organisation Flashcards
define cells
cells are the basic building blocks of all living organisms
define tissues
a tissue is a group of cells with a similar structure and function
define organs
organs are aggregations of tissues performing specific functions
describe the relationship between organs, organ systems and organisms
organs are organised into organ systems, which work together to form organisms
what is the digestive system
an example of an organ system in which several organs work together to digest and absorb food
what are the products of digestion used for
they’re used for building new carbohydrates, lipids and proteins; some glucose is used in respiration
what are carbohydrates broken down by and into
they’re broken down by carbohydrase enzymes like amylase (which breaks down starch) into simple sugars like glucose and maltose
what are proteins broken down by and into
they’re broken down by protease enzymes into amino acids
what are lipids broken down by and into
they’re broken down by lipase enzymes into 3 fatty acid molecules and glycerol
first stage of the digestive system (mouth)
mechanical digestion takes place by chewing in the mouth and salivary glands secrete amylase which begins catalysing the digestion of starch, breaking it down into simple sugars like glucose and maltose
path of food in the body
mouth -> oesophagus -> stomach -> small intestine -> bloodstream (soluble molecules only) -> large intestine -> rectum
stomach functions/adaptations
- has a muscular wall which contracts and churns the food, mixing it to form a liquid, increasing surface area for enzymes to work on
- it secretes pepsin (a type of protease enzyme) which breaks down proteins into amino acids
- it produces hydrochloric acid which both kills harmful microorganisms in the food and provides optimal pH conditions for the pepsin to work
role of the pancreas in digestion
the pancreas secretes lipase, protease and carbohydrase enzymes into the small intestine to digest the food and the small intestine itself produces all of these enzymes in smaller amounts
where is bile made and stored
bile is made in the liver and stored in the gall bladder
where does bile get released into and why
the small intestine, and it
- neutralises the hydrochloric acid from the stomach to provide optimal alkaline pH conditions for the pancreatic enzymes to work
- emulsifies fats to form small droplets which increases the surface area for lipase enzymes to work on and digest more quickly
the alkaline conditions and large surface area increase the rate of fat breakdown by lipase
what happens once the molecules are broken down into smaller, soluble ones e.g. amino acids, fatty acids, glycerol and simple sugars
they’re absorbed across the lining of the small intestine and into the bloodstream via diffusion and active transport
what do digestive enzymes do e.g. lipase
they convert food into small soluble molecules that can be absorbed into the bloodstream and used by cells
what happens to the remaining material that isn’t absorbed into the bloodstream
it passes into the large intestine where excess water is absorbed back into the blood and faeces remain which are then stored in the rectum and excreted
amylase enzymes:
- help break down [..] into [..]
- made in the [..]
- work in the [..]
- help break down starch into sugars
- made in the salivary glands, pancreas and small intestine
- work in the mouth and small intestine
protease enzymes:
- help break down [..] into [..]
- made in the [..]
- work in the [..]
- help break down proteins into amino acids
- made in the stomach, pancreas and small intestine
- work in the stomach and small intestine
lipase enzymes:
- help break down [..] into [..]
- made in the [..]
- work in the [..]
