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GCSE AQA Biology > Topic 1- Cell Biology > Flashcards

Topic 1- Cell Biology Flashcards

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1
Q

What are all living things made of?

A

Cells

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2
Q

What can a cell be?

A

Eukaryotic or prokaryotic

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3
Q

Define eukaryotic cells.

A

They are complex and include all animal and plant cells.

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4
Q

Define prokaryotic cells.

A

They are smaller and simpler, e.g. bacteria.

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5
Q

Define eukaryotes.

A

They are organisms that are made up of eukaryotic cells.

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6
Q

Define prokaryote.

A

It is a prokaryotic cell (it’s a single- celled organism)

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7
Q

What are subcellular structures?

A

Different parts of a cell.

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8
Q

Give 5 subcellular structures of an animal cell.

A
  1. Nucleus
  2. Cytoplasm
  3. Cell membrane
  4. Mitochondria
  5. Ribosomes
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9
Q

Define nucleus.

A

It contains genetic material that controls the activities of the cell.D

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10
Q

Define cytoplasm.

A

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

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11
Q

Define cell membrane.

A

It holds the cell together and control what goes in and out.

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12
Q

Define mitochondria.

A

These are where most of the reactions for aerobic respiration take place.

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13
Q

What does respiration do?

A

It transfers energy that the cell needs to work.

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14
Q

Define ribosomes.

A

These are where proteins are made in the cell.

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15
Q

List 3 subcellular structures of a plant cell.

A
  1. Rigid cell wall
  2. Permanent vacuole
  3. Chloroplasts

(A plant cell also has all the subcellular structures that animal cells have?

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16
Q

Define rigid cell wall.

A

It is made of cellulose. It supports the cell and strengthen it.

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17
Q

Define permanent vacuole.

A

It contains cell sap, a weak solution of sugar and salts.

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18
Q

Define chloroplasts.

A

These are where photosynthesis occurs, which makes food for the plant.

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19
Q

What do chloroplasts contain?

A

Green substance called chlorophyll, which absorbs the light needed for photosynthesis.

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20
Q

What replaces the nucleus in a bacterium?

A

A single circular strand of DNA that floats freely in the cytoplasm.

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21
Q

List 5 subcellular structures of a bacterium cell.

A
  1. Cytoplasm
  2. Cell membrane
  3. Cell wall
  4. Single circular strand of DNA
  5. Plasmids
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22
Q

What are plasmids?

A

Small rings of DNA.

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23
Q

Give 2 subcellular structures which a bacterium cell does not have.

A
  1. Chloroplasts

2. Mitochondria

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24
Q

Give the function of a microscope .

A

It let us see things that we can’t see with the naked eye.

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25
Q

What developed over the years as technology and knowledge developed?

A

Microscopy techniques

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26
Q

What are light microscopes?

A

They use light and lenses to form an image of a specimen and magnify it.

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27
Q

What does it mean to magnify it?

A

Make it look bigger.

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28
Q

What does a light microscope let us see?

A

Individual cells and large subcellular structures, like nuclei.

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29
Q

What are electron microscopes?

A

They use electrons instead of light to form an image.

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30
Q

What makes an electron microscope better than a light microscope?

A
  1. Higher magnification

2. Higher resolution

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31
Q

Define resolution.

A

It is the ability to distinguish between two points.

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32
Q

What does a higher resolution give?

A

A sharper image.

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33
Q

What does an electron microscope let us see?

A

Smaller things in more detail.

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34
Q

Give examples of what an electron microscope can let us see.

A

The internal structure of mitochondria and chloroplasts. They even let us see tinier things like ribosomes and plasmids.

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35
Q

Give the formula for magnification.

A

Magnification= image size/ real size

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36
Q

Define differentiation.

A

It is the process by which a cell changes to become specialised for its job.

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37
Q

Describe what a cell develop as it changes.

A

It develops different subcellular structures and turn into different types of cells. This allows them to carry out specific functions.

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38
Q

When does most differentiation occur?

A

As an organism develops.

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39
Q

What happens to an animal cell after it is specialised?

