GSCE Science - Biology - B2




  • Levels of Organisation
  • The Digestive System
  • Enzymes
  • Required Practical 4
  • Required Practical 5
  • The Lungs
  • The Heart
  • The Content of Blood
  • Blood Vessels
  • Cancer
  • The Idea of Healthy Living, Risk and Disease
  • Heart Disease
  • Heart Transplants
  • Structure of Plants and Organ Systems
  • Transpiration
  • Translocation
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A - Levels of Organisation

Levels of Organisation

Multi-cellular organisms have different levels of organisation making up their systems. These groups of levels making up a wider body in term forming the organism. Without the cells being organised, the organism would not be able to function.

  • Cells

All living things are made up of these and they are the basic building blocks in the formation of an organism. Many of these cells are specialised to make them more useful and adapted to their function. 

Examples: sperm, muscle, root hair, phloem/xylem 

  • Tissue

This is a group of similar cells working together in a unanimous from to support that tissue's function. Each tissue may contain different types of cells. In the stomach, the lining of this organ is made up of different tissues. Like the muscular tissue which churns food and digestive juices together. There is also the glandular tissue which produces enzymes which break down food. Finally, there is the epithelial tissue which lines the stomach.

Examples: connective, epithelial, muscle, nervous


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B - Levels of Organisation

Levels of Organisation

  • Organs

A group of tissues together forms an organ. These tissues, which there may be more of one of, work together to aid the function of an organ.

Examples: heart, lungs, stomach, brain

  • Organ System

A group of organs which work together to aid a process in an organism. They work together in a chain.

Examples: circulatory system, digestive system, reproductivity system

  • Organism

A group of organ systems that work together to achieve the seven life processes.

Examples: humans, mammals 

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C - Levels of Organisation

Levels of Organisation

The digestive system is one example of an organ system. Humans depend on this system as it absorbs and gathers nutrients and glucose from the food we eat. It connects to the excretory and circulatory systems. 

Organs: mouth, oesophagus/gullet, stomach, small intestine, large intestine, colon, rectum, anus

The circulatory system is important as it provides food and oxygen and removes waste products to/from our body. It is vital and connects to all other systems. 

Organs: heart, arteries, capillaries, veins, blood

The nervous system provides an internal communication system between the brain and other parts of the body. It connects the outside world and our perception of it to the brain. Since it provides a response to things it connects to all other systems. 

Organs: nerves, brain, spinal cord

The muscle system provides the form of our body and the underlayer from the integumentary system and an overlayer for the skeletal system. It connects to the nervous system and provides movement as a reaction to signals from the brain.

Organs: muscles, joints

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D - Levels of Organisation

Levels of Organisation

The respiratory system is key to our survival, as it takes in and removes products from the air. It connects to the nervous and digestive systems.

Organs: mouth, lungs, nose, trachea, epiglottis, diaphragm, bronchi

 Other examples:

  • Urinary - eliminate, remove and store waste products - bladder
  • Reproductive - create and distribute offspring - reproductive organs
  • Integumentary - provide a layer of protection for under layers - skin
  • Skeletal - provides support and structure - bones - circulatory, muscle
  • Lymphatic/Immune - provides support when the body is under attack
  • Endocrine - gives out hormones - circulatory 
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A - The Digestive System

The Digestive System

The digestive system is made up of many organs which work together to gather the nutrients and energy from food. Food enters the mouth and then passes through it pass the salivary glands which produce amylase. The food then travels down the oesophagus and into the stomach where the digestion process continues. The food then continues to pass through the pancreases, liver and gall bladder before the reaching the duodenum which is part of the small intestine. After passing through the ileum, the food, which has been dissolved, reaches the opening of the large intestine, which is called the colon. The large intestine is composed of three parts, the colon, rectum and anus. The rectum is where the faeces are stored before being excreted by the anus, where the faeces leave through the alimentary canal. 

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B - The Digestive System

The Digestive System

The food which enters the digestive system is made up of three things: carbohydrates, proteins and fats. Since food molecules are too large to be broken down by one enzyme, they have to break down up several to make smaller molecules.

