Section 2 i) Summary

In plants, excretion happens primarily through gas exchange. Oxygen and carbon dioxide are excreted from photosynthesis and respiration respectively. Toxins within the plant will collect within a dying leaf so it can be removed from the plant.

In humans however, it is more complicated.
We excrete through our skin: sweat contains water, salts and urea. This is also important for osmoregulation and homeostasis.
We excrete through our lungs: we breathe out carbon dioxide and water vapour, which again aids osmoregulation.
And finally, we excrete through urination. Urine contains water, salts and urea.

Urine is excreted through this system. It is important to not get confused between the urethra and the ureter.

Urea, the key part of urine, is made in the liver. Excess amino acids are broken down in a process called deamination. The urea then enters the blood, which must now be cleaned as urea is a toxic chemical containing nitrogen. The blood is cleaned in the kidneys

The most important part is the nephron, the filtration unit. There are about 1.25 million units in each kidney. In the nephron, blood is passed through the glomerulus at a high pressure, forcing out smaller molecules: Urea, water, salt, and glucose.

The solution created is known as glomerular filtrate. It enters the Bowman's capsule, then the proximal convoluted tubule. This is where glucose is selectively reabsorbed using active transport. Water and mineral salts are also reabsorbed. The filtrate then enters the loop of Henle. In the first hald, just water is reabsorbed, and in the second just mineral salts. The distal convoluted tubule continues to reabsorb water and mineral salts. This is now urine, which is about 95% water and 2% urea, the rest being excess salts and nutrients. The urine travels down the collecting duct and ureter into the bladder, where it is stored until excreted.

Osmoregulation
The amount of water in the body is regulated by the hypothalamus which causes the pituitary gland to release ADH, anti-diuretic hormone.

Excess of water detected by hypothalamus > Pituitary gland stimulated to produce less ADH > less ADH travels through the blood into the nephron > Tubules become less permeable > Less water is reabsorbed > Normal water content level achieved

Deficit of water detected by hypothalamus > Pituitary gland stimulated to produce more ADH > more ADH travels through the blood to the nephron > Tubules become more permeable > More water is reabsorbed > Normal water content level achieved

Section 2 h) Summary

Multicellular organisms require transport systems, because their surface area to volume ratio makes it impractical for just diffusion osmosis and active transport. Unicellular organisms are able to function on these transport processes alone because they're so small.

Flowering Plants

In flowering plants, the transport system is made of the xylem and phloem vessels, arranged in vascular bundles as so:

Xylem vessels are made of dead cells, with the cell walls at either end broken down. Their walls are thick and function secondarily as support. Primarily, though, they transport water and mineral ions throughout the plant. 

Phloem vessels are made of living cells, but their top and bottom cell walls contain holes, and are called sieve plates. These vessels carry glucose and amino acids around the plant for use by cells. The process is know as translocation.

These nutrients are only able to get to the plant via absorption, which the root hair cells do via osmosis and diffusion. Their long, hair like structure increases the rate of diffusion and makes it ideal for absorbing water and nutrients. 

Inside the plant, water is transported up the stem by the transpiration stream. Water molecules are cohesive (they stick together), so when water is evaporated from the leaves it causes the root hair cells to take in more in. The water is removed from the leaves via evapotranspiration, where the water first evaporates, then the vapour diffuses into the environment. This creates a sort of tension pull in the xylem, causing more molecules to take the place of the evaporated ones. This makes a larger water potential gradient about the roots, and causes more water to be sucked in.

The rate of transpiration is affected by the following factors:

These variables can be investigated using a potometer.

1. Set up apparatus so it is watertight, allowing a bubble to form in the capillary tube. The shoot should be cut diagonally to maximise surface area. Take note of where the bubble starts. 
2. Start a stopwatch and record the distance moved by the bubble per unit of time (e.g. cm/h)
3. Record on a graph, and see how it changes with different variables. 

All of the variables should cause it to change proportionally. 

Humans
Transport in humans happens through the circulatory system. 

It is a double circulation system, involving the pulmonary system and the larger circulation system.

