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What are Carbohydrates?
Long chain organic compoundsmade containing elements carbon, oxygen and hydroden
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Relatively small organic molecules & provide building blocks for the larger carbohydrates. Their name is determined by the amount of carbon atoms in the molecule (e.g. glucose)
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Consist of two monosacchairde units linked together by a glycosidic bond (in a condensation reaction - elimination of water)
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Glucose + Glucose =
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Glucose + Fructose =
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Glucose + Galactose =
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Storage polysaccharide found in plant cells in the form of starch grains. Starch is made of alpha glucose chains. It is insoluable, compact and does not draw water towards it by osmosis
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Main storage product in animals. Readily hydrolysed to alpha glucose which is soluable and can then be transported to areas where energy is needed
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Cellulose I
Consists of parallel chains of beta glucose cross-linked to each other by hydrogen bonds. The chain has adjacent molecule rotated by 180 this allowed H bonds to be formed between hydroxyl groups of adjacent parallel chains.
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Cellulose II
The chains are grouped together into microfibrils a number of which are arranged in parallel groups called fibres. The large number of H bonds contibute to the structural stability of cellulose.
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Lipids contain carbon, hydrogen and oxygen but in proportion to the carbon and hydrogen they contain less oxygen. They are non-polar so are insoluable to water. An ester bond is formed in the condensation reaction of lipids.
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Formed by condensation reaction between glycerol and three fatty acid chains. The glycerol is always the same but the fatty acids can change (unsaturated and saturated).
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Chemical properties of Lipids
1) Insoluable in water but dissolve in organic substances such as alcohols. 2) Fats are solid at room temperature, whereas oils (unsaturated lipids) are liquids
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Functions of lipids
1) Energy Storage. 2) Triglycerides produce a lot of metabolic water when oxidised. 3) Protection of internal organs (e.g. kidneys). 4) Insulation. 5) Waterproofing.
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The lipid tail is non-polar and insoluable in water. The phosphate head is polar and dissolves in water. Phospholipids allow lipid-soluable substances to enter/leave the cell and and prevent water-soluable substances entering/leaving the cell
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Contain carbon, hydrogen, oxygen and nitrogen. Many also contain sulphur and phosphorus.
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Bonding proteins
The amino acid group on one amino acid bonds wit the carboxyl group of another with the elimination of water. The bond is called a peptide bond. One peptide bond makes a dipeptide. Multiple create a polypeptide.
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Primary protein structure
The sequence of amino acids in the polypeptide chain.The proteins differ from each other in the variety, number and order of amino acids linked by the peptide bond.
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Secondary protein structure
The shape that the polypeptide chain forms as a result of hydrogen bonding. It is most often a alpha helix, but it can also be a beta pleated sheet (occuring as a zig zag chain).
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Tertiary protein structure
Formed by the bending and twisting of the polypeptide helix into a compact structure. This gives the molecule its 3D shape. The shape is maintained by disulphide, ionic and hydrogen bonds.
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Quaternary protein structure
A combination of two or more peptide chains in tertiary form. These are associated with non-protein groups and form large complex molecules (e.g. haemoglobin)
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Fibrous proteins
Perform structural functions. Consist of polypeptide parallel chains/sheets with numerous cross-linkages to form long fibres. Insoluable in water, strong and tough. A single fibre consists of 3 polypeptide chains twisted around each other.
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Globular proteins
Variety of different functions; enzymes, antibodies, plasma proteins and hormones. They are compact and folded as spherical molecules. Soluable in water.
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Macronutrients: Magnesium
Constituent of chlorophyll in leaves
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Macronutrients: Iron
A constitiuent of haemoglobin in blood
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Macronutrients: Phosphate
Found in the plasma membrane, nucleic acid, ATP
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Macronutrients: Calcium
A constituent of bones and teeth.
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Copper and Zinc (needed in trace amounts)
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Water: Transparency
Allows light to pass through it, enabling aquatic plants to photosynthesise effectively.
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Water: Cohesion
Has no overall charge. Oxygen end has a slightly - charge, Hydrogen end has a slightly + charge. When two H2O molecules are in contact, the opposing charges attract - forming a H bond. Forms a lattice & stick together: can be drawn up xylem
