Topic 2: Cells Flashcards
Who created the microscope and when?
Robert Hooke in 1665
When was the electron microscope created
1940s
What equation links magnification, image size and actual size
image size = magnification x actual size
Define magnification
the enlargement of an image
how many times bigger the image of a specimen observed is in compared to the actual (real-life) size of the specimen
Define resolution
the ability to clearly distinguish between two points of an image
What would happen if you were to only increase the magnification
resolution would decrease
How do you convert from mm - micrometers
x1000
How do you calculate scale diagrams
1) measure scale bar with ruler on mm side
2) calculate how many micrometres is 1mm
3) measure the diameter and multiply by micrometres to get actual size
How do light microscopes work
use a pair of convex glass lenses that can resolve images 2um apart
what restricts the resolution of a light microscope
longer wavelength of light
(electrons have shorter wavelengths)
what are the two types of electron microscopes
TEM and SEM
What is TEM
transmission electron microscopes which works when a beam of electrons passes through the sample (must be thin)
What is SEM
scanning electron microscopes –> beam of electrons scatters across the surface which results in a 3D image
why is a vacuum required for electron microscopes to work
so air particles dont deflect electrons out of beam alignment
what are limitations of electron microscopes
-living specimins cannot be observed
-a complex staining process is required
-a thin sample is needed for TEM
-SEM has a lower resolving power than TEM
-concentrated beam of electrons may destroy specimin
How would you improve the resolution of an image
move the fine focusing knobs
Define cell fractionation
the process where we break up cells and separate out individual organelles
What occurs before cell fractionation
the tissue is placed in a solution that is cold (to reduce enzyme activity), of the same water potential (to prevent bursting and shrivelling) and buffered (to maintain constant pH so organelle structure wont be affected)
What are the two steps to cell fractionation
1) homogenation
2) Ultracentrifugation
What occurs during homogenation
the cell is blended to release all the organelles. The resulting liquid solution is called the homogenate and is filtered to remove debris
What occurs during ultracentriguation
the test tubes of the filtrate are spun. At first speeds are slow and then begin building up fast. At slow speeds the heavier organelles (nuclei) are separated. The supernatent (remaining substance) is removed and spun again at higher speeds
What is the order of organelle separation
1) nucleus
2) chloroplasts/mitochondria
3)golgi apparatus, endoplastic reticulum
4) ribosomes, vesicles, lysosomes
What are advantages of light microscopes
good/cheap method of observing larger cells
can visualise living organisms
What are disadvantages of light microscopes
-must be a thin specimen
-low magnification (x400)
-2D images only
-low resolution due to long wavelengths of light
What are advantages of TEM
provides highest degree of magnification and resolution
What are disadvantages of TEM
-specimen must be extremely thin
-2D images only
-cannot observe living things
-concentrated beam of electrons may destroy specimen
What are advantages of SEM
-provides 3D image
-higher resolution than light microscopes as electrons have shorter wavelengths
-easier to stain with colour
What are disadvantages of SEM
-lower resolution than TEM
-cannot observe living cells
-concentrated beam of electrons may destroy specimen
what is the waxy cuticle
a protective layer of protein on the leaf
What is the function and adaptations of the upper epidermis
secretes protein wax to protect
waterproof
transparent
What is the palisade mesophyll
-tall and thin
-squashed to maximise chloroplast content
-main site of photosynthesis
What is the spongy mesophyll
tissue that has lots of air gaps for gas exchange and diffusion
What is the xylem and phloem
vascular bundles
xylem = transports water + minerals
phloem = sugars and photosynthesis products
What is the lower epidermis
form the stomata
contains leafs content
protective
what is the stomata
contains guard cells
let CO2 in and O2 out
-regulates transpiration and gas exchange
name 5 membrane bound organelles
nucleus
endoplasmic reticiulum
mitochondria
lysosome
vacuole
name 3 features of prokaryotic cells
-plasma/rings of DNA
-cell wall made of murein
-small ribosomes
define transcription
the process by which a DNA system is copied into a RNA sequence by the enzyme RNA polymerase
define translation
the process that takes the information passed from DNA as messenger RNA and turns it into a series of amino acids bound together with peptide bonds.
What is the structure of the nucleus
-outer nuclear membrane
-inner nuclear membrane
-chromatin
-nucleolus
-nuclear pores
-rough endoplasmic reticulum
What is the function of the nucleus
-contains DNA (genetic information) either loose as chromatin or tightly wound in the nucleolus
-controls the activities of the cell by controlling transcription by DNA
-pores allow movement of nucleic acids in and out
What is the structure of the golgi apparatus
group of membrane bound sacs filled with fluid
What is the function of the golgi apparatus
Process and package new lipids and proteins into vesicles for them to move out the cell
Can also modify proteins/lipids
What is the structure of the smooth endoplasmic reticulum
system of membranes
What is the function of the smooth endoplasmic reticulum
-processes and packages lipids into vesicles
-Different to the golgi apparatus as it is found further from the nucleus and does not package proteins – only large lipids such as triglycerides
What is the structure of lysosomes
contains hydrolyctic enzymes
What is the function of the lysosomes
-vesicles contain hydrolytic enzymes
-fuse with vesicles
-bind to an release digestive enzymes to break down organelles or pathogens within the cell
-releases soluble proteins into cytoplasm to use as building material and insoluble products are egested from cell into the blood, kidney and urine
What is the structure of the plasma membrane
-phospholipid bilayer with carrier/channel proteins embedded in the tissue
What is the function of the plasma membrane
-controls the movement of substances in and out of the cell
-will have receptor proteins on surface which are used to release hormonal signals from other parts of the body
what is the structure of the mitochondria
-cristae
-matrix
-inner membrane
-outer membrane
What is the function of the mitochondria
-the mitochondria is the site of aerobic respiration for the cell
-produces ATP from glucose which is used to release energy for cell processes
What is the structure of ribosomes
=made of large and small protein sub-units
-2 types of ribosomes –> 80S (eukaryotic),70S (prokaryotic)
What is the function of ribosomes
-found either attached to REM or free in the cytoplasm
-site of protein synthesis (translation)
-only apparatus not bound by a membrane
What is the structure of the rough endoplasmic reticulum
system of membranes with ribosomes attached
-the structure of folded proteins determine function/structure of proteins
What is the function of the rough endoplasmic reticulum
always found near nucleus. - Folds and processes the proteins that have been made of ribosomes using nucleic acids from the nucleus
What are chloroplasts
where photosynthesis takes place in plants. Stacks of grana containing chlorophyll pigments which absorb light energy. Enzyme filled space for light reaction called stroma
What is the cell wall
contains cellulose bound together with pectin proteins. Forces cells to resist osmotic pressure and maintains cell structure
what are some similarities and differences between a prokaryote and a eukaryote
prokaryotes have smaller ribosomes
the cell wall of prokaryotes are made of murein where it is made of cellulose in plant cells
prokaryotes have no membrane bound organelles
prokaryotes divide by binary fission whereas eukaryotes divide by meiosis/mitosis
what are the cell walls of fungi made from
chitin
what is embedded in plasma membranes
proteins and cholesterol
what percentage of the cytoplasm is made of water
70%
what do the pores in the nuclear envelope control
passage of ions, molecules and RNA between the nucleoplasm and cytoplasm.
what are viruses
-viruses are acellular and non-living, they include genetic material, a capsid and attachment proteins
-viruses are not living as they cannot reproduce independently, not made of living cells, have no nucleus etc
-viruses are made of nucleic acids
Viruses have attachment glycoproteins that bind to complementary receptors on host cells.
They then inject DNA or RNA into the host cell.
