Biology Unit 1

Unit 1

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Carbohydrates contain three elements, carbon, hydrogen and oxygen and are divided into three categories according to sizes:

Monosaccharide - single sugars' e.g Glucose, Fructose and Galactose

Disaccharide- 'double suars' e.g Sucrose, Maltose, Lactose

Polysaccharide - multiple sugars - e.g Starch, Glclogen and Cellulose

Monosccarides and Disaccharides are both soluble and sweet solids, whereas a polysaccharide is neither sweet or soluble. They are also polymers which are made up of long a chain of monomers usually glucose , proteins are also polymers but lipids are not, this makes starch a better storage molecule.

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 The most common Monosaccharide is Glucose this exists in two forms alpha glucose and beta glucose, the diffrent forms affect the overall propertis of the polymer that contain glucose.

Glucose + Glucose -----------> Maltose + Water

This reaction is known as a condensation reaction as water is produced, the two glucose molecules are joined together by a bong known as a gycosidic bond.


Common examples of disccharides are maltose formed by (glucose and glucose), sucrose formed by (glucose and fructose) and lactose formed by (glucose and galactose).


The three main polysaccharides are starch, cellulose and glycogen, they all are polymers formed by hundreds of thousands of glucose units.

starch is the main storing compound in plants, storage compounds need to be insoluble, compact and eacily converted to energy.

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Carbohydrate Digestion

Polyscaccharides and Disaccharides must be digested into monosaccharides to be assimalated by the body.

The digestion starts in the mouth this is when the enzyme amylase which is found in the saliva begins to hydrolyse into maltose, this is onlt partially broke down at best, this is due to food not being in the mouth for long enough, (hot food can also denature the enzyme) and the acidic conditions in the stomach denature the enzyme. There is no significant digestion in the stomach, but after that the pancreatic amylase digests the carbohydrate into Maltose the carbohydrate digestion is them completed by enzymes fixed to the membrane of the epithelial cells known as the brush border. The three main enzyes found on the brush border are , sucrase, moltase and lactase.

Sucrase hydrolyses sucrose into glucose and fructose
Lactase hydrolyses lactose into glucose and galactose
Maltase hydrolyses maltose into glucose and glucose

Lactose intolderant

This is a condition when an indiviual can not make lactase so can't digest Lactose undigested lactose is used by gut bacteria this results in abdominal pain, bloating and diarrhoea.

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Biochemical Tests

Proteins - To test for proteins, biurettes reagent is added to solutions and the liquid should change to blue/puple if a protein is present.

Reducing Sugar -add benedicts reagent to the sample and heat if the clear liquid turns to redy/orange a reducing sugar is present if not . . .

Non reducing sugar -Take a fresh sample and heat with a dilute acide and bring to boil, this hydrolyses it, then neutralise it using an alkali to make a neutral using a ph test to make sure, then add benedicts and heat again. If a non reducing sugar is present it should change from a clear solution to an organge red solution.

Lipids -disolve the sample into ethanol, then slowly pour into water slowly and if lipids are present a white emultion forms on the surface.

Starch - Add iodine to the solution and if the clour changes from orange/red to a blue/black then starch is present.

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An enzyme is a protein molecule which acts as a biological catalyst, an enzymes catalyses one specific reaction. An enzyme has two main parts to it, the first is the active site this is complimentary to only one substrate, which is why it is specific to only one substrate, one the enzyme and the substrate collide an enzyme substrate complex is formed. this was once believed to be known as the lock and key hypothesis this is when the the shapes are exact, but now the induced fit is believed to be more accurate this is when the enzyme's active site is slightly larger than the substrate allowing it to mould around the substrate.

Rate limiting factors
An enzyme can't die it can only be denatured. this is caused by environmental condition which cause the structure to break down these are:ph levels,temperature, substrate concentration.Another limiting factor of enzymes there are two main competitive and non competitive, competitive inhibitors are a complementary shape to the active site so effectively get in the way of the over substrates being broken down or built but if there was more substrate there would be a lower concentration of the inhibitors so wouldn't have a significant effect. Whereas the non-competitive inhibitor binds to another part of the enzyme know as the allosterix site this then alters the tertiary structure of the enzyme making the enzyme not a complimentary shape so the active site is no longer complimentary to the substrate.

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Uses of proteins

  • Enzymes which help us control metabolism
  • antibodies, to fight of against disease and are vital part of the immune system
  • actin and myosin cause muscle contraction
  • involved in blood clotting
  • vital in cell membrane for transport, and cell recognition


  • made up from sub-units of amino acids (the sequences could create andinfinite amount of different proteins) when two amino acids join together they create a peptide bond and water is a product of the reaction.
  • there are 20 different amino acids making 400 different dipeptides and protein chains are hundreds or even thousands in length which means that is potentially an infinate amount
  • there are four levels of the structure, primary secondary,tertiaryand quaternary
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Protein Structure


The primary structure is the sequence of amino acids in the polypeptide.