A

It loses the ability to differentiate

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40
Q

.True or false, does a plant cell lose their ability to differentiate.

A

False

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41
Q

What are the cells that differentiate in mature animals mainly used for?

A

Repairing and replacing cells, such as skin or blood cells.

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42
Q

Define stem cells.

A

Undifferentiated cells

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43
Q

What are sperm cells specialised for?

A

Reproduction

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44
Q

Give the function of a sperm cell.

A

To get the male DNA to the female DNA.

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45
Q

Describe the structure of a sperm cell.

A

It has a long tail and a streamlined head to help it swim to the egg.

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46
Q

What does a sperm cell contain?

A
  1. Mitochondria

2. Enzymes

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47
Q

Why does a sperm cell contain mitochondria?

A

To provide the energy needed.

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48
Q

Why does a sperm cell contain enzymes in its head?

A

To digest through the egg cell membrane.

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49
Q

What are nerve cells specialised for?

A

Rapid signalling

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50
Q

Give the function of a nerve cell.

A

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

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51
Q

Describe the structure of nerve cells.

A

These cells are long and have branched connections at their ends.

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52
Q

Why do nerve cells have long cells?

A

To cover more distance.

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53
Q

Why do nerve cells have branched connections at their ends?

A

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

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54
Q

What are muscle cells specialised for?

A

Contraction

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55
Q

Give the function of a muscle cell.

A

To contract quickly.

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56
Q

Describe the structure of a muscle cell.

A

These cells are long and contain lots of mitochondria.

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57
Q

Why are muscle cells long?

A

To have space to contract.

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58
Q

Why do muscle cells contain lots of mitochondria?

A

To generate the energy needed for contraction.

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59
Q

What are root hair cells specialised for?

A

Absorbing water and minerals.

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60
Q

What is the function of a root hair cell?

A

To give the plant a big surface area for absorbing water and mineral ions from the soil.

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61
Q

Where are root hair cells located on a plant?

A

On the surface of plant roots.

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62
Q

What do root hair cells grow into?

A

Long “hairs” that stick out into the soil.

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63
Q

What are phloem and xylem cells specialised for?

A

Transporting substances.

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64
Q

What do phloem and xylem cells form and what do they do?

A

They form phloem and xylem tubes, which transport substances such as food and water around plants.

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65
Q

How do xylem and phloem cells form tubes?

A

The cells are long and joined end to end.

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66
Q

Describe the structure of a xylem cell.

A

Hollow in the centre.

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67
Q

Describe the structure of a xylem cell.

A

Hollow in the centre.

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68
Q

Describe the structure of a phloem cell.

A

It has very few subcellular structures, so that stuff can flow through them.

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69
Q

How is the genetic material formed in the nucleus?

A

It is in the form of chromosomes

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70
Q

Define chromosomes.

A

They are coiled up lengths of DNA molecules.

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71
Q

What does each chromosome carry?

A

A large number of genes.

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72
Q

What do different genes control?

A

The development of different characteristics, e.g. hair colour.

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73
Q

How many chromosomes do body cells usually have?

A

Two copies of each chromosome.

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74
Q

Where does each copy of a chromosome come from?

A

One from the organism’s ‘mother’, and one from it ‘father’.

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75
Q

How many chromosomes does a human cell have?

A

23 pairs of chromosomes (46 chromosomes).

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76
Q

What do body cells in multicellular organisms do as part of the cell cycle?

A

Divide to produce new cells.

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77
Q

What is mitosis?

A

It is the stage of the cell cycle when the cell divides.

78
Q

What do multicellular organisms use mitosis for?

A

To grow or replace cells that have been damaged.

79
Q

Describe the results of the end of the cell cycle.

A

It results in two new cells identical to the original cell, with the same number of chromosomes.

80
Q

What are the 2 stages of cell cycle?

A
  1. Growth and DNA replication

2. Mitosis

81
Q

Give an example of a bacteria.

A

E. coil

82
Q

How long does it take for E. coil to replicate in the right conditions?