The host cell divides as normal and the virus is replicated.
Virus replication –> invade and hijack a host cell which divides
what is the DNA like in prokaryotes
short, circular and not associated with proteins
Give examples of 6 specialised cells
red blood cells
neutrophils
-guard cells
-sperm cells
-ciliated epithelium
-squamous epithelium
How is the red blood cell specialised
has no nucleus so can carry more haemoglobin, biconcave disc to increase surface area, no membrane bound organelles
How is neutrophil specialised
flexible membrane to engulf the pathogen, glycogen = energy store, phagosome contains lethal acidic enzymes to break down pathogen
How are guard cells specialised
thin outer walls for rapid osmosis, more than one vacuole to retain water (controls turgidity of cell), epidermal cells strengthen against osmotic gradient, cellulose microfibrils = strong
How are sperm cells specialised
lots of mitochondria = energy, nucleus = holds genetic information, tail = locomotion, acrosome = filled with digestive enzymes to break membranes of egg so can fertilize
how is the ciliated epithelium specialised
basal membrane maintains ridged, cilia allows substances to waft through breathing, goblet cell secretes mucus
how is the squamous epithelium specialised
proteins and polysaccharides resist bad environments, flat and thin for efficient diffusion pathway
true or false - there are organelles in the cytoplasm of red blood cells
false - no organelles –> only haemoglobin
What do both prokaryotes and eukaryotes have in common
-cell wall present to stop cell from bursting,
-contains ribosomes,
-contains cytoplasm,
-has a plasma membrane
What type of cell has a cytoskeleton and what is the function of this
eukaryotes have a cytoskeleton –> transports vesicles across cytoplasm of the cell
what are the 4 steps of binary fission
DNA replication –> expansion and separation –> constriction –> cytokineses
Describe binary fission in detail
1) DNA replication –> circular DNA and plasmids replicate
2) Expansion and separation –> the prokaryote grows in size and DNA seperates to opposite poles of the cell
3) constriction –> the cell membranes begin to pinch down the middle where it seperates
4) Cytokenesis –> cytoplasm fully separates resulting in two daughter cells (not genetically identical as number of plasmids are different)
What are some differences between binary fission and mitosis
-there are no identical daughter cells in binary fission
-no spindle fibres in binary fission
-no chromosomes in binary fission
who came up with the fluid mosaic model
Singer and Nicholsons’s 1972
why is the plasma membrane described as fluid mosaic
as all components are able to move and it is made of many different components
-Phospholipid molecules can move relative to one another giving the membrane a flexible structure and proteins are embedded which vary in shape/size
what are the 5 purposes of cell membranes
-controls the entry and exit of materials into and out of discrete organelles
-separate organelles from the cytoplasm so that specific metabolic reactions can take place (compartmentalization)
-provide an internal transport system
-isolate enzymes that might damage cells
-provides surfaces on which reactions can occur
name all the parts of the cell membrane
glycoproteins,
glycolipids,
cholesterol,
intrinsic channel proteins, intrinsic carrier proteins, phospholipid bilayer,
extrinsic proteins,
cytoskeleton
what is the function of glycoproteins/glycolipids
allows for cell recognition, act as receptor sites for hormones and allows cell attachment for tissue formation on liver cells
what is the function of cholesterol
maintains stability of the cell membrane and keeps it rigid
Cholesterol acts as a buffer for membrane fluidity. This means at high temperatures, cholesterol prevents fluidity from rising too high, and at low temperatures, cholesterol prevents the membrane from becoming solid.
what is the function of channel proteins
allows water soluble (polar) substances to pass across the cell membrane (facilitated diffusion)
what is the function of carrier proteins
allows for the active transport of large water soluble substances through the cell membrane e.g glucose transporter proteins
what is the function of the phospholipid bilayer
allows small lipid soluble substances to pass across the cell membrane
what is the function of extrinsic proteins
provide additional strength to the membrane
what is the function of the cytoskeleton
coordinates the movement of molecules once inside the cell
describe the phospholipid bilayer of membranes
-the hydrophillic head of a phospholipid is attracted to water, Water is polar and it is attracted to the negative charge on phosphate group
-the hydrophobic tail is repulsed by water which means there is an automatic bilayer formed
-the space between the bilayer is anhydrous (no water present)
what does selective permability mean
only lipid soluble (non-polar) molecules can diffuse through membranes easily
why is the cell membrane selectivley permeable
This is because the membrane has a hydrophillic head on the phospholipids. Therefore ions and other water soluble molecules cannot diffuse through, only small non-polar molecules like CO2 can diffuse through.
how does temperature affect membranes
-below 0 degrees –> not selectively permeable –> phospholipids don’t have much energy so have reduced movement and fluidity. As they are closer together the rigidity changes the structure of the protein causing them to denature and the permeability to increase.
-between 0-45 degrees –> more energy and not tightly packed so membranes are more fluid and proteins are not denatured – normal selective permeability
-45+ degrees —> as temperature increases proteins gain kinetic energy and is no long selectively permeable (it increases).
what does low cholesterol content mean for membranes
more flexible and less rigid (bad)
how are the movement of substances affected by the cell membrane
-The cell surface membrane is a phospholipid bilayer which stops polar molecules diffusing easily whereas it will allow non-polar molecules to diffuse through because non polar molecules are lipid soluble
-channel proteins allow for facilitated diffusion and carrier proteins allow for active transport
-the more channel and carrier proteins the faster rate of diffusion
-cholesterol maintains the structure of the cell membrane
why do bacteria no necessarily need cholesterol in their membranes
they have a cell membrane made of murein which ensures cell shape doesnt change
what are the organelles found in chloroplasts
starch grain
inner/outer membrane
granum
thylakoid
circular DNA
ribosomes
stroma
what is the thylakoid
holds chlorophyll pigments that absorb light energy - light dependent reactions take place
what is the granum
stacks of thylakoid discs to maximise light captured
what is the starch grain
store of energy (glucose) made by photosynthesis in the chloroplast
what is the role of circular DNA in the chloroplast
controls its function
what is the stroma
enzyme filled space for light reaction (contains the substrates needed for photosynthesis)
define an organelle
a structure with a function inside the cell
why is DNA not an organelle
only just a simple polymer
why is the cell surface membrane not an organelle
found outside of the cell
what organelle is common to both chloroplasts and prokaryotes
ribosomes (70s)
How does low temperature affect the permeability of membranes
reduces kinetic energy of substrates causing them to move slow thus reducing rate of transport. Membrane also becomes more rigid which can denature carrier/channel proteins and therefore increases permability
How does high temperature affect the permeability of membranes
High temperatures denature the carrier/channel proteins which increases the permability of membranes
—> both high and low temperatures reduce the selectivity of the membranes by affecting its permability
how does pH affect the permeability of membranes
-increasing or decreasing pH will change the structure of membranes
-lipids are easily attracted by changes to pH and will change their shape
-Carrier and channel proteins in the bilayer will denature and no longer recognise their substrates
-Any change to pH will increase permability but will also kill the cell by destroying the membrane
how does alcohol concentration affect the permeability of membranes
-lipids are soluble in alcohol
-OH groups forms H bonds with the ester bond holding the fatty acid to glycerol
-high concentrations of alcohol will dissolve the phospholipids holding the bilayer and will increase permability
what is the function of pilli in prokaryotic cells
transfer of genetic material
what organelle would enzymes be found in
lysosomes (contains hydrolytic enzymes)
true or false - blue has highest absorbance rate
true
why does the graticule need to be calibrated
scale of graticule depends on the magnification used
suggest two ways a trial could be improved
-double blind trial
-increase sample of participants
in what state does diffusion not happen
solid
what is facilitated diffusion
Facilitated diffusion describes the net movement of particles down a concentration gradient (i.e. from a region of high concentration to a region of lower concentration).
