aqa gcse combined science b2

organisation

what are tissues?

groups of similar cells that act together to perform a similar function

what are organs?

groups of distinct tissues that work together to perform a specific function

what is an organ system?

groups of organs that work together to perform a particular role

what organs are in the digestive system?

* large intestine
* stomach
* liver
* small intestine
* glands

what do enzymes do?

increase the speed of reactions

what happens on an enzyme?

the substrate (reacting chemical) must bind to the enzyme’s active site (will only fit specific substrates)

what factors affect the rate of enzyme action?

* pH
* temperature

where are digestive enzymes made?

in the glands and the lining of the gut

what are digestive enzymes used for?

breaking down large food molecules

what breaks down starch?

amylase

where is amylase produced?

* small intestine
* pancreas
* salivary glands

what is amylase’s purpose?

it breaks down starch into its constituent simple sugars (predominantly maltose)

what are amylase’s sites of action?

* small intestine
* mouth

what breaks down proteins into amino acids?

proteases

what are protease’s sites of action?

* small intestine
* stomach

where are proteases produced?

* small intestine
* pancreas
* stomach

what breaks down lipids into glycerol and fatty acids?

lipase

where is lipase produced?

* small intestine
* pancreas

what is bile?

an alkaline substance that is stored in the gall bladder after having been produced in the liver

why is bile important?

* neutralises stomach acid to stop enzymes in the small intestine becoming denatured
* emulsifies (breaks up) fat into tiny droplets so they have higher SA and increases the rate of reactions that breaks fat down

how do you test for lipids?

add sudan III

red stained oil layer = present

how do you test for starch?

add iodine solution

blue-black = present

how do you test for sugar?

add benedict’s reagent and heat for 2 minutes

green/yellow/red = present

how do you test for proteins?

add biuret solution

mauve/purple = present

what adaptations do arteries have?

* elastic fibres allowing them to stretch and spring back
* thick muscle walls to cope under high pressure

what do capillaries do?

food and oxygen moves out of the blood and into the cells and waste products (such as CO2) move out of the cells and into the blood

what are veins?

they form when capillaries join up after passing through the body

what kind of blood do veins transport?

deoxygenated EXCEPT pulmonary vein from the organs back to the heart

what adaptations do veins have?

* thinner walls because of lower pressure
* wider cross section than arteries to counteract the low pressure hindering blood flow
* valves to prevent the backflow of blood

what makes the heart pump?

a group of cells in the right atrium act as a pacemaker

what happens when a heart beats?

* blood enters the heart via the atria
* the atria contract and force blood into the ventricles
* the ventricles contract and force blood to exit the heart

what happens in the vena cava?

the heart receives deoxygenated blood from the body

what happens in the pulmonary vein?

the heart receives oxygenated blood from the lungs

what happens in the aorta?

the heart pumps out oxygenated blood to the body

what happens in the pulmonary artery?

the heart pumps out deoxygenated blood to the lungs

what happens in the coronary arteries?

supply the heart muscle with oxygenated blood

why is it called the double circulatory system?

the blood passes through the heart twice per circuit?

what happens in the circulatory system?

* deoxygenated blood from the body enters into the right atrium of the heart
* this blood is pumped out of the heart and towards the lungs by the right ventricle
* the deoxygenated blood exchanges CO2 for oxygen and the blood becomes oxygenated
* the blood returns to the left atrium of the heart
* the blood is pumped out of the heart and to the body by the left ventricle through the aorta
* the blood returns to the heart

where does oxygenation of the blood take place in mammals?

in the lungs

what do alveoli do?

they allow oxygen and carbon dioxide to be exchanged between the blood in the capillaries and the air in the lungs by diffusion

what are alveoli?

tiny air sacs in the lungs

how are alveoli adapted for efficiently exchanging substances?

* large surface area
* surrounded by capillaries so they have a rich oxygen supply and the distance for gases to diffuse is small

what is blood made up of?

a fluid called plasma

what is plasma made of?

* platelets
* white blood cells
* red blood cells

what do platelets do?

they are responsible for triggering blood clotting at the sites of wounds and have no nucleus

what do red blood cells do?

transport oxygen from the lungs to all body cells

how are red blood ells adapted?

