Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
282 Cards in this Set
- Front
- Back
|
Give examples of a eukaryotic cell |
Plant , animal , fungi |
|
|
What are eukaryotic cells? |
Cells have membrane bound organelles |
|
|
What is the structure of the cell membrane (plasma)? |
It is made up of protein parts and phospolipid bilayer |
|
|
What is the function of the cell membrane? |
It encloses the contents of the cell. It controls what substances enter and exit the cell (regulates passage) |
|
|
What is the structure of the nucleus? |
Nuclear envelope (a double membrane) , nucleolus and the nuclear plasma |
|
|
What is the function of the nucleus? |
Stores DNA and controls activities of the cell as when dna translated produces enzymes that catalyse reactions Produce ribosomes |
|
|
What is the structure of the mitochondria? |
Oblong shaped organelles found in the cytoplasm , Have a matrix and a double membrane. Inner membrane = cristae for oxidative phosphorylation |
|
|
What is the function of the mitochondria? |
Double membrane controls entry and exit like cell surface membrane Aerobic respiration occurs to release/provide energy for the cell. It produces ATP Matrix has prokayotic like DNA and ribosomes so mitochondria can produce its own enzymes for respiration. |
|
|
What is the structure of a chloroplast? |
Double membrane It has chlorophyll contained in thylakoid membranes Many thylakoid stacked make grana (thylakoids connected via inter granal lamellae) and it also has stroma which is a fluid filled matrix (starch grains found due to LIR) |
|
|
What is the function of the chloroplast? |
Photosynthesis occurs here to provide the plant with respiratory substrates and allow it to grow as produces biomass - thylakoid membrane give large SA for LDR. Stroma has enzymes for LIR and prokaryotic like DNA and ribosomes to produce its own Double membrane controls entry and exit |
|
|
What is the structure of the golgi apparatus? |
Concentrated flat discs of membrane called cisterna - stacked up. Associated golgi vesicles |
|
|
What is the function of the golgi appartus? |
Substances produced by ER pass to golgi. These may be modified e.g chylomicrons. They are then transported via golgi vesicles e.g. exocytosis for cells which are involved in secretions e.g. pancreas with digestive enzymes and can secrete the substances which make up cell walls Form lysosomes by putting lysozymes into vesicles |
|
|
What is the structure of the lysosome/vesicle? Function? |
A small sphere of a plasma membrane that contains the chemicals being transported Provide an internal transport system. Keeps lysozymes (hydrolyse bacteria cell walls in phagocytosis) seperate so dont damage the cell Produced by golgi apparatus Can carry out exocytosis - lysozymes hydrolyses - extra-cellular Can be used to break down worn out cells and organelles |
|
|
Whats the difference between a lysosome and a vesicle? |
The lysosome releases lysozymes which are digestive enzymes - break down pathogens in phagocytosis |
|
|
What is the structure of the ribosomes? Where are they found? |
Tiny organelles made from ribosomal RNA and protein. Have two subunits In the cytoplasm or associatied with endoplasmic reticulum to form rough endoplasmic reticulum |
|
|
What is the function of the ribosomes? |
Proteinsynthesis occurs. |
|
|
What is the structure of the endoplasmic reticulum? |
Folded membrane which is continuous with the nuclear envelope - cisterna RER has ribosomes attached |
|
|
What is the function of the endoplasmic reticulum? |
ReR produces proteins and provides a pathway of transport for them - sends them to golgi SeR produces lipids , stores and transports them to the golgi. Also carbohydrates too |
|
|
Whats the difference between the rough and the smooth ER? |
The rough has ribosomes to make proteins and the smooth doesnt , it makes lipids |
|
|
What is the structure of the plant cell wall? |
Fibrils of cellulose |
|
|
What is the function of the cell wall |
Has strength due to many H bonds between fibrils so can prevent osmotic lysis as prevent bursting - resist pressure (turgid) Water passes along it in transpiration |
|
|
What is the structure of the vacuole? |
Its a plasma membrane (tonoplast) filled with fluid which contains sugars AA mineral salts wastes and a pigment to give a colour |
|
|
What is the function of the vacuole? |
Water is held to support the plant and maintain pressure - make turgid (plant cells dont burst due to cell wall) Hold respiratory substraes Pigment attracts bees for pollination |
|
|
What features of cells are exclusive to plants? |
Cell wall , chloroplasts and vacuole |
|
|
What parts are exclusive to animal cells? |
Microvilli (epithelial) |
|
|
What do microvilli do? |
Increase the surface area |
|
|
What are examples of prokaryotic cells? |
bacteria (viruses are considered to be neither as they are non living) |
|
|
Whats the difference between eukaryotic cells and prokaryotic cells? |
They have no membrane bound organelles (mainly no nucleus) and they are smaller |
|
|
What are prokaryotic cells ribosomes like? |
Smaller (70s) |
|
|
Do prokaryotic cells have a nucleus? |
No , single circular DNA molecule not associated with histones so no chromosomes form |
|
|
What is prokayrotic cell wall made of ? |
Murein (glycoprotein) |
|
|
Are virsuses living? |
No |
|
|
What three features do bacterial cells have that eukaryotic cells dont? |