Facilitated diffusion is a passive process so it does NOT use energy.
what are the factors affecting diffusion
-concentration gradient
-temperature
-membrane surface area
-thickness of membrane
-channel or carrier proteins
what is osmosis
Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution (high water potential) to a concentrated solution (low water potential).
what factors affect the rate of osmosis
The lower the water potential gradient, the slower the rate of osmosis.
The thicker the membrane, the slower the rate of osmosis.
The smaller the surface area, the slower the rate of osmosis
what are the stages of identifying water potential in plant cells
1 Cut and weigh the potato pieces
2 Place chips in boiling tubes with different sucrose concentrations
3 Dry the chips and weigh again to record change in mass
4 Plot a graph and identify the isotonic point
explain why ventillation of the lungs increases the efficiency of gas exchange
pressure inside the lungs decreases so volume of oxygen drawn in increases. this maintains the concentration gradient between alveoli and the lungs
Describe structure and function of cell vacuole
-has single membrane/tonoplast
-maintains rigidity of cell
-contains cell sap/amino acids = temporary food supply
what is the function of the capsule
protects against the host immune system
what part of a prokaryotic cell contains the gene for antibiotic resistance
plasmid/ring of DNA
channel proteins
water filled tubes that allow water soluble ions to diffuse
carrier proteins
bind to ions and change shape in order to move this molecules
cholesterol
makes the membrane less fluid at high temperatures
define diffusion
the net movement of molecules or ions from a region of high concentration to low concentrationuntil equillibrium is reached
what is simple diffusion
passive –> all particles are constantly in motion due to kinetic energy they possess, the motion is random, particles are constantly bouncing off one another as well as off other objects.
how can transport be increased
by an increase in surface area of, or by an increase in the number of protein channels and carrier molecules in, their membranes
what is diffusion proportional to
difference in concentration between two regions
(only occurs in different concentrations between the same substance)
what is facilitated diffusion
Movement of polar molecules is made easier by channel and carrier proteins that span the membrane. Facilitated diffusion is a passive process down a concentration gradient
what has the highest water potential
pure water
define active transport
the movement of molecules or ions into or out of a cell from a low to high concentration using ATP and carrier proteins
what is co transport
the mechanism of transport of glucose and amino acid into the epithelial cells in the ileum. Sodium binds to co-transporter proteins to allow glucose and amino acid to be transported.
golgi apparatus
modifies proteins by often adding non-protein components such as carbohydrates
forms lysosomes
secrete carbohydrates
produce secretory enzymes
add carbohydrate to form proteins
what does a high negative water potential mean
very concentrated (more solute must be dissolved)
where does diffusion, osmosis and active transport take place in living organisms
Diffusion occurs in lungs, blood, small intestine
Osmosis occurs in the xylem, root hair cells, guard cells, large intestine
Active transport occurs in the small intestine (glucose) and root hair cells
define diffusion
The movement of molecules or ions from a region of high concentration to a region of lower concentration until evenly distributed (equillibrium is reached)
what factors affect the rate of diffusion
-temperature
-surface area
-concentration gradient
-thickness of diffusion pathway
what happens to the rate of diffusion as temperature increase
Particles have more kinetic energy which increases the rate of movement of particles by diffusion
why does the plasma membrane only allow small lipid molecules to diffuse
it contains polar phospholipids that only allows non-polar molecules to move through the lipid bilayer. Furthermore, molecules must be small so it can fit through the phospholipid molecules
what is the rate of diffusion proportional to
surface area
difference in concentration
what is the rate of diffusion inversely proportional to
thickness of the exchange surface
how is the alveloi adapted for diffusion
Large surface area to volume ratio so more particles can diffuse quickly. Alevoli has thin membranes which means short diffusion pathway for molecules. Alveoli has a rich blood supply so concentration gradient is maintained
define faciliated diffusion
-The movement of polar molecules or ions from a region of high to low concentration until it reaches equilibrium with the aid of carrier or channel proteins
what are channel proteins
Allow small water soluble IONS to pass through. Different channel proteins permit the passage of different polar molecules and ions.
They have to be specific in shape to the ion in order to regulate ion concentration in different cells with different functions
what are carrier proteins
Allows large MOLECULES to pass through. Firstly molecules attaches, the protein then changes shape, then the substance is released in the other side of membrane e.g glucose (dense molecule)
what is osmosis
-The movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane (e.g channel proteins such as aquaporins)
-Large insoluble molecules are unable to pass through the membrane
-Small water molecules can pass through membrane using aquaporins
why is it effective to put your phone in rice if it gets wet
Rice has a more negative water potential (less water) as it is anhydrous. This causes water molecules inside a phone to diffuse out of the phone and into the rice by osmosis
what is water potential
The pressure created by water molecules and a measure of the tendency of water molecules to diffuse from one place to another. It is represented by psi and is measured in KPa
-Pure water has the highest water potential (zero)
-As a solute dissolves into water the water potential of the solution becomes more negative
isotonic
water potential is equal inside and outside the cell reaching equilibrium
hypertonic
(crenation in red blood cells and plasmolysis in plant cells) –> water potential is lower outside the cell so water moves out the cell by osmosis causing the cell to shrivel
hypotonic
(turgid or hemolysis) water potential is greater outside the cell so water moves into the cell by osmosis causing it to burst
what is active transport
-The movement of polar molecules or ions from a region of low to high concentration using ATP and carrier proteins
-ATP hydrolayse breaks down ATP
-ATP binds to the carrier protein
what is the process of active transport
1) Transport is through carrier proteins spanning the cell membrane
2) Molecule binds to a receptor complimentary to the shape in protein
3) ATP binds to the carrier protein from inside the cell and it is hydrolysed into ADP and Pi
4) This causes the carrier protein to change shape and release the molecule to the other side
5) the phosphate ion is then released and the protein returns to its original shape
what is required to absorb glucose into the lumen
-To absorb glucose from the lumen to the gut there must be a higher concentration of glucose in the lumen compared to the epithelial cell but there is usually more glucose in the epithelial cells so co-transport is required
what is the process of co-transport (sodium potassium pump)
1) Sodium ions are actively transported out of the epithelial cell into the blood
2) This reduces the sodium ion concentration in the epithelial cell
3) Sodium ions can then diffuse from the ileum down their concentration gradient into the epithelial cell
4) the protein the sodium ions diffuse through is a co-transported protein
5) Glucose moves by faciliated diffusion from the epithelial cell to the blood
Name 2 other variables the student should have kept constant during this investigation
-temperature
-concentration of ethanol
how do you calculate gradient
change in y / change in x
How do you calculate the volumes needed from a ratio
Total volume needed / Total of ratio
answer x ratio
What does it mean if more pigment has escaped
the membrane has been damaged
this means there will be greater absorption
Describe a method a student could used to prepare colour standards
