Cells 2 Flashcards
(153 cards)
1
Q
What is the structure of the cell membrane?
A
Phospholipid bilayer with embedded intrinsic & extrinsic proteins
2
Q
What is the function of the cell membrane?
A
Selectively permeable barrier; controls passage of substances in and out of the cell; barrier between internal and external cell environments
3
Q
What structures are found in the nucleus?
A
Nuclear pores, nucleolus, DNA, and nuclear envelope
4
Q
What is the function of the nucleus?
A
Site of transcription & pre-mRNA splicing - mRNA production; site of DNA replication; nucleolus makes ribosomes; nuclear pore allows movement of substances to/from cytoplasm
5
Q
What is the structure of mitochondria?
A
Double membrane with inner membrane folded into cristae, 70S ribosomes in matrix, small circular DNA, enzymes in matrix.
6
Q
What is the function of mitochondria?
A
Site of aerobic respiration, produces ATP.
7
Q
What is the structure of chloroplasts?
A
Thylakoid membranes stacked to form grana, linked by lamellae, stroma contains enzymes, contains starch granules, small circular DNA, and 70S ribosomes.
8
Q
What is the function of chloroplasts?
A
Chlorophyll absorbs light for photosynthesis to produce organic molecules (glucose).
9
Q
What organisms contain chloroplasts?
A
Plants and Algae
10
Q
What is the structure of the Golgi apparatus?
A
It consists of cisternae and has a cis face and a trans face.
11
Q
What is the function of the Golgi apparatus?
A
It modifies proteins received from the RER, packages them into vesicles for transport to the cell membrane for exocytosis, and makes lysosomes.
12
Q
What is a lysosome?
A
A type of Golgi vesicle containing digestive enzymes.
13
Q
What structures are associated with the Golgi apparatus?
A
Nuclear envelope, nuclear pore, ribosomes, smooth endoplasmic reticulum, secretary vesicle, and lysosome.
14
Q
What is the function of lysosomes?
A
Contains digestive enzymes to hydrolyse pathogens and cell waste products.
15
Q
What is the function of the rough endoplasmic reticulum?
A
Site of protein synthesis, folds polypeptides to secondary and tertiary structures, and packages them into vesicles for transport to the Golgi.
16
Q
What is the function of the smooth endoplasmic reticulum?
A
Synthesises and processes lipids.
17
Q
What is the function of the cell wall?
A
Provides structural strength, rigidity, and support to the cell, and helps resist osmotic pressures.
18
Q
What are the components of a ribosome’s structure?
A
Small and large subunit, made of protein and RNA, free floating in cytoplasm & bound to RER.
70S in prokaryotes, mitochondria and chloroplasts; 80S in eukaryotes.
19
Q
What is the function of a ribosome?
A
Site of translation in protein synthesis.
20
Q
What is the structure of the rough endoplasmic reticulum?
A
System of membranes with bound ribosomes, continuous with nucleus.
21
Q
What is the structure of the smooth endoplasmic reticulum?
A
System of membranes with no bound ribosomes.
22
Q
What is the structure of the cell wall in plant cells?
A
Made of microfibrils of cellulose.
23
Q
What is the structure of the cell wall in fungal cells?
A
Made of chitin.
24
Q
What is the structure of the cell wall in bacterial cells?
A
Made of murein.
25
What is the structure of a cell vacuole?
Fluid-filled and surrounded by a single membrane called a tonoplast.
26
What are the characteristics of prokaryotic cells?
Prokaryotic cells are smaller, have no membrane-bound organelles, and have smaller 70S ribosomes.
27
Do prokaryotic cells have a nucleus?
No, they have circular DNA not associated with histones.
28
What is the composition of the prokaryotic cell wall?
Made of murein instead of cellulose or chitin.
29
What are plasmids in prokaryotes?
Loops of DNA.
30
What is the function of the capsule in prokaryotes?
Helps agglutination and adds protection.
31
What is the purpose of flagella in prokaryotes?
For movement.
32
What is the function of the cell vacuole?
Makes cells turgid - structural support.
## Footnote
Temporary store of sugars, amino acids; coloured pigments attract pollinators.
