Section 3 Flashcards
Cells and the immune system
What are antigens?
Proteins that can generate an immune response when detected by the body
Usally found on the surface of cells
Antigens that aren’t found in the body are called foreign antigens - these antigens are the ones that the immune system responds to
Antigens identify pathogens, abnormal body cells, toxins and cells from other individuals of the same species
What is a pathogen and how do they link to antigens?
Organisms that cause disease e.g bacteria, viruses and fungi
All pathogens have antigens on their surface which are identified by the immune system
What is a toxin and how do they cause an immune response? (short)
Toxins are poisons which are molecules - not cells
They can be produced by bacteria
The toxin itself is an anitgen it doesn’t have auntigens on its surface
What is an abnormal body cell and how do they cause an immune response? (short)
Cancerous or pathogen infected cells have abnormal antigens on their surface which trigger an immune response
Describe phagocytosis
1) A phagocyte recognises the foreign antigens on a pathogen
2) The cytoplasm of the phagoctye moves around the pathogen engulfing it
3) The pathogen is now contained in a phagocytic vacuole
4) A lysosome fuses with the phagocytic vacuole and lysozmes break down the pathogen
5) The phagocyte then resents the pathogens antigens on its surface to activate other immune system calles
Describe the role of T cells in the immune response
A T cell is a type of WBC with receptor proteins on it that bind to complimentary antigens presented to it by phagocytes. This activates the T cell.
Helper T cells relsease chemical signals that activate and stimulate phagocytes and cytotoxic T cells which kills abnormal and foreign cells. Helper T cells also activate B cells whcich secrete antibodies
Describe the role of B cells in the immune response
B cells are a type of WBC covered in antibodies - proteins that bind to antigens to form antigen - antibody comples
Each B cell has a different shaped antibody on its membrane so different ones bind to different shaped antigens
When the antibody on the surface of a B cell meets a complimentary shaped antigen they bind this activates the B cell. This process is called clonal selection and the activates B cell divides into plasma cells (clones)
Describe antibody production in the immune response
Plasma cells secrete loads of antibodies specific to the antigen - monoclonal antibodies. The bind to the antigens on pathogens to form complexes
An antibody has two binding sites so can bind to two pathogens at the same time so the pathogens become clumped together this is called agglutination.
What is antigenic variation?
Pathogens can change their surface antigens, different antigens are formed due to changes in the genes of a pathogen.
This means a secondary response can’t happen for the same pathogen and is makes it difficult to make vaccines.
Pathogens that do this are: HIV and influenza
What are the ethical issues surrounding the use of vaccines?
Animal testing/ animal based substances used
Testing on humans - might not work - putting themselves at risk
Side effects
Who gets it first if there is an epidemic and limited supply
What are the difference between active and passive immunity?
Active
Requires exposure to antigen
Takes a while for protection to develop
Memory cells produced
Protection is long term becuase the antibody produced is response to antigen being present in the bodu
Passive
Doesn’t require exposure to antigen
Protection is immediate
Memory cells aren’t produced
Protection is short term becuase the antibodies given are broken down
What is passive immunity?
Immunity from being given antibodies made by a different organism. There are two types…
1) Natrual - when a baby becomes immune due to the antibodies it receives from its mother through the placenta and breast milk
2) Artificial - when you become immune after being injected with antibodies from someone else
What is active immunity?
The immune system makes its own antibodies after being stimulates by an antigen. There are two different types…
1) Natrual - when you become immune after catching a disease
2) Artificial - when you become immune affter a vaccination
What is the difference between the primary and the secondary immune response?
Primary
When an antigen enters the body for the first time it activates the immune system. It is slow becuse there aren’t many B cells that can make the antibody needed to bind to it. This will happen overtime meanwhile the person will show symptoms. After being exposed to an antigen, both T and B cells produce memory cells these remain in the body for a long time, they remember the specific antigen and will recognise it
Secondary
If the same pathogen enters the body again the immune system will produce a quicker stronger immune response. Clonal selection happens faster, memory B cells are activated and divide into plasma cells that produce the right antibody to the antigen. Memory T cells are activated and divide into the correct type of T cells to kills the cell carrying the antigen. This response can get rid of the infectio before symptoms start to show.