1) Use the same concentration of blueberry extract and solvent
2) Set up a dilution series with water and the solution
3) Compare the different solutions with the colour standard to give an estimated value
What is needed to produce ATP
oxygen –> respiration which provides energy
when does facilitated diffusion take place
when there is a concentration gradient as it is a passive process
how would you ensure no oxygen was in the solution
heat up solution and cool it down or add a layer of oil
what does it mean if there is an overlap between standard deviations
there may be no difference and it depends for each person
how are monosaccharides transported
facilitated diffusion
why do enzymes denature at 60 degrees
-more kinetic energy to break hydrogen/ionic/disulfide bonds in the tertiary structure. This means active site changes shape and less enzyme substrate complexes form
suggest on advantage to a bacterium secreting an extracellular protease in its natural environment
protease digests proteins into amino acids so is easier to absorb for growth and repair
suggest on advantage of having greater percentage of cholesterol in red blood cells
the red blood cell is not on a tissue so its structure is not supported by any other type of cell. Therefore high percentage of cholesterol maintains stability/rigidity
describe the mechanism of absorption of amino acids in the ileum
- Facilitated diffusion of amino acid (into cell
when higher concentration in lumen); - Co-transport;
- Sodium ions actively transported from cell to
blood/capillary/tissue fluid; - Creating sodium ion concentration/diffusion
gradient; - Facilitated diffusion of amino acid into
blood/capillary;
what are the two types of molecules from which ribosomes are made
proteins
RNA
Explain why it was important he controlled the volume of water in each tube
if there was too much water in the test tube the concentration of pigment in the solution will be lower
Suggest how the increase in temperature of the water caused the release of red pigment
increase in temperature damages the cell surface membrane which causes channel and carrier proteins to denature thus increasing permability/membrane fluidity
Use your knowledge of water potential to suggest how putting honey on a cut kills bacteria
Water potential in the bacteria cells is higher than in honey so water leaves bacteria by osmosis. This loss of water stops metabolic reactions occuring
Describe how substances move across cell surface membranes by facilitated diffusion
substances move down a concentration gradient using channel and carrier proteins which are complimentary to the substrate
How would the water potential of the sap in the vacuole of cell E differ from the water potential of cell D
the water potential is lower in cell E as there is a greater solute concentration. This means that water is removed
what is the shorthand version of co-transport
-sodium ions are actively transported out of epithelial cells via a sodium and potassium pump into the capillaries
-sodium ions in the ileum then diffuse down this concentration gradient into the epithelial cell with glucose using sodium glucose transporter proteins
-glucose moves by facilitated diffusion from the epithelial cells to the capillaries via glucose specific channel proteins
cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions, explain how
-sodium ions are actively transported out of epithelial cells via a sodium-potassium pump into the capillaries
-there is an increase in concentration of Na+ in the ileum and a low concentration in epithelial cells
-sodium ions in the ileum diffuse down a concentration gradient into the epithelial cells
Explain why the addition of a respiratory inhibitor stops the absorption of amino acids
-without ATP produced through respiration there can be no active transport of Na+ out of the cell into the blood
-this means that Na+ cannot move by facilitated diffusion due to high Na+ concentration in the cell and thus no amino acids can move either by co-transporter protein
Describe how they made 100cm3 of 1000nmoldm3 solution of kinesin inhibitor
100cm3 of KI solution and mix it with 90cm3 of water
Describe how he made a 1 in 10 dilution then used this to make a 1 in 100 dilution
-take 1cm3 of 1 in 10 and mix with 9cm3 to make 1 in 100 dilution
-take 1cm3 of 1 in 100 and mix with 90cm3 of water to make 1 in 1000
what is the isotonic point
point where the graph crosses the x-axis
how is glucose absorbed
from the ileum into the small intestine to the capillaries
transportation of glucose
ileum –> epithelial cells –> capillaries
what are the steps for co-transportation
1) sodium ions are actively transported out of the epithelial cells and into the capillaries via a sodium-potassium pump which inadvertently transports potassium ions into the epithelial cells. This decreases the Na+ concentration inside the epithelial cell thus creating a concentration gradient
2) With the new concentration gradient sodium ions can diffuse into the epithelial cells via glucose-sodium co-transporter proteins. In order to use the co-transporter glucose and sodium ions need to bind to the protein and both need to move into the cell
3) As more glucose moves into the cell using the co-transporter protein, a high concentration of glucose is established inside the epithelial cell. The glucose then moves by facilitated diffusion into the capillaries via a specific glucose channel protein
what are the factors which affect the rate of osmosis
-water potential gradient (the larger the gradient the increase in rate of osmosis)
-thickness of exchange surface (the thinner the exchange surface the greater the rate of osmosis)
-surface area of exchange surface (the larger the SA the greater rate of osmosis)
how can you find the exact water potential of a tissue/cell
we can measure the change in mass of plant tissue using different concentrations of sugar solutions to find the isotonic concentration
1) use a cork borer to cut 5 potato cylinders of the same diameter
2) use a scalpel and a ruler from each potato so they are the same length
preparing dilution series (potato practical)
1) Add 10cm3 of 2 moles of sucrose solution to one test tube and 5cm3 of water to the rest
2) transfer 5cm3 of sucrose solution to 5cm3 of water and mix to create a solution that is half the concentration
3) Repeat by transferring 5mc3 of the halved solution to the next to create a serial dilution that halves each time
how do you calculate dilution series (osmosis practical)
1) calculate the scale factor by dividing the original concentration by the desired concentration
2) Find what volume we need to transfer by dividing the volume by scale
3) find the volume of distilled water needed by calculating difference
steps for potato practical
1) measure mass of each potato and record it as the initial mass
2) place a potato into each tube and leave for 20 minutes so osmosis can take place
3) remove the potato pieces and blot dry with a paper towel and record the final mass and calculate percnegtage change
define chromatin
tightly coiled combination of DNA and histone proteins. Goes on the form chromosomes
define chromosomes
made of one very long condensed DNA molecule organised with histone proteins which organise and condense DNA so it fits into the nucleus
define chromatid
One half of a chromosome – each leg of the X chromosome is a chromatid. These are identical as chromosomes replicate during mitosis
define centromere
the narrow region at the center of the chromosome that binds and holds the two sister(identical) chromatids together
stages of the cell cycle
Gap 1 –> cell grows and many copies of the organelle are made
S phase –> DNA is replicated
Gap 2 –> the cell enlarges in preparation for mitosis
M phase –> chromatids are separated
Cytokenesis –> cell seperates to form 2 identical diploid daughter cells
(G1, S, G2 are all part of interphase)
why is mitosis important
-Growth –> without mitosis cells would not be able to increase in the number of organisms
-Repair –> without mitosis, broken and damaged organs and tissues would not be repaired
-Mutations –> without mitosis, genetically identical cells would not be formed leading to mutations
-Asexual reproduction –> without mitosis, no asexual reproduction would not be able to take place
-the advantage of completing cell cycle in a short amount of time as it means fast/rapid replication
what are the 5 stages of mitosis
interphase, prophase, metaphase, anaphase, telophase
