Tissues, organs and organ systems

Health and diseases

Enzymes and digestion

  • Created by: gradycat
  • Created on: 01-08-21 20:45

cell organisation

Cells - basic building blocks that make up living organisms

Specialised cells - cells that carry out a particular function, organised to form tissues

Diffrentiation - process by which cells become specialised, occurs during the development of a multicellular organism

Multicellular organisms - have different systems inside them for exchanging and transporting materials

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  • tissues include more than one type of cell

Tissue - a group of similar cells that work together to carry out a particular function

Muscular tissue - contracts to move whatever it's attached to

Glandular tissue - makes and secretes substances like enzymes and hormones 

Epithelial tissue - covers some parts of the body (inside of the gut)

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  • organs are made up of different tissues

Organ - a group of different tissues that work together to perform a certain function


  • muscular tissue - helps churn up food
  • glandular tissue - makes digestive juices to digest food
  • epithelial tissue - covers outside and inside of stomach
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organ systems

  • organ systems work together to make entire organisms

Organ system - a group of organs working together to perform a specific function

Digestive system

  • glands (pancreas and salivary) - produce digestive juices
  • stomach - where food is digested
  • liver - produces bile
  • small intestine - food is digested and soluble food molecules are absorbed
  • large intestine - water is absorbed from undigested food, leaving faeces
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  • help get oxygen from the air into the bloodstream so it can get to your cells for respiration
  • helps get rid of carbon dioxide in the blood
  • exchange of gases happens in the lungs
  • air is forced in and out of the lungs by breathing
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  • lungs are in the thorax
  • the thorax is the top part of the body
  • separated from the lower part of the body by the diaphragm
  • lungs are like pink sponges which are protected by the ribcage
  • surrounded by pleural membranes
  • breathe in air through the trachea
  • the trachea splits into two tubes (bronchi)
  • bronchi split into smaller tubes (bronchioles)
  • end of bronchioles are alveoli
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  • air sacs
  • surrounded by a network of capillaries
  • where gaseous exchange takes place
  • blood passing by alveoli contains lots of carbon dioxide
  • oxygen diffuses out of alveoli into the blood
  • carbon dioxide diffuses out of the blood into alveoli to be breathed out
  • blood reaches body cells
  • oxygen released from red blood cells and diffuses into body cells
  • carbon dioxide diffuses out of body cells into the blood then carried back to lungs
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breathing rate

  • breaths per minute = number of breaths ÷ number of minutes

112 ÷ 8 = 14                                           14 breaths per minute

  • number of minutes = number of breaths ÷ breaths per minute

112 ÷ 14 = 8                                                                8 minutes

  • number of breaths = breaths per minute × number of minutes

14 × 8 = 112                                                             112 breaths

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circulatory system function

  • to get food and oxygen to every cell in the body
  • carries waste products (carbon dioxide, urea) to be removed from the body
  • circulatory system includes heart, blood vessels and blood
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double circulatory system

1st circuit

  • right ventricle pumps deoxygenated blood to lungs to take in oxygen 
  • blood then returns to heart

2nd Circuit

  • left ventricle pumps oxygenated blood around body
  • blood gives up oxygen at body cells 
  • deoxygenated blood returns to heart to be pumped to lungs
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heart structure

  • walls of heart made of muscle tissue
  • the heart has 4 chambers (right atrium and ventricle, left atrium and ventricle)
  • 4 main blood vessels (vena cava, pulmonary artery, and vein, aorta)
  • valves - prevent backflow of blood
  • coronary arteries - branch off the aorta, makes sure heart gets all the oxygenated blood
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blood flow in heart

  • blood flows into 2 atriums from the vena cava and pulmonary vein
  • atria contract, pushing blood into ventricles
  • ventricles contract, forcing blood into the pulmonary artery and aorta and out of the heart
  • blood flows to organs through arteries and returns through veins
  • atria fill again 
  • repeats cycle
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  • resting heart rate controlled by a group of cells in the right atrium wall
  • cells produce small electric impulses which spread to surrounding muscle cells causing them to contract
  • artificial pacemaker used if natural cells don't work properly
  • a device implanted under the skin and has a wire going to the heart
  • produces an electric current to keep heart beating
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Arteries - blood vessels that carry blood away from the heart towards the organs


  • artery walls are strong and elastic - blood is at high pressure
  • thick layers of muscle - allow them to stretch and spring
  • thick walls and lumen
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Capillaries - carry blood close to every cell in body to exchange substances with them