This is the shape formed by the amino acid chain when they bend and twist to form the most stable arrangement, the commonest secondary structure is the alpha helix, the beta pleated sheet is another common secondary structure. Different regions of the polypeptide chain will have different forms of secondary structure within them.


This is the overall shape of the polypeptide chain it will bend and fold back on itself due to weak bonds known as hydrogen bonds, this then allows disulphide bridges to be formed between two sulphur containing amino acids.


if the proteins consists of just one polypeptide then the tertiary structure is the overall shape, but if its made up of more than one polypeptide then the quaternary shape is created once the polypeptide chains binds. Such as insulin which has two polypeptide and haemoglobin which has 4 chains.

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There are 4 main processes of transportation for individual molecules or ions to pass through cell membranes.

Diffusion -particles spreading out trying to reach an equilibrium between two locations randomly, always moves from high to low concentration, rate of diffusion is dependant on: surface area, concentration gradient, higher the temperature and distance between the two areas.</span>

Facilitated diffusion - Facilitated diffusion is a mixture of the diffusion and active transport it uses a proteins to be passed through the cell membrane but it goes with the concentration gradient not against it, the two proteins are carrier proteins and ion channels.

Osmosis -is the diffusion of water is passed through partially permeable membrane going with the concentration gradient, water potential is a better word to be used when discussing osmosis.

Active transport - Is a mechanism used by organism to moved substances against the concentration gradient this is done by the input of ATP, to positively charge a specific carrier proteins which this draws in a hydrogen atom and is able to put it into the cell.

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plasma membrane - Surrounds all cells in the body, is able to control the passage of substances into the cells it also surrounds many of the organelles and is recognised individually by the immune system.

Nucleus -Contains the instructions of replication, cell division, protein synthesis and replication. In eukaryotic cells DNA is liner and attached to proteins.

Mitochondria- site of aerobic respiration and majority of cells ATP is made here the increase in folds of the cristae the increase in metabolic reactions.

Rough endoplasmic reticulum - transport system in the cytoplasm, stores, packages and transports the proteins made by the ribosome which surround the endoplasmic reticulum.

Smooth endoplasmic reticulum - synthesis of steroids and lipids it also the site for etoxification such as alcohol.

Golgi apparatus - Receives packages (vesicles) from the ER, synthesis/modify chemicals before secretion out of the cell

Ribosome-site of translation the part of the cell where the genetic code is used to build proteins

Lysosome - breakdown of substances, organelles or whole cells for example used during phagocytosis immune response, to destroy bacteria.

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Magnification and Microscopes (yawwwn)


actual size = apparent size/magnifacation

  • 1km = 1000m
  • 1mm = 0.001m
  • 1um = 0.000001m


  • Optical microscope, passes a beam of light through the specimen, which may be alive or dead could be a section or the whole organism.
  • Transmission microscope, passes a beam of electrons through a specimen which must be a very thin section of either a cell or a small organism.
  • scanning electron microscope, forms an image from electrons reflected from the surface of a specimen
  • transmission electron microscopes and scanning electron microscopes have higher magnification, but preparation of the specimen may introduce artefacts.
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Cell Fractionation and prokaryotic

Cell fractionation

Is the separation of components from a cell by centrifugation, heavier organelles being isolated at lower centrifuge speeds, prior to homogenisation (blending) the solution is kept in a refrigerator, in an isotonic buffered solution to stop any damage coming to the cells.

cells are homogenised --> nuclei pellet --> mitochondria,chloroplast --> ER --> Golgi --> plasma membrane

To achieve this order speeds are increase and centrifuged for longer they all are in small pellet after being centrifuged.

Prokaryotic cell - Bacteria and simple, single celled organisms, known as procaryotic cells, they are small, with very few structures inside, around 1000 bacteria cells could fit inside 1 animal cell.

There are some similarities though: both have a plasma membrane, cytoplasm and ribosome's

Differences- prokaryotic cells have a flagellum to move, circular DNA in contrast to linear, no membrane bound organelles, no cytoskeleton and reproduction is asexual.

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Cholera (rusty water)

Cholera is the biggest killer in the world, caused by a bacteria known as vibrio cholererae, it is usually contracted through drinking water contaminated by faeces from other cholera sufferers, there was an outbreak in the 19th century in England but it is mainly occurring in the developing world.

