literally everything Flashcards
(361 cards)
1
Q
In relation to cm give mm, um and nm. [3]
A
10mm, 10000um, 10000000nm
2
Q
equation for calculating actual size
A
a=i/m
3
Q
Define magnification
A
The number of times an image is larger than the original
4
Q
Define resolution
A
The smallest distance between two points where the two points can still be distinguished
5
Q
What are the two types of microscope? [2]
A
Scanning and Transmission
6
Q
Describe the structure of the nucleus [4]
A
- Surrounded by nuclear envelope
- Nuclear pores allow more molecules movement
- genetic material is found within, usually as chromatin
- the nucleolus is a region within that synthethises ribosomes
7
Q
What are the roles of the nucleus? [3]
A
- To store the genetic material (DNA) of the cell
- To synthesise ribosomes
- Regulate the production of messenger RNA for protein synthesis
8
Q
What are the functions of the cell surface membrane? [3]
A
- Encloses the cell to form the boundary between the cytoplasm and the outside environment.
- The control the movement of substances in and out of the cell, as it’s selectively permeable.
- Contains proteins and important molecules for cell signalling and recognition.
9
Q
How does the structure of the RER relate to it’s function? [2]
A
- Contains ribosomes on it’s surface for synthesis of proteins
- The RER membranes spread extensively throughout the cell for the transport of proteins
10
Q
How is the structure of the RER different to the SER?
A
The smooth endoplasmic reticulum does not have ribosomes on it’s surface.
11
Q
What is the function of the smooth endoplasmic reticulum?
A
Synthesises and transports lipids
12
Q
Describe the structure of mitochondria [4]
A
- Oval shaped
- Double membrane bound, inner membrane folded into cristae
- contain jelly like fluid called the matrix
- contain circular DNA and 70s ribosomes
13
Q
What important process occurs at the mitochondria?
A
Aerobic respiration, which produces ATP. This is used for energy requiring processes
14
Q
State the function of the golgi body [2]
A
- Modification and packaging of proteins and lipids for exocytosis or distribution within the cell
- Produces lysosomes
15
Q
What are lysosomes?
A
Vesicles from the golgi body that contain digestive enzymes (protease, lipase etc)
16
Q
List the functions of lysosomes [3]
A
- Hydrolyse ingested pathogens in phagocytes
- They digest old, worn out organelles in the cells
- Break down cells after cell death
17
Q
What are the two types ribosome [2]
A
70s and 80s ribosomes
18
Q
Where are the two types of ribosomes found? [4]
A
- 80s ribosomes are found in Eukaryotic cells - in the cytoplasm and on the RER
- 70s ribosomes are found in prokaryotic cells - chloroplasts and mitochondria
19
Q
Describe the structure of ribosomes [2]
A
- Contain two subunits
- Each is made up of a ribosomal RNA molecule and a protein
20
Q
What is the functions of ribosomes?
A
Protein synthesis
21
Q
State the function of centrioles [3]
A
- formation of the spindle during nuclear division
- replicate during cell division
- organise microtubules during mitosis
22
Q
State the functions of microtubules [2]
A
- Make up the cytoskeleton
- to give structure and allow transport with the cell
23
Q
What are microvilli?
A
Small protrusions of the cell membrane
24
Q
How do microvilli aid exchange of substances in cells?
A
They increase the surface area of a cell to increase the efficiency of exchange
25
Describe the structure of chloroplasts [5]
- Have a double membrane
- Contain a fluid called stroma
- inside, thylakoids are arranged into interconnected stacks of grana
- Contain 70s ribosomes
- Circular DNA
26
Name the photosynthetic pigment in chloroplasts
Chlorophyll
27
What is the function of chloroplasts?
Photosynthesis, producing glucose, oxygen and some ATP
28
Which eukaryotic cells contain a cell wall? [3]
- Plant cells
- algae cells
- fungal cells
29
What are plant cell walls made up of?
Cellulose
30
Identify the functions of the plant cell wall [3]
- Provides mechanical strength to the plant
- protects from osmotic lysis
- regulate movement of water
31
In which type of cell are plasmodesmata found? [2]
- Plant
- Algae
32
What are the functions of plasmodesmata? [2]
- To allow undisrupted flow of materials via symplastic route
- Efficient exchange fo substances between cells without having to cross the cell wall and membrane
33
What is the tonoplast
membrane surrounding the large permanent vacuole
34
What are the functions of the large permanent vacuole [3]
- Stores cell sap
- Maintains turgor pressure
- temporary food storage
35
Which organelles/cell structures are found in plant cells but not animal [5]
- A cell wall
- Chloroplasts
- Large permanent vacuole
- Tonoplast
- plasmodesmata
36
What kind of cell are bacterial cells?
Prokaryotic cells
37
Compare size of Eukaryotic and Prokaryotic cells
P is 1-5um while E is up to 40um
38
Describe the genetic material of Eukaryotic and Prokaryotic cells
P has circular DNA (plasmid rings) while E has Linear chromosomes associated with histones
39
Compare the walls of Eukaryotic and Prokaryotic cells
P has peptidoglycan cell walls while E has one made of cellulose
40
Which cell type has a endoplasmic reticulum?
Eukaryotic
41
Key features of viruses [4]
- Acellular structures
- Contain nucleic acids surrounded by a capsid
- No organelles or ribosomes (rely on host cell)
- some may have a phospholipid envelope surrounding the capsid
42
43
44
Question
Answer
45
What does Benedict's test for?
Reducing sugars
46
Outlines the steps in benedicts test [3]
1. Add equal vol of reagent to the sample to be test
2. heat the mixture in a water bath at 100C for 5 mins
3. results - colour change from blue to (green, yellow, orange, brick red)
47
Outline the steps for benedicts test for non reducing sugars [3]
1. Hydrolyse non reducing sugars by adding equal volume of HCl
2. heat in boiling water bath for 5 mins
3. neutralise mixture with hydrogen carbonate solution
48
How can the Benedict's test be made more quantitive? [2]
- Measure time till first colour change is produced
- create standard solutions of known concentrations and compare colour change to estimate concs
49
Outline Biuret test for proteins [2]
1. add drops of the solution to sample and swirl
2. Pos = purple, Neg, stays blue
50
Define monomer
A single subunit that is used to build larger polymers
51
Define polymer [2]
- Large molecule made of repeating subunits (monomers)
- joined by condensation
52
Define Macromolecule
A large biological molecule
53
Define monosaccharide
A single unit of carbohydrate
54
Define Disaccharide [2]
- 2 units of carbohydrate joined by condensation
- held by glycosidic bond
55
Define polysaccharide [3]
- a polymer with monomers of monosaccharides
- joined together by condensation
- held by glycosidic bonds
56
Describe structure of glucose [3]
- Hexagon shape
- 4 alternating OH and H bonds outside
- one CH2OH and one O
57
What is the difference between A and B glucose?