Flagella - for locomotion, capsule of slime to protect them and help bacteria to group(on outside of cell wall) and plasmids which can contain antibiotic resistant genes caused by mutations |
|
|
What is meant by differentiation? |
When cells become specialised to carry out a specific function |
|
|
How do you view a sample using an optical microscope? |
Water on glass slide Thin plant tissue added Stained with iodine in pottassium iodide for starch Glass cover slip put on top with mounted needle |
|
|
How do you view a sample using a transmission electron microscope? |
Dead sample covered in resin to form a block Thin slice is cut and stained with heavy metals Electrons are fired via an electron gun and is focused by electromagnets onto the sample which are absorbed by metal organelles and pass through cytoplasm Electrons which pass through are focused on a flourescent screen giving areas of light and dark (absorption) A photograph is taken of this to produce a photomicrograph |
|
|
How do you view a sample using a scanning electron microscope? |
sample coated in metal layer to increase contrast Electrons are fired and reflected (scattered) to form 3D image via a computer Cells tissues and organims can be seen |
|
|
What are the negatives of the optical microscope? |
Cannot see anything smaller than the wave length of light and it has a low resolution and cannot distinguish between objects closer than the length of the wavelength of light |
|
|
What are the pros and cons of a transmission electron microscope? |
Can see inside and see organelles due to very high resolution (ultrastructure). However , this high resolution isng always achieved as the high energy electrons can destroy the sample and preparation may be difficult resulting in artefacts - confusion. but a dead sample is needed as its in a vacuum and only a black and white image can be produced. Complex staining process required . Extremely thin to allow electrons to penetrate. 2D image |
|
|
What are the pros and cons of a scanning electron microscope? |
Same as TEM apart from thin sections arent required. Can see 3D structure but cannot see ultrastructure Slightly less resolving power than TEM |
|
|
What is the difference between magnification and resolutin? |
Resolution - min distance between two objects for them to appear as seperate items (depends on wavelength used) Magnification- increasing the size of the image only - more blurred image if exceeds resolution |
|
|
What should your units be in a magnification calculation? |
All the same |
|
|
How much smaller are micrometres compared to mm |
1000 |
|
|
How do you convert um to mm |
÷1000 |
|
|
How do you convert mm to um |
x1000 |
|
|
How do you measure the image of a cell? |
Longest plane (if diameter may need to calculate a mean value) |
|
|
What is the magnification calculation? |
Magnification = image ÷ actual |
|
|
What can a cell fractionation be used for? |
Cells are broken up to seperate and collect cell organelles |
|
|
What is the process of using a cell fractionation to seperate cell organelles? |
Sample is put in a homogenizer which breaks open the cells and the homogenate is filtered to remove unbroken cells and large pieces of debris The homogenate is then put in the centrifuge to seperate organelles (ultracebtrifugation) starting at a low speed and the dense pellets (sediment) are removed everytime and then speed is increased , supernate span again. Heaviest to lightest with increasing speed |
|
|
What is the order of cell organelles removed in a centrifuge? |
Nuclei&DNA mitochondria Lysosomes ER&ribosome |
|
|
What does isotonic mean? |
Prevent osmosis so organelles dont burst or shrink - no damage and maintain osmotic pressure |
|
|
Why are the conditions in a centrifuge kept cold? |
To keep enzyme activity low so organelles not broken down |
|
|
Do all cells carry out mitosis? Examples? |
No - red blood cells dont have a nucleus as they are so specialised. Cardiomyocytes are regenerated by a source of unipotent stem cells. Neurones too |
|
|
What is mitosis? |
(Eukaryotic) cells divides to produce two daughter cells , which have identical copies of DNA produced by the parent cell during DNA replication The division part of the cell cycle |
|
|
Eukaryotic cells that can carry out mitosis show... |
A cell cycle |
|
|
What is the purpose of mitosis ? |
Growth of zygote to produce organism with genetically identical cells , repair of tissues to replace identical cells to the ones damaged and asexual reproduction in some species - preserves alleles that allowed parents to survive so offspring will probably survive too |
|
|
What happens during interphase and what stage of the cell cycle is this? |
G1 , S , G2 . The first stage, the cell carries out normal functions and prepares itself for the next division |
|
|
What is G1? |
Rapid growth of cell to reach normal size |
|
|
What is S? |
The DNA is replicated to prepare for mitosis |
|
|
What is G2? |
Second growth phase in which organelles for the new cell produced in mitosis are made - proteinsynthesis |
|
|
Behaviour of chromosomes in interphase: |
Two chromatids joined at centromere to form sister chromatidsdue to dna replicatiob. Not visible and are long and linear |
|
|
Behaviour of chromosomes in prophase ? Why? |
Chromosomes become visible Nuclear envelope breaks down and they shorten and thicken |
|
|
What happens during prophase and what stage of the cell cycle is this? |