What is the difference between the cellular and humoral responses?
Cellular - The T cells and other immune system cells that they interact with (phagocytes) form the cellular response
Humoral - B cells,, clonal selection and the production of monoclonal antibodies form the humoral response
Describe the general structure of an antibody
Proteins - made up of chains of amino acids
The specificity of an antibody depends on its variable regions which form the antigen binding sites
Each antibody depends has a varible region with a unique tertairy structure that is complimentary to one specific antigen
All antibodies have the same constant regions
What are monoclonal antibodies?
Are produced from a single group of genetically identical B cells (plasma cells)
How are monoclonal antibodies used in cancer drugs?
Different cells in the body have different surface antigens
Cancer cells have antigens called tumor markers that are not found on normal body cells
Monoclonal antibodies can be made that will bind to the tumor markers
You can also attach anti cancer drugs to the antibodies
When the antibodies come into contact with cancer cells they will bind to tumor markers and the drug will accumulate in the body where the cancer cells are
How are monoclonal antibodies used in pregnancy tests?
Pregnancy tests detect the hormone hCG thats found in the urine of pregnant women
The application area contains antibodies that are complimentary to the hCG protein bound to a blue coloured bead
When urine is applied to the application area any hCG will bind to the antibody on the beads forming a complex
The urine moves up the strip carrying the beads with it
The strip contains antibodies to hCG that are stuck in place
If there is hCG present the test strip turns blue becuase the attached antibodies bind to hCG with the blue beads
What is the ELISA test?
It can be used in medical diagnosis to test for pathogenic infections or allergies
An antibody is used which has an enzyme attached to it. The enzyme can react with a substrate to produce a coloured product
If there is a colour change it shows the antigen or antibody of interest is present
Describe the direct ELISA test
Antigens from a patient sample are bound to the inside of a well
A detection antibody with an attached enzyme that it complimentary to the antigen of interest is added
If the antigen of interest is present the detection antibody will bind to it
It is then washed out
A substrate solution is added
If the detection antibody is present the enzyme will react with the substrate to give a colour change
The intensity of colour change can be measured by absorption
Describe the indirect ELISA test
Used to detect antibodies in HIV
1) HIV antigens are bound to the well of a plate
2) A sample of the patients blood plasma is added to the well and the HIV antibodies will bind then it is washed out
3) A secondary antibody that had a specific enzyme attached to it is added. It binds to the HIV specific antibody and is washed again. If there is no primary HIV antibody the seconday antibody will be washed away as there is nothing to bind to
4) A solution is added to the well containing a substrate which will react with the enzyme attached to the secondary antibody and produce a coloured product
What are the ethical issues around monoclonal antibodies?
Animals are used
Describe the structure of HIV
Contains RNA and reverse transcriptase needed for virus replication
Outer coating if protein called a capsid
Extra outer layer called an envelope made of membrane stolen from previous host cell
Attachment proteins
Describe HIV replication
1) Attachment proteins attach to receptor molecule on the cell membrane of a host helper T cell
2) The capsid is released into the cell where it uncoats and releases genetic material into the cytoplasm
3) Reverse transcriptase is used to make complimentary strand of DNA from the viral RNA template
4) DNA is made and inserted into the human DNA
5) Host cell enzymes are used to make viral proteins from the viral DNA
6) Viral proteins assemble and leave to infect other cells
How do antibotics work and why don’t they work on viruses?
They interfere with metabolic reactions and target bacterial enzymes and ribosomes
Viruses don’t have their own enzymes and ribosomes
Describe the structure of gills in fish and how water passes through
Water enters the fish through its mouth and passes out through the gills
Each gill is made of lots of thin plates called gill filaments which give a large surface area for exchange of gasses
Gill filaments are covered in lamellae which increase surface area more and have lots of capillaires
Gill > fillament > lamellea
Describe gas exchange in fish
The conc gradient is maintained over the whole length of the gill
Counter current system
Blood flows through the lamelae in one direction and water flows in the opposite direction
So water with a high oxygen conc is always next to blood with a low oxygen conc so a steep gradient is maintained
The gradient is maintained across the whole lengh off the gill
Describe gas exchange in insects
Spiracles (pores) lead to trachea (air filled pipes) branch off into tracheoles (have thin permable walls with go to individual cells)
Oxygen diffuses directly to respiring cells
CO2 moves down its gradient out the spircales
Abdomial pumping moves air in
How do insects prevent water loss?