  • Mouth

In the mouth, the enzyme, amylase is present and breaks starch molecules. The salivary glands produce the enzyme. 

  • Stomach

In the stomach, it produces a protease enzyme which breaks down protein molecules. 

  • Intestine

The intestine contains the most enzymes, it contains maltase, peptidase, bile and lipase. Maltase breaks down maltose, peptidase break down polypeptides, bile and lipase break down fat into fatty acids and glycerol. The pancreas produces amylase, protease and lipase before delivering it into the small intestine. The gall bladder produces bile. 

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C - The Digestive System

The Digestive System

Bile is incredibly important in helping other intestinal enzymes work. Digestive enzymes found in the small intestine, are damaged by strong acidic conditions as it denatures their active sites. To avoid this problem, bile produced by the liver and stored in gall bladder, before being released down the hepatic/bile duct into the duodenum which is the starting module for the small intestine.

Bile neutralises the acidic contents of the stomach, creating an alkaline environment, that is the perfect environment for the enzymes to work. 

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A - Enzymes


  • Definition

Enzymes are biological catalysts, they decrease the amount of time it is meant to take to dissolve a substance. In this case, food, however, they can be used in a variety of other ways. They speed up chemicals reactions that take place inside all cells but continue to work overtime, without being used up in the process. There are a variety of enzymes in the body, and they are adapted and specialised to their function. They are made in the ribosomes. They are basically chains of amino acids, which make up the enzyme. 

  • Uses in the Industry

Enzymes cannot only be used in our body, but they can be used in other products. The protease enzyme can be used to pre-digest food in the process of manufacturing baby food; this enzyme helps create a more digestible food for the baby. Lipase can be used in biological detergents, as it can break down the stains in clothing, into water-soluble substances. Sports drinks contain sugar syrup which was originally starch syrup, so carbohydrase breaks that down into the sugar. In slimming foods, like in sports drinks contains a substance to aid the function. In this case, it is fructose syrup, which has to be broken down from glucose syrup using isomerase. Fructose is much sweeter than glucose and is used in small amounts in slimming foods to add a sweeter taste, rather than using sugar. 

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B - Enzymes


The ways reactants or molecules are broken down is known as the lock and key theory. Substances that are going to be broken down fit into an enzyme's active site. Each enzyme's active site only breaks down a certain reactant, so each enzyme specifically breaks down a certain molecule.

The reactant enters the enzyme's active site and this is known as the enzyme-reactant complex. Then the enzyme breaks the reactant down into products.

Enzyme + Reactant = Enzyme-Reactant Complex = Enzyme + Product

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C - Enzymes


Generally, three enzymes work in the process of digestion.

Amylase is produced in three locations, the salivary glands, the pancreas and the small intestine. The starch in these locations is broken down into sugar. Protease is produced in three locations as well, the stomach, the pancreas and the small intestine. The protease in these locations is broken down into protein into amino acids. Lipase is produced in two locations, the pancreas and the small intestine. The lipids in these locations are broken down into fatty acids and glycerol. 

  • Amylase - Starch into Sugar - Salivary Glands, Pancreas, Small Intestine
  • Protease - Protein into Amnio Acids - Stomach, Pancreas, Small Intestine
  • Lipase - Lipids into Fatty Acids and Glycerol - Pancreas, Small Intestine


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D - Enzymes


Enzymes work in certain conditions, generally alkaline. Bile is important in ensuring in the stomach that the conditions are perfect for the enzymes to work. If the conditions are not right for the enzymes are to work, then the enzymes' active site becomes denatured and is unable to break down reactants into products. Bile neutralises the stomach's contents, which is acid, ph 2, into a neutral solution using bile which is alkali, ph 12. Each enzyme works in a primed condition.

  • Amylase is both acidic and alkaline
  • Protease has two types of enzymes, pepsin which is acidic and trypsin which is alkaline
  • Lipase is just alkaline

By creating a neutral environment, all enzymes not matter their ph can work in unison, in a primed condition. 