A

As little as 20 minutes.

83
Q

How can bacteria divide very quickly?

A

They can divide very quickly if given the right conditions.

84
Q

Give a condition which helps bacteria replicate.

A
  1. Warm environment

2. Lots of nutrients

85
Q

What happens if the conditions become unfavourable for bacteria?

A

The cells will stop dividing and eventually begin to die.

86
Q

What is the mean division time?

A

It is the average amount of time it takes for one bacterial cell to divide into 2.

87
Q

What are undifferentiated cells able to do? (1)

A

They can divide to produce lots more differentiated cells.

88
Q

What are undifferentiated cells able to do? (2)

A

They can differentiate into different type of cells, depending on what instructions they’re given.

89
Q

Where are stem cells found in?

A

Early human embryos

90
Q

Where are stem cells found in adults?

A

Bone marrow

91
Q

What is the difference between stem cells found in bone marrow and in human embryos?

A

Unlike embryonic stem cells, they can’t turn into any cell type at all, only certain ones, e.g. red blood cells.

92
Q

What can you do with stem cells from embryos and bone marrow, when grown in a lab?

A

It can be grown in a lab to produce clones and made to differentiate into specialised cells to use in medicine or research.

93
Q

What can adult stem cells be used for in medicine?

A

To cure disease.

94
Q

Give an example of when adult stem cells are used in medicine.

A

Stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in the patient who receives them.

95
Q

True or false, can embryonic stem cells be used to replace faulty cells in sick people.

A

True

96
Q

What can you make using embryonic stem cells?

A

Insulin-producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries.

97
Q

Identify a type of cloning.

A

Therapeutic cloning

98
Q

What can you do with therapeutic cloning?

A

An embryo could be made to have the same genetic information as the patient.

99
Q

Why is it important for the stem cells to have the same genes?

A

So it wouldn’t be rejected by the patient’s body if used to replace faulty cells.

100
Q

Give a risk of using stem cells in medicine.

A

Stem cells grown in the lab may become contaminated with a virus which could be passed on to the patient and so make them sicker.

101
Q

Why are some people against stem cell research? (1)

A

They feel that human embryos shouldn’t be used for experiments since each one is a potential human life.

102
Q

Why are some people for stem cell research? (1)

A

They think that curing existing patients who are suffering is more important than the rights of embryos.

103
Q

Why are some people for stem cell research? (2)

A

They argue that the embryos used in the research are usually unwanted ones from fertility clinics which, if they weren’t used for research, would probably just be destroyed.

104
Q

Why are some people against stem cell research? (2)

A

They feel that scientists should concentrate more on finding and developing other sources of stem cells, so people could be helped without having to use embryos.

105
Q

Where are stem cells found in plants?

A

Meristems

106
Q

What are meristems?

A

They are parts of the plant where growth occurs.

107
Q

What are clones?

A

Genetically identical cells

108
Q

What are the cells in the meristem tissues able to do in plants?

A

Differentiate into any type of plant cell.

109
Q

What are stem cells able to do in plants? (1)

A

Produce clones of whole plants quickly and cheaply.

110
Q

What are stem cells able to do in plants? (2)

A

They can be used to grow more plants of rare species.

111
Q

Why do people grow more plants of rare species using stem cells?

A

To prevent them from being wiped out.

112
Q

What are stem cells able to do in plants? (3)

A

To grow crops of identical plants that have desired features for farmers, e.g. disease resistance.

113
Q

Define diffusion.

A

It is the spreading out of particles from an area of higher concentration to an area of lower concentration.

114
Q

Where can diffusion happen?

A

In both solutions and gases.

115
Q

Why is diffusion able to occur in gases and solution?

A

The particles in these substances are free to move about randomly.

116
Q

How can you increase the rate of diffusion? (1)

A

The bigger the concentration gradient, the faster the rate of diffusion.

117
Q

What is the concentration gradient?

A

The difference in concentration.

118
Q

How can you increase the rate of diffusion? (2)

A

A higher temperature gives a faster rate of diffusion.