Close their spircales
Waterproof waxy cuticle
Tiny hairs around the spircales which reduced evapouration
How do plants prevent water loss?
Stomata close as they become flacid due to water loss
Xerophytes
Sunken stomata in pits - trap water vapour reducing evapouration
Little hairs on the epidermis to trap vapour around the stomata
Curled leaves with stomata inside protecting them from wind which would increase evapouration
Reduced number of stomata
Thick waxy waterproof cuticle preventning evapouration
Describe what happens in humans during inspiration (breathing in)
The external intercostals and diaphragm contract causing the ribcage to move upwards and out and the diaphragm to flatten
Increasing the volume of the thoracic cavity decreasing the pressure below atmospheric causing air to move down a pressure gradient into the lungs
An active process - requires energy
Describe what happens in humans during expiration (breathing out)
External intercostals and diaphragm relax moving the ribcage downwards and in and the diaphragm domes
Decreasing the volume of the thoracic cavity increaing the pressure above atmospheric cauing air to move down a pressure gradient out of the lungs
Passive process unless forced (blowing out)
Desribe the structure of an alveoli
Walls made from a single layer of thin flat cells called epithelium
Covered in a network of capillaries
The walls are elastic which help them to recoil back to its normal shape after inhaling and exhaling air
Define
Tidal volume
Ventilation rate
Forced expiratory volume
Forced vital capacity
Tidal volume - the colume of air in each breath
Ventilation rate - number of breaths per minuet
Forced expiratory volume - maximum volume of air that can be breathed out in one second
Forced vital capacity - maximum volume of air it is possible to breath forcefully out of the lungs after a deep breath in
Describe the digestion of carbohydrates
Amaylase breaks down starch by breaking glycosidc bonds to produce maltose
Amalyase is produced by the slivary glands and the pancreas
Membrane bound disaccharides are enzymes attached to the cell membrane of the epithelial cells lining the ilem (the final part of the small intestine) they break down disaccharides
Sucrase breaks down sucrose into glucose and fructose
Maltase breaks down maltose into glucose
Lactase breaks down lactose into glucose and galactose
Describe the digestion of lipids
Lipase breakdown lipids into monoglycerides and fatty acids by hydrolysing ester bonds. Lipases are produced in the pancrease
Bile salts are produced by the liver and emulsify lipids creating a larger surface area for lipases to work on
Once the lipid has been broken down the monoglycerides and fatty acids stick with the bile salts to form micelles which allow them to be absorbed
Describe the digestion of proteins
Endopeptidases - hydrolyse peptide bonds within the protein
Exopeptidases - hydrolyse peptide bonds at the ends of proteins
Dipeptidases - work on dipeptides - located on the membrane in the small intestine (membrane bound)
How are digestion products of carbohydates (monosaccharides) absorbed?
Glucose and galactose is absrobed by co transport
Frucose is absrobed by facilitated diffusion
How are digestion products of lipids (monoglycerides and fatty acids) absorbed?
Micelles move monoglycerides and fatty acids towards the epithelium and release them
They are lipid soluble so can diffuse direclty across
How are digestion products of proteins (amino acids) absorbed?
Co transport
What is affinity?
The tendancy a molecule has to bind with oxygen
What is the relationship between affinity and ppO2
ppO2 increases haemoglobin affinity increases
Oxygen onto haemoglobin loads at high ppO2
Oxyhaemoglobin unloads oxygen at low ppO2
Why is the dissociation curve for haemoglobin S -shaped?
When haemoglobin binds with the first O2 molecule the shape alters so its easier for another one to bind
But as the haemoglobin becomes saturated it gets harder for O2 to join
So the curve has a steep bit in the middle where O2 can easilly bind and shallow parts at each end where it is harder
What is the effect of the dissociation curve with CO2?
haemoglobin gives up O2 more easilly as higher ppCO2 to get more O2 to respiring cells during activity
When cells respire they raise the ppCO2 which increases the rate of oxygen unloading so the curve shifts right - the Bohr shift
How do low oxygen enviroments affect organisms haemoglobin?