33
How do protein carriers function?
Bind with a molecule, e.g., glucose, causing a change in the shape of the protein.
## Footnote
This change in shape enables the molecule to be released to the other side of the membrane.
34
What are carrier proteins?
Proteins that bind with molecules to facilitate their transport across the membrane.
35
What are protein channels?
Tubes filled with water enabling water-soluble ions to pass through the membrane.
## Footnote
Selective; channel proteins only open in the presence of certain ions when they bind to the protein.
36
What are the features of viruses?
Viruses are non-living and acellular. They contain genetic material, a capsid, and attachment proteins. Some viruses, like HIV, contain a lipid envelope and enzymes such as reverse transcriptase.
37
What are the three types of microscopes?
The three types of microscopes are: Optical (light) microscopes, Scanning electron microscopes (SEM), and Transmission electron microscopes (TEM).
38
What is magnification?
Magnification is how many times larger the image is compared to the object. It is calculated using the equation: Magnification = Image size / Actual size.
39
What is resolution in microscopy?
Resolution is the minimum distance between two objects in which they can still be viewed as separate. It is determined by the wavelength of light (for optical microscopes) or electrons (for electron microscopes).
40
What is the principle of optical microscopes?
A beam of light is used to create an image, and a glass lens is used for focusing, producing a 2D coloured image.
41
What are the limitations of optical microscopes?
They have poorer resolution due to the long wavelength of light, lower magnification, and can only view living samples. A simple staining method is used, and a vacuum is not required.
42
What is the principle of transmission electron microscopes (TEMs)?
A beam of electrons passes through the sample to create an image, focused using electromagnets, producing a 2D black & white image.
43
What can be observed using transmission electron microscopes?
They can see the internal ultrastructure of a cell, where structures absorb electrons and appear dark.
44
What are the advantages of transmission electron microscopes?
They have the highest resolving power and high magnification.
45
What are the limitations of transmission electron microscopes?
Extremely thin specimens are required, a complex staining method is needed, specimens must be dead, and a vacuum is required.
46
What is a scanning electron microscope?
A device where a beam of electrons passes across a sample to create an image, focused using electromagnets.
47
What type of image does a scanning electron microscope produce?
A 3D, black and white image.
48
What is the evaluation of scanning electron microscopes?
They have high resolving power, high magnification, and can use thick specimens.
49
What are some limitations of scanning electron microscopes?
They require complex staining methods, specimens must be dead, and a vacuum is required.
50
Why is calibration of the eyepiece graticule necessary?
Calibration is required each time the objective lens is changed to determine the distance between each division at that magnification.
51
What is the purpose of cell fractionation?
To break open cells and remove cell debris so organelles can be studied.
52
What is homogenisation?
Process by which cells are broken open so organelles are free to be separated.
## Footnote
Done using homogeniser (blender).
53
What are the conditions for homogenisation?
Cold reduces enzyme activity preventing organelle digestion. Isotonic prevents movement of water by osmosis - no bursting/shrivelling of organelles. Buffered resists pH changes preventing organelle + enzyme damage.
54
What is ultra-centrifugation?
Homogenate solution filtered to remove cell debris, then placed in a centrifuge which spins at low speed initially and then increasingly faster speeds to separate organelles according to their density.
55
What is differential centrifugation?
Supernatant first out (spun at lowest speed) is most dense = nuclei, spun at higher speeds: chloroplasts -> mitochondria -> lysosomes -> RER/SER -> ribosomes (least dense).
56
What is Binary Fission?
Involves circular DNA & plasmids replicating. Cytokinesis creates two daughter nuclei. Each daughter cell has one copy of circular DNA and a variable number of plasmids.
57
What are the stages of the cell cycle?
1) Interphase (G1, S, G2) 2) Nuclear division - mitosis or meiosis 3) Cytokinesis
58
What occurs during Interphase?
Longest stage in the cell cycle when DNA replicates (S-phase) and organelles duplicate while the cell grows (G1 & G2-phase). DNA replicates and appears as two sister chromatids held by a centromere.
59
What is Mitosis?