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Water: Surface tension
At ordinary temperatures, water has the highest surface tension of any liquid (except mercury). In a pond, the cohesion between the water molecules produces surface tension so the body of insects (e.g. pond skaters) are able to be supported
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Water: Solvent
Because water is a polar molecule it will attract other charged particles, such as ions, and other polar molecules, such as glucose. This allows chemical reactions to take place in solution & because they dissolve, it acts as a transport medium.
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Water: Specific heat
Has a high specific heat. A large amount of energy is needed to raise the temperature of water because the H bonds restrict their molecules. Allows aquatic habitats stay stable & enzymes to work efficiently.
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Water: Latent heat
Has high latent heat [of vaporisation]. A lot of energy is needed to change it from liquid to a vapour state. This is important when heat is used for vapourisation of water when sweating. The evaporisation of water from a surface results in cooling
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Water: Density
Maxium density at 4 C. Water in solid form (ice)is less dense than water so it floats on the surface. Ice forms an insulating layer and allows organisms to survive beneath it.
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Prokaryotic cells
1) Found in bacteria & blue-green algae. 2) No membrane bound organelles. 3) DNA lies free in cytoplasm. 4) No nuclear membrane or ER. 5) Ribosomes are smaller. 6) Cell wall contains murein.
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Eukaryotic cells
1) Found in plants, animals fungi & protoctists. 2) Membrane-bound organelles. 3) DNA located on chromosomes. 4) Distinct membrane-bound nucleus. 5) Ribosomes are larger. 6) Cell wall in plants made of cellulose.
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Extremely small. Have no cytoplasm. No Organelles. No chromosomes. Take over cells metabolism & multiply within the host cell.
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Function: to control the cells activities and retain the chromosomes. It has pores in it to allow the transport of mRNA. The nucleoplasm contains chromatin which is made from coils of DNA bound to protein (histones). The nucleolus produces rRNA.
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Double membrane. The inner membrane is folded inwards to form cristae which increase the surface area so more reactions can take place. The interior contains an organic matrix containing chemical compounds. Site of aerobic respiration to form ATP.
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Endoplasmic reticulum
Double membrane. Rough ER: Has ribosomes on the outer surface. Transports proteins made by the ribosomes. Make enzymes that are secreted by the cell. Smooth ER: without ribosomes. Synthesis and transport of Lipids
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Made up of one large and one small sub-unit. They are manufactured in the nucleolus from ribosomal RNA and protein. They are important in protein synthesis.
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Golgi body
Modifies and packages proteins. Also produces secretory enzymes, forming lysosomes, transporting and storing lipids.
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Contain and isolate digestive enzymes, they can then release these enzymes to destroy worn out organelles. Can also digest material that has been taken into the cell.
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Located just outside nucleus in the centrosome. Consists of two hollow cylinders positioned at right angles to each other. During cell division the centrioles move to opposite poles of the cell where they synthesis the microtubules of the spindle.
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Found in cells of photosynthesising tissue. Double membrane inside: the stroma, containing ribosomes, lipids and circular DNA. Within the stroma are granum (sing. thylakoids) - large surface area for trapping light energy.
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Plant cells have a large, permanent vacuole which consists of a fluid-filled sac bound by a single membrane - the tonoplast. Vacuoles contain a sap; storage site for chemicals such as glucose and maintains osmotic pressure
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Cell wall
The cell wall consists of cellulose microfibrils embedded in a polysaccharide matrix. It provides strength and support and permits the movement of water from cell to cell.
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What is a tissue?
A tissue consists of a collection of similar cells that carry out a particular function, for example: epithelial tissue.
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What is an organ?
An organ is composed of several different tissues that are coordinated to perform a function. Organs work together as a single unit or organ system, for example: the digestive system.
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Two proteins in the phospholipid bilayer
Extrinsic proteins: on the surface or partly embedded in the bilayer. Intrinsic proteins: extend across both layers. Increase the rate of diffusion without the need for ATP.
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Define fluid mosaic
The components are free to move with respect to each other and the proteins embedded in the bilayer vary in shape, size and pattern in a mosaic arrangement.
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Cholesterol is found in animal cells. It fits between the phospholipid molecules, increasing the rigidity and stability of the membrane.
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Lipids that have combined with a polysaccharide. Found on the outer layer of the membrane and are thought to be involved in cell-to-cell recognition.
