Unit 2 Biology - Cells Flashcards
1
Q
What are the two main types of cells?
A
Eukaryotes and Prokaryotes.
2
Q
Which are larger, eukaryotes or prokaryotes?
A
Eukaryotes.
3
Q
What are the main organelles shared by most animal cells?
A
Mitochondria, nucleus, ribosomes, endoplasmic reticulum, golgi apparatus, lysosomes.
4
Q
What are the main organelles of plant cells?
A
All animal cell organelles + Vacuole, Chloroplasts and a cell wall.
5
Q
What are the main organelles of fungal cells?
A
Same as plant cells - chloroplasts and they use chitin in cell walls rather than cellulose.
6
Q
What is cell specialisation?
A
The process by which cells develop specific functions and structures to take on certain roles.
7
Q
How are muscle cells specialised to perform their function?
A
Lots of mitochondria in order to produce ATP as they are very active.
8
Q
How are red blood cells specialised to perform their function?
A
They have a biconcave shape and no nucleus to maximise their oxygen carrying. Also have lots of haemoglobin.
9
Q
How are palisade cells specialised to perform their function?
A
They have a long, upright shape and contain chlorophyll to absorb light for photosynthesis.
10
Q
Do both Eukaryotes and Prokaryotes have a plasma membrane?
A
Yes.
11
Q
What are plasma cell membranes?
A
Phospholipid bilayers with proteins and cholesterol molecules embedded in them.
12
Q
What is the function of the plasma membrane?
A
The plasma membrane controls the passage of organic molecules, ions, water and oxygen throughout the cell.
Waste products leave the cell via the membrane.
13
Q
What is the structure of the cytoplasm?
A
Cytoplasm is made up of organelles suspended in the gel-like cytosol.
The cytoplasm contains proteins, sugar, ions and fatty acids.
14
Q
What is the function of the cytoplasm?
A
Metabolic reactions take place here.
Organelles perform functions in the cell whilst suspended in the cytoplasm.
15
Q
What is the nucleus?
A
The nucleus is a big organelle that contains the cell’s DNA.
16
Q
What is the nuclear envelope?
A
A double-membrane structure with a number of pores.
Both membranes are phospholipid bilayers.
17
Q
What is the function of the nuclear envelope.
A
The pores in the nuclear envelope control the passage of ions, molecules and RNA between the nucleoplasm and cytoplasm.
18
Q
What is the structure of the nucleus?
A
There is an area in the nucleus called the nucleolus.
The nucleus contains nucleoplasm, a semi-solid fluid that contains the nucleolus and chromatin.
The nucleus contains linear chromosomes made of DNA.
19
Q
What are the functions of the nucleus?
A
Controls the actions of the cell.
Contains the DNA which has instructions for protein synthesis.
Ribosomal RNA paired with proteins to form ribosomal sub-units.
20
Q
What is chromatin
A
A complex of DNA and protein found in eukaryotic cells.
21
Q
What is the structure of mitochondria?
A
Oval shaped, double membrane organelles that have their own ribosomes and DNA.
Each membrane is a phospholipid bilayers embedded with proteins.
The inner layer of the membrane has folds called cristae.
The area surrounded by the fold is called the mitochondrial matrix, which contains enzymes for respiration.
22
Q
What is the function of mitochondria?
A
Makes ATP for respiration.
23
Q
What is the structure of chloroplasts?
A
They have their own DNA, ribosomes and membranes. (inner and outer)
The space inside contains fluid filled stacks of membrane sacs called thylakoids.
Each stack is called a granum.
24
Q
What is the function of chloroplasts?
A
Photosynthesis in plants to make their own food.
They are only found in plant and algal cells.
25
What is the structure of the Golgi Apparatus?
It is a series of flattened membranous sacs.
26
What is the function of the Golgi Apparatus?
They release Golgi vesicles.
They package and tag proteins and lipids.
27
What is the structure of Golgi vesicles?
They are membrane-bound. fluid filled vesicles located in the cytoplasm.
They are small and round.
Lysosomes are a type of Golgi vesicle.
28
What is the function of Golgi vesicles?
They store and transport modified proteins and lipids from the Golgi apparatus to target cells.
Lysosome vesicles contain lysozyme enzymes that aid the breakdown of proteins, polysaccharides, lipids, nucleic acids and old organelles.
29
What is the structure of ribosomes?
They can be free-floating in cytoplasm or attached to the ER.
They are very small and made of protein sub-units.
They are not membrane-bound.
30
What is the function of ribosomes?