prophase
-Nuclear envelope breaks down. It breaks up into small vesicles which are not visible with a light microscope
-Nucleolus breaks down
-chromosomes condense and become visible. Made of 2 identical sister chromatids joined at the centromere
-centrosomes move to opposite ends of the nucleus where they form the poles of the spindle
metaphase
-each centrosome reaches a pole
-centrosomes help to organise the production of spindle fibers
-chromosomes line up across the equator of the spindle. They are attached by the centrosomes to the spindle
anaphase
-Each chromosome splits at the centromere
-the chromatids start to be pulled apart by spindle fibers
-chromatids move to opposite poles, centromeres first pulled by spindle fibers
telophase
-Nuclear envelope re-forms
-chromatids have reached the poles of the cell which decondense
-cytokenesis –> this is a division of the cytoplasm and the cell by constriction from the edges of the cell
short phrasing of mitosis
Prophase –> chromosomes condense and become visible. Chromosomes appear as two sister chromatids attached at the cnetromere
Metaphase –> chromosomes line up at equator. Spindle fibrers attach to chromosomes at centromere
Anaphase –> spindle fibers shorten. Centromere splits and sister chromatids pulled to opposite ends of cell
Telophase –> nuclear envelope reforms and separate/unwinds chromatids
true or false –> anaphase requires ATP
true
what happens to chromosomes during telophase
chromosomes unwind
Give three functions of proteins in the plasma membrane
-receptors
-channel/carrier
-enzymes
-facilitated diffusion
Describe the method for absorption of amino acids in the ileum
-co -transport
-Na+ ions move out of epithelial cells and into capillaries by active transport which creates a concentration gradient
-amino acids move into the ileum by facilitated diffusion using specific channel proteins
Describe binary fission in bacteria (3 marks)
-nucleoid and plasmids replicate
-cytoplasm begins to divide
-2 non identical daughter cells are formed due to variable no of plasmids + 1 nucleoid
Describe how the complimentary strand of HIV DNA is made
-complimentary base pairs join (A-T, C=G)
-this is then replicated by DNA polymerase enzymes in the nucleus
-nucleotides condense together to form new strands
name the organelle that that will make viral proteins from viral DNA
ribosomes
why are bacterium described as unicellular
not able to join with other cells
why are viruses known as acellular
non-living and require other cells to function
what is the role of centrioles
production of spindle fibres
Bacterial growth graph
Lag = equal rate bacterial of growth and death
Log = more bacterial growth than death
Stationary = equal rate of bacterial growth and death
Death = more bacterial death than growth
Binary fission
1) Single circular DNA (nucleoid) molecule undergoes DNA replication
2) Plasmids within the cell also undergo DNA replication
3) the parent cell divides into 2 cells with the cytoplasm between daughter cells
4) the two daughter cells each contain a single copy of circular DNA and a variable number of plasmids
why does genetic variation arise during binary fission
there are variable number of plasmids which dont contain the same genes in each daughter cells
calculating the number of cells in a culture
-2^number of generations x initial number of bacteria = total number of bacteria
1) total time / time of divisions
2) initial number of bacteria
3) use equation
what is a bacteriophage
a virus that infects and is only replicated by bacterial cells
structure of a bacteriophage
like all viruses bacteriophages are composed of a protective capsid surrounding a form of nucleic acids (either DNA or RNA)
bacterium vs virus
Bacterium = RNA, cell wall, enzyme molecules
Virus = RNA, Capsid
why are viruses abiotic
Viruses are considered abiotic due to being unable to synthesize their own energy and their genetic material originating from different organisms
two ways in which viruses can invade cells
-endocytosis
-insertion
endocytosis
Endocytosis –> virus moves inside the cell through the cell membrane and then releases its viral DNA/RNA when the capsid is broken down
insertion
1) Virus binds to attachment proteins (glycoproteins) on the surface of them cell membrane
2) The virus injects it nucleic acid into the cytoplasm
3) if DNA –> the viral nucleic acid can possibly be replicated using the host cell’s own DNA polymerase enzymes in the nucleus
4) if RNA –> the nucleic acid is translated at the host cell’s ribosomes create new viral material to build more viruses
5) The cell eventually undergoes lysis (bursts) due to the high concentration of viruses inside
explain two environmental variables that would increase the growth of cells
-greater glucose concentration - increased respiration
-increased temp - increased enzyme activity
mitotic index
no of cells in mitosis / total cells
Describe how the presentation of a virus antigen leads to the secretion of an antibody against this virus
-virus antigen is presented on the cell surface membrane of the phagocyte so can be detected by lymphocytes
-the lymphocytes produce t-cells that stimulate b-cells to secrete antibodies through plasma cells which destroy the antigen
suggest how the immune response to this viral protein can result in the development of RA
antigen binds to collagen which destroys the cells as they release toxins
explain why the peptides cause an immune response
seen as an antigen in the intestinal wall which are then destroyed by pathogens
explain how antigenic variability has caused some people to become infected more than once with influenza virus
memory B cells do not recognise new antigens
-antibodies are less specific
describe the role of macrophages in stimulating B lymphocytes
macrophages present antigens to B lymphocytes in the cell membrane which stimulates mitosis
what is another word for white blood cells
leukocytes
examples of non-self cells
-pathogen
-virus infected cell
-cancerous cell
-cell from another organism
Give two types of cell that can stimulate and immune response
cancerous cells
cells infected by a virus
what is an antigen
a foreign protein that stimulates an immune response found on a cell membrane
Describe how a phagocyte destroys a pathogen present in the blood
-phagocyte attaches itself to pathogen and engulfs the pathogen
-phagosome fuses with lysosomes
-enzymes called lysozymes destroy the ingested pathogen by hydrolysis of the cell wall
Describe how phagocytosis of a virus leads to presentation of its antigens
-phagosomes fuse with lysosomes
-enzymes called lysozymes destroy the virus by hydrolysis
-antigens are presented by being placed on the phagocytes cell membrane
The destruction of t-cells by HIV leads to the death of an infected person. Explain how
-not enough t-cells to achieve immune system
-this means that the person is more prone to diseases/infections such as cancer
Similarity and difference between phagocytes and lymphocytes
both are white blood cells
phagocytes ingest and destroy pathogens while lymphocytes are involved in an immune response
phagocyte = non-specific
lymphocyte = specific
How can t-lymphocytes distingush between invader and normal cells
-antigens present on phagocyte’s cell membrane and on body cells
-transplanted cells have different antigens on cell surface membrane
-cancer cells different from normal body cells
chemical defence mechanisms
-Immune system (humoral and cell mediated responses in the form of phagocytes and lymphocytes)
-Sebum (antimicrobial oil that is secreted from small glands within our skin)
-Acidic conditions (inside the stomach is acidic which denatures enzymes of pathogens. Vagina is also slightly acidic)
physical defence mechanisms
-Mucosal membranes (lines respitory and digestive systems and trap pathogens/neutralising them)
-Skin (impermeble to most pathogenic cells)
-Reflective actions (diahorrhoea, coughing, vomiting, sneezing)
specific vs non specific
-Non-specific –> immediate and the same for all pathogens e.g skin or phagocytosis
-Specific –> response is slower and specific to each pathogen e.g lymphocytes
cell mediated vs humoral
Cell-mediated response –> mediated by specific cells targeting pathogens
Humoral response –> mediated by antibody molecules
pathogens
-an organism that causes harm
-Pathogens can cause disease by releasing toxins, killing cells, damaging tissues
-examples –> parasites, fungi, virus, prokaryotes