119
Q

Why can you increase the rate of diffusion with temperature?

A

The particles have more energy, so they move around faster.

120
Q

How can dissolved substances move in and out of cells?

A

By diffusion

121
Q

Give 4 small molecules that are able to diffuse through cell membranes.

A
  1. Oxygen (needed for respiration)
  2. Glucose
  3. Amino acids
  4. Water
122
Q

Give 3 big molecules that are not able to fit through membranes.

A
  1. Protein
  2. Starch
  3. Lipids
123
Q

How can you increase the rate of diffusion in membranes?

A

The larger the surface area of the membrane, the faster the rate of diffusion.

124
Q

How can increasing the surface area, increase the rate of diffusion?

A

More particles can pass through at once.

125
Q

Define osmosis.

A

It is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

126
Q

What will there be if there are a lot more particles on one side of the membrane?

A

There will be a net (overall) movement from that side.

127
Q

What can and what can not pass through a partially permeable membrane?

A
  1. Water (tiny molecule)- can

2. Sucrose (big molecule)- cannot

128
Q

Why are water molecules able to pass both ways through the partially permeable membrane during osmosis?

A

Water molecules move about randomly all the time.

129
Q

Why are water molecules able to pass both ways through the partially permeable membrane during osmosis?

A

Water molecules move about randomly all the time.

130
Q

Where will the net flow be if there are more water molecules on one side than on the other?

A

There will be a steady net flow of water into the region with fewer molecules.

131
Q

What are root hair cells covered in?

A

Millions of microscopic hairs.

132
Q

What does these microscopic hairs give to the plant?

A

A large SA for absorbing water and mineral ions from the soil.

133
Q

Why do plants need mineral ions?

A

For healthy growth

134
Q

Why are root hair cells unable to use diffusion?

A

The concentration of minerals is usually higher in the root hair cells than in the soil around them.

135
Q

What process do root hair cells use to absorb mineral ions?

A

Active transport

136
Q

What does active transport allow the plant to do when absorbing minerals?

A

It allows the plant to absorb minerals from a very dilute solution, against a concentration gradient.

137
Q

What does active transport need?

A

Energy from respiration

138
Q

Where in humans does active transport take place?

A

In taking glucose from the gut and from the kidney tubes.

139
Q

When is active transport used in the gut?

A

When there is lower concentration of nutrients in the gut, but a higher concentration of nutrients in the blood.

140
Q

What process occurs when there is a higher conc. of nutrients in the gut than there is in the blood?

A

Diffusion

141
Q

What process occurs when there is a lower concentration of nutrients in the gut than there is in the blood?

A

Active transport

142
Q

What does active transport allow in the gut?

A

It allows nutrients to be taken into the blood, despite the fact that the concentration gradient is in the wrong way.

143
Q

Why is glucose transferred to the cells?

A

For respiration

144
Q

Why do cells use diffusion?

A

To take in substances they need and get rid of waste producrs.

145
Q

What happens during gas exchange?

A

Oxygen and carbon dioxide are transferred between cells and the environment.

146
Q

What is urea?

A

A waste product produced from the breakdown of proteins.

147
Q

How is urea removed in humans?

A

Urea diffuses from cells into the blood plasma for removal from the body by the kidneys.

148
Q

What does it depend on for how easy it is for an organism to exchange substances with its environment?

A

It depends on the organisms surface area to volume ratio (SA:V).

149
Q

Why can gases and dissolved substances diffuse directly into the cell across the cell membrane in single-celled organisms?

A

They have large SA compared to their volume, so enough substances can be exchanged across the membrane to supply the volume of the cell.

150
Q

What do multicellular organisms have?

A

Smaller SA compared to their volume.

151
Q

What does it mean if multicellular organisms have a small SA to volume ratio?

A

Not enough substances can diffuse from their outside surface to supply their entire volume.

152
Q

What do multicellular organisms need for efficient diffusion?

A

Some sort of exchange surface.

153
Q

What are exchange surfaces?

A

They are adapted to maximise effectiveness.