The centrioles move towards the poles of the cell Nucleolus and nuclear envelope break down Centrioles form spindle apparatus Chromosomes shorten and thicken |
|
|
Behaviour of chromosomes in metaphase : |
Chromosomes line across the equator of the cell |
|
|
What happens in metaphase and what stage of the cell cycle is this? |
The 3rd stage. Spindle fibres attach to centromeres of chromosomes and pull them so they line up across the equator |
|
|
Behaviour of chromosomes in anaphase: |
Chromatids seperate and are pulled towards poles |
|
|
What happens in anaphase and what stage is this.? |
4th stage. The spindle fibres contract using ATP and the sister chromatid sepereates as the centromere breaks and the chromosomes move towards the poles. |
|
|
What is telophase and what stage? |
Stage 5. New nuclear envelope and nucleoi form for seperate cells. Chromosomes are no longer visible as become thinner and longer again Spindle apparatus disintegrates |
|
|
What is cytokinesis? |
Cytoplasm divides to finish cycle and both daughter cells enter interphase to resume normal cell functions |
|
|
What can uncontrolled mitosis lead to? |
The formation of cancerous tumours |
|
|
What is binary fiszion? |
Prokaryotic cells replicate circular dna and plasmids, DNa attaches to cell membrane and new cell membrane grows inbetween copies and then cytoplasm divide to produce daughter cells - new murein (bacteria) cell wall grows |
|
|
Can the number of plasmids from binary fission vary? |
Yes |
|
|
How do cancer treatments work? |
Cell division is prevented which stops the tumour growing . Also cells are killed |
|
|
What do viruses do to replicate themselves? Why cant they divide normally? |
Inject nucleic acid into host cells when attachment proteins bind to cell membrane proteins. These cells begin to replicate the virus particles and then the cell bursts to release new viruses They are non living so need a host cell to replicate |
|
|
What is the main structure of a plasma membrane? |
Phospholipid bilayer |
|
|
What is the structure of a phospholipid? |
It has an inorganic phosphate group head and two fatty acid chain tails |
|
|
Which parts of the phospholipid are hydrophillic/hydrophobic? |
Heads are hydrophillic and tails are hydrophobic |
|
|
What are fats insoluble in? |
Water |
|
|
Therefore.. |
The membrane can control the passage of water into and out of the cell |
|
|
What happens if a cell has too much water? |
It can burst (mammal cells) or become turgid (plant cells) |
|
|
What happens if a cell has too little water? |
It will be rigid/shrivel and not function properly |
|
|
What is formed instead of a bilayer if not many phospholipids are present? |
A micelle (sphere) |
|
|
What two types of proteins exist within the bilayer? |
Intrinsic and extrinsic |
|
|
What are two other words for instrinsic proteins? |
Integral and transmembrane |
|
|
What is another word for extrinsic proteins? |
Peripheral |
|
|
Where are intrinsic and extrinsic proteins located in the bilayer? |
Intrinsic proteins span the whole width of the membrane and extrinsic proteins are confined to the inner or outter surface of the membrane |
|
|
What are the two types of intrinsic proteins? |
Channel and carrier proteins |
|
|
What is the job of the intrinsic proteins? |
Allow the passage of substances that cannot diffuse across the membrane |
|
|
Whats the difference between channel and carrier proteins? |
Channel proteins have a hole and do not change shape. Carrier proteins change shape to carry substances through and they can open and close to control passage |
|
|
What can extrinsic proteins have attatched to them? |
A carbohydrate chain |
|
|
What are the proteins known as if they have this attatched to them? |
Glycoproteins |
|
|
What about phospholipids with a chain attatched? |
Glycolipid |
|
|
What is the function of glycoproteins? |
Act as receptors for hormones , neurotransmitters and can act as antigens too |
|
|
What is the function of cholesterol in the membrane? |
Controls membrane fluidity, provides strength and prevents leakage - seperate environments created either side of membrane |
|
|
What is the newest model of the plasma membrane called? Why? |
The fluid mosaic model Fluid as its flexible due to molecules within moving Mosaic due to intrinsic proteins |
|
|
As cholesterol increases... |
Fluidity decreases |
|
|
Why? |
Restricts movement of other molecules in the membrane |
|
|
What is the importance of cholesterol? |
Keeps membrane stable so cells dont burst |
|
|
What can vesicles do in relation to the cell membrane? |
Fuse with the cell membrane |
|
|
Why? |
To transport substances out of the cell via exocytosis. Secretions |
|
|
What happens to membrane fluidity when you increase temperature? Why? |
Fluidity increases because the lipids gain more kinetic energy so they spread out |
|
|
What happens do fluidity if protein percentage is decreased? Why? |
Increases because proteins provide stability |
|
|
How can the phospholipid chains vary? |
They can be short and unsaturated or long and saturated (the fatty acid chains) |
|
|
How does this effect membrane fluidity? |
Unsaturated chains make the membrane more fluid because double bonds cause kinks in the chains which spreads the lipids out |
|
|
What happens in simple diffusion? |
Particles diffuse across the cell membrane |
|
|
What particles can diffuse across the membrane ? |