- help break down lipids into glycerol and 3 fatty acid molecules
- made in the pancreas and small intestine
- work in the small intestine
why does rate of enzyme activity increase as temperature increases initially
this is because the enzymes have more kinetic energy so are moving more quickly; therefore there are more frequent, successful collisions with substrates, so more enzyme-substrate complexes form per second, increasing rate of catalysation
describe what happens at 37ºC in terms of enzyme activity
at 37ºC, the rate of enzyme activity reaches a maximum (the optimum temperature) where the rate of activity is at its highest
describe what happens past the optimum temperature in terms of enzyme activity
past the optimum temperature, the rate of enzyme activity rapidly decreases to 0 the more you increase the temperature; this is because temperatures that are too high affect the bonds that hold the enzyme together, causing the active site to change shape. the enzyme becomes denatured because the substrate can no longer fit into the active site, so the enzyme can no longer catalyse the reaction
how is the rate of enzyme activity affected by pH
if the pH falls too low or too high above the optimum pH (7), the bonds holding the enzyme in its specific folded shape will begin to dissolve, causing the active site to distort so the substrate molecule no longer fits and the enzyme can no longer catalyse the reaction, so the enzyme becomes denatured and rate of enzyme activity decreases
explain the lock and key model
- enzymes have an active site on their surface which is complementary to the substrate molecule (the reactant)
- the substrate must fit perfectly and be complementary to the shape of the active site in order to bind to it and form an enzyme-substrate complex
- the substrate is then broken down into the products of the reaction
define an enzyme
enzymes are known as biological catalysts; they increase the rate of reaction without being used up
why are enzymes very specific in the chemical reactions that they catalyse
because the active has a specific shape and the substrate must fit perfectly and be complementary to the active site in order to form an enzyme-substrate complex
main function of circulatory system
to get nutrients and oxygen to every cell in the body and take waste products like carbon dioxide and urea to where they can be removed from the body
describe how a single circulatory system works
deoxygenated blood travels from the heart to the gills, for example, where it is oxygenated and then returns back to the heart after it gives oxygen to the cells
problem with single circulatory system
the blood loses a lot of pressure as it only goes to the heart once, so it travels to organs slowly, so cannot deliver lots of oxygen
describe a double circulatory system
deoxygenated blood travels from the heart to the lungs, is oxygenated, returns back to the heart again, is pumped to the organs and then returns back to the heart
advantage of a double circulatory system
this maintains a relatively high blood pressure throughout so that it can travel quickly around the body and deliver oxygen more efficiently
function of the aorta
the main artery which carries oxygenated blood from the left ventricle of the heart to the rest of the body
function of the vena cava
a vein that brings deoxygenated blood from the body into the right atrium of the heart
function of the pulmonary artery
an artery that takes deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation
function of the pulmonary vein
a vein that carries oxygenated blood from the lungs to the left atrium of the heart
function of the coronary arteries
arteries that branch out of the aorta and spread around the heart muscle, in order to provide oxygen to the muscle cells of the heart – this allows heart muscles to respire and release energy needed for muscular contraction
function of the right ventricle
a heart chamber that pumps blood to the lungs where gas exchange takes place
function of the left ventricle
a heart chamber that pumps blood around the rest of the body
function of the heart
an organ consisting mainly of muscle tissue that pumps blood around the body in a double circulatory system
why does the left ventricle have a thicker muscular wall than the right
in order to provide enough force to provide a high blood pressure to pump the blood long distances all around the body
what is the natural resting heart rate controlled by
a group of cells located in the right atrium called pacemaker cells that send electrical impulses, which stimulate the heart muscles to contract rhythmically
what happens if the pacemaker cells stop working
an artificial pacemaker can be implanted, which is an electrical device that corrects irregularities in the heart rate
three different types of blood vessel
arteries, capillaries, veins
function of the arteries
they carry very high-pressure blood from the heart to the organs in the body
adaptations of the arteries
- arteries have very thick muscular walls to withstand the high blood pressure within them
- they have a layer of elastic fibres which help them to stretch when surges of blood pass through, and recoil in between surges, keeping the blood flowing correctly and preventing artery damage due to the high pressure of the blood
- they have narrow lumens to maintain the high blood pressure needed to carry blood from heart to organs
function of the veins
they carry low pressure blood from the body to the heart
adaptations of the veins
- as blood is low pressure and travelling slowly, the blood could move backwards; the veins therefore contain valves to prevent the backflow of low-pressure blood
- they have thin walls; the walls do not need to be thick as the blood is low pressure
- they have a large lumen because they transport blood at low pressure
function of the capillaries
very narrow thin blood vessels that connect branches of arteries to veins
adaptations of the capillaries
- very thin walls (one cell thick) to allow for a short diffusion path, increasing rate of diffusion and exchanging of substances
- their walls are very permeable to allow high rates of diffusion and exchange of substances
- very small lumen to increase the SA:Vol ratio; this facilitates better exchange of oxygen, nutrients and other toxins to and from the blood and tissues.