OH group for alpha is on the bottom while beta is on the top
58
What happens in condensation reactions - with reference to glycosidic bonds & the type of bond [4]
- A chemical bond forms between two molecules
- a molecule of water is produced
- H is removed from one molecule and OH from another
- When this happens between carbs, it's called a glycosidic bond
59
What is meant by reducing and non reducing sugars? [3]
Reducing - able to reduce other sugars to form di or poly saccarides.
due to free free groups which can be condensed. All monosaccharides are reducing sugars
Non reducing - don't have condensable free group to reduce
60
Three examples of reducing sugars
Glucose
Fructose
Maltose
61
Example of a non reducing sugar
Sucrose
62
State how sucrose is formed via the formation of a glycosidic bond [3]
Alpha glucose and fructose form sucrose
via the omission of h2o (condensation reaction)
forming a glycosidic bond between them
63
How are glycosidic bonds broken? What is this known as? [2]
Water used to break the bonds.
Known as hydrolysis
64
Describe the structure of Amylose [3]
1,4 glycosidic bonds
unbranched
helical
65
Describe the structure of amylopectin [2]
1,4 and 1,6 glycosidic bonds
branched
66
How do the structures of both Amylose and Amylopectin relate to their function? [2]
Large - no diffusion out of cells
Insoluble - No osmotic effect on cells
67
How does the structure of Amylose relate to its function? [2]
Amylose has 1,4 glycosidic bonds and is unbranched and helical. These properties make it compact and allow it to store a lot of alpha glucose
68
What do Amylose and amylopectin do
Act as a storage polymer of alpha glucose in plants
69
How does the structure of amylopectin relate to it's function? [2]
It has 1,4 and 1,6 bonds, this means it has many branches, which means it has many terminal ends from rapud hydrolysis into glucose
70
Describe the structure of glycogen [4]
- 1,4 and 1,6 glycosidic bonds
- branched = many terminal ends for hydrolysis
- insoluble
- compact
71
Describe the function of glycogen
Main storage polymer of alpha glucose in animal cells
72
Describe the structure of cellulose [4]
- 1,4 glycosidic bonds
- straight chain, unbranched molecule
- alternate glucose molecules are rotated 180*
- H bond crosslinks between parallel strands form microfibrils (good strength)
73
Describe the function of cellulose
Polymer of beta glucose, gives rigidity to plant cell walls and prevents bursting under turgor pressure.
74
What's the difference between saturated and unsaturated fats? [2]
- Saturated fats have no C=C bonds and are solid at room temp
- Unsaturated fats have one or more c=c bonds and are liquid at room temp due to weak intermolecular forces
75
Describe the structure of a triglyceride, with reference to how it is formed [2]
One molecule of glycerol forms ester bonds with three fatty acids,
these can be saturated or unsaturated - via condensation reactions
76
Relate the structure of triglycerides to their functions [5]
- High energy to mass ratio - energy storage
- insoluble hydrocarbon chain - no effect on water potential of cells (waterproofing)
- slow conductor of heat - thermal insulation
- less dense than water - buoyancy of aquatic animals
- protects organs - resistant to large amounts of force
77
Describe the structure of phospholipids [4]
- Polar
- Glycerol backbone attached to
- 2 hydrophobic fatty acid tails and
- 1 hydrophilic phosphate head
78
Describe the function of phospholipids [2]
- Forms phospholipid bilayer in water
- the hydrophobic tails allow for control of movement of water soluble molecules in and out of cells
79
Describe the common structure of an amino acid [4]
- Amide group
- variable side chain
- carboxyl group
- h atom
80
How are peptide bonds formed? [3]
- The OH is lost from the carboxyl group
- and a H from the Amide group
- forming a peptide bond
81
Describe a name the process by which peptide bonds are broken [3]
- H2O is split into h+oh
- OH returns to the carboxyl group, and H returns to amide group
- hydrolysis reaction
82
What is the primary structure of a protein? [2]
A sequence of amino acids in a polypeptide
held by peptide bonds
83
What is secondary structure? [4]
The regular folding of a polypeptide
into alpha helices
and beta pleated sheets
held by hydrogen bonds
84
What is tertiary structure? [4]
The further coiling of a protein into its functional 3D shape
Held by hydrogen, ionic and disulphide bonds
and hydrophobic interactions
85
What is quaternary structure? [3]
The folding of 2 or more polypeptides into a 3D shape
which may include prosthetic groups
held by hydrogen, ionic, disulphide bonds and hydrophobic interactions
86
Describe the structure of haemoglobin [5]
- Globular structure
- 2 alpha chains and 2 beta chains, 4 prosthetic haem groups
- water soluble (dissolve in plasma)
- Fe2+ haem group forms coordinate bond with O2
- tertiary strcuture changes so its easier for O2 molecules to bind
87
State the difference between blobular and fubrous proteins [2]
- Globular proteins are soluble and involved in physiological processes
- Fibrous proteins are insoluble and have a structural role
88
State the features of a globular protein with reference to haemoglobin [4]
- Spherical and compact
- hydrophilic R groups face outwards and hydrophobic R groupd face inwards
- Involved in promarily in physiological roles
- compact nature means haemoglobin can transport more oxygen per unit of blood
89
Describe the structure of collagen [4]
- Fibrous protein
- made of 3 polypeptide chains coiled to form a triple helix
- every third amino acid is glycine
- collagen molecules lie paralell to form collagen strands, held by staggered cobalent bonds cross bridges between lysine residues
90
How does hydrogen bonding occur in water?
The S+ hydrogen on one water molecule is attarcted to the lone pair of the S- oxygen on another water molecule.
91
What are the properties of water due to hydrogen bonding? [6]
- High surface tension
- Acts as a solvent for water soluble molecules
- high specific heat capacity
- high latent heat of vaporisation
- high boiling point than expected
- ice less dense than liquid water
92
93
Question
Answer
94
What type of protein is an enzyme? [2]
- globular and water soluble
- tertiary structure with hydrophilic r group on outside and hydrophobic r group on inside
95
How do enzymes lower activation energy? [2]
- By holding substrate molecules close together
- placing a physical strain on the bonds so they are weaker and more easily broken
96
Where can enzymes act?
can be intracellular or extracelluar
97
Describe the induced fit model of enzymes [2]
- Substrate of active site changes to create a better fit or stronger binding to substrate
- substrate interacts with r groups of amino acids at active site of the enzyme
98
Describe the lock and key hypothesis
The substrate is complementary in shape to the enzymes active site and binds to it
99
State two ways to investigate progress of enzymatic reactions [2]
- analyse the amount of product from reaction is present
- analyse a colour change indicating removal or addition of product
100
How can we use colorimetry? [2]
Use a colorimeter to build a calibration curve of known concentrations.