Antigens
-A foreign protein that stimulates an immune response
-Anitgens are typically found on the cell surface membrane as glycoproteins or glycolipids
-Toxins are chemicals that damage cells and are also classed as antigens because they have a specific shape
self vs non self cells
Cells originating from the body –> self cells
Material from outside the body –> non-self cells
Lymphocytes
Lymphocytes are immune cells (white blood cells) found in the lymphatic system of the body. They are responsible for the identification of non-self material. There are a variety of lymphocytes each with complimentary receptors to different antigens
Our lymphocytes determine what is self and non-self when we are developing as a foetus
Action of a lymphocyte
1) Lymphocyte comes into contact with the antigens of a cell
2) If it binds to a self cell it undergoes apotosis (programmed cell death) before it begins a full immune response
3) If it binds to a non-self cell it differentiates into a mature lymphocyte and begins the immune response
what are cells that stimulate an immune response
-virus infected cell
-cancerous cell
-cell from another organism
phagocytosis
-A phagocyte is a type of white blood cell and is the active first line of defence
1) The pathogen binds to the cell surface membrane receptors on the phagocyte
2) The pathogen is engulfed and held in a vacuole called a phagosome
3) Lysosomes move into the phagosome and fuse with it thus releasing lysozymes which hydrolyse the cell walls and destroy the pathogen
4) small soluble molecules are used by the phagocyte to build new molecules
5) unusable molecules are removed from the cell by exocytosis
phagocytosis –> presenting antigens
preserves the pathogens antigens and presents them to lymphocytes by placing them on the phagocytes cell membrane
true or false - a phagocyte is non-specific
true
2 types of lymphocytes
T-lymphocytes –> control mediated cell response (attack)
B-lymphocytes –> control the humoral response (make antibodies)
Steps for t-lymphocytes
1) Lymphocyte binds to foreign antigen on the phagocyte membrane
2) Lymphocyte undergoes rapid mitosis to form many clones
3) T-cells aggregate to pathogens to clump them so they cant move
4) Cytotoxic t-cells produce a chemical call perofrin which makes holes in the cell membrane of pathogens so they loose their structural integrity and die
5) When no pathogens are detected, regulatory t-cells begin to suppress the production of cytotoxic t-cells so human cells don’t become damage
what do clones of t-lymphocytes do
-develop into memory cells which enable a rapid future response
-stimulate more phagocytes to carry out phagocytosis
-stimulate B-cells to secrete antibodies
-activate cytoxic t-cells
what are autoimmune diseases
when lymphocytes attack self cells
when are lymphoctyes made
when your a foetus
in your bone marrow
Antigen variability
DNA of pathogens can mutate frequently which codes for a specific antigen thus causing anitgen to change shape. This means previous memory cells will no longer be effective
how do phagocytes bind to pathogens
through receptors that are complimentary in shape
why are T-cells called cell mediated
only respond to antigens which are presented on cells
true or false - antibodies are soluble
true - they are transported in bodily fluids for example blood plasma
What is the role of disulfide bridges in forming the quaternary structure of an antibody
-joins two different polypeptides
Describe and explain the role of antibodies in stimulating phagocytosis
-antibody binds to an antigen on the cell surface membrane of a pathogen
-forms an antibody-antigen complex which acts as a marker to attract a phagocyte
what is a monoclonal antibody
an antibody with the same tertiary structure
Give one example of using monoclonal antibodies in a medical treatment
monoclonal antibodies attach receptors on cancer cells
Describe the role of antibodies in producing a positive result in an ELISA test
-antibody binds to an antigen which is complimentary in shape
-second antibody with enzyme attached is added
-second antibody attaches to antigen
-solution added and a colour change can be seen
B cells vs T cells
-B cells involve antibodies that are present in body fluids such as blood plasma
-T cells are associated with body cells
-T cells mature in the thymus gland whilst B cells mature in bone marrow
-Both are part of the lymphatic system
-both are types of lymphocytes involved in adaptive immunity
humoral immunity
-Involves antibodies which are soluble in the blood and tissue fluid of the body
-Each B cell produces a specific antibody that responds to a specific antigen (complimentary in shape to form an antigen-antibody complex
clonal selection
-The antigen enters the B cell by endocytosis and gests presented on the surface. Helper T cells bind to these processed antigens and simulate B cells to divide by mitosis to form a clone of identical B cells that produce specific antibodies
Primary vs secondary immune response
-Plasma cells secrete antibodies into blood plasma known as the primary immune response
-Memory cells are responsible for the secondary immune reponse –> do not produce antibodies directly but circulate in the blood and tissue fluid, When they encounter an antigen they stimulate the division of plasma cells.
antibodies
-proteins with specific binding sites, synthesised by B cells
-Specific antibody reacts with an antigen on the surface of the non-self material by binding to them
-Each antibody has 2 identical binding sites which are complimentary to the specific antigen
-Antibodies are made up of 4 polypeptide chans with heavy chains and light chains.
-antigen-antibody complex. The binding side is different on each anitobdy so is known as a variable region
-Each binding site consists of a sequence of amino acids that form a specific 3D shape that binds directly a specific antigen. The rest of the antibody is known as the constant region.
how do antibodies assist destruction
-causing agglutination of bacterial cells which clumps the cells together making it easier to be located by phagocytes
-Serve as markers that stimulate/attract phagocytes to engulf the bacterial cells
monoclonal antibodies
-Each antigen will induce a different B cell to multiply and form a clone of itself
-Single type of antibody that can be isolated and cloned
monoclonal antibodies in medical treatment
-monoclonal antibodies are produced that are specific to antigens on cancer cells. These attach to receptors on cacner cells and block chemical signals that stimulate in uncontrolled growth
-Antibodies are non-toxic and highly specific
-indirect monoclonal antibody therpay – attach a radioactive/cyctotoxic drug to monoclonal antibody
-Used for the diagnosis of illnesses such as the flu or hepatitis
-pregnancy test kits use monoclonal antibodies due to hormone which stimulates antibodies to be presented as a coloured line
ethical issues of monoclonal antibodies
-production of these antibodies involved the use of mice
-some deaths associated with the use of monoclonal antibodies
-raised issues about the conduct of drug trials
difference between endocytosis and exocytosis
Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane, and bringing it into the cell. Exocytosis describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell.
How do antigens enter B cells
through endocytosis
Steps for humoral immunity
-antigen enters B cell by endocytosis
-antigen is processed and B cells undergo rapid mitosis
-these new B cells produce antibodies which are complimentary to the antigen and kill it
suggest how one antibody can be specific to both a tick protein and alpha-gal
-tick protein and alpha-gal have similar structures that are complimentary to the antibody
-this means that both can activate the immune response
Explain the increase in specific plasma cells and antibodies in people infected with the ebola virus
-antigen stimulates a specific B cell
-cloning of B-cells
-stimulate plasma cells to r
produce antibodies
Humoral response
1) B-cells are stimulated by t-cells when they encounter a foreign antigen, B-cells will develop into 2 different types
2) Plasma cells will screte antibodies directly producing up to 2000 antibodies per second as part of the primary immune response
3) Memory cells will live for longer in the body, remaining dormant till they encounter the sane antigen which then rapidly divide by mitosis to produce even more plasma cells
