1
Q
What is the role of the mitochondrion?
A
The mitochondrion are usually oval-shaped organelles which produces ATP through aerobic respiration (Krebs cycle and oxidative phosphorylation). They are found in large numbers in cells.
2
Q
What are the structures within the mitochondrion?
A
Double membrane, cristae, matrix
3
Q
What is the role of the double membrane in the mitrochondria?
A
The outer membrane controls entry and exit of material and the inner membrane is folded to form cristae
4
Q
What is the cristae and what is it’s role?
A
It is the inner membrane extentions and it increases the surface area for enzymes and protiens
5
Q
What is the matrix and what is it’s role?
A
The matrix is remainder of the mitochondrion containing proteins, lipids,ribosomes and DNA
6
Q
What is the golgi apparatus and what is it’s role?
A
The golgi apparatus is a stack of fluid-filled flattened sacs (cisternae) with vesicles.Proteins and lipids produced by the ER are modified here. Glycoprotiens/ lipids are produced and are accurately sorted and transported to the correct destination.
7
Q
What is the vacuole and what is it’s role?
A
A membrane-bound sac which contains a solution of minerals, salts, sugars, amino acids, wastes and anthocyanins. Turgidity to herbaceous means good food store and attraction for pollination. They help maintain pressure inside the cell and keep it ridged.
8
Q
What are the chloroplast are what is its role?
A
Chloroplasts are disc shaped organelles (2-10 um) that carry out photosynthesis.
9
Q
What are the structures within the chloroplasts?
A
Envelope, Grana, Stroma
10
Q
What is the envelope in the chloroplasts?
A
The envelope is a selectively permeable double plasma membrane surrounding the organelle.
11
Q
What is grana in the chloroplasts and what is its purpose?
A
A stack of approximately 100 thylakoids containing chlorophyll- the first stage of photosynthesis occurs here.
12
Q
What is the stroma and what is its role in the chloroplasts?
A
The stroma is fluid-filled matrix where the second stage of photosynthesis takes place
13
Q
What are lysosomes?
A
Lysosomes are a type of Golgi vesicle and are formed when Golgi vesicles contains enzymes such as lysozyme that hydrolyse walls of bacteria cells. Contain up to 50 enzymes, lysosomes isolate the enzymes from the rest of the cell before releasing them outside or into the phagocytevesicle.
14
Q
What is the nucleus and what is its role?
A
The spherical nucleus (10-20um) contains hereditary material and regulates cell activities.
15
Q
What structures are located in the nucleus?
A
The nucleus contains nuclear pore, nuclear envelope, nucleoplasm and the nucleolus.
16
Q
What does the size of the nucleus depend on?
A
The size will vary depending on what stage of the cell cycle it is at.
17
Q
What is the nuclear envelope and what is its role?
A
The nuclear envelope is a double membrane associated with the ER that the surrounds the nucleus and controls the movement of genetic material.
18
Q
What is the role of the nuclear pores?
A
There are around 3000 nuclear pore (40-100nm) that allow the passage of large molecules.
19
Q
What is the nucleoplasm?
A
The nucleoplasm is a granular jelly- like material the suspends the nucleus bound structures.
20
Q
What are chromosomes?
A
They are protein bound linear DNA.
21
Q
What is the role of the nucleolus?
A
It manufactures ribosomal RNA and assembles the ribosomes. There may be more than one.
22
Q
Ribosomes:
A
80s- eukaryotic (25nm)
70s- prokaryotic, mitochondria, and chloroplasts, smaller
It is the site of protein synthesis. They are either attached to the RER or float free in the cytoplasm. They are made up of proteins and RNA and is not surrounded by a membrane.
23
Q
What is the cell wall and what is its function?
A
The cell wall is a rigid structure that surrounds some cell types contains cellulose and micro fibrils which provide considerable strength. Algea has cellulose and/or glycoproteins in the cell wall (stronger). Fungi have no cellulose (weaker), polysaccharide chitin and glycan as glycoproteins.
24
Q
What is the endoplasmic reticulum?
A
The endoplasmic reticulum is sheet like membranes spreading throughout the cytoplasm enclosing a network of tubules and flattened sacs called cisternae.
25
What is the role of the RER?