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A - Required Practical 4

Required Practical 4

Required Practical 4 investigates the different food molecules in food by using different food tests. Each of the different tests, test for either starch, glucose, protein or lipids. We used five different foods, biscuit, egg white, pepper, cheese and pasta.

Firstly, you will need to set up the equipment. You will need a test tube rack, test tubes, iodine, benedicts, biuret solution (copper sulphate and potassium hydroxide), ethanol and the different foods. Secondly, set up each different test, for each food, add the solution and check the colour and this will tell you whether the food contains the molecule. Repeat for each food and solution, depending on the number of food, you should have twenty tests to do. 

Each time round, change the food and solution so this is the independent variable. You are measuring the colour, so this is the dependent variable. You keep the amount of food and solution the same so these are both the control variables. 

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B - Required Practical 4

Required Practical 4

Below are the food and the molecules it contains.

  • Biscuit - Starch, Glucose, Lipids
  • Egg White - Protein
  • Pepper - Glucose
  • Cheese - Protein, Lipids
  • Pasta - Starch, Glucose, Lipids

Carbohydrates - are made of molecules which contain carbon, hydrogen and oxygen. They are also made up of complex sugar units which are used for energy and a reactant during respiration.

Sugar - comes in two forms, simple which is one or two units, or complex which is longer chains and more long-term solutions to energy

Lipids - are made of molecules which contain carbon, hydrogen and oxygen. Their structure is made up of four fatty acids, one of which is glycerol. Lipids are fat when they are insoluble and solids and oil when liquid. 

Protein - are made up of molecules of carbon, hydrogen, oxygen and nitrogen. These atoms make up long chains of amino acids which create a 3-D structure and shape.

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A - Required Practical 5

Required Practical 5

Required Practical 5 investigates the effect of ph on enzme activity. Because of the specific environment needed for an enzyme to work, we can predict that the closer the ph is to the natural working conditions of the enzyme, the quicker the reaction will occur. If the ph is too high, the enzyme's active site will become denatured and will not be able to break down food as effectively or not at all. This process usually occurs because of the ph's solution. 

Firstly, you need to set up the equipment in the correct way. You will need a water bath, amylase, starch, ph buffer solution, iodine, a pipette and a spotting tile. Secondly, add the starch, the ph buffer solution, iodine and amylase solution to the test tube. Then place the solution into the water bath to mantain a constant temperature for the solution and to boost the activities of the enzyme. After you have placed the solution into the water bath, take a stop clock and every thirty seconds, take a sample of the solution using the pipette and place it onto the spotting tile. Continue to record the results from the solution until is has returned to the colour of iodine. This means that the starch has been broken down. Repeat the last steps for all the ph buffer solutions. 

Each time round, you are changing the ph of the buffer solution so this is the independent variable. You are measuring the dependent variable which is the time taken to break down the starch mixed in with the iodine, ph buffer solution and enzyme, amylase. You keep the amount of starch, ph buffer solution, amylase and the temperature of the solution are the same

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B - Required Practical 5

Required Practical 5

We used four solutions, ph 5 which broke down the starch in 180 seconds, ph 6 which broke down the starch in 60 seconds, ph 7 which broke down the starch in 210 seconds, and finally, ph 8 which didn't break down the starch in out time limit. We stopped recording as we predicted that the enzyme amylase had denatured and would be unable to continue. These results were the time taken to break down starch using the enzyme amylase in different ph solutions. Our results found out that the optomon solution as it delivered results in one minute, which was the quickest out of all the results. 

To work out the rate of activity you need to divide the time by 1, to get 1/time. The rate for ph 5 was 0.005, the rate for ph 6 was 0.016 and the rate for ph 7 was 0.004. We were unable to get a result for ph 8. The peak of activity for amylase was ph 6 as the number was the highest. Evidently, ph 6 was the best environment for amylase to work in. 