Zooming in, the circulatory system is made of the blood vessels, the heart and the blood.

Blood:
55% Plasma, 45% Red blood cells, and a very tiny amount phagocytes, lymphocytes and platelets. The blood carries nutrients and fights off infection.

The white blood cells are responsible for the immune response.
Phagocytes engulf foreign cells, while lymphocytes detect antigens on pathogens and produce antibodies that mark them for destruction by other white blood cells. The lymphocytes keep a memory of how to make certain antibodies, so upon second infection many antibodies are produced quickly.

Vaccinations play this to our advantage; by injecting inactive or dead pathogens, the lymphocytes are able to detect the antigens and produce antibodies and 'remember' how to for the next infection.

Red blood cells are biconcave to maximise surface area, and have no nucleus. They contain haemoglobin which allows them to carry oxygen around the body.

Platelets are small cell fragments that bond together in fibrin to form clots and scabs. This prevents blood loss and infection.

Plasma carries digested nutrients (sugar, amino acids, etc.), carbon dioxide, urea, hormones and heat energy to where it needs to be in the body.


Blood vessels:
There are three kinds of blood vessels: arteries, veins, and capillaries.

Arteries have small lumen, thick walls, and high pressure. They carry blood away from the heart, and are far under the skin. The largest is the aorta.

Veins have large lumens, thin walls and low pressure. The contain valves to control the direction of flow. Some are quite close to the surface, so these are favourable for injections. (also their thin walls are easier to penetrate and their large lumen allow more space more error)

Capillaries are very tiny. They have very thing walls (one cell thick) for easy diffusion. They carry nutrients to all of the cells and their lumen are tiny.

Heart:
The heart is made up of muscle and fat. The left side is more muscular than the right, because the left must pump blood around the entire body and the right only to the lungs (which must be low pressure as it has to squeeze through tiny capillaries). It is made up of four chambers, the left and right atriums and ventricles.

The atriums receive blood and the ventricles pump it out. In diagrams, the left side of the heart is usually on the right, because of how it lays in the body, it's as if you're facing the person and using their left and right. The right side of the heart deals with deoxygenated blood, and the left with oxygenated blood.

The right atrium is connected to the vena cava. It takes in deoxygenated blood from the body and passes it through the tricuspid valve to the right ventricle.

The right ventricle pumps deoxygenated blood at a low pressure to the lungs (through the semi-lunar valve to the pulmonary artery). This must be low pressure to fit through the tiny capillaries in the lungs without bursting them.

The left atrium receives oxygenated blood from the pulmonary vein, after it has passed through the lungs. The blood is then passed through the biscuspid valve into the left ventricle.

The left ventricle has a thick muscular wall that allows blood to be pumped around the body at high pressure. It squeezes strongly so the oxygenated blood passes through the semi lunar valve into the aorta.


Circulation is affected by adrenaline and exercise:

More exercise means more respiration, meaning there is more carbon dioxide being released into the bloodstream, and a higher demand for oxygen. This causes the heart to pump faster so more oxygen can reach the muscles.

Adrenal glands are hormonal glands that release a chemical called adrenaline. This is released when the organism is threatened. It sends a signal to the brain to make the heart pump faster in order to get more oxygen to the bodily tissues for action (fight or flight)

Section 2 g) Summary

Gas exchange is the process of taking in oxygen and excreting carbon dioxide in organisms. This process is made possible by diffusion, which allows oxygen to travel from an area of high concentration (the air in the atmosphere) to an area or low concentration (e.g. the cells of a leaf, the capillaries surrounding the alveoli, etc.)

Flowering Plants

In flowering plants, gas exchange must happen for both respiration and photosynthesis.
Photosynthesis is essentially the reverse reaction of respiration:

Photosynthesis
Carbon dioxide + Water (+ energy from sunlight) --> Glucose + Oxygen
6CO2 + 6H2O --> C6H12O6 + 6O2

Gas exchange/respiration
Glucose + Oxygen --> Carbon dioxide + Water (+ energy)
C6H12O6 + 6O2 --> 6CO2 + 6H2O

Photosynthesis, however, can only take place during the day, when there is sunlight. During the night, respiration still occurs, but is limited by the stomata closing and preventing gas exchange from taking place in order to preserve water at night.