The rough endoplasmic reticulum has a large surface for ribosomal synthesis of proteins and glycoproteins. Provides a pathway for protein transport.
26
What is the role of SER?
The smooth endoplasmic reticulum lacks ribosomes and is tubular in appearance. Its function is for synthesis, storage and transport of lipids and carbohydrate.
27
What is a Golgi vesicle and what is its role?
The Golgi vesicle is a small fluid filled sac in the cytoplasm, surrounded by a membrane and is produced by the Golgi apparatus. They store lipids and proteins made by the Golgi apparatus and transports them out of the cell.
28
What is the cell surface membrane and what is its function?
The cell surface membrane is a membrane found on the surface of animal cells and just inside the cell wall of other cells. Its mainly made of lipids and proteins. It regulates the movement of substances into and out of the cell. It also has receptor molecules on it which allow it to respond the chemicals like hormones.
29
What measurement can a light microscope distinguish between?
Light microscopes can only distinguish 2um
30
What measurement can an electron microscope distinguish between?
Electron microscopes uses beams of electrons and can distinguish between 0.1nm
31
What are the two examples of electron microscopes?
Transmission electron microscope (TEM) and Scanning electron microscopes (SEM)
32
What is resolution?
The minimum distance apart that two objects can be in order to see them apart
33
What is magnification?
How many times bigger the image is compared to the actual object
34
What is the magnification equations?
I= AxM
A= I/M
M= I/A
35
What is cell fractionation?
Cell are broken up and organelles separated out
36
What are the three main stages of cell fractionation?
- Homogenisation
- Filtration
- Ultracentrifugation
37
What is homogenisation/ what does it consist of?
Cells are broken up using a homogeniser (blender). This breaks the plasma membrane of the cells and releases the organelles into a solution called the homogenate
38
Describe three properties of the solution (homogenate) and explain how each property prevents damage to organelles
- Cold: reduces enzyme activity
- Buffered: maintains pH to prevent enzyme/proteins becoming denatured
- Same water potential of the cell: prevents osmosis so no lyisis
39
What is differentiation?
Differentiation is the process cells undergo to become specialised
40
What happens in cells in order for them to become specialised? (genes)
All cells contain all instructions but only some can be switched on (expressed) in any one cell and the rest switched off (suppressed)
41
What is a pluripotent cell?
A cell that is able to develop into many different types of cells or tissues in the body
42
What is a unipotent cell?
A cell that is able to develop into one type of cell
43
What is a totipotent cell?
A cell the has the ability to develop into a complete organism or differentiate into any type of cell or tissue
44
What is the second stage of cell fractionation?
Filtration
45
What is the third process of cell fractionation?
Ultracentrifugation
46
What is ultracentrifugation/ what does it consist of?
The filtrate is placed into a tube and the tube is placed in a centrifuge. Filtrate is spun in a centrifuge at increasing speeds. Heaviest organelles stay suspended in the solution above the pellet. This solution is known as the supernatant.
Supernatant in re-spun at higher speeds to isolate lighter organelles.
47
What is a centrifuge?
A centrifuge is a machine the separates material by spinning
48
List the order of separation (heaviest to lightest)
- Nuclei
- Chloroplast (in plants)
- Mitochondria
- Lysosomes
- Endoplasmic reticulum
- Ribosomes
49
How does TEMs work?
TEMs uses a condenser magnet to focus electrons from an electron gun onto a specimen (thin section). The focused electrons are either absorbed (dark) or pass through (bright) and a photomicrograph
50
Advantages of TEMs
- Highest magnification
- Highest resolution
51
Limitations of TEMs
- Need a vacuum so living organisms can’t be observed
- Complex staining still doesn’t produce coloured images
- Specimen must be very thin (complex preparation of slide)
- The image may still contain artefacts (things that shouldn’t be there)
52
Limitations of SEMs
- Need a vacuum so living organisms can’t be observed
- Complex staining still doesn’t produce coloured images
- The image may still contain artefacts (things that shouldn’t be there)
53
How do SEMs work?
Directs beams of electrons back and forth. Electrons are scattered based on the contours on the surface of the specimen. Produces 3D image
54
What are the structures found within bacteria?
