Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Biology 2.1.1
AS OCR biology - biological molecules
| Question | Answer |
|---|---|
| Why is water dipolar? | The oxygen nucleus pulls the shared electrons towards it and away from the hydrogen nuclei- the unshared electrons in the oxygen atom give it a slight - charge, and the hydrogen atoms have a slight + charge, so there is uneven charge distribution |
| What type of bond forms between water molecules and why? | Hydrogen bonds form between the negative ends of some water molecules and the positive ends of other water molecules. They are weak and cause molecules to group into clusters. Form a network that allows molcules to move around, breaking and making H bonds |
| What is a hydrogen bond? | A weak electrostatic attraction between the small negative charge on an electronegative atom (e.g. oxygen) and the small positive charge on a hydrogen atom, which is bonded to another electronegative atom |
| List the properties of water | Solvent, high specific heat capacity, high latent heat of vaporisation, cohesive, adhesive, density differs to other compounds, liquid over wide temperature range, transparent |
| Why is water a good solvent? | Many substances have polar atoms or groups which dissociate in water to give polar ion. The force of attraction between ions and dipolar water molecules cause water molecules to cluster around ions so ions are hydrated |
| What are the uses of water as a solvent in living organsisms? | Water transports many dissolved substances (e.g. glucose) around organisms in transport systems. Most metabolic reactions occur in solution. |
| Why does water have a high specific heat capacity and why is this important in living organisms? | A large amount of heat energy is needed to raise the temperature of water as some energy is used to break H bonds which restrict movement of water molecules. So, oceans maintain constant temp allowing aquatic organisms to keep stable body temp for enzymes |
| Why does water have a high latent heat of vaporisation and why is this important in living organisms? | A large amount of heat energy is needed to change liquid water into vapour, energy is needed to break H bonds.Evaporation (panting/sweating) is an effective cooling mechanism, lots of heat energy lost to surroundings, maintain stable body temp for enzymes |
| Why is water liquid over a wide temperature range and why is this important in living organisms? | High specific heat capacity +high latent heat of vaporization (due to H bonds). Oceans remain liquid over wide temp range allowing survival of aquatic organisms. Water is a transport medium (blood/vascular tissues) so remains liquid when body temp changes |
| Why is water cohesive and why is this important in living organisms? | Creation of H bonds due to attraction between opposite poles cause molecules to stick. Surface tension. Transpiration stream relies on cohesion - water rises as continuous column up vascular tissue when pulled from above by transpiration. |
| Why is water adhesive and why is this important in living organisms? | Water sticks to other surfaces due to H bonds. Transpiration stream in plants relies on cohesion- water molecules bind to side of xylem vessel as water rises up vascular tissue when pulled from above by transpiration. |
| What is unusual about the density of water? | The maximum density of water is at 4oC and water expands upon freezing. As temp decreases below 4oC, more H bonds form, producing a lattice in ice crystals which has more air spaces that liquid water. |
| Why is the density of water important in living organisms? | Ice floats on water which insulates the water below, allowing organisms to live below the ice. Water is a dense liquid due to cohesive properties so it can support the weight of animals (e.g. whales) by the upthrust it exerts |
| What is it important that water is transparent? | It allows light to penetrate and reach underwater plants so they can photosynthesise. |
| What are carbohydrates? | Molecules containing the elements carbon, hydrogen and oxygen in the proportion (CH20)n - for every carbon atom there is the equivalent of a water molecule present so carbon is hydrated. |
| What are the roles of carbohydrates? | A source of energy (released from glucose in respiration). A storage of energy e.g. glycogen, starch. Structure e.g. cellulose. |
| What are monosaccharides and what are their properties? | The monomers (basic units) of carbohydrates. Properties: sweet-tasting, white, crystalline structure, water soluble, reducing sugars (in aqueous state they readily reduce other chemicals so gain oxygen atoms and become oxidised- redox) |
| How are monosaccharides grouped? | According to the number of C atoms in each molecule - triose sugars(C3H6O3), pentose sugars (C5H10O5), hexose sugars (C6H12O6) |
| What is an example of a triose sugar? | Glyceraldehyde - intermediate in respiration, found in all cells |
| What are some examples of pentose sugars? | Ribose - forms part of RNA molecule, found in all cells. Deoxyribose (C5H10O4) forms part of DNA molecule, found in all cells. |