Measure samples of reaction solution at equal time intervals and use curve to estimate conc of product
101
factors affecting enzyme reactions [5]
- Temp
- Enzyme conc
- substrate conc
- inhibitor conc
- Ph
102
effect of temp of enzyme activity [3]
- as temp increases substrate molecules gain more energy and more collisions happen
- it reaches a max optimum temp, after that enzyme begins to denature
- activity decreases
103
effect of ph on enzyme activity [2]
- at optimum enzyme activity is highest
- anything above or below messes with bonds in tertiary structure causes change of active site shape
104
function and importance of ph buffers [2]
- maintain ph by minimising changes to ph in a system
- important as product of a reaction may affect a systems ph
105
effect of substrate conc on enzyme activity [3]
- when substrate conc increases, enzyme activity increases as substrate conc is limiting
- more substrate results in more enzyme-substrate complexes formed
- beyond a certain point activity plateaus because all enzyme active sites are filled and vmax is reached
106
describe the mode of action of a competitive inhibitor [2]
- molecule similar in shape to substrate and complementary to active site and binds, blocking substrate
- increasing substrate reverses the inhibition
107
Mode of action of a non competitive inhibitor [2]
- Binds to allosteric site on enzyme causes active site to change shape
- irreversible and lowers rate of reaction and vmax (increasing substrate doesn't do anything)
108
What is km and vmax? [3]
- represents the maximum rate of reaction by the system at max substrate concentration
- km is 1/2 vmax
- can be used to tell affinity of an enzyme to substrate (lower km = higher affinity)
109
Describe how an enzyme can be immobilised [2]
They are immobilized by attaching them to an insoluble, inert material.
This forms a gel capsule around them thus holding them in place during the reaction.
110
State the advantages of immobilising enzymes [4]
- More stable (can withstand diff Ph and temps)
- Easily separated after reaction
- Reusable
- Can be continually used
111
How do reactions of free enzymes differ to those of immobilised enzymes?
- immobilisation allows for increased resistance to denaturing conditions.
- this means that even if solution conditions change reactions will proceed to a larger range than if free enzymes were involved
112
113
Question
Answer
114
State the components of the phospholipid bilayer [5]
- Phospholipids
- Cholesterol
- Extrinsic and Intrinsic proteins
- Glycolipids
- Glycoproteins
115
Describe the fluid mosaic model of membranes [2]
- Fluid - individual phospholipids can move laterally or flip between monolayers, membrane is flexible
- Mosaic - Extrinsic and intrinsic proteins of different sizes and shapes form a pattern.
116
State the role of phospholipids in the phospholipid bilayer [3]
- form the basic structure
- hydrophilic heads face outwards and hydrophobic tails face inwards on either side of the bilayer
- These interactions allow lipid soluble molecules to cross but prevent water soluble molecules from crossing
117
Describe cholesterol in the phospholipid bilayer [3]
- Polar (has a hydrophilic heads + hydrophobic tails)
- fit between phospholipids
- head at membrane surface
118
Describe the function of cholesterol in the phospholipid bilayer
- Mechanical stability (without, membranes quickly break and cells burst open)
- In higher temps it helps stabilise cells, otherwise membranes could become too fluid
- can increase fluidity in cold temps and prevents it becoming too rigid
119
State the role of glycolipids in cell membranes
Involved in cell signalling and cell recognition
120
Outline the functions of the extrinsic (peripheral proteins) [3]
- Binding sites/receptors for hormones and drugs
- Help cells adhere to each other
- Involved in cell signalling
121
State the role of glycoproteins in cell membranes
Serve as recognition sites for chemicals
122
Outline the functions of intrinsic (integral) proteins in membranes [3]
- Electron carriers (respiration/photosynthesis)
- Channel proteins (facilitated diffusion)
- Carrier proteins (facilitated diffusion/active transport)
123
How are cholesterol, glycolipids and glycoproteins arranged in the bilayer [2]
- Cholesterol is dispersed in the membrane alongside the phospholipids
- Glycolipids and glycoproteins extend from either lipid or protein components within the membrane
124
Describe the functions of the cell surface membrane [3]
- Isolates cytoplasm from extracellular environment
- Selectively permeable to regulate transport of substances
- Involved in cell signalling/cell recognition
125
Outline the process of cell signalling [5]
Specific stimulus (e.g. light)
→ sender cell manufactures chemical to be sent
→ molecules (e.g. ligands) released by exocytosis and transported through bloodstream to target cell
→ binds to complementary receptor
→ effector cell stimulated
126
Define osmosis [2]
- diffusion of water across a partially permeable membrane from an area of higher water potential to an area of lower water potential
- This occurs until an equilibrium
127
What is water potential (Ψ)? [2]
- Pressure created by water molecules, measures in kPa
- The greater the concentration of water in a membrane, the more kinetic energy the system has, and therefore the greater the water potential.
128
How does osmosis affect plant and animal cells? [4]
Osmosis into cell:
- Plant - protoplast pushes against cell wall, turgid
- Animal - lysis
Osmosis out of cell:
- Plant - protoplast pulls away from cell wall, flaccid
- Animal - crenation
129
Define simple diffusion [2]
- Net spreading out of particles from an area of higher concentration to an area of lower concentration, down their concentration gradient
- passive process requiring no energy (atp)
130
Define facilitated diffusion
The net movement of substances from a higher concentration to a lower one (down a conc gradient) through transport proteins without the use of energy
131
Explain how channel proteins work [3]
- Form selective pores in phospholipid bilayer
- allow polar and charged molecules to pass through
- some channel proteins may be gated, opening or closing depending on the binding of a specific molecule or ion
132
Explain how carrier proteins work [2]
- Specific shape for the molecule they transport
- binds to complementary molecule, conformational change passes molecule to other side of membrane
133
Define active transport
Active movement of substances from a low conc to a high conc (against conc gradient) with use of energy in the form of ATP
134
Outline the process of active transport in cell membranes [5]
- Molecule binds to carrier protein with complementary shape
- ATP binds to separate binding site on carrier protein
- Carrier protein changes shape, moving molecules to the other side of the membrane
- Molecules released via ATP hydrolysis
- Carrier protein changes back to original shape
135
Define exocytosis
The bulk transport of substances out of a cell via vesicle that fuses with the plasma membrane using energy in the form of ATP
136
Define endocytosis
The bulk uptake of substances into a cell by invagination of the membrane to form a vesicle trapping the substances inside the cell with the use of energy in the form of ATP
137
Name 5 factors that affects the rate of diffusion [5]
- Temp
- Diffusion distance
- surface area
- size of molecule
- difference in conc (how steep the conc gradient is)
138
How to calculate surface area to volume ratio
find the surface area then the volume. then state sa:v
139
How does surface area to volume ratio impact the rate of diffusion?
the greater the surface area to volume ratio, the greater the rate of diffusion
140
What is transduction?
occurs during cell signalling and is the process of converting a signal from one method of transmission to another
141
142
Question
Answer
143
How long is DNA
2nm
144
What is the Centromere [3]
Holds the two chromatids together.
