Chapter 1. Cell Biology Flashcards
(106 cards)
1
Q
What are the 3 statements of the cell theory?
A
- All living things are composed of cells (or cell products –> virus).
- A cell is the smallest unit of life, nothing smaller can live independently.
- Cells can only arise from pre-existing cells.
2
Q
3 Common Features of a Cell
A
- Every living cell is surrounded by a membrane;
- Contains genetic materials which stores all of the instructions needed for the cell’s activities;
- Have their own energy release system which powers all the cell’s activities;
3
Q
3 Atypical Examples to the Cell Theory
A
- Straited muscle fibres;
- Aseptate hypha;
- Giant algae;
4
Q
Discrepancies
A
Exceptions to a general trend.
5
Q
What are the 7 functions of life?
A
Metabolism; Response; Homeostasis; Grow; Reproduction; Excretion; Nutrition;
6
Q
What are the drawbacks of having a small surface area to volume ratio?
A
- Waste products will accumulate because they are produced more rapidly than they are excreted.
- Cells will overheat because metabolism produces heat faster than it is lost over the surface (membrane).
7
Q
What are the drawbacks of having a bigger-tha not-normal surface area to volume ratio?
A
There is a lack of reactants and enzymes stored in the cell because of its limited size. Hence, the metabolic rate will be considerably slow.
8
Q
Stem cell
A
A stem cell is the zygote and the cells of the early embryo.
All the tissues of the adult stem from them.
9
Q
State the two key properties of stem cells.
A
- Stem cells have the ability to divide to produce copious quantities of new cells. Hence, they are useful for growth and replacement.
- Stem cells are not fully differentiated. They can differentiate along different pathways to produce different cell types.
10
Q
Where can stems cells be found in an adult?
A
Buried deep in many tissues such as bone marrow and liver.
11
Q
What is the full name of Stargardt’s disease?
A
Stargardt’s macular dystrophy
Macular [有斑点的]
Dystrophy [营养不良]
12
Q
What is Stargardt’s Macular Dystrophy?
A
A genetic disease develops in children aged 6~12. It is caused by mutation in a recessive gene (ABCA4). The mutation causes a membrane protein used for active transport in the retinal cells to malfunction, leading to the degeneration of photoreceptive cells in the retina. The patient’s vision becomes progressively worse, and eventually can become blind.
13
Q
What does the evolution of multicellular organisms allow?
A
Cell differentiation and cell replacement
14
Q
State the procedures to cure Stargardt’s disease using stem cells.
A
- Make embryonic stem cells develop into retinal cells.
- Inject the cells into the patient’s eyes.
- If the foreign cells are not rejected, the cells will attach to the retina and remain.
- Improvement in vision!
15
Q
Trials of using embryonic stem cells to cure the Stargardt’s disease.
A
Mice with a condition similar to Stargardt’s disease are tested.
In November 2010, the first human trial was approved in the U.S. An old lady at her 50s was injected with 400,000 retinal cells that had developed from embryonic stem cells.
16
Q
Bone marrow
A
A soft tissue in the hollow centre of large bones such as femur or pelvis.
17
Q
What is a normal adult white blood cell count?
A
4,000~11,000/mm3
18
Q
What does a white blood cell count of > 30,000/mm3 mean?
A
That person MAY have leukaemia.
19
Q
What does a white blood cell count of >100,000/mm3 mean?
A
That person has ACUTE leukaemia.
20
Q
State the procedures of curing leukaemia using stem cells.
A
- A large needle is inserted into an patient’s bone marrow (of pelvis) to remove fluid.
- Adult stem cells are extracted from the fluid and are stored by freezing them. The adult stem cells have the potential for producing blood cells.
- Chemotherapy drugs are given to the patient to kill all the cancer cells. The bone marrow loses its ability of producing blood cells.
- The stem cells are then returned to the patient’s body. They re-establish themselves in the bone marrow, multiply and start to produce red and white blood cells.
21
Q
Pros of using embryonic stem cells for therapeutic uses
A
- Very versatile, can differentiate into almost all cell types.
- Young cells, less accumulation of genetic mutation –> less potential genetic damage to the patient than using adult stem cells.
22
Q
Cons of using embryonic stem cells for therapeutic uses
A
- The cells extracted are likely to be genetically different from the cells of the patient.
- Higher potential risk that cells will develop into tumours (e.g. teratomas).
- Extraction of cells from the embryo kills it, unless only one or two are removed, which is far less than useful.