function of the lungs
the organ where gas exchange occurs
function of the trachea
it brings air into the lungs and is supported by rings of cartilage which prevent it collapsing
function of the bronchi
branches off the trachea to bring air into the lungs; also supported by rings of cartilage
function of the bronchioles
branches off the bronchi which carry air to the alveoli
function of the alveoli
site of gaseous exchange
define blood
a tissue consisting of plasma, in which the red blood cells, white blood cells and platelets are suspended
function of plasma in blood
transports nutrients, hormones and proteins to parts of the body that need it; removes waste products in the blood
function of the atria
they contact, pushing blood into the ventricles
function of red blood cells in blood
they transport oxygen from the lungs to other tissues and cells in the body
function of white blood cells
idk fill this in
function of platelets
they help the blood to clot at a wound and stop microorganisms entering at the wound
what can a lack of platelets cause
excessive bleeding and bruising
adaptations of red blood cells
- biconcave disc shape which increases SA:Vol ratio to maximise the absorption of oxygen
- no nucleus to allow more room to carry oxygen
- contains lots of haemoglobin which binds to the oxygen in the lungs (to form oxyhaemoglobin) and releases it in body tissues
- very small diameter to allow them to fit through narrow blood vessels
adaptations of white blood cells
- some have cytoplasm which can flow, making it possible for the cell to change shape, in order to surround and engulf bacteria
(specific ones for the three types of WBC in another flashcard)
why does someone with CHD lack oxygen in their heart
layers of fatty material build up inside the coronary arteries, narrowing them. this reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle
what are stents and how do they work
wire meshes that are inflated and physically widen the artery and keep it open to allow more blood to flow through them
what are statins and how do they work
drugs that reduce the level of LDL cholesterol in the blood, which slows down the rate at which fatty material builds up in the coronary artery walls
pros and cons of stents
PROS:
- blood can flow normally through the coronary artery, reducing the risk of heart attacks; hence they’re very effective
- effective for long periods of time and the recovery time from surgery is relatively quick
CONS:
- the stent will not prevent any other regions of coronary arteries from narrowing, because it does not treat the underlying cause of the disease
- a surgery is required, meaning the patient is more at risk of developing blood clots and infections
pros and cons of statins
PROS:
- they are proven to be effective in reducing the risk of CHD, strokes and heart attacks
- they increase the amount of HDL cholesterol which is good
CONS:
- statins have unwanted and harmful side-effects e.g. liver problems, kidney failure and memory loss
- statins are not instant; they take a while to begin to work
- the patient could forget to take them
consequence of heart valves becoming faulty (too stiff)
this leads to muscle fatigue of the heart, as it has to work much harder to pump the same amount of blood, which can lead to enlargement of the heart
consequence of heart valves developing a leak
this causes blood to flow in the wrong direction, causing pumping blood to be less efficient; this makes the patient feel weak and tired, as their blood pressure drops
how can faulty heart valves be replaced
using a mechanical metal valve or using a biological valve from an animal e.g. pig
how can CHD be treated
using a stent or using statins
pros and cons of mechanical heart valves
PROS:
- they can last a lifetime
CONS:
- they require anti-clotting drugs; the patient could forget to take them
- they have a tendency to form blood clots which could be fatal
pros and cons of biological heart valves
PROS:
- patients do not need to take drugs
CONS:
- they don’t last as long as mechanical heart valves
- because they don’t last as long, the patient has to have surgeries more frequently, which exposes the patient to a higher risk of infection and blood clots
- some people may ethically or religiously object to having a biological valve implant because the animal cannot consent
how can heart failure be treated
getting an artificial hearts or getting a heart (or heart-and-lung) transplant
pros and cons of artificial hearts
PROS:
- they can be used as a temporary solution until a donor is found or to allow their damaged heart to rest
- they are less likely to be rejected by the immune system because they’re not biological material
CONS:
- they increase the risk of blood clotting and strokes; the patient can take blood-thinners to solve this, but this will affect their daily life, e.g., cuts will not heal as quickly
- artificial hearts are not a long-term solution to heart failure
pros and cons of heart transplants
PROS:
- heart transplants are proven to lead to a longer, better quality of life for most patients
- most patients say they have extra energy and feel more able to cope with everyday activities
CONS:
- there are not enough heart donors to treat every patient, so there will be long waitlist; some patients may die before even getting a donor heart
- higher risk of immune rejection
