m
-4-(-7) = -4 + 7 = 3

177
Q

List the components of both plant and animal cells

5

A 
● Nucleus
● Cytoplasm
● Cell membrane
● Mitochondria
● Ribosomes
178
Q

List the additional cell components found in plant

cells (3)

A

● Chloroplasts
● Permanent vacuole
● Cell wall

179
Q 
Other than storing genetic information, what is the
function of the nucleus?
A

Controls cellular activities

180
Q

Describe the structure of the cytoplasm

A

● Fluid component of the cell.
● Contains organelles, enzymes and dissolved
ions and nutrients.

181
Q

What is the function of the cytoplasm?

A

Site of cellular reactions e.g. first stage
of respiration.
Transport medium.

182
Q

What is the function of the cell membrane?

A

Controls the entry and exit of materials

into and out of the cell

183
Q

What is the function of the mitochondria?

A

Site of later stages of aerobic respiration

in which ATP is produced

184
Q

What is the function of the ribosomes?

A

Joins amino acids in a specific order
during translation for the synthesis of
proteins

185
Q

What is the plant cell wall made of?

A

Cellulose

186
Q

What is the function of the plant cell wall?

A

● Provides strength.
● Prevents the cell bursting when water
enters by osmosis.

187
Q

What does the permanent vacuole

contain?

A 
Cell sap (a solution of salts, sugars and
organic acids).
188
Q

What is the function of the permanent vacuole?

A

Supports the cell, maintaining its

turgidity.

189
Q

What is the function of chloroplasts?

A

Site of photosynthesis

190
Q

Describe how sperm cells in animals are adapted to

their function

A

● Haploid nucleus contains genetic information.
● Tail enables movement.
● Mitochondria provide energy for tail movement.
● Acrosome contains enzymes that digest the egg cell
membrane.

191
Q

Describe how nerve cells in animals are

adapted to their function

A

● Long axon allows electrical impulses to be transmitted all over
the body from the central nervous system.
● Dendrites from the cell body connect to and receive impulses
from other nerve cells, muscles and glands.
● Myelin sheath insulates the axon and speeds up the
transmission of impulses along the nerve cell.

192
Q

Describe how muscle cells in animals

are adapted to their function

A

● Arrangement of protein filaments allows them to
slide over each other to produce muscle contraction.
● Mitochondria to provide energy for muscle
contraction.
● Merged cells in skeletal muscle allow muscle fibre
contraction in unison.

193
Q

Describe how root hair cells in plants are adapted to

their function

A

● Large surface area to absorb nutrients and
water from surrounding soil.
● Thin walls that do not restrict water
absorption.

194
Q

Describe how xylem cells in plants are adapted to

their function

A

● No upper or lower margins between cells
to provide a continuous route for water to flow.
● Thick, woody side walls strengthen their
structure and prevent collapse.

195
Q

Describe how phloem cells in plants are adapted to

their function

A

● Sieve plates let dissolved amino acids and
sugars be transported up and down the stem.
● Companion cells provide energy needed for
active transport of substances along the
phloem.

196
Q

What is cell differentiation?

A

The process by which cells become

specialised.

197
Q

Why is cell differentiation important?

A

Allows production of different tissues and
organs that perform various vital
functions in the human body.

198
Q

At what point in their life cycle do most

animal cells differentiate?

A

Early in their life cycle

199
Q

For how long do plant cells retain the

ability to differentiate?

A

Throughout their entire life cycle

200
Q

What is the purpose of cell division in

mature animals

A

Repair and replacement of cells

201
Q

What changes does a cell go through as

it differentiates?

A

Becomes specialised through acquisition
of different sub-cellular structures to
enable a specific function to be
performed by the cell.

202
Q

Define magnification

A

The number of times bigger an image
appears compared to the size of the real
object.

203
Q

Define resolution

A

The smallest distance between two

objects that can be distinguished.

204
Q

How does a light microscope work?

A

Passes a beam of light through a specimen
which travels through the eyepiece lens,
allowing the specimen to be observed.

205
Q

What are the advantages of light

microscopes? (4)

A

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

206
Q

What is the disadvantage of light

microscopes?

A

Limited resolution

207
Q

How does an electron microscope work?

A

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

208
Q

Name the two types of electron microscope

A

Transmission electron microscope (TEM)

Scanning electron microscope (SEM)

209
Q

What is the advantage of electron

microscopes?

A

Greater magnification and resolution.

210
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.

211
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.

212
Q

What are the disadvantages of electron

microscopes? (4)

A

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

213
Q

How can the magnification of an image be

calculated?

A

magnification = size of image / size of real object

214
Q

How do bacteria multiply?

A

Binary fission (simple cell division)

215
Q

How often do bacteria multiply?

A

Once every 20 minutes if enough
nutrients are available and the
temperature is suitable.

216
Q

State 2 ways in which bacteria can be

grown

A

● Nutrient broth solution

● Colonies on an agar gel plate

217
Q

What nutrients make up a nutrient broth solution?

A

All nutrients required for bacteria to grow
including nitrogen for protein synthesis,
carbohydrates for energy and other
minerals.

218
Q

What are uncontaminated cultures of

microorganisms needed for?