23
Q
Functions of separate compartments in cells
A
Allows specialised reactions to take place.
24
Q
Functions of separate compartments in cells
A
Allows specialised reactions to take place.
25
State the functions of plasma membrane
1. It provides a site for the regulation of the passage of molecules into and out of the cell. It is selectively permeable with carrier mechanisms for molecules.
2. It also provides a location for the enzymes concerned with metabolic activities.
26
Lysosomes
Contains digestive enzymes for breaking down nutrient molecules and dead cell parts for recycling.
27
State the function of cytoplasm.
Contains many enzymes and salutes needed for metabolic reactions within the cell, as well as dissolving mineral ions, nutrients and waste.
28
State the function of nucleus.
Membrane-bonded nucleus contains all genetic information in chromosomes. The nucleus controls activities within the cell through the regulation of protein synthesis and enzymes.
29
State the function of nucleolus.
The nucleoli a is a densely-packed area of DNA. It makes ribonucleic acid (RNA) and assemble ribosomes.
30
State the function of ribosomes.
Site of protein synthesis.
The proteins that are synthesised by free ribosomes remain within the cell.
The ones synthesised by ribosomes attached to the rER are modified by the Golgi apparatus and secreted out of the cell.
31
State the function of mitochondria and its internal structures.
Mitochondria are the sites for aerobic cell respiration.
The matrix (fluid) contains enzymes involved in the Krebs cycle.
The reactions producing ATP take place on the cristae.
32
State the two functions of rER.
1. Protein transport to the sites where they are needed, or to the Golgi apparatus for further modifications.
2. Provides increased surface area for cellular reactions.
33
State the function of the Golgi apparatus.
Modification of protein synthesised on the rER. Vesicles containing modified proteins bud off from the Golgi apparatus and are secreted out of the cell by exocytosis.
34
Pros of being Compartmentalised
1. Much more concentrated enzymes and substrates in certain sites for particular processes.
2. Damaging substances can be kept inside the membrane of an organelle (e.g. digestive enzymes are kept and stored inside the lysosome membrane).
2. Different pHs can be maintained for different processes.
4. Organelles (compartments) and the contents can move around within the cell.
35
State the function of flagella.
Flagella (single. flagellum) beat for locomotion (movement).
36
State the function of pili.
Used for adhesion to another cell surface to transfer genetic material between cells (e.g. bacteria).
37
Amphipathic
If a molecule is amphipathic (e.g. phospholipid molecules), part of the molecule is hydrophilic and part is hydrophobic.
38
Hydrophilic
Substances are attracted to water.
39
Hydrophobic
Substances are NOT attracted to water.
40
Why phospholipid form bilayers in water?
Due to the amphipathic property of phosphate molecules, the structure will be more stable if the molecules form a bilayer.
41
Different models of the plasma membrane
1. 1920s: Gorter-Grendel Model: proposed phospholipid bilayer;
2. 1930s: Davson-Danielli Model: sandwich model, the phospholipid bilayer is enclosed between two layers of protein;
3. 1966: Singer-Nicolso's fluid mosaic model: the phospholipid molecules and proteins are able to move in both layers.
42
Three pieces of evidence that falsified the Davson-Danielli Model
1. Freeze-etched electron micrographs;
2. Structure of membrane proteins;
3. Fluorescent antibody tagging.
43
Explain clearly how did the freeze-etched electron micrographs falsify the Davson-Danielli Model.
The freeze-etched method involves rapid freezing of cells and fracture them.
Globular structures that scattered through freeze-etched images of the centre of membranes are examined, and were found out to be transmembrane proteins.
44
Explain how did the structure of membrane proteins falsify the Davson-Danielli Model.
Membrane proteins extracted varied in size and globular in shape, which is not like the type of structural protein that would form continuous layers.
Also, membrane proteins were found out to be hydrophobic, which means they are NOT attracted to water, but to the hydrophobic hydrocarbon chain (tail) of phospholipids instead.
45
Explain how did the fluorescent antibody tagging experiment falsify the Davson-Danielli Model.
Red/green markers were attached to antibodies. The membrane proteins of some cells are tagged with antibodies with red markers, and other with antibodies with green markers. The cells were fused together. Within 40 minutes the red and green markers were mixed throughout the membranes of the fused cells.
The experiment shows that membrane proteins are not fixed in the peripheral layer. Instead, they are free to move within the membrane.