| What are some examples of hexose sugars? | Glucose - substrate for respiration, found in all cells. Fructose - fruit sugar. Galactose-milk sugar. |
| How is glucose suited to its function? | It has many polar OH groups so is water soluble and can be transported around organisms dissolved in water e.g. blood |
| What are the isomers of glucose? | Alpha glucose - on the C1 atom, H is above and OH group is below. Beta glucose - on the C1 atom, OH is above and H is below. |
| What is a disaccharide? | A sugar whose molecule is formed when two hexose sugar molecules react together in a reversible condensation reaction, and a new covalent bond called a glycosidic bond is formed. |
| What is a condensation reaction? | A reaction where two smaller molecules join together to form a larger one, forming a new covalent bond and releasing a molecule of water - anabolic and reversible |
| What is a hydrolysis reaction? | Where a large molecule reacts with water and splits into two smaller moelcules, so a covalent bond is broken. This is catabolic and reversible. This is the way that a disaccharide is broken into two monosaccharides. |
| What is a dimer? | A disaccharide made up of two identical monosaccharides |
| What are common disaccharides, their subunits and their uses? | Maltose- 2x alpha glucose-intermediate in formation/breakdown of starch, in germinating seeds. Sucrose-alpha glucose+fructose -form sugar is transported in plants, energy stores in cane/beet. Lactose-alpha glucose+galactose- carb source in mammalian milk |
| What are the properties of the disaccharides? | Crystalline structure, water soluble, maltose and lactose are reducing sugars but sucrose is a non-reducing sugar |
| What are polysaccharides? | Complex carbohydrates whose molecules are long chains built up by the condensation of many monomers (monosaccharides) so are condensation polymers |
| What properties do starch and glycogen share? | Both energy-storage molecules- both insoluble in water so stored glucose doesn't change water potential and have an osmotic effect, both compact due to helical structure, so store lots of glucose which is reformed by hydrolysis when needed for respiration |
| What is starch - location, subunits, role? | An energy store in plants, a polymer of alpha glucose, made in plants from glucose and stored as grains in stroma of chloroplasts, mixture of two types of chain - 20% amylose and 80% amylopectin (%s are species dependent) |
| What are the properties of amylose? | Made of many alpha glucose monomers condensed, helical structure due to bulky residue group whicih is accommodated for by tilting each monomer at slight angle, unbranched chains, each chain contains around 300 monomers, one turn per 6 monomers |
| How is amylopectin formed? | Many alpha glucose monomers condense together in two ways, forming 1,4 and 1,6 glycosidic bonds |
| What are the properties of amylopectin? | Chain have a helical structure, one branch every 10 monomers (branches mean enzymes can digest it quickly), 1,500 monomers per chain, stores more glucose than amylose |
| What is the role / properties / structure of glycogen? | Energy store in animals and fungi. Many a-glucose monomers condense in 2 ways forming 1,4 and 1,6 glycosidic bonds. More branched and shorter. 10-20 monomers per chain. Helical. Branches mean enzymes digest it quickly. Granules in liver + muscle. |
| Why is it important that glycogen stored more glucose than starch? | Animals have a higher metabolic rate so need to respire more, so more glucose is needed - glycogen is more compact than amylopectin and can therefore store more glucose |
| What is the role / structure of cellulose? | Structural. B-glucose subunits, 1,4 glycosidic bonds. Fibres in plant cell wall. Unbranched, straight chains, 10,000 monomers, alternate molecules rotated 180o, H bonds between adjacent chains, 1 every 2 monomers. Microfibrils, macrofibrils, pectin matrix |
| How is the structure of amlyose suited to its function? | * insoluble in water * compact due to helical structure |
| How is the structure of glycogen suited to its function? | * insoluble in water * compact due to helical structure * stores more glucose due to branches * branches mean enzymes can digest it quickly |
| How is the structure of cellulose suited to its function? | *H bonds produces macrofibirls - high tensile/mechanical strength, structure, support to plant, prevent overexpansion *polymer so insoluble in water no osmotic effect *macrofibril arrangement allows water to move through, determines how cells grow/shape |
| What is chitin and peptidoglycan? | Chitin - structural carbohydrate, polymer of glucosamine (B-glucose + amino acid), forms exoskeleton of arthropods Peptidoglycan - structural cabrohydrate, forms basis of bacterial cell walls |
| What is ATP + when is it produced? | Adenosine triphosphate is a molecule used to temporarily store energy in organisms and is broken down into adenosine diphosphate and phosphate to release energy to drive metabolic processes. Made from energy released in respiration - glucose -> CO2 + H2O |