A

Investigating disinfectant and antibiotic

action.

219
Q

Describe the preparation of an
uncontaminated culture using aseptic
technique

A
  1. Use pre-sterilised plastic Petri dishes or sterilise glass Petri dishes and agar gel before using an autoclave.
  2. Pour the sterile agar gel into the Petri dish and allow time to set.
  3. Sterilise the inoculating loop by passing it through a Bunsen burner flame.
  4. Dip the inoculating loop into the solution of microorganisms and make streaks
    with the loop on the surface of the agar.
  5. Put the lid on the Petri dish and secure it with tape. Label accordingly then
    turn and store upside down.
  6. Incubate the culture at 25oC in school laboratories.
220
Q

Why must Petri dishes and culture media before

sterilised before use?

A

To kill any bacteria already present.

221
Q

Why must inoculating loops be sterilised
by passing them through a Bunsen
burner flame?

A

To kill any bacteria present on the

inoculating loop.

222
Q

Why must the Petri dish lid be secured with adhesive

tape and the whole dish stored upside down?

A

Stops bacteria in the air contaminating the culture.
The lid is not fully sealed to prevent the growth of
anaerobic bacteria in a lack of oxygen.
Upside down to prevent condensation from forming
and dripping down onto the colonies.

223
Q

Why are cultures incubated at 25oC in

school laboratories

A

Harmful pathogens are less likely to to

grow at this temperature.

224
Q

What is the formula used to calculate
cross-sectional area of a bacterial colony
or clear area around a bacterial colony?

A 
πr2 = 3.14
r = radius (diameter/2)
225
Q

How is the number of bacteria in a
population after a certain time calculated
from the mean division time?

A
  1. Calculate the number of times the bacteria will divide in the given time period
    from the mean division time.
  2. Use the following equation to calculate the number of bacteria:
    Number of bacteria in population at end of time period = number of bacteria at
    the beginning of the time period x 2number of divisions in the time period .
    Express the answer in standard form if possible.
226
Q

Calculate the number of bacteria that will
be present after 3 hours for a population
that divides every 15 mins and has 5
bacterium present now

A

15 minutes = 0.25 hours
3/0.25 hours = 12 divisions
5 x 212 = 20480 or 2.048 x 104

227
Q

What are chromosomes made up of

A

Chromosomes consist of DNA molecules
combined with proteins. They contain
genes which provide the instructions for
protein synthesis.

228
Q

What is a gene?

A

A section of DNA which codes for a

protein.

229
Q

How many chromosomes are found in

the nucleus of human body cells?

A

46

230
Q

How many chromosomes are found in the

nucleus of gametes?

A

23

231
Q

How are chromosomes arranged in the nucleus

of a body cell?

A

Arranged in pairs - 46 chromosomes

form 23 pairs.

232
Q

What are the three main stages of the cell

cycle?

A
  1. Replication of DNA and synthesis of
    organelles
  2. Mitosis
  3. Division of cell
233
Q

Why is mitosis important?

A

● Produces identical cells which all have the
same genetic information.
● Produces additional cells for growth and
repair.

234
Q

Describe the first stage of the cell cycle

A

Longest stage - cells grow and increase
in mass, replicate DNA and synthesise
more organelles (eg. mitochondria,
ribosomes).

235
Q

Describe the second stage of the cell cycle

A

Each chromosome in a pair is pulled to
opposite poles of the cell, then the nucleus
divides.

236
Q

Describe the third stage of the cell cycle

A

The cytoplasm and cell membrane divide -

two identical daughter cells are produced.

237
Q

What is a stem cell?

A

An unspecialised cell which is capable of
differentiating into other cell types and of
self-renewal.

238
Q

What is the function of stem cells in embryos

A

Embryonic stem cells can replicate themselves and
differentiate into many other types of cells.
Embryonic stem cells may be able to treat conditions
such as paralysis and diabetes by dividing to replace
damaged cells.

239
Q

What is the function of stem cells in adult bone

marrow?

A

Adult stem cells can differentiate into several cell
types to replace dead or damaged tissues. For
example, bone marrow stem cells can form many
different types of blood cell.

240
Q

What is the function of stem cells in plant

meristems?

A

Meristem stem cells retain the ability to
differentiate into any type of plant cell throughout
their lifespan - they can differentiate into any cell
which is required by the plant.

241
Q

What is therapeutic cloning?

A

A cloning method where an embryo is produced
with the same genetic makeup as the patient.
The stem cells which originate from the embryo
will not be rejected by the patient’s immune
system, so can be used to treat certain medical
conditions.

242
Q

What are the advantages of cloning plants using

meristem stem cells?

A

● Can prevent rare plants from becoming extinct.
● Can produce large numbers of plants with a
favourable characteristic.
● Can produce identical plants for research.

243
Q

What are issues are associated with the use

of embryonic stem cells?

A

● Many embryonic stem cells are sourced from aborted embryos -
some people have an ethical/religious objection.
● Development of stem cell therapies is slow, expensive and difficult.
● Adult stem cells infected with viruses could transfer infections to
patients.
● If donor stem cells do not have a similar genetic makeup to the
patient, an immune response could be triggered.

Biology (7 decks)

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