- due to higher risk, the patient must take immunosuppressants to stop donated heart from being rejected by the body’s immune system; puts patient at higher risk of severe symptoms and frequent infections because their immune system is weakened
define health
the state of physical and mental well-being
what are communicable diseases
diseases that can be spread from person to person and are spread by pathogens like bacteria and viruses
what are non-communicable diseases
diseases that cannot be passed from person to person (e.g., coronary heart disease)
major factor + other factors of diseases (communicable + non-communicable)
MAJOR: ill-health
OTHER:
- poor diet (undernutrition or obesity)
- high levels of stress
- life situations
the ways different types of disease may interact
- defects in the immune system mean that an individual is more likely to suffer from infectious diseases; e.g. people with HIV/AIDS have a defective immune system, increasing their risk of developing diseases like the influenza and tuberculosis
- viruses living in cells can be the trigger for cancers; e.g. HPV increases the risk of cervical cancer
- immune reactions caused by a pathogen can trigger allergic reactions; e.g. skin rashes (dermatitis) and worsen symptoms for asthma sufferers
- severe physical ill health can lead to depression and other mental illness; e.g. a disease that has caused paralysis causing depression
what are non-communicable diseases caused by
risk factors
define a risk factor
something that is linked to an increase in the probability of developing a certain non-communicable disease in their lifetime – they do not guarantee that someone will get the disease
what can risk factors either be
- aspects of a person’s lifestyle e.g. exercise
OR - substances in the person’s body or environment e.g. air pollution
define a causal mechanism
correlation does not mean evidence for cause; it simply suggests that they may be linked
many diseases are caused by the interaction of one factor (T/F)
F!
they’re mainly caused by a number of factors
how would you investigate whether a disease is linked to a diet
- ideally, have to carry out census for entire population, monitoring what they eat and linking it to risk of developing disease
- not practically possible so scientists use sampling of small group to represent entire population
- PROBLEM; sample may not be representative for entire population of country
- assume that they are the average but this may not be the case – hence we cannot use results to draw conclusions about whole country
- to avoid bias, we need to take as large a sample as possible and must be as random as possible
risk factors for cardiovascular diseases
- diet is a major risk factor for CHD; diet high in fat and low in vegetables increases levels of LDL cholesterol in blood, increasing the rate at which fatty material deposits in the walls of the coronary arteries
- diet high in salt can increase blood pressure, increasing risk of developing certain cardiovascular diseases
- risk for cardiovascular diseases is also massively increased by smoking, but risk is decreased in people who exercise regularly
risk factor for type 2 diabetes
obesity is a major risk factor for developing t2diabetes; risk factors can interact – e.g., drinking excess alcohol can lead to obesity which can increase the risk of type 2 diabetes
risk factor for liver and brain function
excessive drinking increases the risk of liver cirrhosis and liver cancer, as well as affecting the brain, leading to addiction and memory loss
risk factor for lung disease and lung cancer
smoking is a major risk factor for lung disease and lung cancer because cigarette smoke contains carcinogens
risk factors for unborn babies
- smoking when pregnant increases the risk of miscarriage, stillbirth and premature birth
- drinking alcohol can also affect an unborn baby, as it can cause foetal alcohol syndrome, leading to learning difficulties and mental or physical problems
risk factor for cancer
carcinogens increase the risk of cancer, including exposure to ionising radiation (emitted from things like radon gas)
define cancer
the result of changes in cells that lead to uncontrolled growth and division (this is how tumours form)
what are benign tumours
growths of abnormal cells which are contained in one area, usually within a membrane. they do not invade other parts of the body
what are malignant tumours
growths of abnormal cells which invade neighbouring tissues and spread to different parts of the body in the blood, where they form secondary tumours
function of epidermal tissues
they protect the surface of the leaf
adaptation of upper epidermis
it is transparent, to allow light to pass through to the photosynthetic palisade cells below it
function of palisade mesophyll
- photosynthetic cells packed full of chloroplasts that contain chlorophyll, absorbing the light energy needed for photosynthesis to take place
function of waxy cuticle
covers the upper epidermis, and is a thin layer of oily material which helps to reduce water loss by evaporation
adaptation of lower epidermis
has pores in it called stomata to allow gas exchange to take place; also controls amount of water vapour leaving the leaf
function of spongy mesophyll
a tissue full of air spaces to allow oxygen and carbon dioxide to diffuse through it easily
function of xylem
tissue that transports water from the roots to the leaves, providing the water needed for photosynthesis and other reactions to take place; they also transport dissolved mineral ions including magnesium, which is used to make chlorophyll, and nitrate ions, which are used to make proteins