Leaves are adapted for gas exchange as they have stomata and guard cells, as well as air spaces to increase the surface area for diffusion. The guard cells become turgid during the day, opening the stomata and allowing air to flow in and out. During the night, to reduce water loss, the guard cells become flaccid and close the stomata. The leaves themselves are thin to decrease distance, and flat to increase surface area to volume ratio.

Net gas exchange in plants is affected by light levels overall. This is because photosynthesis happens more than respiration does, so it greatly affects the gas levels. We can investigate this using hydrocarbonate indicator which detects changes in CO2 levels.

1. Choose 3 leaves of similar sizes from the same plant, and suspend in a sealed boiling tube containing hydrogen carbonate indicator.
2. Leave one tube in the light, cover another tube in foil so it is in total darkness, cover another in gauze so it receives dim light, then leave a control without a leaf in the light. 
3. The hydrogen carbonate indicator will start off red in all, but each will end up with different results. The one in darkness will be yellow, the one in dim light will stay orange/red, the one in light will become yellow, and the control will not change in colour. 

Humans

Gas exchange in humans happens through the process of breathing, or ventilation.
This process happens in the thorax of the body, and involves a range of different structures for everything to work.

This diagram depicts some of the most important structures in the thorax for ventilation. This is how breathing in, then breathing out, involves each of them:

1. The intercostal muscles contract, the ribs move up, and the diaphragm contracts and moves down. This increase the volume and decreases the pressure within the chest and allows air to rush into the lungs.
2. The air outside at atmospheric pressure rushes through the larynx, and trachea, held open by the rings of cartilage, and then half the air travels down one bronchus in to one lung, and the other down the other. The air enters the bronchioles and is split down the branches. 
3. When the air reaches the alveoli (which are moist to dissolve the oxygen, as well as thin to decrease the diffusion distance and with a large surface areaa to increase diffusion. Oxygen diffuses from the air into the bloodstream and capillaries surrounding and bonding with haemoglobin in the red blood cells to form oxyhaemoglobin, and be transported around the body for respiration. 
4. Carbon dioxide diffuses out of the blood stream and into the alveoli. At this point, the intercostal muscles relax, the ribs move down, and the diaphragm relaxes and moves up. The volume of the chest is decreased, and the pressure increased, causing air to rush out into the atomsphere.  

The pleural membrane and fluid surrounding the lungs holds them in place, but allows them to move easily.

The rate of breathing is affected by exercise, because when in movement more oxygen is required for respiration to power the cells and bodily tissues.
We can investigate the way exercise affects breathing through this experiment:

1. Measure the rate of breathing while stationary (breaths per minute) by counting the number of breaths in fifteen seconds, then multiplying by four.
2. Exercise at a sustained and measured level for 1 minute (perhaps by running on a treadmill, which allows you to control your speed), then measure the rate of breathing again. Repeat after two minutes of exercise, then three, then four, and so on.
3. Draw a graph based of the length of time exercised (on the x-axis) and the breathing rate (on the y-axis), and you will see that the breathing rate is proportional to the time exercised.

This can also be done by using a spirometer to measure the depth of breath.


Smoking

Smoking is very bad for the lungs, it creates a number of problems with the different contents found in cigarettes.

• Cilia and mucus: Tar damages and paralyses the cilia, preventing them from moving mucus out of the lungs (causing mucus buildup) and leading to infections. This is CHRONIC BRONCHITIS.
• Alveoli: Tar fuses the alveoli together, decreasing surface area and making it more difficult to breathe. This is EPHYSEMA.
• Lungs, mouth and throat cancer: Cigarettes contain many carcinogens that cause cells to mutate and cancer to form in the mouth, throat and lungs. This is CANCER.
• Bloodstream: Carbon monoxide in cigarettes is favoured by haemoglobin, so it fuses to the protein and prevents oxygen from getting around the body, increasing heart rate and blood pressure. This is CARBON MONOXIDE POISONING.