Small non-polar and non-charged lipid-soluble |
|
|
Can water diffuse across the membrane? |
Yes but slowly as its polar (osmosis?) |
|
|
What is facilitated diffusion? |
Substances diffuse into the cell via channel and carrier intrinsic proteins as cannot diffuse across phospholipid bilayer due to its restrictive nature |
|
|
What type of substances diffuse via the intrinsic proteins? |
Ions and larger molecules |
|
|
What is the importance of a vacuum in the scanning electron microscope? |
So high energy electrons arent absorbed by molecules in the air |
|
|
What may a scanning electron microscope not work? |
Preperation wasnt good or the high energy electrons destroy the specimen |
|
|
What is a tissue? |
Made up of many similar cells which carry out the same function come together to form a tissue that carrys out a function |
|
|
What is the definition of diffusion? (Simple) |
Diffusion is the net movement of particles down a concentratiom gradient from an area of high concentration to an area of low concentration until eqm is reached |
|
|
When does net movement stop? |
Equillbrium is reached (particles still move though due to kinetic energy they possess) |
|
|
Are channel proteins specific? |
Yes so they only transport specific substances |
|
|
Can channel proteins open/close? |
Yes in certain conditions |
|
|
Do carrier proteins act in both directions? |
No only one |
|
|
How carrier proteins work? |
Particle binds to receptor /binding site of carrier protein , this changes its shape so the protein transports the substance through |
|
|
What is the definition of osmosis? |
Water molecules move from a region of high water potential to a region of more negative water potential across a partially permeable membrane until equilibrium is reached |
|
|
What is the symbol for water potential? |
A greek Y |
|
|
What does a water potential value of 0 mean? |
Pure water |
|
|
What does a negative number for water potential mean? |
Its a solution |
|
|
What is saltier -0.4 or -0.2? |
-0.4 (more negative) |
|
|
What does isotonic mean? |
Same water potential on the outside and the inside of the cell so osmosis is prevented |
|
|
What is plasmolysis? |
Water potential outisde is lower so water moves out of cell and it shrinks |
|
|
This is known as... |
Plasmolyzation |
|
|
What is required in active transport? |
Energy (ATP) |
|
|
What is the definition of active transport? |
Movement of particles from a low concentration to a high concentration (against concentration gradient) it requires energy in the form of ATP and involves carrier proteins |
|
|
What is the energy used for? |
To open carrier protein so substance can enter cell. ATP is hydrolised for this to take place. Energy from hydrolysis causes shape change |
|
|
What are the benefits of co-transport compared to active transport? |
Amount of energy required is reduced so it is more efficient |
|
|
What happens when a glucose molecule is taken in via a carrier protein? |
A sodium ion goes in with it (into epithelial cell) - co-transport in the same direction |
|
|
Do the glucose and sodium diffuse into blood together? |
No seperately , glucose through normal carrier but sodium via a sodium pottasium pump carrier protein |
|
|
What part of co-transport involves energy? |
The sodium pottasium pump |
|
|
How many pottasium ions are put into the cell for every 3 sodium ions into the blood? |
2 |
|
|
Why? |
To prevent osmosis from occuring as the concentration is balanced |
|
|
What does sodium going into the blood induce? |
More sodium ions moving into the cell which pulls glucose in with it |
|
|
Why is this helpful? |
Glucose goes into cell due to Na+ conc gradient set up so energy not directly required. This co-transport is indirect active transport |
|
|
What is the illeum? |
Small intestine |
|
|
What is a lumen? |
A hole |
|
|
What is epithelial tissue? |
A tissue that covers organs |
|
|
Why do red blood cells need more cholesterol than cells in the illeum? |
Travel around vessels under high pressure so need more stability so they dont burst - cholesterol provides strength and reduces fluidity |
|
|
Which intrinsic proteins are used in active transport? |
Only carrier proteins |
|
|
What is another word for the internal structure of a cell? |
The ultrastructure |
|
|
The function of the cristae? |
Increases surface area for oxidative phosphorylation |
|
|
What forms lysosomes? |
Golgi forms lysosomes from golgi vesicles (manufactured lysozymes within) |
|
|
What type of cells is a zygote? |
Stem cells (totipotent) |
|
|
What are stem cells? |
Unspecialised and undifferentiated |
|
|
Why do cells become specialised? |
Expressed gene in dna |
|
|
What is generally the best microscope? |
TEM |
|
|
How many pairs of chromosomes are in a human? |
23 |
|
|
Specifically how are two identical cells made via mitosis? |
In interphase the dna is replicated Replication occurs via complementary base pairing to form two identical dna strands (semi conservative) This forms 2 identical sister chromatids and each of the chromatids move to opposite poles of the cell in anaphase |
|
|
2 reasons for having a thin specimen under an optical microscope? |
One layer of cells and if the specimen is thin more light can get through which forms a clearer image |
|
|
What are control groups given? |
Normal lifestyle with placebo perhaps - anything that allows comparison (control variables) |