They are in charge of protein synthesis.
This is why they are present in practically every cell.
31
What is the structure of the Endoplasmic Reticulum?
A series of interconnected membranous sacs and tubules.
Membrane is a phospholipid bilayers embedded with proteins.
The Smooth ER has no ribosomes but the Rough ER has many.
32
What is the function of the Endoplasmic Reticulum?
RER: Responsible for processing and folding proteins.
SER: Makes and processes lipids.
33
What is the structure of the Cell wall?
In plant and algal cells it is a cellulose wall that protects the cell.
34
What is the function of cell walls?
Provides structural support and provides shape to the cell.
35
What is the structure of the cell Vacuole?
Surrounded by a membrane called the tonoplast and contain a weak solution of salts and sugars called cell sap.
Found in the cytoplasm of plant cells.
36
What is the function of the cell Vacuole?
Allows the cell to remain rigid.
Can store chemicals/waste.
Stores nutrients and water.
37
How is DNA presented in prokaryotes?
Can be found as a circular molecule in the cytoplasm.
Some prokaryotes have small off-shoots called plasmids which are not part of the main DNA.
Bacteria can exchange plasmids.
38
What are flagella, puli and fimbriae?
Flagella are tail-like, used for motion.
Pili are used to exchange genetic info during conjugation.
Fimbriae are used by bacteria to attach to a host.
39
What is binary fission?
The way in which unicellular organisms such as prokaryotes reproduce.
40
What is the process of binary fission?
1. Replication of genetic info and plasmids.
2. The two sets of genetic material migrate towards opposite poles.
3. The cytoplasm divides.
4. Two identical daughter cells.
41
What is the structure of viruses?
They are made up of nucleic acids, surrounded by a capsid.
They are smaller than bacteria.
42
Why are viral cells not considered to be living?
They have no nucleus, membrane, cytoplasm or ribosomes.
They are not made of cells.
They cannot reproduce independently.
43
How do viruses replicate?
They invade and hijack a host cell with glycoproteins that bind to complementary receptors on the cell.
They then inject nucleic acid into the cell meaning that when the host cell divides, the virus replicates.
44
What is the equation for magnification?
Magnification = Size of image / Size of object.
45
What is resolution in microscopy?
The ability of a microscope to distinguish two adjacent structures as separate.
The higher the resolution, the better the clarity of the image.
46
What is cell fractionation?
The process of separating organelles according to size to allow them to be studied in an electron microscope.
47
What is homogenisation?
When the cell tissue’s membrane is broken to release the organelles. This is usually done in a blender.
48
What are the conditions that the tissue sample must be kept in during homogenisation?
Ice cold (reduces enzyme activity that may damage organelles)
Isotonic solution (prevents osmosis that may burst organelles)
Buffered solution (keeps pH constant and avoids damaging protein structures)
49
What are the 4 steps of cell fractionation?
Homogenisation, Filtration, Ultracentrifugation, Order of fractionation.
50
What is filtration in cell fractionation?
The tissue sample is filtered into tubes via a gauze.
The gauze separates large components from small organelles.
51
What is ultracentrifugation in cell fractionation?
The samples are spun at a low speed in a centrifuge.
Heavier samples are forced to the bottom of the tube and lighter organelles move to the top.
Cell debris such as cell walls form a pellet at the bottom, leaving the liquid (supernatant) containing the organelles.
This process is repeated at increasingly higher speeds.
52
What is the order of fractionation?
After being in the centrifuge, organelles are ordered in fractions from heaviest to lightest.
53
What is the cell cycle?
Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication and division.
54
What are the two major phases of the cell cycle?
Interphase (cell growth and DNA replication)
Mitotic phase (separation of cell content and division)
55
What are the two types of cell division in eukaryotes?
Mitosis and meiosis.
56
What are the three stages of interphase?
G1: the cell grows.
S: DNA synthesis occurs.
G2: more cell growth.
57
What is the mitotic phase?
The part of the cell cycle in which the cell divides to form two identical daughter cells, each with identical copies of DNA.
58
What are the stages of mitosis before interphase?
Prophase, metaphase, anaphase and telophase.
59
What happens in prophase?
The nuclear envelope breaks down and nucleolus disappears, leaving chromosomes in the cytoplasm.
Chromosomes coil tightly.
Centrioles move to the poles of the cell.
Microtubules form mitotic spindle between centrioles.
60
What happens in metaphase?
Chromosomes line up along the middle of the cell. They are maximally condensed.
They are attached to the mitotic spindle by the centromere.