One round of cell division resulting in two diploid, genetically identical daughter cells. It is involved in growth and repair (e.g. clonal expansion) and is comprised of prophase, metaphase, anaphase, and telophase.
60
What happens during Prophase?
Chromosomes condense and become visible. The nuclear envelope disintegrates. In animals, centrioles separate and spindle fibre structure forms.
61
What occurs during Metaphase?
Chromosomes align along the equator of the cell. Spindle fibres released from poles attach to the centromere and chromatid.
62
What is the main event in Anaphase?
Spindle fibre contracts (using ATP) to pull chromatids, centromere first, towards opposite poles of the cell. The centromere divides in two.
63
What happens to chromosomes during Anaphase?
Chromosomes at each pole become longer and thinner again.
64
What occurs during Telophase?
Spindle fibres disintegrate and the nucleus reforms.
65
What is the mitotic index?
Used to determine the proportion of cells undergoing mitosis.
## Footnote
Mitotic index = The number of cells in mitosis / The total number of cells × 100 for percentage.
66
How is the mitotic index calculated?
Calculated as a percentage or decimal.
67
What does the fluid mosaic model describe?
Describes the lateral movement of membranes with scattered embedded intrinsic and extrinsic proteins.
68
What components are found in the fluid mosaic model?
Contains glycoproteins, glycolipids, phospholipids, and cholesterol.
69
How do phospholipids align in membranes?
Phospholipids align as a bilayer with hydrophilic heads attracted to water and hydrophobic tails repelled by water.
70
What role does cholesterol play in membranes?
Present in eukaryotic organisms to restrict lateral movement of the membranes and adds rigidity to the membrane.
## Footnote
Cholesterol makes membranes resistant to high temperatures and prevents water and dissolved ions from leaking out.
71
What is a selectively permeable membrane?
A membrane that allows only certain molecules to pass through based on specific properties.
72
What types of molecules can pass through the plasma membrane?
Lipid soluble molecules (e.g., hormones like oestrogen), very small molecules, and non-polar molecules (e.g., oxygen).
73
What is simple diffusion?
The net movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.
## Footnote
It is a passive process.
74
What is facilitated diffusion?
A passive process that uses protein channels or carriers to move molecules down the concentration gradient.
## Footnote
It is used for ions and polar molecules (e.g., sodium ions) and large molecules (e.g., glucose).
75
What is osmosis?
The net movement of water from an area of higher water potential to an area of lower (more negative) water potential across a partially permeable membrane.
76
What is water potential?
The pressure created by water molecules, measured in kPa and represented by the symbol U. Pure water has a water potential of 0 kPa.
## Footnote
The more negative the water potential, the more solute must be dissolved.
77
What is a hypertonic solution?
A solution with a water potential more negative than that of the cell, causing water to move out of the cell by osmosis.
## Footnote
Both animal and plant cells will shrink and shrivel.
78
What is a hypotonic solution?
A solution with a water potential more positive (closer to zero) than that of the cell, causing water to move into the cell by osmosis.
## Footnote
Animal cells will lyse (burst) and plant cells will become turgid.
79
What is an isotonic solution?
A solution where the water potential is the same as the water potential inside the cell, resulting in no net movement of water.
## Footnote
Cells would remain the same mass.
80
What is active transport?
The movement of ions and molecules from an area of lower concentration to an area of higher concentration using ATP and carrier proteins.
81
What is the role of carrier proteins in active transport?
Carrier proteins act as selective pumps to move substances.
82
What happens when molecules bind to the receptor in active transport?
ATP will bind to the protein on the inside of the membrane and is hydrolysed to ATP/Pi.
83
What occurs after ATP is hydrolysed in active transport?
The protein changes shape and opens inside the membrane.
84
What is co-transport?
The movement of two substances across a membrane together, when one is unable to cross the membrane itself.
85
What is required for co-transport?
It involves a cotransport protein and active transport.
86
Give an example of co-transport.
Absorption of glucose/amino acids from the lumen of intestines.
87
What types of molecules can lymphocytes identify?
Pathogens (bacteria, fungi, viruses), cells from other organisms of the same species (transplants), abnormal body cells (tumour cells), and toxins (released from bacteria).
88
What are antigens?