46
Function of phospholipid bilayer
Form a barrier that charged ions and hydrophilic molecules cannot easily pass.
47
Functions of membrane proteins
1. Bond to other cells/molecules: cell adhesion to form tight junctions between groups of cells in tissues and organs.
2. They are hormone receptors: provides binding sites for hormones (e.g. insulin receptor).
3. Immobilise enzymes with their active site pointing outwards (e.g. In the small intestine).
4. Cell-to-cell communication: some proteins are receptors for neurotransmitters at synapses; cell signalling; immunity).
5. Channels for facilitated diffusion of hydrophilic molecules.
6. Pumps for active transport which use ATP to move particles across the membrane.
48
Main components of cell membrane
1. Phospholipid bilayer;
2. Membrane proteins;
3. (Cholesterol)
49
Define cholesterol
A type of lipid (not fat or oil): belongs to a group called steroids.
It is non-polar.
Most of it is hydrophobic so it can be embedded in the hydrophobic hydrocarbon tails of the phospholipids.
One end has a hydroxyl (-OH) group that is hydrophilic so that end is attracted to the hydrophilic heads of the phospholipids in the peripheral layer.
50
Why the fluidity of cell membranes in animals needs to be carefully controlled?
Too fluid: hard to control what substances pass through.
Too rigid: movements of the cell and substances across the membrane would be restricted.
51
Function of cholesterol
Controls the fluidity of the plasma membrane in animal cells.
52
How cholesterol can control the fluidity of plasma membranes?
1. It disrupts the regular packing of hydrophobic tails. This prevents them crystallising and behaving as a solid.
2. Restricts molecular motions within the membrane and therefore fluidity.
3. It reduces the permeability to hydrophilic particles (e.g. sodium and potassium ions).
4. Help membranes to curve into concave shapes, which helps in the formation of vehicles during endo/exo-cytosis.
53
Function of peripheral proteins
Respond to chemicals inside/outside the cell and alter their shapes to allow certain ions or particles that are needed by the cell to pass through by facilitated diffusion.
54
Function of integral protein
1. Channels for facilitated diffusion of hydrophilic particles (e.g. aquaporin for osmosis);
2. Pumps for active transport;
3. Immobilise enzymes for chemical reactions;
55
Function of glycoproteins
They are markers for cellular recognition (to identify self and non-self cells) (e.g. antigens).
56
Functions of glycolipids
1. Provide energy;
| 2. Markers for cellular recognition (e.g. antigens).
57
State the two functions of rER.
1. Protein transport to the sites where they are needed, or to the Golgi apparatus for further modifications.
2. Provides increased surface area for cellular reactions.
58
State the function of the Golgi apparatus.
Modification of protein synthesised on the rER. Vesicles containing modified proteins bud off from the Golgi apparatus and are secreted out of the cell by exocytosis.
59
Pros of being Compartmentalised
1. Much more concentrated enzymes and substrates in certain sites for particular processes.
2. Damaging substances can be kept inside the membrane of an organelle (e.g. digestive enzymes are kept and stored inside the lysosome membrane).
2. Different pHs can be maintained for different processes.
4. Organelles (compartments) and the contents can move around within the cell.
60
State the function of flagella.
Flagella (single. flagellum) beat for locomotion (movement).
61
State the function of pili.
Used for adhesion to another cell surface to transfer genetic material between cells (e.g. bacteria).
62
Amphipathic
If a molecule is amphipathic (e.g. phospholipid molecules), part of the molecule is hydrophilic and part is hydrophobic.
63
Hydrophilic
Substances are attracted to water.
64
Hydrophobic
Substances are NOT attracted to water.
65
Why phospholipid form bilayers in water?
Due to the amphipathic property of phosphate molecules, the structure will be more stable if the molecules form a bilayer.
66
Different models of the plasma membrane
1. 1920s: Gorter-Grendel Model: proposed phospholipid bilayer;
2. 1930s: Davson-Danielli Model: sandwich model, the phospholipid bilayer is enclosed between two layers of protein;
3. 1966: Singer-Nicolso's fluid mosaic model: the phospholipid molecules and proteins are able to move in both layers.
67
Three pieces of evidence that falsified the Davson-Danielli Model
1. Freeze-etched electron micrographs;
2. Structure of membrane proteins;
3. Fluorescent antibody tagging.
68
Explain clearly how did the freeze-etched electron micrographs falsify the Davson-Danielli Model.