Nicotine, a substance found in cigarettes, is highly addictive and affects the central nervous system, causing problems with blood pressure and coronary heart disease. 

Section 2 f) Summary

Respiration is the chemical breakdown of sugars to release energy in living cells.
This is very important, without it we wouldn't have the energy for any of the other life processes. Notable everyday energy-requiring processes include:

• nerve impulses
• cell division
• muscle contraction
• homeostasis and thermoregulation
• protein synthesis
• active transport

Aerobic respiration is releasing energy from glucose by reacting it with oxygen:

Glucose + Oxygen --> Carbon dioxide + Water (+ Energy)

C6H12O6 + 6O2 --> 6CO2 + 6H2O (+ Energy)

Anaerobic respiration is releasing energy from glucose without oxygen. It releases different toxic by-products in plants and animals, and less energy than aerobic respiration:

Plants: Glucose --> Carbon dioxide + Ethanol (+ Some energy)

Animals: Glucose --> Carbon dioxide + Lactic acid (+ Some energy)

The rate of respiration is affected by enzymes and their optimum temperature and pH. 

We can investigate respiration through the following experiments:

Rising dough (yeast):

1. Place dough into oiled measuring cylinders, and record their height. 
2. Place each measuring cylinder into a water bath (regular intervals of 10℃), with three cylinders in each bath so an average for each can be found.
3. Measure the height of the dough every 10 minutes, for 30 minutes.
4. Record the average heights in a table, then find the average percentage change in height. 

Seeds:

1. Fill one vacuum flask with living seeds, and thee other with surface-sterilised seeds. Place a thermometer in each and seal the top with cotton wool.
2. Record starting temp, then wait 30 minutes. 
3. The flask containing the living seeds will have increased in temperature, and the one with dead seeds will not. 

Heat is a by-product of the use of the energy for respiration. 

Humans: 

You can see that we produce carbon dioxide by blowing into a straw in a boiling tube containing lime water - it goes cloudy - or hydrogen carbonate indicator - it goes from red to yellow. 

Section 2 e) Summary

Flowering Plants
Plants don't need to eat, they get all of their nutrients by absorbing mineral ions from the soil, and carrying out photosynthesis.
Photosynthesis is the process by which plants generate glucose (which is stored as starch) using sunlight:

Carbon dioxide + Water -(sunlight)-> Glucose + Oxygen
6CO2 + 6H2O -(light energy)-> C6H12O6 + 6O2

They are able to do this because their cells contain organelles called chloroplasts, which contain a green pigment known as chlorophyll. Chlorophyll is the chemical that carries out photosynthesis.

Factors affecting photosynthesis:

• Temperature: As temp. increases, the particles move faster and the rate of photosynthesis is increased, but after reaching optimum temperature for the enzymes they begin to denature at any higher temp. and the rate of photosynthesis drops steeply.
• Light intensity: More intense light means more photosynthesis, but only up until a certain point as the number of chloroplasts is limited.
• Carbon dioxide concentration: Higher concentrations of CO2 mean more photosynthesis, but only up until a certain point as the number of chloroplasts is limited.
• Chlorophyll: Variagated leaves will photosynthesize less than single coloured leaves, lighter coloured leaves will photosynthesize less than darker ones due to the number of chloroplasts available to carry out photosynthesis

The diagram below shows the structure of a leaf

 Each layer has a different function:
The waxy cuticle protects the cell from damage, and prevents water loss.
The upper epidermis is thin and clear, and provides a layer of protection.
The palisade mesophyll is made up of column-shaped palisade cells, which are densly packed with chloroplasts to maximise absorption of light, and therefore photosynthesis.
The spongy mesophyll contains air pockets to increase diffusion in gas exchange and photosynthesis.
The lower epidermis contains stomata and guard cells which control photosynthesis by opening during the day, and closing at night to minimise water loss through evapotranspiration.
The lower wax cuticle provides protection to the underside of the leaf.

Plants don't just need glucose, though. They require mineral ions, which they can absorb from the soil using active transport and diffusion.