  • supply food and oxygen to cells
  • take away waste products (carbon dioxide)


  • really small
  • permeable walls - allow substances to diffuse in and out, increases the rate of diffusion
  • narrow - gives large surface area, increases the rate of diffusion
  • no lumen
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Veins - carry blood to the heart


  • thin walls - blood is at low pressure
  • larger lumen - help blood flow
  • valves - keep blood flowing in the right direction 
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rate of blood flow

  • rate of blood flow = volume of blood ÷ number of minutes

1464 ÷ 4.5 = 325                                                       325 ml/min

  • volume of blood = rate of blood flow × number of minutes

325 × 4.5 = 1464                                                            1464 ml

  • number of minutes = volume of blood ÷ rate of blood flow

1464 ÷ 325 = 4.5                                                           4.5 mins

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Blood -  is a tissue


  • transport substances around the body


  • made up of red and white blood cells, platelets which are all in a liquid called plasma
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red blood cells


  • transport oxygen around the body


  • biconcave shape - gives a large surface for absorbing haemoglobin which carries oxygen
  • no nucleus - allows more room for haemoglobin which carries oxygen
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transporting oxygen

  • in lungs, oxygen diffuses into the blood
  • oxygen combines with haemoglobin to become oxyhaemoglobin
  • in body tissue, oxyhaemoglobin splits into haemoglobin and oxygen 
  • releases oxygen into the cells
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white blood cells


  • defend against microorganisms that cause disease
  • engulf unwanted microorganisms and digest them
  • produce antibodies to fight microorganisms
  • produce antitoxins to neutralise toxins produced by microorganisms


  • have a nucleus unlike red blood cells
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Platelets - small fragments of cells


  • no nucleus


  • help the blood to clot to prevent excess loss of blood
  • stops microorganisms from getting in at the wound
  • lack of platelets can cause excessive bleeding and bruising
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Plasma - a pale straw-coloured liquid that carries just about everything in blood


  • carries red and white blood cells and platelets
  • carries nutrients that get absorbed from the small intestine and taken to cells
  • carries carbon dioxide from organs to lungs
  • carries urea from the liver to kidneys
  • carries hormones and proteins
  • carries antibodies and antitoxins produced by white blood cells
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plant organisation

  • made of organs (stems, roots, and leaves)
  • epidermal tissue - covers the whole plant
  • palisade mesophyll tissue - part of the leaf where photosynthesis happens
  • spongy mesophyll tissue - contains big air spaces to allow gases to diffuse in and out of the cell
  • xylem and phloem - transport water, minerals, and food around the plant
  • meristem tissue - able to differentiate into different types of plant cell allowing plant to grow
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leaf structure

Epidermal tissue

  • covered with a waxy cuticle
  • helps reduce water loss by evaporation

Upper epidermis

  • transparent so light passes through to palisade layer

Palisade layer

  • lots of chloroplasts
  • near the top of the leaf to get the most light

Xylem and phloem

  • deliver water and other nutrients to the entire leaf
  • take away glucose produced by photosynthesis
  • help support the structure
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adaptations of leaf tissue

Lower epidermis

  • full of little holes (stomata)
  • let carbon dioxide diffuse directly into the leaf

Spongy mesophyll

  • air spaces 
  • increase rate of diffusion
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  • made of columns of elongated living cells
  • has small pores in end walls to allow cell sap to flow 

Cell sap - liquid made up of the substances being transported and water


  • transport food substances made in leaves to rest of plant
  • translocation
  • goes from leaves to roots
  • or goes from roots to leaves
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  • made of dead cells joined end to end
  • no end walls between them
  • have a hole down the middle
  • strengthened with lignin


  • carry water and mineral ions from roots to stem and leaves

Transpiration - movement of water from roots through xylem and out leaves

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Transpiration - loss of water from a plant

Transpiration stream - the movement of water through a plant from roots to leaves

Transpiration stream

  • water from inside the leaf evaporates
  • then diffuses out of the leaf through stomata on the underside of the leaf
  • creates a shortage of water in the leaf
  • water is drawn up from the rest of the plant through xylem vessels
  • more water is drawn up from roots
  • constant transpiration stream of water through the plant
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adaptations of transpiration


  • gases can be exchanged easily
  • more water inside the plant than in the air outside
  • water escapes leaf through stomata by diffusion
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factors affecting transpiration rate

Light intensity

  • brighter the light, greater transpiration rate
  • stomata close when it's dark, photosynthesis can't happen