|
|
Give an example of a physical barrier the body has to prevent the entrance of pathogens. What type of response is this? |
Skin , mucus , tears Non-specific - the same for all pathogens |
|
|
What inside protection does the body have? |
The immune system ( if the physical barriers fail) |
|
|
What type of responses does the immune system have? |
Specific and non-specific |
|
|
Which white blood cells are non-specific? |
Phagocytes |
|
|
Which are specific? |
Lypmphocytes ( helper T and B) |
|
|
What are antigens? |
Material recognised as non-self by lymphocytes which initiates an immune response (Usually proteins on all cell membranes , specific to every cell and identifies it) |
|
|
What do antigens do? |
Identify cells. Self ? Cool. Non self? Immune response! |
|
|
How? |
There is a helper T and B cell specific to every possible antigen and when come into contact either T cell recognises as non-self (only if its on an antigen presenting cell) and is activated or B cell carries out processing of the antigen |
|
|
What are examples of foreign cells in the body? |
Pathogens , other peoples (same species different individual), abnormal body cells and toxins |
|
|
What do phagocytes do when they identify foreign antigens? |
Firstly they've been attracted by chemical products and receptors bind to chemicals on surface /antigens recognising as non-self They engulf athe pathogen by forming a vesicle known as a phagosome from cell membrane which fuses with the lysosomes in the cells. The lysozymes in the lysosome break down the pathogen via hydrolysis and products of the break down are absorbed by the cytoplasm of the cell , insoluble removed via exocytosis, antigens of pathogen presented on the cell surface membrane so becomes an antigen presenting cell |
|
|
What is the name for that process? |
Phagocytosis |
|
|
What is an antigen presenting cell? |
One that presents the antigens of a pathogen that has infected it /it has engulfed / B cell antigen processing on its cell surface membrane |
|
|
What is the importance of this? |
Help to trigger a specific immune response because helper T cells can only be activated by antigen presenting cells - not lone antigens. Antigens must be attached to a cell |
|
|
What are the two types of specific responses? |
Cell-mediated and humoral |
|
|
What lymphocytes carry out humoral? |
B cells |
|
|
What lymphocytes carry out cell mediated? |
T cells |
|
|
What do helper T cells do when they recognise foreign antigens? |
They are activated and produce a chemical signal which stimulates cytotoxic T cells , phagocytes and they activate the specific B cells to divide and produce antibodies. Form memory cells for immunity |
|
|
How are memory cells formed? |
Rapid mitosis - clonal selection |
|
|
How long do the memory cells remain? |
Forever (or a very long time atleast) |
|
|
How do cytotoxic T cells destroy pathogens? |
They sectete a protein called perforin which burst cells infected by viruses by making holes in their membranes which destroys them as they become permeable to all substances and breaks them down - gets rid of viruses as cant multiple without host cells |
|
|
What happens when the B cells are stimulated by the activated helper T cells? |
They multiply rapidly(mitosis/clonal selection) to form many memory cells and some differentiate to form plasma cells that can produce specific antibodies |
|
|
What do plasma cells do? |
Produce antibodies specific and complementary to the foreign antigens that were recognised by the white blood cells |
|
|
What do antibodies do? |
They lead to the destruction of pathogens |
|
|
Why are booster vaccines used? |
To put more antigens into the body to stimulate the production of more memory cells so greater secondary immune response |
|
|
Why are large amounts of people vaccinated? |
So the virus is destroyed and cannot replicate Herd immunity |
|
|
What is an antibody? |
A protein produced by B lymphocytes in response to the presence of a foreign antigen. Antibody complementary to antigen and leads to its destruction |
|
|
What happens in agglutination? |
Antibodies have two binding sites so they bind to several pathogens ( form antigen-antibody complex) which results in many pathogens clumping together so increases chances of phagocytosis occuring leading to final destruction of the pathogen |
|
|
Which results in... |
Increased phagocytosis |
|
|
How many polypeptide chains are antibodies made out of? |
4 (has a quarternary structure) 2 heavy 2 light |
|
|
What bonds exist between the polypeptide chains? |
Disulfide bonds |
|
|
What is the region at the top called and why? |
The variable region as the primary structure of amino acids varies between different antibodies to result in different specific tertiary structures as they are complementary to different antigens |
|
|
What is the region at the bottom called and why? |
Constant region , very similar primary structure of amino acids in all antibodies |
|
|
What does the binding site bind to? |
Antigens specific to that antibody |
|
|
What is formed when an antigen and an antibody bind? |
Antigen-antibody complex |
|
|
What happens during primary response (features of it)? |
There is a time lag as the antigen needs to be identified by the one specific lymphocyte and the plasma cells need to produce the specific antibodies- numbers need to build up via mitosis/clonal selection. After removal of the pathogen memory cells remain so secondary response will occur next time |