There are not genes in this region.
It is the region that becomes attached to the spindle fibres in divison
145
What do telomeres do
They prevent parts of genes being lost after DNA replication and stop uncontrolled cell division.
146
Why are telomeres important
Because they prevent uncontrolled cell division, which can lead to tumors which can be cancerous
147
What are Chromatids [2]
They contain 1 DNA molecule, which is composed of genes.
They are held together by a centromere formed during interphase.
148
What is a centrosome
An organelle made up of two centrioles, near the nucleus in animal cells and is involved in the formation of the spindle prior to nuclear divison.
149
What is chromatin [3]
A material containing protein,
it is present in the nucleus of eukaryotic cells at interphase,
and turns into DNA
150
When are chromosomes visible
When stained during nuclear division
151
What are sister chromatids
Either of the two identical chromatids formed by the replication of a chromosome
152
What are the components that make up a chromosome [5]
- DNA
- Histone Protein
- Sister chromatids
- Centromere
- Telomeres
153
What is the purpose of Mitosis [3]
Produces 2 genetically identical daughter cells for:
- Growth
- Cell Replacement
- Asexual reproduction
154
What is the cell cycle
Regulated cycle of cell division with intermediate periods of growth
155
Outline the stages of the cell cycle
1. Interphase
2. Mitosis
3. Cytokinesis
156
Outline what happens during interphase [3]
• G1 - Cell synthesises proteins for replication (e.g. tubulin for spindle fibres), cell size doubles
• S - DNA replicates, chromosomes consist of two sister chromatids joined at a centromere
• G2 - Organelles divide
157
What are the 4 stages of mitosis
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
158
Outline what happens in prophase [3]
1. Chromosomes condense and become visible X shaped, two sister chromatids joined at centromere
2. Centrioles move to opposite poles of the cell and mitotic spindle fibres form
3. Nuclear envelope and nucleolus break down, leaving chromosomes free in the cytoplasm
159
Outline what happens during metaphase
Sister chromatids line up at the cell equator attached to the mitotic spindle by their centromeres
160
Outline what happens during anaphase [3]
1. Spindle fibres contract, centromeres divide
2. Sister chromatids separate into two distinct chromosomes and are pulled to opposite poles of the cell (looks like V shape)
3. Spindle fibres break down
161
What does anaphase require to happen
ATP from hydrolysis
162
Outline what happens during telophase [3]
1. Chromosomes decondense and can no longer be observed
2. New nuclear envelopes form around each set of chromosomes - two new nuclei each with one copy of each chromosome
3. Cytoplasm constricts
163
What happens during cytokinesis [2]
1. Cell membrane cleavage furrow forms
2. Contractile division of cytoplasm
164
What are stem cells
Cells that are unspecialised and retain the ability to differentiate into a range of cell types
165
What are the 4 types of stem cell
* Totipotent
* Pluripotent
* Multipotent
* Unipotent
166
What are totipotent stem cells
can develop into any cell type including the placenta and embryo
167
What are Pluripotent stem cells
can develop into any cell type excluding the placenta and embryo
168
What are multipotent stem cells
can only develop into a few different cell types
169
What are unipotent stem cells
can only develop into one type of cell
170
What are 2 uses of stem cells
1. Repair of damaged tissue
2. Drug testing on artificially grown tissues.
171
Why is regulation of the cell cycle important
Irregular growth of cells where repair is not required can result in the formation of cell masses, which can lead to cancer
172
What are telomeres [2]
- Multiple repeat units of short sequence DNA that cap chromosome tips.
- The DNA that makes up telomeres is rich in guanine and cytosine
173
State the role of telomeres [3]
- prevent the progressive loss of DNA in replication
- the enzyme responsible for the replication cannot replicate the full length of the chain
- Telomeres provide protection against any loss of coding DNA
174
Where can stem cells be found in adult humans? [5]
- bone marrow
- skin
- gut
- heart
- brain
175
Uses of stem cells [4]
- repair of damaged tissue after myocardial infarction
- drug testing on artificially grown tissues
- treating neurological diseases
- researching developmental biology
176
177
Question
Answer
178
Describe the structure of a nucleotide [3]
Main central structure is a pentagon
on the top left corner there is a phosphate group
and on the right top corner ther's a nitrogenous base
179
Name the pentose sugars in RNA and DNA [2]
- Deoxyribose in DNA
- Ribose in RNA
180
Describe the structure of DNA [4]
- Double stranded polymer of nucleotides twisted to form a double helix
- joined by phosphodiester bonds
- Hydrogen bonds form between complementary base pairs, A and T, C and G
- Antiparallel strands
181
Name the purine bases [2]
Adenine and Guanine
182
Describe the structure of the purine bases
two ring molecules
183
Name the pyrimidine bases [3]
Thymine, Cytosine and Uracil
184
What is complementary base pairing? [3]
- Describe how hydrogen bonds form between complementary purine and pyrimidine bases
- Two bonds form between A and T (or U)
- Three bonds form between G and C
185
Why is DNA replication described as semiconservative? [3]
- Strands from original DNA molecule act as templates
- New DNA molecule contains 1 old strand and 1 new strand
- Specific base pairing enables genetic material to be conserved accurately
186
How is a new strand formed during semiconservative replication? [3]
1. Free nucleotides from nuclear sap attach to exposed bases via complementary base pairing
2. DNA polymerase joins adjacent nucleotides on a new strand in a 5' to 3' direction via condensation reactions to form phosphodiester bonds
3. Hydrogen bonds form between complementary base pairs
187
Outline the role of DNA ligase in DNA replication [3]
- As DNA replicates in an antiparallel fashion, the leading strand (5' 3') is replicated continuously whereas the lagging end (3' 5') is replicated discontinuously
- Short nucleotide sequences are formed
- DNA ligase catalyses the formation of phosphodiester bonds between the nucleotide sequences
188
Describe the structure of RNA [3]
- Single stranded polymer of nucleotides
- nucleotides joined by phosphodiester bonds
- hydrogen bonds form between complementary base pairs (A and U) and (C and G)
189
What is the function of mRNA?
Carries genetic information from the nucleus to the ribosomes for protein synthesis
190
How do genes determine the structure of proteins? [4]
- DNA base triplets code for amino acids
- Triplet sequence determines amino acid sequence
- Sequence of amino acids determines proteins's primary structure
- Protein primary structure determines where bonds form when folding into tertiary structure
191
What is a mutation? [3]
- A random alteration to the DNA base sequence, altering the order of coded amino acids
- This may result in a change in protein structure.
- Mutations often arise spontaneously during DNA replication
192
What are the three types of gene mutation? [3]
- Substitution
- Insertion
- Deletion
193
What are the consequences of substitution mutations [3]
- Silent mutation (no consequence) as DNA is degenerate
- Mutation may alter the amino acid coded for. This can alter the structure of the polypeptide causing it to no longer function
- Mutation may lead to the production of a stop codon. The length of the polypeptide chain is shorter
194
What are the consequences of insertion/deletion mutations?