61
What happens in anaphase?
Chromosomes break into two chromatids, which separate at the centromere.
Spindles contract and pull them to each pole of the cell.
62
What occurs in telophase?
The chromatids reach the opposite poles and begin to decondense to become chromosomes again.
New nuclear envelopes are formed.
The cytoplasm splits and two daughter cells are formed.
63
What occurs after telophase?
The cell cycle starts again with interphase and it is repeated.
64
What is the equation for the mitotic index?
Mitotic index = number of cells in mitosis / total number of cells.
65
What is the cell mechanism that allows cancer?
Uncontrolled cell division.
66
How are tumours created?
Small uncorrected errors are passed to daughter cells.
Each generation of cells produces more non-functional proteins.
Mutations accumulate and may uncontrollably grow.
67
How do mutations cause cancers?
All cancers start when a mutation gives rise to a faulty protein that plays a role in cell reproduction.
68
What is a mutation?
Change in the structure of a gene due to the alteration of single base units in DNA resulting in variation.
69
What factors impact membrane permeability?
Temperature, pH, solvent concentration.
70
How does temperature impact membrane permeability?
Higher temperature increases the fluidity, increasing the permeability.
71
How does pH impact membrane permeability?
pH impacts protein structure in the cell.
72
How does solvent concentration impact cell membrane permeability?
The more easily dissolvable the bilayer, the more permeable it is.
73
What is diffusion?
Diffusion is the passive movement of particles in a high concentration to a low concentration down a concentration gradient.
74
What is facilitated diffusion?
When molecules diffuse through carrier or channel proteins across the membrane as they are too large or polar and are repelled by the membrane.
75
What are channel proteins? Give an example.
They are proteins that allow polar compounds to avoid the non-polar layer of the plasma membrane.
E.g Aquaporins allow water to pass through.
76
What are carrier proteins?
Substances bind to these as they allow passage through the membrane when they change shape.
77
What are some factors that impact the rate and of diffusion?
Concentration gradient, temperature, membrane surface area, membrane thickness and transport proteins.
78
How does concentration gradient impact the rate of diffusion?
The bigger the difference in concentration in two areas, the greater the gradient and the faster the rate of diffusion.
79
How does temperature impact rate of diffusion?
The higher the temp, the faster the rate.
80
How does membrane surface area impact the rate of diffusion?
The larger the SA of the membrane, the faster the rate of diffusion.
81
How does the thickness of a membrane impact the rate of diffusion?
The thicker it is, the slower the rate is.
82
How do transport proteins impact the rate of diffusion?
The more proteins, the faster the rate.
83
What is osmosis?
Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution to a concentrated solution.
84
What is meant by a partially permeable membrane in osmosis?
A membrane that only allows water through, but not larger molecules dissolved in water.
85
How does water move in osmosis?
It moves down a concentration gradient (no energy) in order to make the water potential the same on both sides of the membrane.
86
What is meant by water potential?
The likelihood of water molecules diffusing.
87
What factors impact the rate of osmosis?
Water potential gradient, membrane thickness and surface area.
88
What is active transport?
A process that moves substances from an area of low to high concentration, against the gradient and requiring energy.
89
What are the main factors impacting active transport?
The SA of cell membranes.
The number of carrier proteins.
90
What are two examples of active transport?
Mineral absorption in plants for ions.
Sugar absorption in the gut for respiration.
91
What is co-transport?
A mechanism of transport for glucose and amino acids into the epithelial cells in the ileum. Sodium bonds to co-transporter proteins to carry the molecules.
92
What is the immune system?
Specialised cells that respond specifically to foreign objects and protect an individual from harm.
93
What do cells in the immune system detect?
Abnormal body cells (cancer cells), cells from other organisms, toxins (secreted by pathogens), pathogens.
94
What are antigens?
Molecules that are present on the membrane of all cells.
They signal to the immune system if a cell is foreign.
95
How is the immune response triggered?
When an antibody from an immune cell binds to a foreign antigen.
96
What are the four stages of the immune response?
Phagocytosis (non-specific), activation of T cells, B cells and antibody production.
97
What is phagocytosis?
When pathogens are engulfed and infested by phagocytes, which are a type of white blood cell.
The pathogens are destroyed by enzymes.
98
What is meant by the activation of T cells?
T lymphocyte cells are activated after phagocytosis.
There are two types: helper T cells and cytotoxic T cells.
This is the cellular response.
99
What is the activation of B cells?
T helper cells activate B lymphocyte cells, which divide into plasma cells.
This is the humoral response.