  • warmer it is, faster transpiration happens
  • water particles have more energy to evaporate to diffuse 


  • better airflow, greater transpiration rate
  • poor airflow, water vapor stays by leaf, slower diffusion
  • good airflow, water vapor leaves, quicker diffusion


  • drier the air, faster transpiration happens
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investigating transpiration rate

  • measure uptake of water by a plant


  • set up apparatus
  • record starting position of air bubble
  • start stopwatch
  • record distance moved by bubble per unit of time
  • keep conditions constant through the experiment
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calculating transpiration rate

  • rate of transpiration = distance moved ÷ time taken

66 ÷ 60 = 1.1                                                        1.1 mm/min

  • distance moved = time taken × rate of transpiration

60 × 1.1 = 66                                                                66 mm

  • time taken = distance moved ÷ rate of transpiration

66 ÷ 1.1 = 60                                                              60 mins

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guard cells

Guard cells - open and closes the stomata in a leaf

  • two guard cells surround each stoma


  • the plant has lots of water, guard cells fill, go turgid, stomata open, gases can be exchanged
  • plant short of water, guard cells lose water, go flaccid, stomata close, stops water vapor escaping
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adaptations of guard cells

Thin outer and inner walls

  • make opening and closing work

More stomata on the underside of the leaf

  • close at night to save water without losing photosynthesis
  • sensitive to light
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estimating total number of stomata

  • number of stomata = (area of field of vision ÷ total area of surface) × average number of stomata per field of vision

The average number of stomata per field of vision 

  • count stomata on different fields of vision
  • repeat this 3 times
  • work out the average
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Health - state of physical and mental wellbeing

Diseases - responsible for causing ill health

Communicable diseases - spread from person to person or between animals and people (contagious or infectious)

  • causes are bacteria, viruses, parasites, and fungi
  • for example - measles and malaria

Non-communicable diseases - can't spread between people or between animals and people

  • last a long time and get worse slowly
  • for example - asthma, cancer, and coronary heart disease
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interaction of diseases

Immune system

  • increased chance of suffering from communicable diseases
  • body less likely to defend itself against pathogens
  • for example - catching the flu


  • hepatitis virus causes long term infections
  • more likely to develop liver cancer
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factors affecting health


  • a balanced diet provides the body with everything it needs
  • poor diet affects physical and mental health


  • being under lots of stress leads to health issues

Life situation

  • easy access to medicines to treat illnesses
  • vaccines to prevent getting ill in the first place
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cardiovascular disease

Coronary heart disease

  • coronary arteries get blocked by fatty materials
  • causes arteries to become narrow 
  • blood flow is restricted to the heart
  • lack of oxygen to the heart muscle
  • result in a heart attack
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Stents - wire mesh tubes that inserted inside arteries to widen them and keep them open


  • keep coronary arteries open
  • make sure blood passes to heart muscles
  • keeps person's heart beating


  • lowers the risk of heart attack
  • effective for a long time
  • quick recovery time


  • risk of complications and infection
  • risk of developing blood clot near the stent (thrombosis)
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Statins - drugs that reduce the amount of 'bad' cholesterol in the bloodstream

Cholestrol - a lipid that your body produces and needs to function properly, however too much can cause health problems


  • reduce risk of strokes, coronary heart disease, and heart attacks
  • reduce the amount of 'bad' cholesterol
  • increase amount of 'good' cholesterol


  • someone could forget to take them
  • negative side effects (headaches, memory loss, kidney/liver failure)
  • effect of statins isn't instant
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artificial hearts

Artificial hearts - mechanical devices that pump the blood for a person whose heart has failed


  • less likely to be rejected by the body


  • surgery can lead to bleeding and infection
  • increase in the chance of blood clots and strokes
  • may be uncomfortable for patient
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replacement heart valves

Biological valves - valves taken from humans or mammals

Mechanical valves - man-made

  • replacing valves is less drastic than an artificial heart
  • still problems with blood clots
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artificial blood

Artificial blood - a blood substitute to replace lost volume of blood

  • replace the function of lost red blood cells
  • no need for a blood transfusion
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risk factors

Risk factors - things that are linked to an increase in the chance for a person to develop a disease


  • exercise
  • air pollution
  • substances already in the body
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risk factor examples


  • damages wall of arteries and cells in lungs


  • struggles to control the concentration of glucose in the blood


  • damages intestines, brain function, and nerve cells


  • reduces the amount of oxygen


  • damages cell's DNA 
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human cost