Produce a frameshift, altering each subsequent codon and rendering the protein non functional
195
Describe the structure of tRNA [5]
- Single strand of 80 nucleotides
- Folded into clover shape
- Anticodon on one end, amino acid binding site on the other
- Anticodon binds to complementary mRNA codon
- Amino acids corresponds to anticodon
196
What do transcription and translation produce and where do they occur? [2]
- Transcription produces mRNA, occurs in nucleus
- Translation produces proteins, occurs in the cytoplasm in ribosomes
197
Outline the process of transcription [5]
1. DNA Helicase unwinds section of dna, breaking hydrogen bonds between the DNA strands. Antisense strands acts as a template
2. RNA polymerase binds to promoter region on a gene
3. Free RNA nucleotides align next next to their complementary bases
4. RNA polymerase joins adjacent RNA nucleotides, forming phosphodiester bonds.
5. RNA polymerase reaches stop codon and detaches. mRNA complete
198
Define exon
Regions of DNA or RNA that code for amino acid sequences
199
define intron
Non coding sequences of DNA found between exons
200
What happens after a strand of mRNA is transcribed? [4]
1. RNA polymerase detaches at terminator region
2. Hydrogen bonds reform and DNA rewinds
3. Splicing removes introns from pre-mRNA in eukaryotic cells, leaving only exons
4. mRNA moves out of nucleus via nuclear pore and attaches to ribosome
201
Outline the process of translation [5]
1. mRNA attaches to groove between subunits of ribosome
2. Ribosome moves along mRNA until start codon is reached
3. Amino acid-tRNA complex anticodon attaches to complementary mRNA codon via hydrogen bonding. Another complex binds.
4. Peptide bond forms between adjacent amino acids in the complexes
5. Ribosome moves along one codon and release empty tRNA. Process continues to form polypeptide chain until stop codon is reached
202
Describe the structure of the pyrimidine bases
Single ring structure
203
Define anticodon
A sequence of three nucleotide bases at one end of a tRNA molecule that is specific to an mRNA codon
204
What are the types of bonding between base pairs in RNA and DNA? [2]
Phosphodiester bonds in DNA
Hydrogen bonds in RNA
205
What’s the role of tRNA? (4)
- attaches to a specific amino acid
-transports amino acid to ribosomes
- helps form primary structure of protein
- anticodon identifies specific amino acid
206
207
Question
Answer
208
Why do plants require a transport system? [2]
- To ensure all cells receive a sufficient supply of the nutrients they require
- Especially important as a plant must be able to transport substances up their stem, against gravity
209
What is the xylem?
A non living, heavily lignified plant transport vessel responsible for the transfer of water and minerals from the roots to the shoots and leaves.
210
What is the phloem? [2]
A living plant transport vessel responsible for the transfer of assimilates to all parts of the plant.
The phloem consists of sieve tube elements and companion cells.
211
State what is meant by the term "vascular bundle" in plants
The vascular system in dicotyledonous plants. It consists of two transport vessel, the xylem and the phloem.
212
Relate the structure of the xylem to its function [3]
- Long, continuous columns made of dead tissue, allowing the transport of water.
- Contains pits which allow sideways movement of water between vessels.
- Thickened with a tough substance called lignin which provides structural support
213
Relate the structure of the phloem to its function [3]
- Sieve tube elements transport sugars around the plant
- Companion cells designed for active transport of sugars into tubes
- Plasmodesmata allow flow of substances between cytoplasm of different cells
214
Describe the arrangement of the vascular bundle in dicotyledonous roots [4]
- Vascular bundle enable transport as well as structural support
- Xylem vessels arranged in the an X shape in centre of vascular bundle. This enables plant to withstand various mechanical forces such as pulling.
- X shape arrangement of xylem vessels is surrounded by endodermis, an outer layer of cells which supply xylem vessels with water
- Inner layer of meristem cells known as the pericycle
215
Describe the arrangement of the vascular bundle in dicotyledonous stems [3]
- Xylem located on inside in non wooded plants to provide support and flexibility to stem
- Phloem found on outside of vascular bundle
- Layer of cambium in between xylem and phloem. This made of meristem cells which are involved in productions of new xylem and phloem tissue
216
Describe the arrangement of the vascular bundle in dicotyledonous leaves [2]
- Vascular bundles form the midrib and veins of a leaf.
- Dicotyledonous leaves have a network of veins, starting at midrib and spreading outwards which are involved in transport and support
217
State the importance of water potential in the movement of water from roots to shoots [3]
- Water moves down a water potential gradient
- Roots have a high concentration of minerals. Water moves from the soil into the root, down the water potential gradient.
- Water potential decreases as you move up the plant. This results in a water potential gradient, facilitating the movement of water through the plant by osmosis
218
Define transpiration [2]
- The evaporation of water from the leaves of a plant via open stomata
- Consequence of gaseous exchange. Occurs when the plant opens the stomata to exchange oxygen and carbon dioxide
219
Name the factors that affect the rate of transpiration [5]
- Increased light increases
- Increased temp increases
- Increased humidity decreases
- Increased air movement increases
- Waxy cuticle prevents transpiration
220
Explain what is meant by the apoplastic pathway [3]
- One of the three pathways by which water and minerals move across the root
- Water moves through intercellular spaces between cellulose molecules in the cell wall
- Water reaches the casparian strip and is forced through the symplastic pathway
221
Explain what is meant by the symplastic pathway [3]
- One of three pathways by which water and minerals move across the root
- Water enters the cytoplasm through the plasma membrane and moves between adjacent cells via the plasmodesmata
- To begin this pathway, water must be actively transported into cells.
222
Explain the cohesion-tension theory [2]
- Water molecules form hydrogen bonds with each other, causing them to stick together
- The surface tension of the water also creates this sticking effect, preventing water slipping down the xylem. As water is lost through transpiration, more can be drawn up the stem from the roots.
223
Define the term zerophyte
Plants that are adapted to live and reproduce in dry habitats where water availability is low.
224
Give adaptations of xerophytes that allow them to live in dry conditions [5]
- Small/rolled leaves
- Densely packed mesophyll
- Thick waxy cuticle
- Stomata often closed
- Hairs to trap moist air
225
State what is meant by source to sink
The movement of plant assimilates from a producing or storage region, the "source" to a region of requirement, the "sink"
226
Define translocation
The bulk movement of organic compounds in plants from sources to sinks via the phloem
227
Summarise the mechanism of translocation [5]
- Companion cells actively transport H+ to surrounding tissue, establishing a concentration gradient
- H+ flows down their concentration gradient via a cotransporter along with sucrose
- Sucrose builds up in companion cells and diffuses into sieve tube elements via plasmodesmata
- This lowers water potential, causing water to move in from xylem
- Assimilates move along sieve tube towards areas of lower hydrostatic pressure. Sucrose diffuses into surrounding cells where it is needed.