The freeze-etched method involves rapid freezing of cells and fracture them.
Globular structures that scattered through freeze-etched images of the centre of membranes are examined, and were found out to be transmembrane proteins.
69
Explain how did the structure of membrane proteins falsify the Davson-Danielli Model.
Membrane proteins extracted varied in size and globular in shape, which is not like the type of structural protein that would form continuous layers.
Also, membrane proteins were found out to be hydrophobic, which means they are NOT attracted to water, but to the hydrophobic hydrocarbon chain (tail) of phospholipids instead.
70
Explain how did the fluorescent antibody tagging experiment falsify the Davson-Danielli Model.
Red/green markers were attached to antibodies. The membrane proteins of some cells are tagged with antibodies with red markers, and other with antibodies with green markers. The cells were fused together. Within 40 minutes the red and green markers were mixed throughout the membranes of the fused cells.
The experiment shows that membrane proteins are not fixed in the peripheral layer. Instead, they are free to move within the membrane.
71
Function of phospholipid bilayer
Form a barrier that charged ions and hydrophilic molecules cannot easily pass.
72
Functions of membrane proteins
1. Bond to other cells/molecules: cell adhesion to form tight junctions between groups of cells in tissues and organs.
2. They are hormone receptors: provides binding sites for hormones (e.g. insulin receptor).
3. Immobilise enzymes with their active site pointing outwards (e.g. In the small intestine).
4. Cell-to-cell communication: some proteins are receptors for neurotransmitters at synapses; cell signalling; immunity).
5. Channels for facilitated diffusion of hydrophilic molecules.
6. Pumps for active transport which use ATP to move particles across the membrane.
73
Main components of cell membrane
1. Phospholipid bilayer;
2. Membrane proteins;
3. (Cholesterol)
74
Define cholesterol
A type of lipid (not fat or oil): belongs to a group called steroids.
It is non-polar.
Most of it is hydrophobic so it can be embedded in the hydrophobic hydrocarbon tails of the phospholipids.
One end has a hydroxyl (-OH) group that is hydrophilic so that end is attracted to the hydrophilic heads of the phospholipids in the peripheral layer.
75
Why the fluidity of cell membranes in animals needs to be carefully controlled?
Too fluid: hard to control what substances pass through.
Too rigid: movements of the cell and substances across the membrane would be restricted.
76
Function of cholesterol
Controls the fluidity of the plasma membrane in animal cells.
77
How cholesterol can control the fluidity of plasma membranes?
1. It disrupts the regular packing of hydrophobic tails. This prevents them crystallising and behaving as a solid.
2. Restricts molecular motions within the membrane and therefore fluidity.
3. It reduces the permeability to hydrophilic particles (e.g. sodium and potassium ions).
4. Help membranes to curve into concave shapes, which helps in the formation of vehicles during endo/exo-cytosis.
78
Function of peripheral proteins
Respond to chemicals inside/outside the cell and alter their shapes to allow certain ions or particles that are needed by the cell to pass through by facilitated diffusion.
79
Function of integral protein
1. Channels for facilitated diffusion of hydrophilic particles (e.g. aquaporin for osmosis);
2. Pumps for active transport;
3. Immobilise enzymes for chemical reactions;
80
Function of glycoproteins
They are markers for cellular recognition (to identify self and non-self cells) (e.g. antigens).
81
Functions of glycolipids
1. Provide energy;
| 2. Markers for cellular recognition (e.g. antigens).
82
State the two functions of rER.
1. Protein transport to the sites where they are needed, or to the Golgi apparatus for further modifications.
2. Provides increased surface area for cellular reactions.
83
State the function of the Golgi apparatus.
Modification of protein synthesised on the rER. Vesicles containing modified proteins bud off from the Golgi apparatus and are secreted out of the cell by exocytosis.
84
Pros of being Compartmentalised
1. Much more concentrated enzymes and substrates in certain sites for particular processes.
2. Damaging substances can be kept inside the membrane of an organelle (e.g. digestive enzymes are kept and stored inside the lysosome membrane).
2. Different pHs can be maintained for different processes.
4. Organelles (compartments) and the contents can move around within the cell.
85
State the function of flagella.
Flagella (single. flagellum) beat for locomotion (movement).
86
State the function of pili.
Used for adhesion to another cell surface to transfer genetic material between cells (e.g. bacteria).