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A - The Lungs

The Lungs

The lung's main function is to supply oxygen and input it into the bloodstream, to supply the body's cells for respiration and remove the waste product of carbon dioxide from the air and in your body. And these processes all occur in your lungs when you breathe in and out.

The lungs are located in the thorax, which is the top of the body. They are surrounded by the ribcage which protects them. In between the lungs are the intercostal muscles which provide an important role in ventilating the lungs. Beneath the lungs is a muscular sheet which is the diaphragm. Within the lungs, there is a network of tubes which air passes through. The air is warmed, moistened and filtered as it travels through the mouth and nasal passages and into the trachea, the opening passage. It then travels down to the two bronchi and into one of the lungs, the bronchi breaks off from the trachea and into the many bronchioles and then finally into tiny air sacs called alveoli for gas exchange. 

Inhale: intercostal muscles contract, expanding rib cage outwards and upwards, the diaphragm contracts, pulling downwards to increase the volume in the chest, the pressure is lowered and the air is sucked in

Exhale: intercostal muscles relax, ribcage drops inwards and downwards, the diaphragm relaxes, moving back upwards to decrease the volume in the chest, the pressure is increased and the air is forced out.

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B - The Lungs

The Lungs

Within the alveoli, gas exchange occurs between the gases inside the alveoli and the blood by diffusion. Blood arriving in the alveoli has returned from to the lungs from the rest of the body so therefore contains a lot more carbon dioxide and a lot less oxygen. Oxygen diffuses out of the alveoli and into the blood and carbon dioxide diffuses into of the alveoli and out of blood. When the blood reaches the cells, red blood cells release oxygen and diffuses into the cells. 

To maximise the effectiveness and efficiency of the alveoli, it has many adaptations:

  • Large Surface Area - bigger space for gaseous exchange
  • One Cell Thick Walls - diffusion can occur quicker
  • Surrounded by Blood Capillaries - ensuring a good blood supply, also maintains the concentration gradient (blood - air)
  • Well Ventilated - removing waste and replenishing oxygen


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A - The Heart

The Heart

The heart is the key organ in the circulatory system. The heart is a pump that sends some blood to the lungs and some blood to the rest of the body every time it beats. The blood on the left side is kept separate from the blood on the right side. This is called a double circulatory system and is a more efficient way of delivering oxygen to the tissue that single circulation. 

Blood carries oxygen and dissolved nutrients to the body's cells and waste products away from them. The circulatory system consists of, the heart, veins, arteries and capillaries. 


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B - The Heart

The Heart

The path of blood around the body works in a double circulatory system and divides up both oxygenated and deoxygenated blood. 

  • Left Side - deoxygenated blood

Vena Cova → Heart → Right Atrium → Valves → Contracts → Right Ventricle → Valves → Contracts → Out of the Heart → Pulmonary Artery → Lungs → Picks up Oxygen

  • Right Side - oxygenated blood

Pulmonary Vein Heart → Left Atrium → Valves → Contracts → Left Ventricle → Valves → Contracts → Out of the Heart → Aorta → Rest of the Body

The right side of the heart contains oxygenated blood which has arrived from the lungs and this blood arrives in the right ventricle. The left side of the heart contains deoxygenated blood which has arrived from the rest of the body and this blood arrives in the left ventricle.  The atrium pumps the blood into the ventricle. Since the ventricles have to cope with a higher pressure they have thicker walls than the atria. And the left ventricle have thicker walls than the right ventricle as they have to pump blood all around the body rather than just to the lungs. The valves are important in stopping reverse blood flow.

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C - The Heart

The Heart

Your resting heart rate is controlled by a group of cells in the right atrium wall that act as a pacemaker. These cells produce small electrical impulses that spread around the surrounding muscular cells causing them to contract. Since you don't need a rapid amount of blood, these natural pacemakers help keep your heart rate constant and your body supplied with plenty of oxygen and dissolved nutrients in the blood. 

An artificial pacemaker is often used to replace the natural pacemaker cells if they do not function efficiently. It is a device that is implanted under the skin and produces an electric pulse to keep the heart rate constant and steady. 