228
Whats the empty space in a stem called?
Parenchyma
229
How are plant nutrients transported in plants?
Minerals ions and organic compounds are dissolved in water to be transported
230
What is parenchyma?
- basic plant tissue used as packing tissue between specialised structures
231
232
Question
Answer
233
What does closed circulatory system mean?
The blood pumped by the heart is contained within blood vessels and doesnt come into direct contact with cells
234
Describe the journey of blood through the circulatory system [9]
- Heart
- pulmonary artery
- lungs
- pulmonary vein
- heart
- aorta
- body
- vena cava
- heart
235
Define the term double circulatory system
The blood flows around the heart in two circuits
236
Advantages of a closed system [2]
- Lower blood vol required to keep system moving
- Pressure can be controlled and maintained
237
Advantages of a double circ system [4]
- Maintains blood pressure around whole body
- More efficient uptake of oxygen
- Effient delivery of oxygen and nutrients
- Blood pressure can differ in pulmonary and systemic systems
238
Relate structure of arteries to function [5]
- Thick muscular walls to withstand high pressure
- Elastic tissue allows stretching and recoil to prevent pressures surges
- Narrow lumen to maintain pressure
- smooth muscle which enables them to vary blood flow
- lined with smooth endothelium to reduce friction and ease blood flow
239
Relate vein structure to function [4]
- Wide lumen eases blood flow
- thin walls eases compression by skeletal muscles
- Require valves to prevent backflow of blood
- less muscular and elastic tissue as they dont have to control blood flow
240
Relate capillary structure to function [3]
- Walls only one cell thick giving short diffusion distance
- Narrow Lumen, red blood cells squeeze through decreasing the diffusion distance
- numerous and highly branched, providing large surface area
241
Relate arteriole structure to function [2]
- Branch off arteries and veins in order to feed blood into and take blood away from the capillaries
- Smaller than arteries and veins so that the change in pressure is more gradual as blood passes through increasingly small vessels
242
Describe structure of erythrocyte (red blood cell) (3)
- Large surface area
- biconcave disks
- no nucleus and no organelles to maximize O2 carrying ability
243
Describe the structure of neutrophils [2]
- irregular lobed nucleus
- cytoplasm contains fine granules
244
Describe structure of lymphocytes [3]
- Very large nucleus in proportion to cell size
- small amount of cytoplasms
- round nucleus
245
What is tissue fluid? [2]
- A fluid surrounding cells and tissues that contains glucose, amino acids, oxygen and other nutrients.
- It supplies these to cells, while removing any waste material
246
Outline the different pressures involved in the formation of tissue fluid [2]
- Hydrostatic pressure - higher at arterial end of capillary than venous end
- Oncotic pressure - changing water potential of the capillaries as water moves out, induced by proteins in the plasma
247
How is tissue fluid formed? [2]
- As blood is pumped through increasingly smaller vessels, hydrostatic pressure is greater than oncotic pressure.
- So fluid moves out of the capillaries, it then exchanges substances with the cells
248
Why does blood pressure fall along the capillary? [2]
- Friction
- Lower volume of blood (Dispersion of blood through capillaries)
249
What happens at the venous end of the capillary [2]
- Oncotic pressure is greater than hydrostatic pressure
- fluid moves down its water potential gradient back into the capillaries
250
How is tissue fluid removed? [2]
- Tissue fluid drains into the lymphatic system where it is referred to as 'lymph'
- the lymph returns to the blood via the subclavian veins
251
What is the main component of both blood and tissue fluid?
water
252
Why is water important in body fluids? [2]
- Water acts as a solvent in order to transport material in biofluids
- Water has a high specific heat capacity. Meaning, a large amount of energy is required to change its temperature, keeping the body at a consistent temperature.
253
Describe the role of haemoglobin [3]
- Present in red blood cells
- oxygen molecules bind to haem groups and are transported around the body
- They are released where oxygen is needed in respiring tissues
254
How does partial pressure of oxygen affect oxygen haemoglobin binding? [3]
- Haemoglobin has a variable affinity for oxygen depending on the partial pressure of xygen
- at high p(O2), oxygen associates to form oxyhemoglobin
- At low p(O2) oxygen disassociates to form deoxyhaemoglobin
255
How is carbon dioxide carried from respiring cells to lungs? [3]
- transported in aqueous solution in the plasma
- As hydrogen carbonate ions in the plasma
- Carried as carbaminohaemoglobin in the blood
256
What is the chloride shift?
- Process by which chloride ions move into the erythrocytes in exchange for hydrogen carbonate ions which diffuse out of the erythrocytes
257
Why is the chloride shift important?
It maintains the electrochemical equilibrium of the cell
258
What is the function of carbonic anhydrase
- Catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid
259
State the Bohr effect
The loss of affinity of haemoglobin for oxygen as the partial pressure of carbon dioxide increases
260
Explain the role of carbonic anhydrase in the Bohr shift [4]
- Carbonic anhydrase is present in red blood cells
- Catalyses the reaction of carbon dioxide and water to form carbonic acid, which dissociates to produce H+ ions
- H+ ions combine with the haemoglobin to form haemoglobinic acid
- Encourages oxygen to dissociate from haemoglobin
261
Why is a higher conc of red blood cells important for human populations living at high altitudes? [2]
- High altitude, low p(O2), oxygen saturation in red blood cells will decrease
- To carry an equal volume of O2 in blood, a higher conc of red blood cells is required
262
What is plasma [2]
- Main component of the blood (yellow liquid) that carries red blood cells
- Contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste. Also distributes heat
263
Describe and explain the shape of a dissociation curve for adult hemoglobin
- Sigmoidal curve (s shape)
- When the first O2 molecule binds, it changes the tertiary structure of haemoglobin so that it's easier for the second and third molecules to bind
- Third molecule changes the tertiary structure of hemoglobin so that it is more difficult for the fourth molecule to bind
264
Describe what happens during cardiac diastole [4]
- Heart is relaxed
- Blood enters the atria, increasing the pressure and opening the atrioventricular valves
- This allows blood to flow into the ventricles
- Pressure in the ventricles is lower than in the arteries, so semilunar valves remain closed
265
Describe what happens during atrial systole [2]
- The atria contract, forcing the AV valves open.