154
Q

Give an exchange surface for multicellular organisms. (1)

A

They have a thin membrane, so substances only have a short distance to diffuse.

155
Q

Give an exchange surface for multicellular organisms. (2)

A

They have a large SA so lots of a substance can diffuse at once.

156
Q

Give an exchange surface for multicellular organisms. (3)

A

Exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly.

157
Q

Give an exchange surface for multicellular organisms. (4)

A

Gas exchange in animals (e.g. alveoli) are often ventilated too- air moves in and out.

158
Q

Give the function of a lung.

A

It is to transfer oxygen to the blood and to remove waste carbon dioxide from it.

159
Q

What does the lung contain?

A

Millions of little air sacs called alveoli.

160
Q

Where does gas exchange take place?

A

In alveoli

161
Q

What are alveoli specialised for?

A

To maximise the diffusion of oxygen and carbon dioxide.

162
Q

Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (1)

A

An enormous SA (about 75m² in humans).

163
Q

Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (2)

A

A moist lining for dissolving gases.

164
Q

Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (3)

A

Very thin walls

165
Q

Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (4)

A

A good blood supply

166
Q

What is the inside of the small intestine covered with?

A

Millions and millions of these tiny little projections called villi.

167
Q

What do villi do?

A

They increase the SA in a big way so that digested food is absorbed much more quickly into the blood.

168
Q

What does villi have? (1)

A

A single layer of surface cells.

169
Q

What does villi have? (2)

A

A very god blood supply to assist quick absorption.

170
Q

What gas exchange occurs the leaf?

A

CO₂ diffuse into the air spaces within the leaf, then it diffuses into the cells where photosynthesis happens.

171
Q

What is underneath the leaf?

A

An exchange surface

172
Q

What is covered underneath the leaf?

A

Little holes called stomata which the CO₂ diffuses in through.

173
Q

Give 2 things which diffuse out of the stomata.

A
  1. Oxygen (produced in photosynthesis)

2. Water vapur

174
Q

What is the size of the stomata controlled by?

A

Guard cells

175
Q

Give the function of a guard cell.

A

These close the stomata if the plant is losing water faster than it is being replaced by the roots.

176
Q

Give another exchange surface in leaf.

A

The walls of the cells inside the leaf.

177
Q

What increases the area of the exchange surface in a leaf?

A

The flattened shape of the leaf.

178
Q

How is there a higher chance for CO₂ to get into the cells of the leaf?

A

The air spaces inside the leaf increase the area of this surface.

179
Q

What happens to the water vapour inside the leaf?

A

The water vapour evaporates from the cells inside the leaf.

180
Q

What happens after the water vapour evaporates inside the leaf?

A

It escapes by diffusion because there’s a lot of it inside the leaf and less of it in the air outside.

181
Q

Give the exchange surface of a fish.

A

Gills

182
Q

Explain the exchange that occurs inside a fish. (1)

A

Water (containing O₂) enters the fish through its mouth and passes out through the gills.

183
Q

Explain the exchange that occurs inside a fish. (2)

A

As this happens, O₂ diffuses from the water into the blood in the gills and CO₂ diffuses from the blood into the water.

184
Q

What is each gill made of?

A

Lots of thin plates called gill filaments.

185
Q

What does a gill filament give?

A

A big SA for exchange of gases.

186
Q

What are the gill filaments covered in?

A

Lots of tiny structures called lamellae.

187
Q

What does lamellae do?

A

It increases the SA even more.

188
Q

How does lamellae speed up diffusion?

A

It have lots of blood capillaries.

189
Q

What does lamellae have (which is beneficial)?

A

A thin surface layer of cells

190
Q

Why does lamellae have a thin surface layer?

A

To minimise the distance that the gases have to diffuse.

191
Q

How is a large concentration gradient maintained between the water and the blood in a fish?

A

Blood flows through the lamellae in one direction and water flows over in the opposite direction.

192
Q

How is O₂ able to diffuse from the water to the blood in a fish?

A

The concentration of O ₂ in the water is always higher than that in the blood.

GCSE AQA Biology (7 decks)

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