|
|
What happens during secondary response? |
No time lag due to memory cells already existing. Greater probability antigen identified and amount of antibodies quickly increases- dont have to build numbers as much as more than 1 already exist. The amount of memory cells you have increase further and you experience no symptoms |
|
|
What is passive immunity? Temporary? |
Introduction of antibodies from an outside source such as your mother , doesnt involve contact with a pathogen or antigen Temporary as no immune response occurs so no memory cells are produced. All antibodies eventually broken down |
|
|
What is active immunity? Temporary? |
Immune response has occured resulthing in the production of antibodies from your own plasma cells - occurs from contact with pathogens or antigens. This could be from getting ill (natural)or having a vaccine (artificial) It is long lasting as memory cells are produced |
|
|
What are vaccines? |
When a small amount of a foreign (disease) antigen is introduced into the body to stimulate an immune response which will produce memory cells specific to this disease so if you come into contact with the pathogen your response will be immediate(secondary immune response occurs) and you wont experience any symptoms |
|
|
What is herd immunity? |
Where a whole population is protected from disease as such a large number of people are vaccinated that it is highly improbable someone not vaccinated will come into contact with an infected person. The pathogen cannot spread. This provides protection for the weak who cannot be vaccinated |
|
|
What does the HIV virus cause? |
AIDS |
|
|
What does the HIV virus have on its outside? |
A lipid envelope with attatchment proteins - that allows host cell infection |
|
|
What does a HIV virus have on the inside? |
A capid with RNA and reverse transcriptase on the inside |
|
|
What is the role of reverse transcriptase? |
DNA is produced from RNA |
|
|
Why is HIV known as a retrovirus? |
Has RNA instead of DNA in capsid and inserts DNA produced from RNA into host cells DNA |
|
|
What protein does the protein on the surface of HIV bind to? |
CD4 |
|
|
Where is CD4 found? |
Mostly on the surface of helper T cells |
|
|
What happens after these cell surface proteins bind? |
The capsid fuses with the cell surface membrane of the helper T cell and the RNA and reverse transcriptase is transferred into the helper T cell |
|
|
What happens after this fusion? |
Reverse transcriptase produces DNA from RNA and the virus DNA produced moves into the nucleus of the helper T cell and is inserted into the host cells DNA |
|
|
How is HIV replicated? |
Attachment protein binds to CD4 protein found mostly on helper T cell membranes - capsid fuses with membrane and DNA produced from RNA using reverse transcriptase. DNA inserted into host cells DNA in the nucleus. mRNA is produced from the virus DNA using free RNA nucleotides , DNA helicase and RNA polymerase in the cell-transcription occurs. The mRNA leaves the nucleus via the nuclear pore and uses the cells ribosomes to produce HIV proteins which make up the particles which break away with a part of cell surface membrane to form the lipid envelope - mRNA also forms new RNA in particle |
|
|
Where does the RNA in the new cells come from? |
It is mRNA produced via transcription of viral DNA |
|
|
Why does AIDS develop a lot later after you are HIV positive? |
HIV goes into dormancy for years |
|
|
What effect does HIV attacking the helper T cells have on the immune system? |
Weakens the immune system |
|
|
Why? |
The number of helper T cell is decreased significantly. Therefore the body doesnt have an effective immune response as Tc cells , antibodies are not produced and memory cells can be infected and destroyed - lose immunity |
|
|
Why do people die when they have AIDs? |
They are killed by secondary diseases as their immune system is to weak to fight off pathogens as the HIV destroys T cells and reduces their numbers - including memory cells so lose immunity. Response is weaker cannot fight off pathogens Secondary diseases = symptoms of aids |
|
|
How do antibiotics kill bacteria? |
Inhibit enzymes which synthesise peptide cross links in strong cell walls. Therefore cells can no longer withstand osmotic pressure so they burst when osmosis occurs instead of becoming turgid |
|
|
Why arent antibiotics effective against viruses? |
Viruses use host cellls so they dont have metabolic mechanisms or structures (cell walls to be weaked so osmosis and bursting can occur) which can be disrupted by antibiotics. Also viruses cannot be reached as they are within host cells |
|
|
What are monoclonal antibodies? |
The same type of antibody , they are identical and produced by the same plasma cell |
|
|
What can we use monoclonal antibodies to treat? |
Cancer |
|
|
Why? |
Antibodies are specific to antigens so we can use them to target cancer cells as cancer cells have their own antigens different to healthy cells |
|
|
How can monoclonal antibodies treat cancer? |
A drug that kills cells is attatched to the antibodies so when the antibodies attatch - form complex- to the cancer cell they are killed |
|
|
What needs to be done to animal antibodies before theyre used in treatmemt? |
The need to be humanised so they are not rejected by the immune system |
|
|
How can antibodies be used in medical diagnosis? |