The bacteria releases toxins which effect the permeability of the epithelial cells of the small intestines, which allow large amounts of water and salts to be lost from the cells into the lumen of the small intestines, the toxins cause the carrier proteins to be constantly open which means that salts and ions created a low water potential which keeps water flowing into the small intestines.

treatments for cholera is oral re-hydration therapy which is liquid which contains the salts and ions that the sufferer has lost to replace them and to stop him from becoming dehydrated and ill.

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The heart is constantly working to provide a constant supply of oxygenated blood to the body, this is done by:

Atrial systole/ Ventricular diastole - blood which starts off in the left atrium, this is blood which has just come from the lungs once the pressure becomes higher than it is in the ventricle then the valves open, it then flows into the left ventricle.

ventricular systole/atrial diastole - the ventricles contract quickly raising the pressure in the ventricles forcing the atria-ventricular valves close, however the pressure is too low in comparison to the main arteries which means that the aortic and pulmonary valves stay shut. The contracting continues and once the pressure in the ventricles is higher than the main arteries then the valves open and blood is ejected into the pulmonary artery and aorta to travel around the body.

ventricular diastole/atrial diastole - The ventricles relax reducing the pressure, which means there is a higher pressure in the pulmonary and aorta forcing the aortic and pulmonary valves to close.

Controlling the cardiac cycle

The sinoatrial node is the hearts natural pacemaker which initiates electrical impulses around the heart causing it to contract to create the pressures and and the electrical impulses are passed around the heart by special, conducting muscle fibres known as purkyne fibres

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Heat Diseases

myocardial infarction (heart attack)

A myocardial infarction is caused by a reduces supply of oxygen due to a blockage which is known as thrombosis, but the thrombosis may not be due to a blockage it could have a being a blockage elsewhere in the body and has travelled this is called an embolism. Due to a lack of oxygen it means that the heart has to respire anaerobically which doesn't release sufficient energy which means the muscle will fatigue and may die. A process called atherosclerosis which is the formation of atheromas which is a build up of fats acids and glycerol.

Increasing the risk

  • eating fatty foods containing cholesterol
  •  high level of cholesterol
  • smoking 
  • high blood pressure, angry person
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Breathing is the exchanging of oxygen and carbon dioxide, it is done inside of the lungs called alveoli which are small sacks with a thin and a large surface area surrounded by capillaries for a fast a high diffusion rate. 

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Lung Diseases

Fibrosis - Fibrosis is a process by which normal tissue of an organ suffer damage and are replaced by fibrous connective tissue 'scar tissue' the alveoli is especially vulnerable to fibrosis.

Tuberculosis - Bacterial disease, caused by mycobacterium tuberculosis and myobacterium bovis the immune response cause scar tissue which means that the alveoli are less effective, but if somebody with a weakened immune system (AIDS sufferer) were contract the infecting then the infection is likely to become fatal.

Emphysema -permanent lung damage, the scarring such as fibrosis means the alveoli walls are thickening and there is a reduced surface area, healthy lungs are elastic and doesn't, require much effort to inhale and exhale but with emphysema breathing requires more effort to breath out.

Asthma - most common lung disease, its the difficulty during breathing caused by a constriction of the smooth muscle that makes up the terminal bronchioles, the muscular walls secrete and produce more mucus. During an asthma attack the flow of air is reduced so ventilation is less efficient, but the actual surface area of the alveoli is unchanged and people are able to recover with no damage caused, the attack are caused by an allergic reaction or reaction to: exercise, air pollution and cold air.

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Immune system

Non-specific immune response

First line of defence - The first example of first line defence is the skin this a barrier for any infection to get into the body or the blood stream, another example could be eye lashes which stop antigens (foreign proteins which triggers an immune response) getting into your eye. Another first line defence is chemicals this could be gastric juices found in the stomach part of the digestive system which denatures the antigen before it is able to get any further.

Second line of defence - The second line of defence are controlled by the body, there are three main examples and these are: Phagocytes these are un-matured macrophages and engulf all foreign antigens which they do not recognise, another example is interferon these are chemical signals which are released by cells if it has being invaded by a foreign antigen to surrounding cells who are then able to put there defences up, finally the last example is inflammation this is when histamine proteins open blood vessels to flood the infection with blood which will contain white blood cells to then destroy the infection.

Specific immune response (third line of defence)

  • The macrophage engulfs the the Antigen, and presents it on the outside of the cell.
  • The T-helper cells then attach to the antigen, and then send out chemical markers to let the B-cells know what its like.
  • The B-Cells are then activated and become, plasma cells these release the antibodies which will then make the cell burst (lyse), place a chemical marker for phagocytes to destroy.
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