Topic 1- Cell Biology Flashcards
1
Q
What are all living things made of?
A
Cells
2
Q
What can a cell be?
A
Eukaryotic or prokaryotic
3
Q
Define eukaryotic cells.
A
They are complex and include all animal and plant cells.
4
Q
Define prokaryotic cells.
A
They are smaller and simpler, e.g. bacteria.
5
Q
Define eukaryotes.
A
They are organisms that are made up of eukaryotic cells.
6
Q
Define prokaryote.
A
It is a prokaryotic cell (it’s a single- celled organism)
7
Q
What are subcellular structures?
A
Different parts of a cell.
8
Q
Give 5 subcellular structures of an animal cell.
A
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
9
Q
Define nucleus.
A
It contains genetic material that controls the activities of the cell.D
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.
11
Q
Define cell membrane.
A
It holds the cell together and control what goes in and out.
12
Q
Define mitochondria.
A
These are where most of the reactions for aerobic respiration take place.
13
Q
What does respiration do?
A
It transfers energy that the cell needs to work.
14
Q
Define ribosomes.
A
These are where proteins are made in the cell.
15
Q
List 3 subcellular structures of a plant cell.
A
- Rigid cell wall
- Permanent vacuole
- Chloroplasts
(A plant cell also has all the subcellular structures that animal cells have?
16
Q
Define rigid cell wall.
A
It is made of cellulose. It supports the cell and strengthen it.
17
Q
Define permanent vacuole.
A
It contains cell sap, a weak solution of sugar and salts.
18
Q
Define chloroplasts.
A
These are where photosynthesis occurs, which makes food for the plant.
19
Q
What do chloroplasts contain?
A
Green substance called chlorophyll, which absorbs the light needed for photosynthesis.
20
Q
What replaces the nucleus in a bacterium?
A
A single circular strand of DNA that floats freely in the cytoplasm.
21
Q
List 5 subcellular structures of a bacterium cell.
A
- Cytoplasm
- Cell membrane
- Cell wall
- Single circular strand of DNA
- Plasmids
22
Q
What are plasmids?
A
Small rings of DNA.
23
Q
Give 2 subcellular structures which a bacterium cell does not have.
A
- Chloroplasts
2. Mitochondria
24
Q
Give the function of a microscope .
A
It let us see things that we can’t see with the naked eye.
25
What developed over the years as technology and knowledge developed?
Microscopy techniques
26
What are light microscopes?
They use light and lenses to form an image of a specimen and magnify it.
27
What does it mean to magnify it?
Make it look bigger.
28
What does a light microscope let us see?
Individual cells and large subcellular structures, like nuclei.
29
What are electron microscopes?
They use electrons instead of light to form an image.
30
What makes an electron microscope better than a light microscope?
1. Higher magnification
| 2. Higher resolution
31
Define resolution.
It is the ability to distinguish between two points.
32
What does a higher resolution give?
A sharper image.
33
What does an electron microscope let us see?
Smaller things in more detail.
34
Give examples of what an electron microscope can let us see.
The internal structure of mitochondria and chloroplasts. They even let us see tinier things like ribosomes and plasmids.
35
Give the formula for magnification.
Magnification= image size/ real size
36
Define differentiation.
It is the process by which a cell changes to become specialised for its job.
37
Describe what a cell develop as it changes.
It develops different subcellular structures and turn into different types of cells. This allows them to carry out specific functions.
38
When does most differentiation occur?
As an organism develops.
39
What happens to an animal cell after it is specialised?
It loses the ability to differentiate
40
.True or false, does a plant cell lose their ability to differentiate.
False
41
What are the cells that differentiate in mature animals mainly used for?
Repairing and replacing cells, such as skin or blood cells.
42
Define stem cells.
Undifferentiated cells
43
What are sperm cells specialised for?
Reproduction
44
Give the function of a sperm cell.
To get the male DNA to the female DNA.
45
Describe the structure of a sperm cell.
It has a long tail and a streamlined head to help it swim to the egg.
46
What does a sperm cell contain?
1. Mitochondria
| 2. Enzymes
47
Why does a sperm cell contain mitochondria?
To provide the energy needed.
48
Why does a sperm cell contain enzymes in its head?
To digest through the egg cell membrane.
49
What are nerve cells specialised for?