Secondary immune response
1) Antigen of the invaded pathogen are taken up by memory cells
2) B cells present anitgens on their membrane surface
3) Helper t-cells attach to the antigens and activate the B-cell
4) B cells divide by mitosis to produce more plasma cells
5) These plasma cells produce antibodies complimentary to the antigens of the pathogen and destroy them
6) Some b-cells remain as memory cells which can respond to future infections faster by recalling specific anitgens
structure of an antibody
–produced by b-cells
-specific binding site complimentary to antigens
-4 polypeptide chains (2 heavy and 2 light)
-have a variable region whose shape is complimentary
-hinge region that provides flexilibty to bind to antigens
-held by strong disulfide bridges
3 types of antibody action
agglutination or anti toxins or cell shielding
agglutination
-with two binding sites antibodies can bind two pathogens at the same time and clump them together for phagoctyes to easily engulf and digest
anti toxins
-some antibodies have complimentary shapes to the toxins that pathogens create. Therefore they can bind to toxins and neutralise them before phagocytes destroy them
cell shielding
-antibodies can lurk outside self cells and bind to antigens of a pathogen before they can bind to a host cell, preventing the pathogen from harming the cell
antibody-antigen complex
-antibodies have a specific tertiary and quaternary structure
-this means that their binding site is complimentary to one antigen found on one type of cell
-antigens bind and form an antibody-antigen complex
production of monoclonal antibodies
1) antigen is injected in a small mamal e.g mice
2) plasma cells produce antibodies to destroy this antigen
3) tumor cells are injected into the mouse to produce a hybridoma cell
4) monoclonal antibodies are produced
uses of monoclonal antibodies
identification of cells/substances and cancer treatment
cell/substance identification
-Manufacture antibodies that are complimentary in shape to specific substances/antigens can identify the location of toxins if they are attached to a flourescent marker
cancer treatment
-attaching a cytotoxic drug to the monoclonal antibody can cause death of a cancer cell when an antibody forms its antibody-antigen complex with the cancer cell
pregnancy testing
-Monoclonal antibodies that are complimentary to beta HCG which is a hormone produced in the early stages of pregnancy that can be placed on a test strip and attached to coloured particles that activate when the second binding site is used
active vs passive immunity
Passive immunity:
-produced by the introduction of antibodies into individuals from an outside source that makes the individual immune to disease for a short amount of time e.g breastfeeding/antibody infections
-faster
Active immunity:
-produced by stimulating production of ones own antibodies either through natural infection with a disease causing pathogen so b-cells mass produce own antibodies or artificial when receiving a vaccination with an inactive form of the pathogen
Vaccinations
1) Vaccine containing an inactive pathogen inserted into the body
2) phagocyte presents the antigen on its membrane surface
3) t-cells with complimentary receptors will bind to the antigen
4) t-cells stimulate b-cells with the correct complimentary antibody onto its membrane surface
5) b-cells undergo mitosis to form clones, cell producing large amounts of the complimentary antibody
successful vaccination programmes
-economically viable –> cost of preventing disease should be cheaper than cost of treating disease
-side effects –> must be minimal so people are not deferred from taking the vaccine
-production and administration –> should be easy and efficiently made and administered properly with sufficient training
-herd immunity –> must be possible to vaccinate most of the population to induce herd immunity among the vulnerable
herd immunity
-arises when most of the population are vaccinated against a disease
-if people are not immune they can receive and pass on a pathogen to all who come in contact with it
-if enough people are immune to a disease the rate of transmission is lower
why cant vaccines eliminate a disease completley
-pathogens such as viruses mutate often and their antigens change shape so are no longer complimentary to the antibodies the vaccine programme created
-individuals can object to vaccine over misinformation spread around their safety
-some diseases have many varieties such as the common cold and it Is impossible to create every possible vaccine that will compliment that many antigens
what type of nucleic acid is found in HIV
RNA (reverse transcriptade)
Y is a protein –> describe the other function of Y than transporting cellulose molecules
-enzyme –> joins beta glucose in cellulose
what evidence in figure 3 is that the phospholipid bilayer part of the cell membrane
cell wall forms outside of phospholipid bilayer
the rate of cell division is important in investigations into cancer. Suggest why
-faster rate of division = faster cancer growth
-by measuring this we can see how effective treatment would be
describe how HIV is replicated
-attachment proteins attach to receptors on lymphocytes
-nucleic acid enters cell
-reverse transcriptase converts RNA to DNA
-viral protein produced
Name two features of HIV particles that are not found in bacteria
-viral RNA
-lipid envelope
Describe the structure of HIV
-retrovirus that contains outer lipid layer w attachment proteins
-capsid with viral RNA and reverse transcriptase
Describe how HIV is replicated once inside helper t-cells
-reverse transcriptase converts viral RNA into DNA within cytoplasm of host cell
-viral DNA incorporated into the host’s own DNA
-the viral DNA can then be transcribed into mRNA
-the viral mRNA is translated into viral proteins at the ribosomes to make new HIV
Explain why AIDS leads to death
-no b or t cells
-more vulnerable to other diseases
-damaged host cells from inside by reproducing and producing toxins
Explain why a vaccine may not be effective against HIV
-HIV enters cells before antibodies can destroy it
-antibodies cannot enter cells
define a retro virus
a virus that converts RNA into DNA e.g HIV
transcription vs translation
Transcription involves the conversion of DNA into RNA, while translation involves the conversion of RNA into protein
attachment protein
lipid envelope
capsid
-Attachment proteins are structures which allow the virus to bind to membrane receptors on other cells
-Lipid envelope allows viruses to easily leave cells without disrupting the cell membrane
-Inside the virus is a capsid containing viral RNA and enzymes called reverse transcription which are important in viral replication
components of HIV
-attachment protein
-viral RNA
-protein capsid
-reverse transcriptase
-lipid envelope
HIV replication
-Viruses cannot undergo mitosis so they must use other cells called host cells to produce new components
1) HIV circulates the body and its attachment proteins attach to receptors on membrane of helper t-cells
2) HIV capsid fuses with membrane and its RNA and reverse transcriptase enter the host cell
3) The reverse transcriptase converts viral RNA into DNA within cytoplasm of host cell
4) The viral DNA is incorporated into the helper t-cell’s DNA within the nucleus and transcribed into mRNA
5) This viral mRNA is then transcribed at ribosomes to create new viral proteins to create new viruses within the host cell
AIDS
-when infected with HIV, a person is said to be HIV positive, but the virus often goes into dormancy and replication. When it commences years later it can become serve and develop into AIDS
Formation of AIDS:
1) An uninfected individual normally has between 800 and 1200 helper t-cells per mm3 of blood whereas an individual with AIDS can have below 200 helper t-cells per mm3
2) Without sufficient helper t-cells the immune system cannot stimulate b-cells to produce antibodies or cytotoxic t-cells to kill the cells infected by pathogens
3) When an individual is unable to produce a sufficient immune response, the sufferer becomes more susceptible to other diseases that eventually causes death
purpose of ELISA test
-used to test for the presence of antibodies against a specific pathogen
-can also be used to test for presence of certain proteins in an individual
ELISA test
1) Antigens for a specific pathogen e.g HIV are bound to the surface of a dish.