Proteins on the cell-surface membrane that trigger an immune response when detected by lymphocytes.
89
What is antigenic variability?
When pathogenic DNA mutates causing a change in shape of antigen, making previous immunity ineffective.
90
What happens to memory cells during antigenic variability?
Memory cells don't recognize the new shape of the antigen, so specific antibodies no longer bind.
91
What are physical barriers in the immune system?
Anatomical barriers to pathogens, such as skin, stomach acid, and lysozymes in tears.
92
What is the role of phagocytes in the immune response?
Phagocytes become antigen-presenting cells after destroying a pathogen.
93
What are T lymphocytes?
Made in bone marrow and mature in thymus gland.
## Footnote
Involved in cell-mediated immune response.
94
What do T lymphocytes respond to?
They respond to antigen-presenting cells.
## Footnote
Antigen-presenting cells (APCs) present non-self antigens.
95
What are antigen-presenting cells?
Any cell that presents a non-self antigen on their surface.
## Footnote
Examples include infected body cells, macrophages after phagocytosis, cells of transplanted organs, and cancer cells.
96
What is the role of T helper cells?
Have receptors on their surface that attach to antigens on APCs and become activated through clonal selection.
97
What are the roles of cloned T helper cells?
Some remain as helper T cells and activate B lymphocytes, stimulate macrophages for phagocytosis, become memory cells for that shaped antigen, and become cytotoxic killer T cells.
98
What do cytotoxic T cells do?
They destroy abnormal or infected cells by releasing perforin, causing cell death.
99
Where are B lymphocytes made and matured?
B lymphocytes are made and mature in the bone marrow.
100
What is the role of B lymphocytes in the immune response?
They are involved in the humoral immune response and produce antibodies.
101
What happens when an APC activates a B cell?
The B cell undergoes clonal selection and expansion, rapidly dividing by mitosis.
102
What do B cells differentiate into?
They differentiate into plasma cells and memory B cells.
103
What do plasma cells do?
Plasma cells make antibodies.
104
What are B memory cells derived from?
B memory cells are derived from B lymphocytes.
105
What is the function of B memory cells?
They remember specific antibodies for particular antigens and rapidly divide and differentiate into plasma cells upon secondary encounter.
106
What are antibodies?
Proteins made of four polypeptide chains.
107
What is the variable region of an antibody?
The different shaped binding site that is complementary to a specific antigen.
108
What is the structure of an antibody?
Consists of a light chain, heavy chain, variable region, and constant region.
109
What is agglutination?
The process by which antibodies clump pathogens together, making it easier for phagocytes to locate and destroy them.
110
What is passive immunity?
Immunity where antibodies are introduced into the body without the production of plasma and memory cells.
## Footnote
It results in short-term immunity and is fast acting.
111
What is active immunity?
Immunity created by own immune system - antibodies made.
## Footnote
Involves exposure to antigen.
112
What are the characteristics of natural active immunity?
After direct contact with pathogen through infection, the body creates antibodies and memory cells.
## Footnote
Provides long term immunity.
113
What is artificial active immunity?
Creation of antibodies and memory cells following introduction of an attenuated pathogen or antigens.
## Footnote
This is achieved through vaccination.
114
What are vaccinations?
Small amounts of dead or attenuated pathogens injected/ingested to activate the humoral response.
## Footnote
Memory cells can divide rapidly into plasma cells when re-infected.
115
What is the role of memory cells in active immunity?
Memory cells are able to divide rapidly into plasma cells when re-infected.
## Footnote
This contributes to long-term immunity.
116
What is the primary response?
The primary response is the body's first exposure to a pathogen, resulting in a longer time for plasma cell secretion and memory cell production.
117
What occurs during the secondary response?
During the secondary response, memory cells divide rapidly into plasma cells, leading to a large number of antibodies being made rapidly upon reinfection.
118
What is herd immunity?
Herd immunity occurs when enough of the population is vaccinated so that the pathogen is not transmitted and spread easily, providing protection for those without the vaccine.
119
What are monoclonal antibodies?
Monoclonal antibodies are a single type of antibody that can be isolated and cloned, identical and derived from one type of B lymphocyte, and complementary to only one antigen.
