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Biological Molecules
Unit 2 Module 1 OCR Biology AS
| Term | Definition |
|---|---|
| Metabolism | All the chemical reactions that take place within the cells of an organism. |
| Covalent bonds | Formed when electrons are shared between atoms, these bonds are very strong. |
| Monomer | A single, small molecule that can be joined to others to form polymers. (Lipids can't be polymers) |
| Condensation | 2 molecules join together with a covalent bond, forming a larger molecule. A water molecule is released from the reaction. |
| Hydrolysis | A molecule is broken down into 2 smaller molecules by the addition of a water molecule. Covalent bond is broken. |
| Hydrogen bonds | Form when a slightly negatively charged part of a molecule comes into contact with a slightly positively charged hydrogen atom, most easily seen in water. Very weak bonds. |
| Carbohydrate elemental composition | C, H , O in the proportions 1:2:1 |
| Monosaccharides | Monomers of carbohydrates, they are soluble in water, sweet tasting and from crystals. E.g glucose and deoxyribose. |
| Alpha glucose | H above OH at carbon 1 |
| Beta glucose | OH above H at carbon 1 |
| Glycosidic bond | The covalent bond between carbohydrate molecules joined in a condensation reaction. |
| Polysaccharide | A polymer of many monosaccharides covalently bonded together. E.g starch/glycogen(a glucose) and cellulose(b glucose). |
| Starch | Long straight chained amylose molecules and branched amylopectin. Can be broken down into glucose. |
| Glycogen | Made up of alpha glucose subunits. Large branched molecule, can be broken down to release glucose. Different to amylopectin in that branches tend to be shorter. |
| Cellulose | The most abundant structural polysaccharide in nature, only found in plants. 60-70 cellulose molecules link by hydrogen bonds to from microfibrils. These are held together by more hydrogen bonds to form macrofibrils. |
| Protein elemental composition | C, H, con O, and N, some may contain S. |
| Amino acid structure | Amine group at one end, nitrogen in the middel and an acid group the other end. Each has a R group, a specialised region. |
| Amino acids in plant | Plants can manufacture the amino acids they need, providing they can obtain nitrates from the soil, which is converted into amino groups, and bonded to organic groups made from the products of photosynthesis. |
| Peptide bond | Formed through a condensation reaction between the acid group of one amino acid, and the acid group of another-forming a covalent bond. |
| Dipeptide | Two amino acids. |
| Primary structure | A unique amino acid sequence of polypeptides. |
| Secondary structure | Formed when the amino acid chain forms an alpha helix/beta pleated sheet. Main hydrogen bonds hold the coils in place. |
| Tertiary structure | The coils/folds coil and fold on themselves giving the 3D shape. |
| Quaternary structure | Proteins that only function if multiple polypeptide subunits are joined together. E.G haemoglobin and insulin. |
| Globular proteins | Compact globe, hydrophobic R groups on the inside, hydrophilic R groups on the outside. Usually soluble, metabolic roles. E.g enzymes, plasma proteins, and antibodies. |
| Fibrous proteins | Form fibres, usually insoluble, structural roles. E.g collagen and keratin. |
| Haem | Iron containing prosthetic group of haemoglobin. |
| Lipid elemental composition | C, H, O, the proportions of O are very low, much lower than carbohydrates. |
| Unsaturated fatty acids | Have double carbon bonds, so have less hydrogen bonds. |
| Saturated acids | All possible hydrogen bonds are made. |
| Triglyceride | One glycerol molecule, bonded to three fatty acids by an ester bond. Hydrophobic. |
| Phospholipid | Glycerol molecule with 2 fatty acid tails bonded by condensation reactions to produce ester bonds. |
| Cholesterol | Small molecule of 4 carbon-based rings. Hydrophobic. Used to form steroid hormones, e.g testosterone and oestrogen. |
| Nucleotide | Monomer of nucleic acids, made up of a phosphate group, a sugar molecule and a organic nitrogenous base; joined by covalent bonds. |
| Purines | Adenine and guanine, both have a double ring structure. |
| Pyrimidines | Thymine, Uracil and cytosine, all have a single ring structure. Smaller than purines. |
| Semi-conservative replication | Each DNA molecule consists of a conserved strand and a newly built strand. |
| RNA | Different to DNA in that: Uracil not thymine, ribose not deoxyribose, single stranded, three forms- tRNA, rRNA, mRNA. |
| Enzymes | Globular proteins, have an active site, specific to one substrate, act as catalysts, affected by temperature and pH. |
| Lock and key mechanism | Enzyme splits the substrate molecule into two smaller products. |
| Induced fit mechanism | When the substrate is binded to the active site, the enzyme changes shape to fit the substrate better, forming the enzyme-substrate complex. |
| pH | A measure of the hydrogen ion concentration. 7 is neutral, 7- is acidic 7+ is alkali. |
| Competitive inhibitors | Have a similar shape to the substrate. Can occupy active site forming enzyme-inhibitor complexes. |
| Non-competitive inhibitors | Attach to the enzyme in a region separate to the active site, distorting the tertiary structure which alters the active site so it is no longer complementary to the substrate. |
| Coenzyme | An organic non-protein molecule that binds temporarily to an enzyme active site, Essential for enzyme activity. |
| Biosenser | Uses enzyme-controlled reactions to detect the presence of substances, this is highly sensitive and specific. |
Created by:
grace.bradshaw
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