2) A patients blood sample is added. If they possess complimentary antibodies then they will bind to antigens on the plate
3) The blood sample is washed off to remove unbound antibodies
4) A second antibody that is complimentary to host antibody with an enzyme attached. The sample is washed for a second time
5) A substrate is added which will be converted into a coloured product which will indicate the presence of an antibody
explain the purpose of boiling the agar
so no contamination –> kills bacteria
suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration
-amino acids used in protein synthesis
-more enzymes to make plasmids
describe how you would determine a reliable mitotic index for tissue observed with a light microscope
-count cells in mitosis in field of view
-divide by total no. of cells in field of view
-repeat at least 5 times
describe the mechanism for the absorption of amino acids in the ileum
-facilitated diffusion of amino acids into cell
-co -transport
-sodium ions actively transported from cell to blood
-concentration gradient created for sodium ions to diffusion down by facilitated diffusion
Explain why antibody B is important
-prevents a false positive as it shows antibody A has moved up the strip
Explain why HSV only affects nerve cells
-HSV has specific attachment proteins which are complimentary to receptors on nerve cells
-these are only found on the nerve cells membrane
suggest one advantage of programmed cell death
prevents viral replication
inactive virus =
can no longer replicate
two ways which pathogens can cause disease
-release toxins
-bursting of cells/cell death
describe how the appearance of the area containing DNA in a TEM image of a eukaryotic cell would differ from that shown in a bacterium
-found in the nucleus
-nuclear membrane
suggest how bacteria with a thicker capsule are more likely to survive and cause lung disease
-thicker capsule = more difficult for phagocytes to bind to murein on cell wall os bacteria
-thus cannot be engulfed by pathogens so can replicate and spread disease in the lungs
increased fluidity
caused by increased unsaturated fatty acids
use your knowledge of the cell cycle to explain the results shown in figure 4
-mass of DNA = 1 indicates early interphase
-mass of DNA = 2 indicates mitosis
-Mass of DNA between 1 and 2 indicates some of DNA has been replicated
explain consequences of errors occuring when toms and lucys blood samples are tested
Tom = healthy donor not allowed to donate = less blood collected
Lucy = gives blood which many not be safe for her to do so and may not help patients
Outline the similarities and differences between the structure of chloroplasts and mitochondria
-both have double membrane
-starch grain in chloroplasts but not in mitocondria
-both contain ribosomes
-chloroplasts = granum
-mitochondria = cristae and matrix
what is an antibody
a protein produced by B cells
explain how the xylem tissue is adapted for its function
-tubes with no end walls = continious water columns
-no cytoplasm for easier flow of water
give 3 structural features found in all virus particles
genetic material
capsid
attachment protein
explain why viruses are described as acellular and non-living
-no cell surface membrane so no metabolic reaction
give one reason why antibotics are not effective against viruses
-viruses do not have bacterial structures
describe the role of cholesterol
-maintains membrane fluidity
-the more cholesterol the less fluid and more rigid the membrane is
high standard deviations
= more uncertainty
key point for evaluating/coming up with a conclusion
correlation doesnt prove causation
standard deviation
measure of values around the mean
standard deviations
significant = no overlap
non significant = overlap
Calculate the SD’s for each number so it easier to compare in an exam questions
chi square
-unit 6 + 7
-used when comparing differences between observed results and expected results
T-test
used when we are simply measuring or comparing differences between a control variable and different experimental groups
P value
0.05 or 95%
if P<0.05 (less than) then results are significant so you should reject the nul hypothesis and accept the alternate hypothesis
why did he put the plant root in acid
break up tissues into individual cells
reliable sample
-select snails at random
-use large sample
role of antibodies in stimulating phagocytosis
-antibodies bind to antigen
-causes agglutination / attracts pathogens
why does this shown an electron microscope
-can view nuclear membrane / ribosomes
-high resolution
structural difference of ribosomes in chloroplasts and other parts of the cell
chloroplast ribosomes are smaller than cytoplasmic ribosomesl
limitations of TEM
-cannot colour
-cannot view living things due to vacumn
-thin sample must be used
suggest and explain why the offspring produced from farmed trout are sterile
-too many chromosomes
-homologous pairs do not form
-no meiosis occurs
what happens to chromosomes in telophase
unwind
describe and explain the prcoesses that occur during meiosis that increase genetic variation
-homologous chromosomes pair up
-independent segregation
-maternal and paternal chromosomes shuffled in any combination
-corssing over leads to exchange of chromatids
-creation of new combination of alleles
explain how the shape of ATP synthase allows it to have the functions
-structure is compimentary to ADP + Pi so enzyme substrate complex forms
suggest one reason why there are no data fro group G and H after day 8
mice died
suggest two further investigations that should be done before ADC is tested on human breast cancer patients
-repeat on other mammals
-try on healthy humans
suggest the meaning of a genetic tendency to chrons disease
-people have a gene that increases chance of…..
increase in cytokine
= increase in swelling
viruses
reproduce inside a host cell and cause cell lysis
aceullar as not connected ti cell membrane
no nucleus
how is HIV managed
antiretroviral drugs
physical barriers
-skin (thick from keratin)
-stomach acid
-gut and skin (bacteria outcompetes pathogens)
-mucus and cilia in respiritory systems
phagocytosis
-phagocyte receptors make contact with antigens and binds
-phagocytes engulf antigens by extending cell membrane and holds inside a phagosome
-lysosomes fuse with phagosome
-release of lysosomes = hydrolysis
types of active immunity
natural active immunity -> exposure to a specific pathogen and develop memory cells
aritifical active immunity -> vaccinations
explain why viruses are described as aceullar and non-living
-no nucleus or cell surface membrane
-need a host cell to reproduce
explain why the anti-AQP4 antibody only damages these cells
-specific teritary structure
-binding site complimentary to only one antigen
-only forms antigen antibody complex with these nerve cells
what is the impact of lysozymes on bacteria
hydrolyse cell wall made of meurin = unable to survive/grow
too many b cells =
unable to undergo apotopis = autoimmune reponse (attack self cells)
how do t cells produce genetically identical cells
-pathogens invade body cells and phagocyte presents antigens on its cell surface membrane
-receptors on T-cells bind to complimentary antigens
-mitosis to form clones
describe what happens to cloned t cells during infection
-b cells = memory cells
-phagocytosis
-activate cytoxic t cells
-mitosis + secrete antibodies
why might a cellular response be more effective than humoral
virus invade body cell = hidden from antibodies
antigen present to t lymphocyte by phagocyte (antigen presenting cell)
function and structure of nucleus
nucleolus = production of ribosomes
nuclear enveloples and pores = stores genetic material for polypepetides
-chromosomes = DNA replication
experiment to calculate water potential
- Record mass/length before and after;
- Place in sea water for (specified/equal) time;
- Method to remove surface water;
- Increase in mass/length shows water has been
absorbed by osmosis
OR
Increase in mass/length shows cells have lower
water potential;
OR - Put tissue/cells on (microscope/glass) slide;
- Add seawater (and leave)
- Observe under (optical) microscope;
- If cells become flaccid they do not have a lower
water potential than seawater
OR
(If cells become) turgid cells show water is
absorbed by osmosis
OR
(If cells become) turgid cells show c
pregnancy test
-urine passes through reaction site
-reaction site contains free antibodies with dye enzymes attached
-hcg hormone from urine binds with antibodies in reaction site
-forms antibody-antigen complex in test site
-no complex in reaction site
it was suggested that the ra data showed that the type III vaccines was the most effective. Give 2 reasons why this would be unreliable
-sample size is too small
-differences in exposure to injection
explain why a statistical test should be applied to the data obtained in this investigation
to determine the probability of results being due to chance
convert cm3 to m3
divide by (100)2
cm3 to mm3
x10^3
describe how you would make a temporary mount of plant tissue
-add drop of water to glass slide
-obtain thin slice of plant specimin
-add iodine in potassium iodide
-place cover slip using mounted needle to prevent air bubbles
TEM =
can view internal organelles
suggest a more appropirate control experiment
boiled saliva = amylase is denatured = view impact of chewing not what is being chewed
heating to constant mass
weigh samples are regular intervals during drying process
colorimeter
measures the amount of light that is absorbed by the solution
absorption is directly proportional to the concentration of the coloured compound presetn
higher absorbance =
more pigment = more membrane damage
describe a method this student could use to prepare colour standards and use them to give data from the total anthocyanin extracted
-use known conc of the anthocyanin pigment
-prepare dilution series
-compare results with colour standards to give concentration
high atmospheric CO2
more stomata closed
decrease in transpiration
structure for evaluation questions
-what is the relationship in the data
-what is the link to content from the relationship in the data
-what is missing from the experimental design
-what assumptions are made about the IV and DV
how would you advise the student to use her calculated ratio’s to determine the water potential of eggs
-IV = concentration of sugar solution
-plot calibration curve
-interpolate from ratio of 1
-change concentration into water potential
how are pathogens like bacteria detected
by releasing toxins/chemicals
artifical active immunity example
vaccination
how would you produce a calibraiton curve for glucose
-use glucose solution and water to make dilution series
-add benedicts reagent and heat
-volume - same vol benedicts reagent
-measure absorbance using colorimeter
-plot curve conc of glucose vs absorbance on the y-axis
explain why plants cannot absorb nitrate ions in waterlogged soil
-nitrate ions absorbed by active transport = moves from low to high concentration
-this requires ATP (energy) from respiration
-aerobic respriation requires oxygen but little oxygen is available in waterlogged soil