- Cell wall
- Ribosomes
- Flagellum
- Pili (small hairs on the surface)
- Nucleoid (single, circular chromosomes/ genetic material)
- Cell membrane
- Plasmid
- Slime capsule
55
What is the cell wall? (PROKARYOTIC)
Physical barrier that excludes certain substances and protects against mechanical damage and osmosis lysis
56
What is the cell surface membrane? (PROKARYOTIC)
Acts as a differentially permeable layer which controls the entry and exit of chemicals
57
What is a capsule? (PROKARYOTIC)
Protects bacterium from other cells and helps groups of bacteria stick together for further protection
58
What is circular DNA? (PROKARYOTIC)
Posses the genetic information for the replication of cells
59
What are plasmids? (PROKARYOTIC)
Posses genes that may aid survival of bacteria in adverse conditions eg. enzyme that breaks down bacteria
60
What structures do viruses contain?
Envelope, viral genome, enzyme, envelope protein and capsids
61
What are viruses know as and why?
Viruses are known as acellular, non-living particles and this is due to them needing a host to reproduce
62
How small are viruses?
20-300nm
63
What is mitosis?
Mitosis is a cell division that results in each daughter cell having an exact copy of the DNA of the parents cell
64
List the stages of mitosis in order
Stage 1: Interphase
Stage 2: Prophase
Stage 3: Metaphase
Stage 4: Anaphase
Stage 5: Telophase and cytokinesis
65
What is involved in Interphase?
DNA replication occurs here. The two copies of DNA after replication remain joined at the centromere. DNA is present as un condensed chromatin. Centrosomes and organelles have been replicated. Cell is enlarged for duplication.
66
What is involved in Prophase?
DNA supercoils and chromosomes condense. Centrosomes move to the opposite poles and form microtubule spindle fibres. Spindle fibres attach to centromeres. Nuclear membrane breaks down
67
What is involved in Metaphase?
Chromosomes align along the equatorial plane of the cell. Microtubule spindle fibres fully connected to the centromere of each chromosome. Microtubule depolymerisation causes spindle fibres to shorten.
68
What is involved in Anaphase?
Continued depolymerisation causes sister chromatids to separate and are pulled apart. Genetically identical chromatids move to opposite poles of the cell
69
What is involved in Telophase?
Once chromosome sets arrive at the poles, spindle fibres dissolve. Chromosomes decondense to form chromatin. Nuclear membrane reforms around each set of chromosomes. Cytokinesis (splitting of cell membrane) occurs concurrently (at the same time)
70
What process do prokaryotic cells undergo to replicate
Binary fission
71
What is filtration/ what does it consist of?
Homogenate is filtered through a gauze to remove large debris. Organelles remain in the filtered solution
72
What are chromatids?
The two identical halves of a replicated chromosome that are joined at the centromere before cell division
73
Describe the process of binary fission
1. Circular DNA and plasmids replicate and both copies attach to the cell membrane
2. Cell membrane begins to grow between the two molecules of DNA and divide the cell into two. Cytoplasm splits
3. A new cell wall forms between the two molecules of DNA dividing the cells into two genetically identical daughter cells
74
CELL CYCLE AND TUMOURS
75
What is the model of the cell membrane called? and break down the name
The arrangement of the various molecules in the cell surface membrane is known as the fluid mosaic model
Fluid= individual phospholipids that can moves relative to one another
Mosaic= the proteins that are embedded vary in shape, size and pattern
76
What are the two main ways that the proteins are embedded and interspersed throughout the bi-layer?
- Some occur in the surface of the bi-layer and never extend across it. They provide mechanical support and act as receptors
- Integral proteins:
Proteins channels are water filled tubes
Carrier proteins bind to substances and change shape to move them across
77
What substances are should within the cell surface membrane?
- Phospholipids
- Channel proteins
- Carrier proteins
- Cholesterol
- Peripheral proteins
- Glycoproteins
- Glycolipids
78
What is the role of cholesterol in the cell surface membrane?
- Reduces fluidity
- Less permeable to small water-soluble molecules
- Separates tails to prevent crystallisation
- Helps anchor peripheral proteins
79
What is the role of glycoproteins in the cell surface membrane?
- Act as cell surface receptors specifically for hormones, neurotransmitters and self-recognition
- Help with adhesion
80
What is the role of glycolipids in the cell surface membrane?