  • non-communicable diseases
  • tens of millions of people around the world die per year
  • people with these diseases may have a lower quality of life or a shorter lifespan
  • affects themselves and loved ones
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financial cost

  • non-communicable diseases
  • cost to NHS for researching and treating the diseases
  • families may have to adapt their home to help ill family member
  • an ill family member will have to stop working so reduced family income
  • reduction in the number of people able to work also affects the country's economy
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Cancer - caused by uncontrolled cell growth and division

Benign tumours - tumour grows until there is no more room

  • tumour stays in one place
  • not normally dangerous
  • isn't cancerous

Malignant tumours - tumour grows and spreads to neighbouring healthy tissues

  • invade healthy tissues elsewhere
  • form secondary tumours
  • are dangerous
  • can be fatal
  • are cancerous
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risk factors for cancer

  • anyone can develop cancer
  • risk factors increase the chance of developing cancer
  • associated with aspects of person lifestyle
  • associated with genetics
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risk factor cancer examples


  • linked to lung cancer


  • linked to bowel, liver, and kidney cancer

UV Exposure

  • exposed to UV rays by the sun, the higher chance of skin cancer


  • viruses were shown to increase chances of developing cancers
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genetic risk factors

Genes - control activities of cells and characteristics

  • inherit genes from parents
  • can inherit faulty genes
  • make you more susceptible to cancer

For example - mutations in the BRCA genes have been linked to an increased chance of getting breast and ovarian cancer

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Catalyst - a substance that increases the speed of reaction without being changed or used up in reaction

Enzymes - large proteins that act as biological catalysts

Proteins - made of chains of amino acids

  • living things produce enzymes that act as biological catalysts
  • enzymes reduce the need for high temperatures
  • have enzymes to speed up chemical reactions in the body
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active sites

Substrate - a substance that an enzyme acts on

  • each enzyme has an active site
  • enzymes only catalyse one specific reaction
  • for an enzyme to work, the substrate has to fit in active site
  • if substrate doesn't fit, the reaction won't be catalysed
  • 'lock and key' method

'Induced fit' model

  • active site changes shape a little as substrate binds
  • to get a tighter fit
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enzyme conditions

Optimum conditions - enzymes need the right conditions to work 


  • higher temperature, increases the rate of reaction
  • too hot, bonds holding enzymes together break
  • too hot, changes the shape of the active site so substrate doesn't fit
  • results in enzyme being denatured
  • enzymes normally work best at 37⁰C 


  • too high or too low, breaks bonds holding enzymes
  • too high or too low, changes shape of active site so substrate doesn't fit
  • results in enzyme being denatured
  • most enzymes work best around pH 7 but can change
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calculating enzyme reaction rate

  • rate = 1000 ÷ time

1000 ÷ 90 = 11s‾¹

  • rate = change ÷ time

24cm³ ÷ 50s = 0.48cm³/s

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digestive system

Digestive system - nutrients get absorbed in body from gut

Mechanical digestion - teeth grind food, stomach churns it

Chemical digestion - enzymes help to break down the food

1. mouth/salivary glands

2. liver

3. gall bladder

4. stomach

5. pancreas

6. small intestine

7. large intestine

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digestive enzymes

  • work outside body cells
  • produced by cells in the gut lining
  • released into the gut to mix with food molecules
  • enzymes break down big, insoluble molecules into smaller, soluble ones
  • small molecules pass easily through walls 
  • used to make new carbs, proteins, and lipids
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  • convert carbohydrates into simple sugars
  • an example is an amylase
  • breaks down starch


  • made in salivary glands, pancreas, and small intestine
  • works in the mouth and small intestine
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  • catalyse the conversion of proteins into amino acids
  • made in stomach, pancreas, and small intestine
  • work in the stomach and small intestine
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  • catalyse the conversion of lipids into glycerol and fatty acids
  • made in the pancreas and small intestine
  • work in the small intestine
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  • produced in liver
  • stored in the gall bladder
  • released into the small intestine
  • bile is alkaline
  • neutralises acid and makes conditions alkaline
  • digestive enzymes work best in alkaline conditions
  • emulsifies fat
  • breaks down fat into tiny droplets
  • gives a bigger surface area for lipase to work on
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food tests


  • prepare water bath and add benedict's solution
  • has sugar = colour is from blue to green, yellow or red


  • iodine solution
  • has starch = colour is from browny-orange to black 


  • biuret solution
  • has protein = colour is from blue to purple


  • sudan III solution
  • has lipids = mixture separates in two layers, top layer is red
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