- Blood flows into the ventricles
266
Describes what happens during ventricular systole [3]
- The ventricles contract
- The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves
- Blood flows into the arteries
267
Explain how the heart contracts [3]
- SAN initiates and spreads impulse across the atria, so they contract. Thick fibrous wall prevent impulse spreading directly to the ventricles
- AVN receives, delays and then conveys the impulse down the bundle of His
- Impulse travels into the purkyne fibres which branch across the ventricles, so they contract from the bottom up
268
Why do the walls of the chambers of the heart vary in thickness? [2]
- Walls of both atria relatively thin, only have to cap blood in ventricles as they fill mostly passively
- Left ventricle wall significantly thicker than right, left must provide pressure for systemic flow, right only has to supply pulmonary system. Both are thicker than atria
269
270
Question
Answer
271
What are the parts of the human gas exchange system? [6]
- lungs
- trachea
- bronchi
- bronchioles
- alveoli
- capillary network
272
which structures are cartilage found? [2]
trachea and bronchi
273
What does cartilage do? [3]
- keeps airways open
- keep air resistance low
- prevents collapse during pressure changes
274
What is cartilage like in the trachea
C shaped
275
What is cartilage like in bronchi?
irregular blocks of cartilage
276
what are goblet cells?
cell that produce mucus that traps pathogens and dust etc
277
what are mucus glands
gland that produce mucus that traps pathogens and dust etc
278
where are goblet cells found? [2]
trachea and bronchi
279
describe the structure of goblet cells [2]
- upper part of cell is swollen with mucin droplets
- rest of cell, containing nucleus is thin
280
where are mucus glands located?
beneath the epithelium
281
what is the ciliated epithelium? [2]
- specialised tissue that line all tubes of airways
- each have projections of cili which waft mucus away from lungs to be swalowed
282
describe the squamous epithelium of the alveoli [2]
- thin (one cell thick)
- permeable
283
which structures can smooth muscle be found? [3]
trachea, bronchi and bronchioles
284
what does smooth muscle do?
regulates air flow by relaxing when more air is needed and constricting when less is needed
285
where can elastic fibres be found? [2]
lining of airways and the walls of the alveoli
286
what do elastic fibres do?
to recoil and maintain the original structure.
287
how can you recognise cartilage? [2]
- glassy appearance
- no nerves or blood vessels
288
how can you recognise ciliated epithelium? [2]
- narrow bodies and hair like cilia
289
how can you recognise goblet cells? [3]
- can be found scattered amoun ciliated epithelium of trachea and bronchi
- lack cilia
- the nucleus is found at the bottom of the cell with a large golgi apparatus and mucus granules
290
how can you recognise squamous epithelium?
thin flat squamous cells
291
how can you recognise smooth muscle? [2]
- cells are tightly packed and beneath ciliated epithelium
- dont show cross stripes under microscope
292
how can you recognise capillaries? [2]
- tiny diameter
- single layer of epithelial cells
293
features of aleovli [4]
- one cell thick
- large surface area
- walls have elastic fibres
- surrounded by network of capillaries
294
describe the process of gas exchange between the alveoli and blood [6]
- carbon dioxide removed from blood and oxygen into blood
- oxygen flows down a concentraion gradient from a higher conc
- across squamous epithelium
- oxygen binds ot Hb
- steep gradient maintained by ventilation
295
How are mammals adapted for gas exchange?
- Alveoli provide a large surface area and thin diffusion pathway, maximising the volume of oxygen absorbed from one breath
- They also have a good blood supply, maintaining a steep concentration gradient
296
Describe the structure of the bronchi and their function in the mammalian gaseous exchange system [3]
- Supported by rings of cartilage and lined by ciliated epithelial and goblet cells
- Narrower than the trachea
- Allow passage of air into the bronchioles
297
Describe the structure of the bronchioles and their function in the mammalian gaseous exchange system [4]
- Narrower than the bronchi
- No cartilage
- Contain elastic fibres and smooth muscle which allows constriction to restrict airflow
- Allow passage of air into alveoli
298
What is the primary gaseous exchange surface in humans?
Alveoli
299
300
Question
Answer
301
Define the term infectious disease
A disease caused by a pathogen which can be transmitted
302
Define the term non infectious diease [2]
- A disease that cannot be transmitted by direct contact between individuals (lung cancer, sickle cell anaemia)
303
State the binomial name and pathogen type for cholera [2]
- Vibrio cholerae
- bacterium
304
State the binomial names and pathogen type for malaria [5]
- Plasmodium ovale
- Plasmodium falciparum
- Plasmodium malariae
- Plasmodium vivax
- Protoctist
305
State the binomial names and pathogen type for tuberculosis [3]
- Myocbacterium tuberculosis
- Mycobacterium bovis
- bacerium
306
State the pathogen type for HIV/AIDS
Virus
307
What does HIV stand for?
Human immunodeficiency virus
308
What does AIDS stand for?
Acquired immunodeficiency syndrome
309
What causes HIV/AIDS? [4]
1. The HIV virus is transmitted by direct contact with blood, semen, rectal fluids, vaginal fluids and breast milk
2. Attachment proteins bind to complementary CD4 receptor on Th cells
3. HIV particles replicate inside Th cells, killing or damaging them
4. AIDS develops when there are too few Th cells for the immune system
310
How is HIV/AIDS treated?
Taking a combo of antiretroviral drugs prevents HIV replication. PEP can prevent infection after exposure
311
What causes tuberculosis? [4]
1. Transmitted by droplet infection
2. trigger inflammatory response by infecting phagocytes in lungs
3. Infected phagocytes are sealed in waxy coated tubercules so bacteria remain dormant. Primary TB has no symptoms
4. If another factor weakens the immune system, bacteria become active. Secondary TB destroys lung tissue
312
Outline primary treatment of TB
Patients take a combination of antibiotics for several months
313
How is cholera transmitted? [2]
- Fecal/oral transmission
- Ingesting contaminated food or water
314
How is cholera treated? [2]
- Rehydration (fluid and electrolytes)
- Antibiotics
315
Why might incidence and prevalence of communicable diseases change over time? [4]
- Development of vaccines
- Development of treatments (antibiotics)
- Random mutations cause antigen variability in pathogens. Memory cells no longer complementary
- Random mutations result in treatment resistant strains
316
How can spread of HIV be prevented? [6]
- Take PEP or PrEP
- Multi drug treatment
- Use clean needles
- Screen blood donations
- Education on safe sex and the disease
- Use of condoms
317
How can spread of TB be prevented? [4]
- Combination of drugs and vaccines
- Cover mouth and nose when coughing and sneezing
- Quarantine
- Improved sanitation
318
How can transmission of cholera be prevented? [2]
- Education on water sanitation
- Education on contamination of water supply
319
Outline the mode of transmission and infection of the plasmodium spp parasite [2]
- Female mosquitos act as vectors when it transfers saliva to another organism during feeding
- Parasite reproduces asexually in red blood cells in liver causing lysis
320
How is endemic malaria controlled? [3]
- Preventing mosquito bites
- controlling mosquito numbers
- drug treatment
321
How does penicillin act as an antibiotic? [2]
- Penicillin inhibits the syntheses of the pepdigoglycan wall in bacteria, preventing new cell walls forming. The cell bursts
- This class of antibiotic is bactericidal. They work by preventing cell wall synthesis or disrupting protein synthesis
322
Why do antibiotics have no effect on viruses
Work by targeting machinery found in bacteria (prokaryotic cells). Viruses dont have this machinery, meaning they have no effect
323
Why is it important antibiotics do not effect eukaryotes?