They can form an antibody antigen complex with extra/ proteins produced by illnesses . Levels of protein can be measured/protein presence can be detected (ElISA Test) |
|
|
How are antibodies used in pregnancy testing? |
It involves the antibody hCG pregnancy hormone complex which provokes a colour change as antibodies linked tocoloured particles so when trapped coloured line appears on strip if complex has formed |
|
|
What is the ELISA test used for? |
Medical diagnosis To detect the presence and quantity of proteins in a sample using antibodies - which can indicate if someone has a disease e.g hiv antigens = hiv positive |
|
|
How does the ELISA test work? |
A sample is put on a surface and unattached antigens/proteins trying to detect are washed away. Specific antibodies are added to form the complex and excess antibodies are washed away. (Washings prevent false positive) Another antibody - complementary to first- with an enzyme attatched is added. The colourless substrate complementary to the enzyme is added and if a enzyme substrate complex is formed a colour change will happen as the enzyme catalyses the formation of the coloured product. This indicates a positive result and the colour intensity indicates the quantity of protein present in the sample |
|
|
Bacteria have a capsule not a... |
Capsid (made of protein) |
|
|
If cellulose forms on the outside how do we know it is a cell surface membrane? |
Cellulose forms cell walls of plant cells |
|
|
Why are mutations against HIV not a result of natural selection? |
HIV is a relatively new virus and there is low exposure |
|
|
Viruses do not have |
Cell surface membrane or cytoplasm or ribosomes |
|
|
Why must HIV use host cells to multiply? |
It is acellular and non-living so cannot synthesise its own proteins etc- cannot carry out mitosis |
|
|
What are the advantages of using monoclonal antibodies to treat cancer over other methods such as chemotherapy? |
Will not effect healthy cells as specific to cancer cell antigens only. As specific can use in small doses which is cheaper |
|
|
Why do B cells have a well developed rough endoplasmic reticulum? |
Need it for the proteinsynthesis of many antibodies |
|
|
Define monoclonal antibody? |
An antibody produced by a single clone of cells - all specific to the same antigen |
|
|
What does the same pathogen result in the activation of many different lymphocytes? |
One pathogen can have many different antigen on its surface which all set off a different immune response and the production of many different antibodies which leads to its destruction. If it produces toxins antibodies can be produced against these too |
|
|
How does the activation of B cells via activated T cells occur? |
Firstly the B cell has its antibodies presented on its surface and it must have come into contact with the antigen specific to it ( B cell exists for every possible antigen) . When complementary binds antigen taken in via endocytosis and presented on surface. Activated T cell receptors bind to antigen presented which activates B cell to divide via mitosis/clonal selection |
|
|
What is the life span of a plasma cell compared to memory B cell? |
Short but if reinfected memory cells form plasma cells to quickly produce specific antibody |
|
|
Define immunity? |
The ability to resist infection from a pathogen |
|
|
What is antigen variability? How does this effect disease prevention (vaccines)? |
Mutation occurs which changes primary structure of antigen so shape changes and memory cells which once meant immunity no longer do as the antigen is not recognised as this pathogen anymore - initiates primary respone. Old antibodies no longer complementay. No longer immune so vaccine no longer gives protection |
|
|
Why can rare diseases spread rapidly through a population? |
If rare no one will be immune yet as no exposure so primary response inititated in everyone. During this time lag people are infectious so it is easily spread between people |
|
|
Why does having HIV may not mean you have AIDs? |
Must have symptoms of secondary dieseases and a low number of helper T cells |
|
|
When can pigment leak out of cells? |
The plasma membrane is damaged and fluidity is increased |
|
|
What are the two different examples of co-transport? |
2 substances going in same direction at the same time through a carrier protein Or going in different directions at the same time |
|
|
How do the bases of DNA provide stability? |
Form H bonds which are collectively strong |
|
|
Purpose of the nucleolus ? |
Produces ribosomal RNA to make up ribosomes |
|
|
In what case will mitosis produce non-identical daughter cells? |
Mutation to DNA during dna replication in interphase |
|
|
What makes carrier and channel proteins specific? |
Are proteins so have specific tertiary structure - binding site |
|
|
What is plasmolysis of red blood cells called? |
Haemolysis |
|
|
What is water potential a measure of? |
Ability of water molecules to move freely in solution . So pure water = greater freedom so higher WP |
|
|
Why does diffusion occur if it is a passive process? |
All particles possess kinetic energy which causes them yo move randomly so end up spreading out |
|
|
What is the importance of receptors in tissue formation? |
Cells can attach to eachother and tissue is made up of many cells |
|
|
Why dont plant cells burst via osmosis?importance? |