| Why can't most animals digest beta-glucose? | They only have enzymes that break down alpha-glucose - the arrangement of the H and Oh in beta-glucose is different and enzyme function is based on shape, as enzymes are highly specific for their substrate. No enzyme present to break it down. |
| What are lipids? | Organic compounds whose molecules contain carbon, hyrogen and oxygen atoms only. The ratio of hydrogen to oxygen atoms is greater than 2:1 |
| Are lipids water soluble and why? | No - they are non-polar so are insoluble in water, but can dissolve in organic, non-polar solvents e.g. alcohols |
| How are triglycerides produced? | Formed when a molecule of glycerol combines with 3 fatty acids in a reversible condensation reaction - 3 ester (covalent) bonds are produced and three molecules of water are released |
| What is a property of glycerol? | C3H8O3 (glycerol) is polar so is water soluble |
| What is the structure of fatty acids? | Carboxyl group (COOH) and a hydrocarbon tail (residue group) usually containing 18 carbon atoms |
| What are the properties of fats? | Saturated lipids, single bonds, solid at room temp, straight chains, energy stores in animals e.g. stearic acid |
| What are the properties of oils? | Unsaturated lipids, one carbon-carbon double bond in tail, liquid at room temp, kink in tail, energy stores in seeds (e.g. sunflower seeds) and in fish (e.g. cod liver oil) - example is oleic acid |
| What are essential fatty acids? | Humans can't make essential fatty acids from other molecules in the body so they must be consumed in the diet in triglycerides |
| What are the functions of triglycerides and how does their structure suit this? | * energy store - compact, release twice as much energy as carbohydrates, insoluble in water so no osmotic effect. * stored as fat for thermal insulation and protection around organs |
| What is the structure of waxes? | Single hydrocarbon chain linked to an alcohol |
| What are the functions of waxes and why is this possible? | * form waterproof covering in organisms to prevent water loss and dehydration e.g. insects' chitin exoskeletons have a waxy layer and leaves have a waxy cuticle * bees have glands for making wax that they build into a honeycomb. Animals can't digest wax |
| What is cholesterol, role + structure? | Steroid, 4 carbon-based rings, small, forms basis of hormones - oestrogen + testosterone, maintains mechanical strength of membranes and helps form a barrier against free passage of molecules, made in liver + supplied in diet |
| What are the dangers of excess cholesterol? | Can produce gallstones in bile and can cause atheroschlerosis - it is deposited on the inner linings of blood vessels leading to circulatory problems |
| How are phospholipids formed? | Two fatty acid molecules, one phosphate molecule, and one glycerol molecule react together in a reversible condensation reaction - 3 ester (covalent) bonds are produced and 3 water molecules are released |
| Are phospholipids water soluble? | Phosphate head is hydrophilic as it has polar OH groups which are attracted to dipolar water molecules - so head is water soluble. Rest of molecule including fatty acid tails is hydrophobic and non polar so doesn't dissolve in water. |
| What affects the fluidity of the membrane? | The number of unsaturated fatty acids present - more means increased fluidity |
| What are amino acids and their structure? | Monomers of proteins. An amino group, a carboxyl group and a R group which differs between amino acids and determines properties. There are 20 types of amino acids. |
| What can amino acids form? | 2 amino acids react in a reversible condensation reaction to form a dipeptide and release 1 molecule of water, catalysed by enzymes. Many condense to form polypeptides. |
| What is the name of the bonds between amino acids? | Peptide bonds |
| Where are polypeptides manufactured? | In protein synthesis on ribosomes in cells according to the sequence of bases in mRNA |
| In a polypeptide 4 amino acids long, how many possibilities are there for the order of amino acids? | 20 to the power of 4, which is 160,000 |
| What are lysosomes (contents+ role)? | Lysosomes are membrane-bound sacs containing protease enzymes which catalyse the hydrolysis of polypeptides/ dipeptides. Involved in the digestion of food and breakdown of hormones to prevent effects being permanent |
| How do animals and plants make amino acids / proteins? | Plants take nitrate from the soil, convert it into amino groups, and bond them to organic groups to make amino acids which are built into proteins. Animals consume protein in the diet which is digested into amino acids, and these are built into proteins. |
| What are essential amino acids? | Amino acids that can't be made from other molecules in the body so must be consumed in the diet. |
| What is dangerous about an excess of amino acids? | Amino groups make amino acids toxic in excess, so the amino group is removed in deamination. In mammals, amino groups are converted into urea in the liver and are removed in the urine |