Rapid signalling
50
Give the function of a nerve cell.
To carry electrical signals from one part of the body to another.
51
Describe the structure of nerve cells.
These cells are long and have branched connections at their ends.
52
Why do nerve cells have long cells?
To cover more distance.
53
Why do nerve cells have branched connections at their ends?
To connect to other nerve cells and form a network throughout the body.
54
What are muscle cells specialised for?
Contraction
55
Give the function of a muscle cell.
To contract quickly.
56
Describe the structure of a muscle cell.
These cells are long and contain lots of mitochondria.
57
Why are muscle cells long?
To have space to contract.
58
Why do muscle cells contain lots of mitochondria?
To generate the energy needed for contraction.
59
What are root hair cells specialised for?
Absorbing water and minerals.
60
What is the function of a root hair cell?
To give the plant a big surface area for absorbing water and mineral ions from the soil.
61
Where are root hair cells located on a plant?
On the surface of plant roots.
62
What do root hair cells grow into?
Long "hairs" that stick out into the soil.
63
What are phloem and xylem cells specialised for?
Transporting substances.
64
What do phloem and xylem cells form and what do they do?
They form phloem and xylem tubes, which transport substances such as food and water around plants.
65
How do xylem and phloem cells form tubes?
The cells are long and joined end to end.
66
Describe the structure of a xylem cell.
Hollow in the centre.
67
Describe the structure of a xylem cell.
Hollow in the centre.
68
Describe the structure of a phloem cell.
It has very few subcellular structures, so that stuff can flow through them.
69
How is the genetic material formed in the nucleus?
It is in the form of chromosomes
70
Define chromosomes.
They are coiled up lengths of DNA molecules.
71
What does each chromosome carry?
A large number of genes.
72
What do different genes control?
The development of different characteristics, e.g. hair colour.
73
How many chromosomes do body cells usually have?
Two copies of each chromosome.
74
Where does each copy of a chromosome come from?
One from the organism's 'mother', and one from it 'father'.
75
How many chromosomes does a human cell have?
23 pairs of chromosomes (46 chromosomes).
76
What do body cells in multicellular organisms do as part of the cell cycle?
Divide to produce new cells.
77
What is mitosis?
It is the stage of the cell cycle when the cell divides.
78
What do multicellular organisms use mitosis for?
To grow or replace cells that have been damaged.
79
Describe the results of the end of the cell cycle.
It results in two new cells identical to the original cell, with the same number of chromosomes.
80
What are the 2 stages of cell cycle?
1. Growth and DNA replication
| 2. Mitosis
81
Give an example of a bacteria.
E. coil
82
How long does it take for E. coil to replicate in the right conditions?
As little as 20 minutes.
83
How can bacteria divide very quickly?
They can divide very quickly if given the right conditions.
84
Give a condition which helps bacteria replicate.
1. Warm environment
| 2. Lots of nutrients
85
What happens if the conditions become unfavourable for bacteria?
The cells will stop dividing and eventually begin to die.
86
What is the mean division time?
It is the average amount of time it takes for one bacterial cell to divide into 2.
87
What are undifferentiated cells able to do? (1)
They can divide to produce lots more differentiated cells.
88
What are undifferentiated cells able to do? (2)
They can differentiate into different type of cells, depending on what instructions they're given.
89
Where are stem cells found in?
Early human embryos
90
Where are stem cells found in adults?
Bone marrow
91
What is the difference between stem cells found in bone marrow and in human embryos?
Unlike embryonic stem cells, they can't turn into any cell type at all, only certain ones, e.g. red blood cells.
92
What can you do with stem cells from embryos and bone marrow, when grown in a lab?
It can be grown in a lab to produce clones and made to differentiate into specialised cells to use in medicine or research.
93
What can adult stem cells be used for in medicine?
To cure disease.
94
Give an example of when adult stem cells are used in medicine.
Stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in the patient who receives them.
95
True or false, can embryonic stem cells be used to replace faulty cells in sick people.
True
96
What can you make using embryonic stem cells?
Insulin-producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries.
97
Identify a type of cloning.
Therapeutic cloning
98
What can you do with therapeutic cloning?
An embryo could be made to have the same genetic information as the patient.
99
Why is it important for the stem cells to have the same genes?
So it wouldn't be rejected by the patient's body if used to replace faulty cells.