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Functions of the cell plasma membrane
1) Providing structural support. 2) Allowing active transport across the membrane by forming ion channels. 3) Forming recognition sites by identifying cells. 4) Acting as carriers transporting water-soluable substances across the membrane.
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The movement of molecules or ions from a region of higher concentration to a region of lower concentration until equal distribution.
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Rate of diffusion can be affected by...
1) The concentration gradient. 2) Distance of travel. 3) Surface area of the membrane. 4) Thickness of the membrane. 5) Temperature.
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Channel proteins
Consist of pores lined with polar groups allowing charged ions to pass through. Each channel protein is specific for one type of ion. They can also open and close to the specific needs of the cell.
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Carrier proteins
Allows diffusion of larger polar molecules such as sugars and amino acids. A particular molecule attaches to the carrier protein at its binding site and causes the carrier protein to change shape, releasing the molecule through the membrane.
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Active transport
Energy-requiring (in the form of ATP) process in which ions and molecules are moved across the membrane against the concentration gradient (from a region of lower concentration to an area of higher concentration). Occurs through the carrier proteins.
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The passage of water from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.
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Water potential =
Solute potential + pressure potential
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What is pressure potential?
When water enters a plant cell vacuole by osmosis, a hydrostatic pressure is set up, the cell wall develops an opposing force called the pressure potential. This is usually positive.
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When the WP of the external solution is lower than that of the solution inside the cell. Water flows out of the cell.
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When the WP of the external solution is higher than that of the solution inside the cell. Water flows into the cell.
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Occurs when a plant cell is placed in a hypertonic solution it looses water by osmosis. The vacuole shrinks and the cell membrane begins to move away from the cell wall (just coming away is called incipient plasmolysis).
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Tertiary globular proteins where the protein chain is folded back on itself into a spherical/globular shape. Biological catalysts, but only a small region, the active site, is functional.
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Properties of enzymes
1) Enzymes are specific. 2) Very efficient and have a high turnover number. 3) Lower activation energy for reactions.
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How does temperature affect enzymes?
Above the optimum, the increasing vibration of the molecules causes the H bonds to break, causing a change in tertiary structure of the enzyme. This alters the shape of the active site - it is then 'denatured'.
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How does pH affect enzyme reactions?
The charges on the amino acid side-chains of the active site are affected by free hydrogen/hydroxyl ions. The charges on the AS must be complimentary to the charges on the substrate - if not, they will repel.
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Competitive inhibition
Structurally similar to the substrate and competes for the active site of the enzyme.
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Non-competitive ihibition
The inhibitor binds to the enzyme at a site away from the active site. This alters the overall shape of the enzyme molecule, including the active site, in such a way that the active site can no longer accommodate the substrate.
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Immobilised enzymes
Enzyme molecules that are fixed, bound or trapped on an inert matrix (such as alginate beads).
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Advantages of immobilised enzymes
1) Enzymes can tolerate a wider range of conditions. 2) Enzymes are easily recovered for reuse thus reducing overall cost. 3) Several enzymes with differing pH or temperature optima can be used together. 4) Enzymes can easily be added or removed.
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Association of an enzyme with a transducer, which produces an electrical signal in response to the substrate transformation. The strength of the signal can be measured with a meter.
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Use of biosensers I
In the detection of blood sugar in diabetics. The electrode probe, which has a specific enzyme immobilised in a membrane, is placed in the blood sample. If glucose is present, it diffuses through the membrane and forms an ESC.
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Use of biosensers II
The reaction produces a small electric current, which is picked up by the electrode (the transducer). This current is read by a meter which produces a reading for blood glucose. Normal levels are around 3.89 - 5.83 mmol dm ^-3
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Relatively small organic molecules & provide building blocks for the larger carbohydrates. Their name is determined by the amount of carbon atoms in the molecule (e.g. glucose)

Card 3




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Card 4


Glucose + Glucose =


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Card 5


Glucose + Fructose =


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