120
What are the uses of monoclonal antibodies?
Monoclonal antibodies are used in medical treatment to target drugs by attaching to antibodies complementary to tumor cell antigens and in medical diagnosis, such as pregnancy tests.
121
What is the primary response?
The primary response is the body's first exposure to a pathogen, resulting in a longer time for plasma cell secretion and memory cell production.
122
What occurs during the secondary response?
During the secondary response, memory cells divide rapidly into plasma cells, leading to a large number of antibodies being made rapidly upon reinfection.
123
What is herd immunity?
Herd immunity occurs when enough of the population is vaccinated so that the pathogen is not transmitted and spread easily, providing protection for those without the vaccine.
124
What are monoclonal antibodies?
Monoclonal antibodies are a single type of antibody that can be isolated and cloned, identical and derived from one type of B lymphocyte, and complementary to only one antigen.
125
What are the uses of monoclonal antibodies?
Monoclonal antibodies are used in medical treatment to target drugs by attaching to antibodies complementary to tumor cell antigens and in medical diagnosis, such as pregnancy tests.
126
What is the purpose of the ELISA test?
To detect the presence and quantity of an antigen, used for medical diagnosis.
## Footnote
Example: Testing for hCG in pregnancy tests.
127
What does the ELISA test utilize?
It uses 3 monoclonal antibodies and enzymes to test for hCG.
128
What are ethical issues associated with monoclonal antibodies?
They require mice to produce antibodies and tumor cells, and a full cost-benefit analysis is necessary.
129
What is the core structure of HIV?
The core consists of RNA and reverse transcriptase.
130
What is the function of the HIV capsid?
It serves as a protein coat.
131
What is the lipid envelope of HIV derived from?
It is taken from the host's cell membrane.
132
What do attachment proteins in HIV do?
They allow HIV to attach to Helper T cells.
133
What receptor does HIV attach to on helper T cells?
HIV attaches to the CD4 receptor on helper T cells.
134
What happens after HIV fuses with the cell membrane?
RNA and enzymes enter the cell.
135
What is the role of reverse transcriptase in HIV replication?
It makes a DNA copy of the viral RNA, which is then inserted into the nucleus.
136
What occurs in the nucleus during HIV replication?
The nucleus synthesizes viral proteins.
137
What happens when HIV destroys too many T helper cells?
The host is unable to produce an adequate immune response to other pathogens.
138
What makes the host susceptible to opportunistic infections?
The destruction of T helper cells by HIV.
139
What is the first step in the ELISA process?
The first antibody added is complementary to the antigen in the well and attaches.
140
What happens after the first antibody attaches in ELISA?
A second antibody with an enzyme is added, which attaches to the first antibody.
141
What is the result of adding a substrate solution in ELISA?
The enzyme can produce a color change.
142
What is a potential risk of an inactive virus?
It may become active, leading to viral transformation.
143
What can happen to a non-pathogenic virus?
It can mutate and harm cells.
144
What are some side effects of the immune response?
People may test positive for the disease.
145
Why are antibiotics ineffective against viruses?
Viruses are inside host cells where antibiotics cannot reach. Antibiotics affect parts of bacteria that viruses do not have (e.g the cell wall).
146
What is the purpose of washing well in ELISA?
Removes unbound 2nd antibodies; otherwise, enzyme may be present → colour change → false positive.
147
What are pathogens?
Microorganisms that cause a disease by releasing toxins or killing cells/tissues.
148
What is cytokinesis?
Final stage in the cell cycle when the cytoplasm splits in two, creating two new cells.
149
What can uncontrolled cell division lead to?
Uncontrolled cell division can lead to the formation of tumours and cancers.
150
What are many cancer treatments directed at?
Many cancer treatments are directed at controlling the rate of cell division.
151
What happens during viral replication?
Following injection of their nucleic acid, the infected host cell replicates the virus particles.
152
What are cell adaptations for rapid transport across membranes?
Increase in surface area or membrane; increase in the number of protein channels and carrier molecules in the membranes.
153
What is the antigen-antibody complex?
When a complementary antibody binds to an antigen, this clumps pathogens together (agglutination).