A variety of different experiments can be done to test different parts of a flowering plant's nutrition.

Experiment 1: Oxygen and water plants

1. Choose the variable you wish to change (temp, light intensity, etc.) 
2. Place containers of water and water plants of about the same size in the different conditions. 
3. Count the bubbles that are formed in a certain length of time. 

Experiment 2: Starch and light intensity

1. Put 3 leaves from the same plant of similar sizes in different light conditions: One in a dark room, one in direct sunlight, and one in shaded light. Leave for 48 hours.
2. Test leaves for starch by boiling each in water for 1 minute, then placing in ethanol, then returning it to the water and finally spreading on a petri dish. Add iodine solution to see which leaves test positive for starch 

Experiment 3: Chlorophyll
Test variagated leaves for starch. You can see the green parts test positive for starch while the white parts do not.

Experiment 4: Carbon dioxide
Place a plant in a sealed plastic bag with a container of sodalime (which removes CO2), then test for starch.

Experiment 5: Carbon dioxide
Place water plants in different light levels for 12 hours, with hydrogencarbonate indicator. At the start, indicator should be red, then change to purple for low levels of CO2 (In sunlight) and change to yellow for high levels of CO2 (In darkness)

Experiment 6: Mineral ions
Place cuttings of the same plant into different mineral ion solutions: One with a complete ion solution, each of the others missing one ion and one containing just water. Place them together in controlled conditions (light, temp, etc.), then after a week or two check the plants to see any changes.

Humans

Humans gain nutrients from eating food, which has to pass through the digestive tract.
The essential nutrients are:

These are represented in the correct proportions by the eatwell plate:

This gives a good indication of what proportions of food we should be eating, but the total energy intake varies from person to person. Generally, you need more energy if:

• You have more body mass
• You are a man
• You are pregnant
• You are active
• You are a teen. After puberty, energy requirements gradually decrease, and children require less energy than adults. 

Below is a diagram of the digestive system. This is the system within your body where food is digested and nutrients absorbed. But how does this work?

1. First, food is ingested through the mouth.

It is mechanically digested, by chewing, and chemically digested, by salivary amylase. The teeth break up the food to increase its surface area (aiding chemical digestion later on) and to make it easier to swallow in food bolus.
The food is then swallowed, (the epiglottus closes over the trachea to avoid food from falling into the lung) and it travels down the oesophagus through peristalsis: waves of contraction and relaxation of circular and longitudinal muscles. Peristalsis pushes the bolus of food into the stomach.

2. The stomach is a large muscular bag that contracts and relaxes to churn the food. The food is held here for 2-4 hours, during this time mixing with gastric juice (a combination of HCl and pepsin, a form of protease), which breaks down protein in the food. 

The stomach is lined with mucus-producing goblet cells, which helps to prevent the highly acidic HCl from damaging the stomach. Food then passes through into the duodenum.

3. The duodenum is the first part of the small intestine, it is where digestion is completed. Digestive enzymes (Carbohydrases, proteases and lipases) are secreted in pancreatic juice, from the pancreas. 

Bile is also released after being made in the liver and stored in the gall bladder. It emulsifies lipids to increase their surface area. The fully digested nutrients are then transported to the ileum.

4. The ileum is where absorption takes place. The surface of the intestine is folded into tiny villi, which increase the surface area for maximum absorption. It can take place passively, through diffusion, or via active transport. 

The villi contain capillaries and lacteals (lymph vessels) which absorb digested lipids, amino acids and glucose. After being absorbed, a process called assimilation takes place, where the nutrients are used or stored by the body. 

The above diagram is of two villi. 

Villi are small, hair-like protrusions in the lining of the small intestine. Their shape increases the surface area, helping to absorb nutrients more quickly. Each villus is covered in micro-villi, which further increase the surface area.
The walls of the villi are just one cell thick to decrease the distance and increase the rate of absorption.
Villi each contain a lacteal, a vessel connected to the lymphatic system. This absorbs fatty acids and glycerol, then transports them away from the small intestine.
Each villus contains a network of capillaries connected to blood vessels. Glucose and amino acids are absorbed into the bloodstream through them.