100
What is the production of antibodies?
Plasma cells secrete antibodies, which are proteins that bind to specific antigens on pathogens.
101
What are the stages of phagocytosis?
1. Foreign antigen bind to phagocyte receptor proteins.
2. The phagocyte engulfs the pathogen and puts it in a phagosome. (vacuole)
3. The phagocyte has lysosomes which bind with the phagosome to release proteolytic enzymes into the pathogen.
4. Pathogenic antigens are presented on the cell surface to signal to other cells.
102
What are the steps involved in the T-lymphocyte process?
1. The T-helper cells bind to the pathogen’s antigens on the phagocyte.
2. T-helper cells activate more phagocytes, T-cytotoxic cells and B-cells.
3. T-Cytotoxic cells release toxins that kill foreign cells in the body.
103
What are the steps in the process of B-lymphocytes?
1. Divide into identical plasma cells until they get the matching receptor (clonal selection)
2. The B-cell then divides to produce identical plasma cells that have the antibodies (clonal expansion)
3. Antibodies attach to the pathogen antigens.
4. Aggulationn clumps the pathogens together to be engulfed by phagocytes.
104
What are antibodies?
They are proteins produced by plasma cells during the immune response. These are called monoclonal antibodies.
105
What are variable regions in an antibody?
Each antibody has two different variable regions.
They bind specifically to specific antigens.
One can bind to two antigens, good for aggulation.
106
What are constant regions in antibodies?
Each one has the same constant region.
107
What role do disulphide bridges have in antibodies?
They connect the two heavy and two light chains.
108
What is the role of the hinge protein in antibodies?
It connects the variable region and the constant region in antibodies.
109
How can monoclonal antibodies be used medically?
Medical diagnosis: Used to indicate the presence of a specific antigen e.g HCG in pregnancy tests.
Targeted medication: Binding specifically to the antigens on cancer cells.
110
What is the ELISA test?
Enzyme-linked immunosorbent assay.
Tests for infections.
111
What are the steps of ELISA testing?
1. The antigen being tested for is immobilised at the bottom of a beaker.
2. A sample of blood is added to the beaker to test for antibody binding.
3. The beaker is washed.
4. Secondary antibody bound to an enzyme is added.
5. A solution is added and if a colour change is observed the patient is infected.
112
What is primary immune response?
The response that an individual omits after being infected by a pathogen for the first time.
It is slow as it takes time for the antigens to be detected.
113
What are memory cells and what are they produced by?
Produced by T and B cells, memory cells remain in the body and make it much quicker for the immune system to detect a specific pathogen.
114
What is the secondary immune response?
When an individual is infected with a pathogen for the second time.
Response is much quicker due to memory cells as they can produce the correct antibodies.
115
What is a vaccine?
A weakened version of a pathogen that is inserted into the body either orally or by injection.
116
How does a vaccine work?
Vaccines induce the primary response.
This involves the creation of memory cells.
These cells provide immunity.
117
What is the purpose of booster vaccinations?
They may be given over time to make sure memory cells are still in the body.
118
Why are vaccinations continuously being changed?
Antigens are evolving at a rapid rate to avoid detection from the immune system. E.g HIV.
119
What is meant by herd immunity?
It’s the concept that if enough people in a population are immune against a disease, the entire population are less likely to be infected.
120
What is passive immunity?
Where an individual receives antibodies from an external source. This can either be natural (antibodies in breast milk) or artificial (an injection).
121
What is active immunity?
Where the immune system has created its own antibodies. These may be natural (in response to a pathogen) or artificial (in response to a vaccine).
122
What is the structure of HIV?
There is a capsid in the centre which contains genetic information and enzymes.
The genetic information is two strands of RNA.
This is all enclosed by a viral envelope, which has glycoproteins on its surface.
123
What enzymes does HIV contain?
Reverse transcriptase and integrase.
124
How does HIV replicate?
1. Glycoproteins bind to proteins on the T-helper cells.
2. The capsid is then injected into the cells, including the enzymes and RNA.
3. Reverse transcriptase converts RNA into double-stranded DNA.
4. Integrase moves this into the nucleus.
5. Genes in HIV DNA are expressed in the helper cell and new HIV proteins and RNA is made.
6. New HIV viruses are released.
125
How does AIDS develop from HIV?
During replication, the T-cells are killed and the immune system is weakened.
This makes an individual more vulnerable to infections from other pathogens.
126
How can HIV potentially be treated?
Antiviral drugs can be produced to target reverse transcriptase enzyme.