function of phloem
a tissue that transports sugars like glucose from the leaves to the rest of the plant, in order to carry out respiration to release energy; or the sugars can be stored as starch
function of meristem tissue and where its found
found at the growing tips of shoots and roots, and contain stem cells which can differentiate into different types of specialised plant tissue
define translocation
the movement of sugars and other molecules through phloem tissue
describe how water enters and leaves the plants
- enters through root hair cells
- water constantly evaporating from surfaces of leaves (transpiration)
- transpiration starts with evaporation of water from palisade cells inside leaf
- the water vapour then diffuses through the air spaces in spongy mesophyll and out of leaf via pores in lower epidermis called stomata
- as water is lost, more water is absorbed by the roots + passes into leaf via xylem in order to replace water that has been lost
define transpiration
the process of water evaporating from the leaves
what is the transpiration stream
the constant stream of water loss and replacement; it is driven by the transpiration (evaporation of water) in the leaves
why is transpiration important
- it brings water to the leaf, which is required for photosynthesis; the transpiration stream also transports dissolved mineral ions like magnesium into the leaf
- transpiration also cools the leaf down, especially in warm weather, allowing cells to function optimally
factors that effect transpiration and how
1) temperature - greater temperature, greater rate of transpiration
2) wind intensity - as wind intensity increases, rate of transpiration increases; more wind removes water vapour quickly once it has diffused out of the leaf. makes a greater concentration gradient between water vapour inside the leaf and water vapour outside the leaf, leading to an increased rate of diffusion and transpiration outside the leaf
3) humidity - the greater the humidity, the slower the rate of transpiration; if the air is more humid, there is a less steep concentration gradient, so reduced rate of diffusion and transpiration
4) light intensity - the greater the light intensity, the greater the rate of transpiration; as light intensity increases, so does the rate of photosynthesis
how do guard cells function in light vs in dark
- more light means more photosynthesis takes place; this means more water is produced and lost, and, to allow more carbon dioxide in, the guard cells open to widen the stomata, increasing rate of transpiration
- when it is dark, stomata close, as less CO2 is needed due to lack of photosynthesis
what happens to the plant in hot conditions
the plant closes its stomata to reduce water loss by transpiration, but the plant cannot photosynthesise
what happens to the plant during high light intensity
the guard cells swell and change their shape as they become turgid, causing stomata to open to allow carbon dioxide to ender the leaf
what happens to the plant when there is lots of water available
water will move into the guard cells via osmosis from dilute to concentrated solution, causing it to swell, become turgid and open the stomata to allow more carbon dioxide to diffuse into the leaf
what happens to the plant when there is little water
guard cells become flaccid (limp), as water moves out of the guard cells via osmosis from the dilute solution inside to the concentrated solution, closing stomata to reduce water loss but the plant will be unable to photosynthesise due to a lack of carbon dioxide
why do guard cells have thin outer walls and thick inner walls
to make the opening and closing work, so that when turgid, they open, and when flaccid, they close
why are guard cells sensitive to light and why do they close at night
to save water without losing out on photosynthesis
why are more stomata found on the lower epidermis
because the lower surface is shaded and cooler, so less water is lost by transpiration than if they were on the upper epidermis – guard cells are thus adapted for gas exchange and controlling water loss
how to investigate distribution of stomata and guard cells
1) either peel epidermal tissue off the leaf and place it on slide with water and cover slip OR apply varnish to underside, allow it to dry, then use piece of tape to remove varnish
2) once in slide with large water droplet, view slide using a microscope
3) draw and clearly label. estimate total number of stomata on surface by counting sample of them in your field of vision
4) count in several different fields of vision and calculate mean; use this and total area of leaf to estimate how many stomata there are in total
5) compare distribution of stomata in different areas of leaf or between different leaves
why can you estimate the rate of transpiration by measuring the uptake of water
because you can assume that water uptake but the plant is directly related to water loss by the leaves
how to investigate rate of transpiration
1) set up apparatus
2) record starting position of air bubble
3) start stopwatch and record distance moved by the bubble per unit time
4) keep conditions constant throughout e.g. temperature, air humidity
what are root hair cells adapted for
the efficient uptake of water by osmosis, and mineral ions by active transport
what is the role of stomata and guard cells
to control gas exchange and water loss