- Extends the membrane into the extra cellular fluid where it is a receptor for specific chemicals as well as tissue adhesion
81
What is meant by adhesion?
Two cells sticking together to form a tissue
82
Why is diffusion described as passive?
The energy comes natural from the particles rather than an external source such as ATP
83
Define (simple) diffusion
The net movement of molecules or ions from a region of high concentration to low until equilibrium is reached. Down the concentration gradient
84
What is facilitated diffusion?
Diffusion through carrier proteins and channel proteins
85
What are channel proteins?
Transmembrane proteins form water filled hydrophilic channels to allow water-soluble ions to pass through. They are always open
86
What are the types of carrier proteins?
Ligand-gated
Mechanically-gated
Voltage-gated
87
How does a ligand-gated carrier proteins work?
- A neurotransmitter, the ligand, is required to open the ion channel
- Chemical stimulus opens the channel
- Ions move in response to the gradient
88
How does a mechanically-gated carrier proteins work?
Mechanically-gated channels open when mechanical forces like pressure, touch or sound waves physically distort the cell membrane which causes a change in proteins shape that opens the channel pore
89
How does a voltage-gated carrier proteins work?
Open and close in response to changes in electrical voltage allowing specific ions to flow across the
90
What is osmosis?
The passage of water from a region of high water potential to a region of low water potential through a selectively permeable membrane
91
What is water potential and what is the water potential of pure water?
Water potential is the pressure created by water molecules. Pure water has 0 water potential (at 25 degrees and 1000kPa)
92
What does having a low water potential mean for the solution and how can you further lower water potential?
Having low water potential means there are more solutes in the solution. Adding more solutes will further lower the water potential
93
What effect does an isotonic solution have on a red blood cell?
No effect, the osmatic movement in and out of the cell would be at equilibrium
94
What effect does an hypotonic solution have on a red blood cell?
Red blood cell will swell due to the inward movement of water
95
What effect does an hypertonic solution have on a red blood cell?
Red blood cell would shrink (crenated) due to the outwards movement of water
96
What effect does an isotonic solution have on a plant cell?
None (flaccid), no net change due to water moving in and out of the cell equally
97
What effect does an hypotonic solution have on a plant cell?
The cell would be turgid, water enters the cell and the vacuole expands. The cell wall prevents bursting
98
What effect does an hypertonic solution have on a plant cell?
The plant cell would become plasmolyzed, water leaves the cell, protoplast shrinks, cell wall is partially or completely removed- cell wall and cell membrane are separated
99
What is active transport?
The movement of molecules or ions into or out of a cell from a region of lower concentration to higher concentration using ATP and carrier protiens
100
What is co-transport?
Moving molecules with a concentration that has already been set up
101
What is the process of active transport?
1. molecules or ions bind to the receptor on the carrier protien
2. ATP binds to the carrier protien on the inside of the cell
3. the carrier protien will undergo a conformation change in shape and opens
4. the molecule or ion is released to the other side of the membrane
5. when the phosphate released the carrier protien will return to its original shape
102
What is a uniport?
A membane protien that allows a single molecule or ion move across the membrane
103
What is a symport?
A membrane protien that moves two different substances across a cell membrane in the same direction
104
What is a antiport?
A membrane protien that moves two different substances across the membrane in two different directions
105
What are the ileum epithelial cells lined with and why?
They are lined with microvilli. This provides a larger surface area for the insertion of carrier and channel protiens
106
What is the effect of continuous digestion?
Continuous digestion maintains a higher concentration gradient of glucose and amino acids in the lumen
107
What is the effect of continuously circulating blood on the ileum and blood?
Continuously circulating blood combined with the absrobtion into respiring cells helps maintain a concentration gradient between the ileum and the blood. The blood continuously moves products of digestion away
108
Explain how the product of starch digestion (glucose) are absorbed from the ileum into the blood
1. Na+ move from the epithelial cells into the blood by active transport
2. This decreases the concentration of Na+ in the epithelial cell, creating a Na+ concentration gradient between the cell and the lumen of the ileum
3. Na+ and glucose move from the lumen into the epithelial cell by co-transport
4. Glucose moves from the epithelial cell into the blood by facillitated diffusion
109
What is an infection?
An interaction between pathogen and the body’s defences
110
What are the two types of defence mechanisms and what are examples of both?