100
Give a risk of using stem cells in medicine.
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
Why are some people against stem cell research? (1)
They feel that human embryos shouldn't be used for experiments since each one is a potential human life.
102
Why are some people for stem cell research? (1)
They think that curing existing patients who are suffering is more important than the rights of embryos.
103
Why are some people for stem cell research? (2)
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
Why are some people against stem cell research? (2)
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
Where are stem cells found in plants?
Meristems
106
What are meristems?
They are parts of the plant where growth occurs.
107
What are clones?
Genetically identical cells
108
What are the cells in the meristem tissues able to do in plants?
Differentiate into any type of plant cell.
109
What are stem cells able to do in plants? (1)
Produce clones of whole plants quickly and cheaply.
110
What are stem cells able to do in plants? (2)
They can be used to grow more plants of rare species.
111
Why do people grow more plants of rare species using stem cells?
To prevent them from being wiped out.
112
What are stem cells able to do in plants? (3)
To grow crops of identical plants that have desired features for farmers, e.g. disease resistance.
113
Define diffusion.
It is the spreading out of particles from an area of higher concentration to an area of lower concentration.
114
Where can diffusion happen?
In both solutions and gases.
115
Why is diffusion able to occur in gases and solution?
The particles in these substances are free to move about randomly.
116
How can you increase the rate of diffusion? (1)
The bigger the concentration gradient, the faster the rate of diffusion.
117
What is the concentration gradient?
The difference in concentration.
118
How can you increase the rate of diffusion? (2)
A higher temperature gives a faster rate of diffusion.
119
Why can you increase the rate of diffusion with temperature?
The particles have more energy, so they move around faster.
120
How can dissolved substances move in and out of cells?
By diffusion
121
Give 4 small molecules that are able to diffuse through cell membranes.
1. Oxygen (needed for respiration)
2. Glucose
3. Amino acids
4. Water
122
Give 3 big molecules that are not able to fit through membranes.
1. Protein
2. Starch
3. Lipids
123
How can you increase the rate of diffusion in membranes?
The larger the surface area of the membrane, the faster the rate of diffusion.
124
How can increasing the surface area, increase the rate of diffusion?
More particles can pass through at once.
125
Define osmosis.
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
What will there be if there are a lot more particles on one side of the membrane?
There will be a net (overall) movement from that side.
127
What can and what can not pass through a partially permeable membrane?
1. Water (tiny molecule)- can
| 2. Sucrose (big molecule)- cannot
128
Why are water molecules able to pass both ways through the partially permeable membrane during osmosis?
Water molecules move about randomly all the time.
129
Why are water molecules able to pass both ways through the partially permeable membrane during osmosis?
Water molecules move about randomly all the time.
130
Where will the net flow be if there are more water molecules on one side than on the other?
There will be a steady net flow of water into the region with fewer molecules.
131
What are root hair cells covered in?
Millions of microscopic hairs.
132
What does these microscopic hairs give to the plant?
A large SA for absorbing water and mineral ions from the soil.
133
Why do plants need mineral ions?
For healthy growth
134
Why are root hair cells unable to use diffusion?
The concentration of minerals is usually higher in the root hair cells than in the soil around them.
135
What process do root hair cells use to absorb mineral ions?
Active transport
136
What does active transport allow the plant to do when absorbing minerals?
It allows the plant to absorb minerals from a very dilute solution, against a concentration gradient.
137
What does active transport need?
Energy from respiration
138
Where in humans does active transport take place?
In taking glucose from the gut and from the kidney tubes.
139
When is active transport used in the gut?
When there is lower concentration of nutrients in the gut, but a higher concentration of nutrients in the blood.
140
What process occurs when there is a higher conc. of nutrients in the gut than there is in the blood?
Diffusion
141
What process occurs when there is a lower concentration of nutrients in the gut than there is in the blood?
Active transport
142
What does active transport allow in the gut?
It allows nutrients to be taken into the blood, despite the fact that the concentration gradient is in the wrong way.
143
Why is glucose transferred to the cells?
For respiration
144
Why do cells use diffusion?
To take in substances they need and get rid of waste producrs.
145
What happens during gas exchange?
Oxygen and carbon dioxide are transferred between cells and the environment.
146
What is urea?
A waste product produced from the breakdown of proteins.
147
How is urea removed in humans?