87
Amphipathic
If a molecule is amphipathic (e.g. phospholipid molecules), part of the molecule is hydrophilic and part is hydrophobic.
88
Hydrophilic
Substances are attracted to water.
89
Hydrophobic
Substances are NOT attracted to water.
90
Why phospholipid form bilayers in water?
Due to the amphipathic property of phosphate molecules, the structure will be more stable if the molecules form a bilayer.
91
Different models of the plasma membrane
1. 1920s: Gorter-Grendel Model: proposed phospholipid bilayer;
2. 1930s: Davson-Danielli Model: sandwich model, the phospholipid bilayer is enclosed between two layers of protein;
3. 1966: Singer-Nicolso's fluid mosaic model: the phospholipid molecules and proteins are able to move in both layers.
92
Three pieces of evidence that falsified the Davson-Danielli Model
1. Freeze-etched electron micrographs;
2. Structure of membrane proteins;
3. Fluorescent antibody tagging.
93
Explain clearly how did the freeze-etched electron micrographs falsify the Davson-Danielli Model.
The freeze-etched method involves rapid freezing of cells and fracture them.
Globular structures that scattered through freeze-etched images of the centre of membranes are examined, and were found out to be transmembrane proteins.
94
Explain how did the structure of membrane proteins falsify the Davson-Danielli Model.
Membrane proteins extracted varied in size and globular in shape, which is not like the type of structural protein that would form continuous layers.
Also, membrane proteins were found out to be hydrophobic, which means they are NOT attracted to water, but to the hydrophobic hydrocarbon chain (tail) of phospholipids instead.
95
Explain how did the fluorescent antibody tagging experiment falsify the Davson-Danielli Model.
Red/green markers were attached to antibodies. The membrane proteins of some cells are tagged with antibodies with red markers, and other with antibodies with green markers. The cells were fused together. Within 40 minutes the red and green markers were mixed throughout the membranes of the fused cells.
The experiment shows that membrane proteins are not fixed in the peripheral layer. Instead, they are free to move within the membrane.
96
Function of phospholipid bilayer
Form a barrier that charged ions and hydrophilic molecules cannot easily pass.
97
Functions of membrane proteins
1. Bond to other cells/molecules: cell adhesion to form tight junctions between groups of cells in tissues and organs.
2. They are hormone receptors: provides binding sites for hormones (e.g. insulin receptor).
3. Immobilise enzymes with their active site pointing outwards (e.g. In the small intestine).
4. Cell-to-cell communication: some proteins are receptors for neurotransmitters at synapses; cell signalling; immunity).
5. Channels for facilitated diffusion of hydrophilic molecules.
6. Pumps for active transport which use ATP to move particles across the membrane.
98
Main components of cell membrane
1. Phospholipid bilayer;
2. Membrane proteins;
3. (Cholesterol)
99
Define cholesterol
A type of lipid (not fat or oil): belongs to a group called steroids.
It is non-polar.
Most of it is hydrophobic so it can be embedded in the hydrophobic hydrocarbon tails of the phospholipids.
One end has a hydroxyl (-OH) group that is hydrophilic so that end is attracted to the hydrophilic heads of the phospholipids in the peripheral layer.
100
Why the fluidity of cell membranes in animals needs to be carefully controlled?
Too fluid: hard to control what substances pass through.
Too rigid: movements of the cell and substances across the membrane would be restricted.
101
Function of cholesterol
Controls the fluidity of the plasma membrane in animal cells.
102
How cholesterol can control the fluidity of plasma membranes?
1. It disrupts the regular packing of hydrophobic tails. This prevents them crystallising and behaving as a solid.
2. Restricts molecular motions within the membrane and therefore fluidity.
3. It reduces the permeability to hydrophilic particles (e.g. sodium and potassium ions).
4. Help membranes to curve into concave shapes, which helps in the formation of vehicles during endo/exo-cytosis.
103
Function of peripheral proteins
Respond to chemicals inside/outside the cell and alter their shapes to allow certain ions or particles that are needed by the cell to pass through by facilitated diffusion.
104
Function of integral protein
1. Channels for facilitated diffusion of hydrophilic particles (e.g. aquaporin for osmosis);
2. Pumps for active transport;
3. Immobilise enzymes for chemical reactions;
105
Function of glycoproteins
They are markers for cellular recognition (to identify self and non-self cells) (e.g. antigens).
106
Functions of glycolipids
1. Provide energy;
| 2. Markers for cellular recognition (e.g. antigens).