Humans are eukaryotic. If antibiotics affected eukaryotic cells they could potentially kill the recipient
324
How does antibiotic resistance occur? [2]
- Spontaneous mutation of bacterial plasmids can occur which may lead to improved tolerance to an antibiotic. These cells are able to survive long enough to divide, increasing the prevalence of the mutation and making the population more resistant to a particular antibiotic.
- Resistance can be spread 'horizontally' - the movement of genetic material between unicellular and/or multicellular organisms (conjugation) other than by the 'vertical' transmission of DNA from parent to offspring via reproduction.
325
How can we mitigate bacterial resistance? [8]
- Complete full course of antibiotics
- Don't overuse antibiotics
- dont use antibiotics in animal feed
- reduce contamination in hospitals
- aseptic techniques in hospitals
- Isolation of infected patients
- emphasis on hygiene
- reduce use of antibacterial hand gel
326
327
Question
Answer
328
Define the term phagocyte
Specialised white blood cells that engulf and destroy pathogens. there are two types: neutrophils and macrophages
329
Define the term phagocytosis
The process by which phagocytes engulf and destroy pathogen
330
Outline the process of phagocytosis [5]
1. Phagocyte move toward pathogen via chemotaxis
2. Phagocyte engulf pathogen via endocytosis
3. Phagosome fuses with lysosome forming a phagolysosome
4. Lysozymes digest pathogen
5. Product of pathogen hydrolysis absorbed by the phagocyte or released into the cytoplasm
331
Define the term immune response
The body response to 'non self' antigens. It consists of a non specific phase involving neutrophils and macrophages, and a specific phase involving T and B lymphcytes
332
What is an antigen?
A chemical present on the surface of a cell that induces an immune response
333
What is meant by the term self antigen?
Antigens present on an organism's cells that are tolerated by their own immune system. They induce antibody formation
334
What are antigen presenting cells?
Any type of immune cell which displays parts of a pathogen on its surface to elicit an immune response
335
What is meant by the term non self antigen?
Foreign antigens that originate from outside the body and induce an immune response
336
What are the types of T lymphocyte? [4]
- T helper
- T killer
- T memory
337
What do T helper do?
Bind to antigens on antigen presenting cells and secrete interleukins
338
What do t killer do?
Secrete perforin (hydrogen peroxide) , destroying pathogens with a specific antigen
339
What do t memory do
provide immunological memory
340
Describe the structure of B lymphocytes [2]
- Mature in bone marrow
- many specific receptors and immunoglobulins on surface
341
What are the main types of B lymphocyte? [3]
- Plasma cells
- B effectors
- B memory
342
What do plasma cells do?
Produce antibodies specific to a particular pathogen
343
What do B effectors do?
Divide to form plasma cells
344
What do memory do?
provide immunological memory
345
Define the humoral immune response
Immunity regulated specifically by the production of antibodies. Associated with B lymphocytes
346
Outline the process of the cell mediated response [3]
- Complementary T helper lymphocytes bind to foreign antigens on antigen presenting cell.
- T cells undergo clonal expansion
- 4 main types of T lymphocyte produced
347
Outline the process of the humoral response [4]
- Complementary T helper lymphocytes bind to foreign antigens on antigen presenting T cells
- Cytokines released that stimulate the clonal expansion of complementary B lymphocytes
- B lymphocytes differentiate into plasma cells
- Plasma cells secrete antibodies with complementary variable region to antigen. Antibodies destroy the pathogen
348
Compare the primary and secondary immune responses [2]
Primary immune response - initial response when a pathogen is first encountered. A small number of antibodies produced slowly
Secondary immune response - pathogen encountered for a second (3rd, 4th etc) time. Immunological memory gives a rapid production of a large number of antibodies
349
What is the function of memory cells? [2]
- They remain in the body for a long time following an infection and provide long term immunity.
- If the organism encounters the same pathogen in the future, they can rapidly divide to provide an effective secondary immune response
350
Describe the structure of an antibody [3]
- Y shaped. Two light chains bonded to two longer heavy chains by disulphide bridges
- Binding sites on variable region of light chains have specific tertiary structure complementary to an antigen
- The rest of the molecule is known as the constant region
351
How do antibodies destroy pathogens? [4]
- Agglutinins form antigen-antibody complexes to enhance phagocytosis (pathogens clump, engulfing occurs more efficiently)
- Bind to foreign cells and attract 'complement', a collection of proteins which form pores in the cell surface membrane of pathogens, destroying them
- opsonins mark microbes for phagocytosis
- Antitoxins make toxins insoluble via precipitation/neutralisation
352
Outline hybridoma method [3]
- An antigen is injected into a mammal to stimulate clonal expansion of complementary B cells.
- These B cells are harvested and fused with a myeloma, which can undergo mitosis an indefinite number of times
- The hybrid cell is called a hybridoma
353
How can monoclonal antibodies be used in diagnosis? [2]
- MAs for specific antigens can be attached to radioactive markers, allowing for specific cells or proteins to be found in the body
- Also useful in blood typing and tissue matching
354
How can monoclonal antibodies be used in treatment? [2]
- Can bind to certain cells, marking them for destruction
- Useful in treatment of cancers and autoimmune diseases
355
State an issue with using monoclonal antibodies in treatment and how it is overcome [2]
- MAs require multiple treatment rounds. As they are sourced from animals this may trigger an immune response
- To overcome this, the MAs are humanised by altering the amino acid sequence to those found within humans
356
compare and contrast passive and active immunity [5]
- Both involve antibodies
- no memory cells produced in passive, produced in active
- passive is immediate, active has a time lag
- passive antibodies from external source, active lymphocytes produce antibodies
- passive no direct contact with antigen needed, active needs direct contact with antigen
357
Give examples of passive and active immunity [4]
- Passive natural - antibodies in colostrum or transferred across placenta
- Passive artificial - anti venom, needle stick infections
- Active natural - humoral response to infection
- Active artificial - vaccination
358
Define vaccination
The deliberate expose of an individual to antigens from a pathogen to provide artificial active immunity
359
How do vaccinations that use antigens provide long lasting immunity? [2]
- Antigens in vaccine trigger primary immune response without infection
- If pathogen is encountered, secondary immune response destroys the pathogen before symptoms develop
360
How do vaccines that use antibodies provide short term immunity? [2]
- Antibodies give rapid protection against harmful microorganism
- Allows time for the development of an active immune response
361
How can vaccination programs control the spread of infectious dieases? [3]
- herd immunity - significant proportion of population is vaccinated so pathogeen is likely to affect a non immunised individual. Diseases cannot spread in immune individuals
- Ring vaccination - all individuals within a radius of a known case are immunised, preventing spread from localised areas
- Boosters - Where a vaccine does not induce a strong response, these maintain immunity.