Urea diffuses from cells into the blood plasma for removal from the body by the kidneys.
148
What does it depend on for how easy it is for an organism to exchange substances with its environment?
It depends on the organisms surface area to volume ratio (SA:V).
149
Why can gases and dissolved substances diffuse directly into the cell across the cell membrane in single-celled organisms?
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
What do multicellular organisms have?
Smaller SA compared to their volume.
151
What does it mean if multicellular organisms have a small SA to volume ratio?
Not enough substances can diffuse from their outside surface to supply their entire volume.
152
What do multicellular organisms need for efficient diffusion?
Some sort of exchange surface.
153
What are exchange surfaces?
They are adapted to maximise effectiveness.
154
Give an exchange surface for multicellular organisms. (1)
They have a thin membrane, so substances only have a short distance to diffuse.
155
Give an exchange surface for multicellular organisms. (2)
They have a large SA so lots of a substance can diffuse at once.
156
Give an exchange surface for multicellular organisms. (3)
Exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly.
157
Give an exchange surface for multicellular organisms. (4)
Gas exchange in animals (e.g. alveoli) are often ventilated too- air moves in and out.
158
Give the function of a lung.
It is to transfer oxygen to the blood and to remove waste carbon dioxide from it.
159
What does the lung contain?
Millions of little air sacs called alveoli.
160
Where does gas exchange take place?
In alveoli
161
What are alveoli specialised for?
To maximise the diffusion of oxygen and carbon dioxide.
162
Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (1)
An enormous SA (about 75m² in humans).
163
Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (2)
A moist lining for dissolving gases.
164
Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (3)
Very thin walls
165
Give a way in which alveoli is specialised for diffusion of oxygen and carbon dioxide. (4)
A good blood supply
166
What is the inside of the small intestine covered with?
Millions and millions of these tiny little projections called villi.
167
What do villi do?
They increase the SA in a big way so that digested food is absorbed much more quickly into the blood.
168
What does villi have? (1)
A single layer of surface cells.
169
What does villi have? (2)
A very god blood supply to assist quick absorption.
170
What gas exchange occurs the leaf?
CO₂ diffuse into the air spaces within the leaf, then it diffuses into the cells where photosynthesis happens.
171
What is underneath the leaf?
An exchange surface
172
What is covered underneath the leaf?
Little holes called stomata which the CO₂ diffuses in through.
173
Give 2 things which diffuse out of the stomata.
1. Oxygen (produced in photosynthesis)
| 2. Water vapur
174
What is the size of the stomata controlled by?
Guard cells
175
Give the function of a guard cell.
These close the stomata if the plant is losing water faster than it is being replaced by the roots.
176
Give another exchange surface in leaf.
The walls of the cells inside the leaf.
177
What increases the area of the exchange surface in a leaf?
The flattened shape of the leaf.
178
How is there a higher chance for CO₂ to get into the cells of the leaf?
The air spaces inside the leaf increase the area of this surface.
179
What happens to the water vapour inside the leaf?
The water vapour evaporates from the cells inside the leaf.
180
What happens after the water vapour evaporates inside the leaf?
It escapes by diffusion because there's a lot of it inside the leaf and less of it in the air outside.
181
Give the exchange surface of a fish.
Gills
182
Explain the exchange that occurs inside a fish. (1)
Water (containing O₂) enters the fish through its mouth and passes out through the gills.
183
Explain the exchange that occurs inside a fish. (2)
As this happens, O₂ diffuses from the water into the blood in the gills and CO₂ diffuses from the blood into the water.
184
What is each gill made of?
Lots of thin plates called gill filaments.
185
What does a gill filament give?
A big SA for exchange of gases.
186
What are the gill filaments covered in?
Lots of tiny structures called lamellae.
187
What does lamellae do?
It increases the SA even more.
188
How does lamellae speed up diffusion?
It have lots of blood capillaries.
189
What does lamellae have (which is beneficial)?
A thin surface layer of cells
190
Why does lamellae have a thin surface layer?
To minimise the distance that the gases have to diffuse.
191
How is a large concentration gradient maintained between the water and the blood in a fish?
Blood flows through the lamellae in one direction and water flows over in the opposite direction.
192
How is O₂ able to diffuse from the water to the blood in a fish?
The concentration of O ₂ in the water is always higher than that in the blood.