5. The remaining material is now passed on to the large intestines, the colon. Here, water and mineral ions are reabsorbed. The leftover undigested food, bacteria, etc. (faeces) is stored in the rectum, then egested via the anus.
The table below shows the most important digestive enzymes to know in this course:

Experiments can be done to determine the energy content of foods:

1. Take a food sample, and light it on fire. Hold beneath a quantity of water with a thermometer in it. 
2. If the sample goes out, quickly relight it. 
3. Note down the temperature rise

Use this equation to calculate the energy content:

energy transferred (J) = mass of water (g) × 4.2 (J/g°C) × temperature increase (°C)

Section 2 d) Summary

There are three ways in which substances can move into and out of cells:

• Diffusion
• Osmosis
• Active transport

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. This can happen in any fluid, and at the end the substance will be evenly dispersed. It is a passive process, meaning it happens in the direction of the concentration gradient and therefore doesn't require any energy. 

Examples include gas exchange in the lungs, gas exchange in the leaf, and assimilation in the small intestine. 

Experiments:
Diffusion can be investigated by placing food colouring or potassium permangenate into water. Then by timing how long it takes for the water to become entirely one colour at different temperatures will tell us how temperature affects diffusion.

Factors affecting the rate of diffusion include

• Distance: Shorter distances mean faster diffusion
• Temperature: Higher temperatures mean more kinetic energy, and faster moving particles
• Surface area: Larger surface area means faster diffusion
• Size of particles: Smaller particles move more quickly
• Concentration gradient: Steeper concentration gradients mean faster diffusion
• Pressure (in gas): This is the same principle as concentration, there is more particles in a smaller volume of space 

Osmosis is the net movement of water particles across a semi-permeable membrane from an area of high water potential to an area of low water potential. 

Examples of this include plants using root hair cells to take in water from the soil, water moving around plant cells for evenly distributed turgidity, which supports the plant. 

Osmosis is relatively similar to diffusion, the difference being osmosis is in reference only to the movement of water particles across a semi-permeable membrane. 

Experiments:

Osmosis can be investigated using Visking tubing, sugar solution and water. (Model cell)
1. Place sugar solution in one sealed Visking tube, and water in another. Weigh each.
2. Place the sugar tube in a beaker full of water, and the water tube in a beaker full of sugar solution.
3. Remove the tubes after 30 minutes and weigh again. Note the changes.
You can see that the sugar tube has increased in mass, because osmosis has caused water to enter the tube. The water tube has lost mass, as osmosis has caused water to leave the Visking tubing.

Osmosis can also be investigated using potato cylinders.
1. Using a cork borer, create a potato cylinder and cut into equal lengths of 3cm.
2. Weigh each cylinder, then place each into different concentrations of sugar solution, making sure to keep track of which is which.
3. After 30 minutes, remove and dry the potato cylinders, then reweigh and note the change in mass for each of them. ( percentage change in mass = (final mass - initial mass) x 100 / initial mass )
These results can be graphed to find the water potential of the potato, as this is the point at which the mass should not change.

Active transport is the movement of particles against a concentration gradient, from an area of low concentration to an area of high concentration. It is an active process; it requires energy from respiration, unlike diffusion and osmosis. 

Examples include reabsorption of glucose in the nephron and root hair cells in a plant taking in mineral ions.

Section 2 c) Summary

Proteins are long chains of amino acids. Made up of carbon, hydrogen, oxygen and nitrogen: CHON

Carbohydrates are long chains of simple sugars. Made up of carbon, hydrogen and oxygen: CHO

Lipids are made of glycerol and three fatty acids. Made up of carbon, hydrogen and oxygen: CHO

Enzymes are biological catalysts, they're specialized proteins that speed up biological reactions, such as digestion, without becoming chemically involved. They are adapted to work in ideal conditions depending on where they should be, for example human enzymes work at an optimum temperature of around 37 ℃, because this is average body temperature.
Protease in the stomach, and enzyme that breaks down proteins into amino acids, works at an optimum pH of 2, which is the acidity of the hydrochloric acid found in the stomach, however salivary amylase, found in the mouth, is denatured in these conditions as the mouth is much less acidic.
An enzyme will become denatured in extremes of pH, as well as high temperatures. Low temperatures will not denature the enzyme, but will slow it so it isn't able to work efficiently.