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Content of Blood

Content of Blood

Blood is made up of four components, plasma, red corpses, white corpses and platelets.

  • Plasma (55%) - yellow liquid, transports blood cells and other substances around your body, like carbon dioxide (from the lungs), urea (from the liver) and soluble products (from digestion)
  • Red Blood Cells (45%) - biconcave discs (increases surface area to volume ratio for diffusion, increased by lack of a nucleus), their function is to pick up oxygen from the air in your lungs and carry it to cells who need it, they are packed with red haemoglobin (making them red) that binds to oxygen making it easier to move
  • White Blood Cells (>1%) - bigger than red blood cells and fewer, contain a nucleus, their function is to fight against bacteria, two types of white blood cells - lymphocytes (form antibodies against microorganisms) and phagocytes (engulf and digest invading bacteria and viruses) 
  • Platelets (>1%) - small fragments of cells, help blood clot around a wound, blood clotting is a series of enzyme-involved reactions that convert fibrinogen into fibre, this blocks the wound from exiting blood and entering bacteria


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Blood Vessels

Blood Vessels

  • Arteries

Carry oxygen-rich blood out of the heart, after being oxygenated by the lungs, strong, able to stretch, thick walls, elastic fibres, smaller lumen, the thick walls allows it to cope with high pressure, the elastic fibres allow it to adapt to the flow of the blood, contractions makes the blood pass through quicker, thick outer wall contains entire stream, smaller lumen keeps the blood at a higher pressure and moving

  • Veins

Carry oxygen-poor blood to the heart, after being used to aid cells, thin walls with valves, thin inner layer with elastic fibre, wide central tube, large lumen, valves prevent blood flowing backwards, large lumen keeps blood under low pressure, thin layer allows adaptation to flow

  • Capillaries

Take nutrients and oxygen into cells, remove waste products, one cell thick walls, narrow central tube, one cell thick walls allows the substances to diffuse in and out quickly and exchange between the membrane, diffusion is suited because of short diffusion gap

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The cell cycle controls which cells are allowed to multiply. Unhealthy cells with damaged DNA and bad genes are repaired and destroyed at checkpoints while healthy cells carry on through the cycle. However, sometimes they get through. The faulty DNA may then tell the cell to multiply at the wrong point and time. If it accumulates too much damage over time, it can become a cancer cell, they multiply out of control, forming a lump or a tumour. 

  • Lung Cancer - come in two types, small cell and non-small cells, they are classified by the size of the cell, the main cause is smoking or other air pollution, to avoid it, stay healthy with a balanced diet and exercise, and stay away from smokers and don't smoke
  • Skin Cancer - come in two types, melanoma (can spread to other organs) and non-melanoma (affects upper layers of skin), causes include, your skin condition and exposure to sun, and family and self-history, by keeping out of the sun you prevent this risk
  • Cervical - caused by human papillomavirus which is transmitted, is prevented safe sex, vaccinations and routine tests
  • Testicular - prevented by safe sex, not smoking and checks
  • Breast - comes in two types, non-invasive, unable to spread, and invasive, able to spread, risks include age, inheritance and race, can be prevented by screenings, exercise, avoiding breastfeeding
  • Brain - can either be cancerous/malignant or non-cancerous/benign, risks include, medical and genetic history, lifestyle and exposure to medical radiation, you can prevent it by not drinking or smoking and maintaining a healthy lifestyle with regular checks 
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Healthy Living, Risk and Disease

Healthy Living, Risk and Disease

Health - a state of physical and mental well being 

Disease - any condition that interferes with the proper functioning of the body or mind

Healthy Living - is made up of many things  diet, exercise, stress, medical help/history and lifestyle, to keep a healthy lifestyle and improve your health, you should eat a well-balanced diet, exercise regularly, reduce stress, seek medical attention for any difficulties, avoid smoking and drink alcohol in moderation

Communicable Disease - can be spread - flu, chicken pox, cold

Non-Communicable Disease - cannot be spread - cancer, allergies, diabetes

Risk - something increasing your chance of getting a disease

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A - Heart Disease

Heart Disease

Heart disease will affect more people in the UK than any other disease, almost half will be from coronary heart disease. This is because of the increase in processed food which contains a high amount of fatty acids. 