| What are the components of proteins? | Made of up one or more polypeptides. Consist of the elements carbon, hydrogen, oxygen, nitrogen and sometimes sulphur. |
| What are the functions of proteins? | -structural components of muscle and bone. -membrane carriers and pores e.g. for active transport and facilitated diffusion. -antibodies, hormones and enzymes are proteins so proteins are involved in metabolism |
| What is the primary structure? | The exact sequence of amino acids in the polypeptide within a protein molecule, highly specific to each protein. |
| What is the secondary structure? | The coiling and pleating of parts of the polypeptdie to form an alpha helix or beta pleated sheet, held together by many weak hydrogen bonds with give stability, non-specific to polypeptides. |
| What is the structure of an alpha helix? | Helical structure, one turn every 3.6 amino acids, hydrogen bonds form between the oxygen of the carboxyl group of an amino acid and the hydrogen of an amine group of an amino acid four places along, more elastic but less strong. |
| What is the structure of a beta pleated sheet? | Anti-parallel sheets - chains running in alternate directions so groups at the end alternate. H bonds form between the O of the carboxyl group in one chain and the H of the amine group of the adjacent chain. Less elastic but strong, high tensile strength |
| What is the tertiary structure of a protein? | Overall 3D structure formed when coils and pleats coil and fold, resulting from bonds between parts of the R-groups of the chain. |
| What are the types of bonds in the tertiary structure of a protein? | H bonds - slight + and - groups attract. Ionic bonds - full + and - groups attract, stronger than H bonds. Disulphide - double covalent, between sulphur atoms of cyestine amino acids. Hydrophobic - weak, when hydrophobic R groups turn away from water |
| How is the tertiary structure linked to the protein function? | Hormones are specifically shaped to fit into the receptor site on the target cell, complementary. Enzymes have specifically shaped active sites that are complementary to the substrate |
| What is denaturation? | When a protein is heated, more kinetic energy, vibrates, breaks some bonds holding tertiary structure in place, tertiary structure unravels, preventing protein function |
| What is the structure of globular proteins? | Roll up to form ball-shaped structures. Hydrophobic R-groups turn inwards to centre, and hydrophilic R groups are on the outsides making the protein water soluble. Usually have metabolic roles e.g. enzymes, plasma proteins, antibodies |
| What is the structure of fibrous proteins? | Form fibres with repetitive sequences of amino acids, insoluble in water, usually have structural roles e.g. collagen is in bone and cartilage, keratin is in fingernails and hair |
| What is the quaternary structure of proteins? | When multiple of the same or different polypeptide chains join together, sometimes with an inorganic component called as prosthetic group, to form a protein whose functioning requires all subunits |
| What is the structure and function of haemoglobin? | Globular, water soluble, 4 polypeptide units, 2 alpha chains, 2 beta chains, prosthetic group is haem group with iron ion (Fe2-), each molecule carries 4 O2 molecules. Function: binds with O2 in lungs, oxyhaemoglobin, releases in tissues |
| What is the structure of collagen? | Fibrous, structural, 3 helix polypeptide chains, no prosthetic, joined by H bonds, 1000 amino acids, repeating sequence glycine, proline, alanine, 1 turn/3. Collagen fibril - many molecules next to each other, many form a collagen fibre |
| What is the function of collagen? | Mechanical strength: prevents high pressure blood in arteries from bursting walls, form tendons which connect skeletal muscle to bond to allow movement, form bones, cartilage + connective tissue, cosmetic treatmeants use collagen e.g. make lips fuller |
| Why is collagen strong? | Covalent bonds called cross links are between fibrils, and collagen molecule endings and cross links are staggered - these then form fibres which are very stronger. |
| How do you test for the presence of reducing sugars? | Heat equal volumes of Benedict's reagent +carbohydrate solution to 80oc/above in hot water bath for 5 mins. Green - yellow - orange -brick red increasing conc of reducing sugars. Colour change caused by e- donation from reducing sugar, precipitate Cu(I)2O |
| How do you test for non-reducing sugars? | Verify non-reducing sugar. Add HCl to hydrolyse non-reducing sugar + split into reducing sugars, neutralise with alkali, heat equal vols of Benedict's reagent + carb solution to 80oc for 5 mins, colour change green-yellow-orange-brick red, increasing conc |
| How do you test for the concentration of reducing sugar present? | Heat equal vols of Benedict's reagent and carb solution 80oc 5 mins. Filter precipitate (higher conc of rs means more prepitate), cuvette, measure amount of light transmitted/absorbed, use a blank sample e.g. water to reset colorimeter, colour filter |
| How do |
Created by:
11043
Popular Biology sets