These two graphs depict enzyme activity based on temperature and pH:

Optimum temperature of enzymes can be found by completing the following experiment:

1. Mixing amylase (protein that breaks down carbohydrates into glucose) with starch in test tubes, and placing them in water baths of varying temperatures (should be regular intervals).
2. Testing samples for starch with iodine every 30 seconds
3. Record how long it takes for the iodine to test negative for starch, this is when the amylase has broken down all or most of the starch.

Graph the results to determine the optimum temperature.

Iodine is an orange-brown colour, but turns black-blue when exposed to starch. This is how we test for starch.

Benedict's solution is blue in colour, but when heated with a simple sugar such as glucose, it turns red. This is how we test for glucose.

Section 2 b) Summary

Cells are made up of different organelles and have different structures; those in the same kingdom will usually share the same basic characteristics, and their differences from other kingdoms is how we chose to classify them.

The table above shows the basic differences between plant and animal cells.

• The plant cell's more regular, rectangular shape is kept rigid by the cellulose cell walls, which provide the cells with support, and in turn support the plant as it doesn't have bones line animals do. 
• The plant cell also contains chloroplasts, which contain a green pigment called chlorophyll which converts carbon dioxide and water into oxygen and glucose with sunlight through photosynthesis. Photosynthesis is a process that allows the organism to create its own food. 
• Large sap vacuoles are found only in plant cells, animal cells may have a small temporary one, but this is not necessary to know. In plant cells, the vacuole is a large 'bag' filled with cell sap and helps to keep the cell turgid. 

Animal and plant cells also share similarities:

• Both have nucleuses or nuclei, which contain chromosomal DNA or 'genetic instructions' which tell the cell what to do: they give the cell its function.
• Both have a selectively-permeable cell membrane that controls what substances can pass through the cell.
• Both contain cytoplasm, the medium in which chemical reactions take place. It is controlled by enzymes. 

Section 2 a) Summary

Living organisms are made up of different levels of organisation, each categorised as follows:

Organelle: found within a cell, it helps the cell to carry out different functions, for example mitochondria respires and therefore provide the cell with energy, and a nucleus contains DNA within chromosomes that direct the cell's actions.

Cell: contains organelles, can be an organism on its own (uni-cellular) or part of a larger organism (multi-cellular). Makes up tissues. Can carry out a specific function, e.g. neurones, or nerve cells, transmit electrical impulses around the body, and in plants the palisade cell contains lots of chloroplasts for photosynthesis.

Tissue: made up of similar cells working together to carry out a specific function. Tissues make up organs and carry out vital roles, e.g. muscle tissue allows animals to move as it contracts and relaxes, connective tissues hold organs together and support them in place

Organ: Made up of a group of different tissues, found within organ systems. Carries out one or more specific function, e.g. the skin protects the body and regulates heat, the eyes pick up light that allows us to see

Organ system: a group of organs that work in a system to carry out life processes, e.g. circulatory system pumps blood around the body so oxygen can reach everywhere for respiration, nervous system transmits electrical impulses so the body can react to stimuli

Section 1 b) Summary

Living organisms are organised into categories based on shared characteristics. The seven taxonomic groups of classification are:

• Kingdom (e.g. Animalia)
• Phylum (e.g. Chordata)
• Class (e.g. Mammalia)
• Order (e.g. Carnivora)
• Family (e.g. Canidae)
• Genus (e.g. Canis)
• Species (e.g. Lupus)

Species are internationally known by their binomial classification, which is a two-part latin name composed of species and genus used to identify groups of organisms that share similar characteristics and are able to breed to produce fertile offspring. In the above example, the species would be known as Canis Lupus (Grey Wolf). 