* haemoglobin - binds with oxygen in the lungs and carries this around the blood before releasing it to the body cells to be used in respiration
* no nucleus - more room for haemoglobin and oxygen
* small size to pass through tiny capillaries
* bioconcave shape to create a large surface areas and allow for rapid diffusion of oxygen

what do white blood cells do?

defend against infections

what adaptations do white blood cells have?

* no nucleus
* can change shape to squeeze through walls of blood vessels into body tissues and to engulf harmful microorganisms

what is health?

a description of an individual’s physical and mental well-being

what is a communicable disease?

a disease that can be spread between organisms

what is a non-communicable disease?

a disease that cannot be spread between organisms

what does HIV suppress?

the immune system - making individuals more susceptible to catching other infectious diseases

what can allergies be triggered by?

an immune reaction to a pathogen

what is a risk factor?

factors that increase the probability of developing a disease

what are the categories of risk factors?

lifestyle and substances

what are examples of links between risk factors and disease?

* poor diet, smoking and lack of exercise - cardiovascular disease
* excessive alcohol consumption during pregnancy - brain damage
* excessive alcohol consumption - liver and brain damage
* exposure to ionising radiation - cancer
* smoking - low birth weight of babies
* smoking - lung disease
* obesity - type 2 diabetes

what is coronary heart disease?

a non-communicable disease where the coronary arteries become narrower because of a build up of fatty deposits which reduces blood flow and leads to a lack of oxygen to the heart

what is heart valve disease?

where valves can become faulty, either by leaking or being unable to fully open

what effect does having leaky valves have?

it allows the backflow of blood which forces your heart to do more work to circulate the same volume of blood qand creates a strain on the heart

what is the effect of having valves that do not fully open?

they will obstruct blood flow and a greater force is required to force the blood through the body which adds to the strain of the heart

how can faulty valves be fixed?

by inserting either animal or artificial valves

what are the benefits of artificial hearts?

* unlikely to be rejected by the patient’s immune system so no immunosuppressant drugs are necessary
* can be used to provide the heart with rest to allow it to recover

what are the drawbacks of artificial hearts?

* can result in long and expensive stays in hospital
* can cause blood clotting - strokes

what are the two common treatments for coronary heart disease?

stents and statins

what are the benefits of stents?

* they keep coronary arties open

what are the drawbacks of stents?

* irritation from the stent causes artery to narrow again as scar tissue builds up
* drugs must be taken to prevent blood clotting on the stent

what are statins?

drugs that can be taken to decrease blood cholesterol levels and slows down the build up of fatty materials

what are the advantages of drugs to treat heart disease?

* often cheap to buy
* no surgery required

what are the disadvantages of drugs to treat heart disease?

* may have side effects
* patient must remember to take them

what are the advantages of using mechanical devices to treat heart disease?

* used in cases where a donor organ is not available

what are the disadvantages of using mechanical devices for heart disease?

* require a power supply
* may eventually wear out and need replacing

what are the advantages of using heart transplants to treat heart disease?

* successfully transplanted organs won’t wear down
* will function like replaced organ

what are the disadvantages of heart transplants to treat heart disease?

* require a suitable donor
* need immunosuppressants
* increases risk of different disease

what are malignant tumours?

they can invade neighbouring tissues and spread throughout the body in the blood, leading to the creation of more secondary tumours

what are benign tumours?

they stay in a specific part of the body, often within a membrane

what are the cancer risk factors?

* lifestyle e.g. smoking, obesity, UV exposure
* genetic

what are examples of plant organs?

* stems
* leaves
* roots
* reproductive structures

what is transpiration?

transports water and the minerals dissolved in it through the plant

what are the factors affecting the rate of transpiration?

* air flow
* humidity
* light intensity
* temperature

what is translocation?

the process by which food in photosynthesis is transported from the leaves to the growing regions of plants and storage organs

what happens in phloem tubes?

translocation

what is transported in xylem vessels?

water and minerals

what strengthens the cell wall of xylem?

lignin

how do root hair cells absorb water form the soil?

via osmosis

what adaptations do root hair cells have?

* lots of mitochondria to ensure enough energy for active transport
* long projections increase surface area

what are stomata?

gaps in the lower epidermis of the leaves that facilitate the diffusion of gases including evaporated water in and our of the leaf

what opens and closes the stomata?

guard cells