They have haemoglobin with a higher affinity for oxygen becuase not much oxygen is avaliable the curve shifts to the left
How do high activity levels affect organisms haemoglobin?
There is high oxygen demand with a lower affinity for oxygen becuase oxygen needs to be easilly unloaded so the curve shifts right
How does size enviroments affect organisms haemoglobin?
Small animals have a higher surface area to volume ratio so they loose heat quickly so they have a high metabolic rate which means they have high oxyen demand
They have a lower affinity for oxygen becuase it needs to unload more easilly so the curve shifts right
What are the function of the coronary arteries?
Provide the heart with blood
Where does …. take blood from and to?
Pulmonary artery
Pulmonary vein
Aorta
Vena Cava
Renal artery
Renal vein
Vessel from Lungs
Pulmonary artery Heart Lungs
Pulmonary vein Lungs Heart
Aorta Heart Body
Vena Cava Body Heart
Renal artery Body Kidneys
Renal vein Kidneys Vena Cava
What is the structure of the arteries?
Thick and muscular walls
Elastic tissue which stretches and recoils which helps maintain the high pressure
The inner lining (endothelium) is folded allowing the artery to stretch and maintain high pressure
What is the function of the arteries?
They carry blood from the heat to rhe rest of the body
Carry oxygenated blood except for the pulmonary arteries which take deoxygenated blood to the lungs
What is the structure and function of arterioles?
Arteries divides into smaller vessels called arterioles which form a network throughout the body
Blood is directed to different areas of demand in the body by muscles inside the arterioles which contract to restrict blood flow or relax to allow full blood flow
What is the structure and function of veins?
Veins take blood back to the heart under low pressure
They have wider lumen and little elastic or muscle tissue
Veins have valves to stop backflow
Blood flow is helped in the veins by the contraction of body muscles surrounding them
All veins carry deoxygenated blood except for pulmonary veins which carry oxygenated blood from the heat to the lungs
What is the structure and function of capillaries?
Arterioles branch into capillaries
Substances are exchanged between cells and capillaries so are adapted for efficient diffusion
They are always near cells, have a one cell thick wall and lots of them
Networks of capillaries are called capillary beds
They connect arterioles and venules together
Venules are small blood vessels that connect to veins
What is tissue fluid?
Fluid that surrounds cells in tissues made from small molecules that leave the blood plasma e.g oxygen, water and nutrients
Cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it
Describe how tissue fluid is formed
Pressure filtration
At the start of the capillary bed nearest the arteries the hydrostatic pressure in the capillaries is greater than in the fluid forcing fluid out of the capillaries and into the space around the cells forming tissue fluid
As fluid leaves the hydrostatic pressure is reduced in the capillaires so it is much lower at the venule end
Due to the fluid loss and an increasing concentration of plasma proteins which don’t leave the capillaries the water potential at the venule end is much lower than the water potential in the tissue fluid
Water re enters the capillaries from the tissue fluid by osmosis
Excess tissue fluid is drained by the lymphatic system and passes it back into the cirulatory system
How do valves work?
If there is greater pressure behind the valve it will be forced open
If there is greater pressure infront of the valve it will be forced shut
Ensuring a one direction flow of blood
Describe the cardiac cycle
1) Ventricels relax atria contract
The volume of the atria decreases increasing the pressure pushing blood into the ventricles
2) Ventricles contract atria relax
Ventricles volume decreases and pressure increases forcing AV valves shut to prevent back flow
The pressure is higher than the aorta and pulmonary artery forcing open the SL valves
3) Both relax
The high pressure in the pulmonary artery and the aorta close the SL valves preventing back flow
Blood returns to the heart and the atria fill again due to the high pressure in the vena cava and pulmonary vein
This increases the pressure of the atria so AV valves open allowing blood to passively flow into the ventricels
The atria contract and the process repeates
What is the equation to do with the heart
Cardiac output = stroke volume x heat rate
Cardiac out put - volume of blood pumped by the heart per minuet
Stroke volume - volume of blood pumped out each heart beat
Heart rate - number of beats per minuet