All living organisms fall under the five kingdoms of classification: Animals, plants, bacteria, fungi and protoctists. Each of these groups is defined by their own set of characteristics:

Animals
Multi-cellular, No cell walls, No chloroplasts = No photosynthesis, therefore they must consume other organisms to gain energy. Cells move freely.

Can move their entire body due to nervous system.
Glycogen - how animals store carbohydrates
Vertebrates are animals with spines/backbones
Invertebrates are animals without spines/backbones

Vertebrates can be split into the following categories:

• Mammals (warm-blooded, secrete milk, give birth to live young, have lungs, most have hair)
• Birds (warm-blooded, feathers, wings, beaks, hard shelled eggs, have lungs)
• Fish (cold-blooded, jelly-coated eggs laid in water, scales, fins and gills)
• Reptiles (cold-blooded, leathery-shelled eggs, scales, have lungs)
• Amphibians (cold-blooded, jelly-coated eggs laid in water, moist skin, gills when young, lungs when mature)

E.g. Cat, Dolphin, Owl, Chicken, Cod, Haddock, Adder, Blue-tongue Lizard, Salamander, Frog

Plants
Multi-cellular, Cellulose cell walls, Chloroplasts for photosynthesis, absorb water through their roots and up the xylem vessel by osmosis.

Move leaves etc. to face the sun
Starch or Sucrose - how plants store carbohydrates
Carnivorous plants: some plants adapt to nutrient-poor soil by attracting, trapping and digesting insects or small animals to gain nutrients from them.

E.g. Sunflower, Cacti, Oak, Yew, Palm

Bacteria
Uni-cellular, No Nucleus (Plasmid and DNA loop instead), Polysaccharide or Protein cell wall, some have Chloroplasts, all have Mesosomes

Some have flagellum for free movement
Glycogen or Lipid food stores

E.g. Lactobacillus Bulgaricus, Pneumococcus, Escherichia Coli (E.Coli), Salmonella

Fungi
Multi- or uni-cellular, Chitin cell walls, organised in fungal hyphal structures with threads/fibres called hyphae, which organise into mycelium.

Fungi feed through saprotrophic nutrition, also known as extracellular digestion. The cells secrete digestive enzymes to break down organic matter, which is then absorbed by the fungus.
Glycogen- how carbohydrates are stored in fungi

E.g. Yeast (uni-cellular), Mucor (multi-cellular)

Protoctists
Uni-cellular, characteristics vary: some resemble animal cells, some resemble plant cells, some are pathogenic

E.g. Amoeba, Plasmodium, Chlorella

Viruses are not classified as living organisms, they are a special case; they don't perform all seven life functions, and they can only reproduce inside a living cell. They are parasitic and pathogenic.

E.g. Human Immunodeficiency Virus (H.I.V), Influenza, Tobacco Mosaic Virus



Pathogens
A pathogen is a disease-causing particle or organism. It infects a living organism and inhibits their normal function. Pathogens can be viruses, bacteria, protoctists or fungi.

Section 1 a) Summary

All living organisms share the seven same basic characteristics:

Movement- the ability to move

Respiration- the ability to create chemical energy

Sensitivity- the ability to sense a change in environment

Growth- the ability to develop and mature/increase in cell size or number

Excretion- the ability to remove waste substance from the body

Nutrition- the ability to obtain nutrients

Using the acronym "MRS GREN" is an easy way to recall all of the processes.
--> read the "key words" and "specification" pages for further explanation and depth.

Each of the life processes plays a key part in ensuring the organism can live.

Movement allows the organism to adapt to avoid predators, catch prey, or produce food.

Respiration gives the organism energy and allows it to carry out all of the other life processes.

Sensitivity allows the organism to react to its surroundings, helping it survive through changes in environment such as increased temperature.

Growth allows the organism to increase in maturity and size so it can carry out other processes more efficiently, e.g. a larger plant has more leaves for photosynthesis.

Excretion allows the organism to remove waste from the body and prevent poisoning from toxic substances such as urea and carbon dioxide.

Nutrition gives the organism the nutrients required for respiration to be carried out, along with other processes such as growth.

If it carries out all of these processes, it is classified as a living organism.