Cellulose cell wall is inflexible so when water enters the pressure builds as prevents it expanding and more water entering so cells simply become turgid. Always bathed in pure water - dont have medium like tissue fluid to prevent osmosis |
|
|
What happens when plant cells shrink? |
Only the cytoplasm and membrane pull away from the cell wall |
|
|
What type of substances cant cross the phospholipid bilayer and require transport proteins? |
Large Charged Polar Not lipid - soluble , water soluble instead |
|
|
When active transport is occuring what is the carrier protein acting as? |
A pump |
|
|
How carrier proteins work in AT? |
Substance binds one side and ATP binds other . Atp hydrolysed and energy released causes protein shape change so substance moved through against conc gradient When Pi is released shape is returned to normal |
|
|
Do plants have centrioles? |
No but still form spindle apparatus |
|
|
What is the difference between chromatin and chromatids? |
Chromatin - DNA- histone complex which makes up chromosome Chromatid - made up of chromatin one strand on a chromosome |
|
|
Why may asexual reproduction be a disadvantage? |
No genetic diversity created. Genetic diversity enables natural selection as may have individuals that suit new selection pressures |
|
|
What stage is the majority of the cell cycle? |
Interphase |
|
|
What causes uncontrolled mitosis? |
Genes which control cell cycle stop working e.g via mutation |
|
|
What is a negative of cancer treatments? |
Most effective on fast dividing cells - including healthy ones like hair |
|
|
What else other than uncontrolled mitosis can lead to cancer? |
Genes for apoptosis damaged so mutant cells not destroyed - can grow and form tumour |
|
|
What makes up the nucleus? |
Nuclear envelope , nucleoplasm within and nucleolus in the nucleoplasm |
|
|
What is the structure and function of the nuclear envelope? |
Double membrane continuous with endoplasmic reticulum (how to decide whether it is ER or golgi) controls entry and exit into nucleus and has nuclear pores to allow the passage of large molecules such as mRNA and transcription factors |
|
|
Where are chromosomes found within the nucleus ? |
In the nucleoplasm |
|
|
What is the function of the nucleolus? |
In the nucleoplasm. Manufactures ribosomal RNA (functional RNA) and assembles ribosomes Can be multiple |
|
|
What plant cells dont have chloroplasts? |
Root cells as not in contact with sunlight |
|
|
Which cells are many lysosomes found in? |
Secretory - carry out lots of exocytosis And phagocytes |
|
|
Which cells are many mitochondira with lots of cristae found in? Why? |
Muscle and epithelial as require a lot of ATP for contraction and absorption via co-transport |
|
|
What are the 2 different types of ribosomes? |
80s and 70s (eukaryotic vs prokaryotic) as prokaryotic ribosomes are smaller - these are also the ones found in mitochondria and chloroplasts |
|
|
What is fungi cell wall made of? |
Chitin |
|
|
Why are viruses said to be acellular? |
They do not divide to replicate - need a host |
|
|
Size of virus compared to bacteria? |
Smaller |
|
|
What is the structure of a light microscope? |
Many convex lenses magnify image |
|
|
Why do electron micoscropes have higher resolutions than optical? |
Electron beam have a shorter wavelength than light so can see smaller objects and distinguish between objects closer together |
|
|
Why would it be beneficial to carry out cell fractionation? |
Study structure and function of specific organelles so we do this to obtain a large isolated number of them |
|
|
Why must the solution for cell fractionation be buffered? |
Maintain a pH as pH changes could alter organelles and enzymes |
|
|
What is the structure of an electron microscope? |
Beam of electrons produced by electron gun is negatively charged so it can be focused by electromagnets (act like the lenses in optical) |
|
|
Why must a vacuum be created in an electron microscope? |
Air molecules can absorb and deflect electrons so need to remove them |
|
|
What piece of equipment is used to directly measure an object under a light microscope? |
Eyepiece graticule |
|
|
What is the structure of an eyepiece graticule? |
Glass disc which is placed in the eye piece. A scale is etched on the glass disc |
|
|
Why must the eyepiece graticule be callibrated before use? |
Each objective lens of the microscope has a different magnification so need to callibrate for each different one |
|
|
What piece of equipment is needed to callibrate the eye piece graticule? |
A stage micrometer |
|
|
How is the eyepiece graticule callibrated? |
Align its scale with the stage micrometer scale. See how many units on each scale are equal. We know the actual units of the stage micrometer so can use this to work out what each division on the eyepiece graticule is equal to |
|
|
Once callibrated how to convert for different magnifications without callibrating again? |
Divide length of one division by how much more or less the magnification is as greater magnification = smaller amount per unit |
|
|
Role of epithelial cells/tissue ? |
Protective and secretory function Short diffusion path Can be cilliated or have microvilli |
|
|
Why is a leaf considered to be an organ? |
Made up of the many tissues pallisade mesophyll Spongy mesophyll Phloem and xylem |
|
|
Why are arteries and veins organs? |
Made up of multiple different tissues which work together to transport blood |