- Non specific (response immediate and the same for all pathogens) EG. Physical barriers and Phagocytosis
- Specific (response is slower and specific to each pathogen) EG. Cell mediated and Humoral response
111
What are the proteins found on the cell surface membrane of pathogens and what makes them unique?
Antigens are on the surface of pathogens and each protein marker is unique due to their specific tertiary structure
112
What are some examples of the body’s first line of defence?
- ear wax
- lysozymes in tears and other secretions
- mucus lining trachea
- intact skin
- rapid pH change in the gut
113
What is the process of phagocytosis?
1. Chemical products from pathogen (or dead/abnormal cell) cause chemotaxis (attract the phagocytes)
2. Receptors on the cell surface membrane of phagocyte attach to the chemicals on the pathogen
3. The phagocyte engulfs the pathogen (endocytosis) to form a vesicle known as a phagosome
4. Lysosomes move towards the phagosome and fuse with it
5. Lysozyme within the lysosome hydrolyse the pathogens cell wall
6. The now smaller soluble products from the pathogens hydrolysis are absorbed or released (exocytosis)
114
What is another name for a phagocyte?
Neutrophil
115
How can you distinguish between a phagocyte and lymphocyte?
A phagocyte has a granular nucleus
116
What are lymphocytes?
Lymphocytes are involved in the immune response and produce antibodies
117
What is the key difference between lymphocytes and phagocytes?
Phagocytes are a non specific response to pathogens. Each lymphocyte is specific to each specific pathogen
118
What is immunity?
Protecting against diseases/toxins by recognising the foreign material (antigens) before it causes harm
119
What is an antigen?
An antigen is a foreign protein that stimulates an immune response
120
What is similar and different between b-lymphocytes and t-lymphocytes?
- Both are produced in the bone marrow
- B-lymphocytes mature in the bone marrow and are associated with humoral immunity
- T-lymphocytes mature in the thymus and are associated with cell mediated immunity
121
What are the different types of antigen presenting cells?
- Phagocytes present the engluf pathogens antigens on its membrane
- Body cells invaded by a virus present viral anitgens on the membrane
- Transplanted cell from indivivduals of the same species have different antigens on the membrane
- Cancer cells present abnormal antigens on the membrane
122
What do T-lymphocytes do?
T-lymphocytes distinguish invader/foreign cells from normal body cells
123
What are the steps in cell mediated immunity?
1. pathogens invade body cells or are taken in by phagocytosis
2. phagocytes or body cells presents antigens from the pathogen on its cell surface membrane
3. receptors on a specific helper T-cell fit exactly onto these antigens
4. The attachment activated the T-cell to divide rapidly by mitosis and form a clone
5. The cloned T-cells:
- develop into memory cells
- stimulate phagocytosis
- stimulate B-cells to divide and secrete the antibody
- activate cytotoxic T-cells (killer T-cells)
124
What is humoral immunity?
Humoral immunity invloves the production of antibodies which are soluble in the blood and interstitial fluid. Humour refers to the blood and tissue fluid. Immunity refers to the lymphocytes response here
125
How does Humoral immunity work?
(steps 4 and 5 happen at the same time)
1. the surface antigens of an invading pathogen are taken up by a B-cell
2. the B-cell processes the antigen and presents them on its cell surface membrane
3. helper T-cells attached to the processed antigens on B-cell, activating it
4. the activated B-cell divides by mitosis to create clones that all produce the same antibody
5. one clones known as plasma cells secrete the specific antibody that exactly fits the antigen on the pathogens surface
6. the antibody attaches to the antigens on the pathogen to destroy them
7. the other clones of the B-cell develop into memory cells. These respond to future infections and can produce plasma cells and subsequent antibodies more rapidly
126
What are antibodies?
Antibodies are polypeptides synthesised by B-cells in response to an infection
127
How many polypeptide chains make up antibodies?
Four
128
What are the two regions found in polypeptides?
Variable region- the antigen binding site is different on different antibodies
Constant region- the rest of antibody is known as the costant region and binds to the receptor
129
What two ways do antibodies prepare pathogens for destruction?
1. Agglution: antigens binds multiple pathogens together and clumps are formed which makes phagocytosis easier
2. Neutralisation: they serve as markers to stimulate phagcytes to engulf the pathogens