  • Atheroma - fatty acids within the wall of the artery

It begins with streaks of fat forming in the side of an artery. The streaks are the accumulation of white blood cells, that have taken up low-density lipoproteins. They enlarge to form an atheromatous plaque which enlarges and restricts the flow of blood.

  • Thrombosis - a blockage which restricts blood flow and leads to high pressure causing damage to the lining of the artery

As the blood flow is restricted, the blood pressure increases which can cause damage to the endothelium lining of the artery. Platelets start to aggregate and lay down a blood clot. This is now a thrombus, it can become dislodged and move around the body which can be incredibly problematic if it enters the lungs. This now mobile thrombus can move to other organs.



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B - Heart Disease

Heart Disease

  • Anewrysm - a thrombus forming and weakening the walls of the artery

Atheromas can lead to the formation of a thrombus that can weaken the walls of the artery. These points weaken and swell like balloons, they contain blood and are called an aneurysm. These can burst which can lead to haemorrhage, this can then lead to blood loss.

  • Myocardial Infarction/MI/Heart Attack

This can be caused by a reduced supply of oxygen to the heart. MI is a symptom of CHD (cononary heart disease). MI reduces blood supply which can be cut off. If the blockage is close enough to the junction of the cononary artery and aorta then the heart will stop beating. 

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C - Heart Disease

Heart Disease - Coronary Heart Disease

CHD affects the coronary arteries which supply the blood with glucose and oxygen, both of which are required for respiration. Fatty acids block the artery which blocks the flow of blood stopping the heart. 

The heart needs its own supply of blood as it requires a large amount of oxygen and nutrients to function efficiently. Since the walls of the heart are so quick diffusion through this membrane would be very difficult, so an artery, called the coronary artery is needed to supply the heart.

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Heart Transplants

Heart Transplants

Because of varies problems with the heart including narrow rigid arteries, leaking heart valves and a faulty pacemaker, you may need a heart transplant. However, it is very difficult to find suitable and healthy hearts to match the tissue type needed by the patient. After the operation, people with heart transplants need to take drugs for the rest of their lives to stop their immune system rejecting the heart, but this increases the risk of infections. 

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Structure of Plants and Organ Systems

Structure of Plants and Organ Systems

A plant is made up of many different cells and tissues and organs which help it in its function and help it stay alive. In the leaf, each part has an adaptation to help it with its particular function. For example, the guard cells, open and close the stoma allowing it exchange gases through the plant.

The male part of the plant is called the stamen and is made up of the anther/pollen which sits on top of the filament inside the petals. 

The female part of the plant is called the pistil and is made up of the stigma, top of the style, style, stalk of the flower which contains the ovary which contains ovules. 

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Transpiration and Translocation

Transpiration and Translocation

  • Transpiration - the loss of water from the plant by evaporation through the transpiration stream, through the plant

Measured with a photometer, factors can affect its efficiency

  • Translocation - the transport of substances like sucrose, amino acids, hormones and minerals, made in parts of the leaf to other parts


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Stomata, Xylem and Phloem

Stomata, Xylem and Phloem

When the guard cell is closed it is flaccid as contains enough water, but when it is open the guard cell is turgid and wants to exchange gases in and out. 

The xylem carries water and minerals in a unidirectional flow through the plant upwards. The xylem tube is coated with dead cells and made up of lignin making it hollow and waterproof. Perforated cell walls known as sieve plates are not present. 

The phloem carries food/glucose in a multi-directional flow through the plant to parts which don't photosynthesise. The phloem tube is coated with living cells, which transport sap-water based solution and are sugar-rich, and made up of cellulose. Perforated cell walls known as sieve plates are present. 

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