Biological molecules

• what is the importance of unusually high boiling point in living organisms and give an example in nature

  -lot energy needed break many hydrogen bonds

  -stable water temperature for aquatic animals, less energy spent on temp control
• what is the importance of ice being less dense than water and give an example in nature

  -creates insulating barrier so water below doesn't freeze, allowing organisms move under water

  -habitat for animals like polar bears on top ice and fish can move under water
• what is the importance of cohesion and give an example in nature

  -cohesion is hydrogen bonding in water

  -water moving through xylem creates high surface tension for insects like water skater to walk on
• what is the importance of adhesion and give an example in nature

  -adhesion is waters attraction to other molecules/surfaces

  -water moving through xylem
• what is the importance of water acting as a solvent and give an example in nature

  -allows mineral ions be transported around plants and animals

  -substances dissolving in bloodstream
• what is the importance of water acting as a transport medium and give an example in nature

  -allows transport of soluble substances

  -transporting substances around body in blood or around plant
• what is the importance of eveporation and give an example in nature

  -is cooling mechanism, the evaporating water takes heat away from body

  -sweating in mammals or panting in dogs to cool them down
• what is the importance of high specific heat capacity and high latent heat vaporisation and give an example in nature

  -high specific heat capacity - takes lot energy heat up water by 1 degree

  -high latent heat vaporisation - takes lot energy change water from liquid to gas form

  -importance = creates stable temp so enzymes can work at their optimum temp, gases remain soluble for aquatic organisms

  - metabolic reactions
• what is the structure of alpha glucose ?

  
• what is the condensation reaction alpha glucose ?

  
• what are the common disaccharides and their monosaccharides ?

  
• what are the properties of one of the polysaccharides of starch ?

  amylose

  -made up of alpha 1,4 glycosidic bonds therefore appear in coiled structure (held together by hydrogen bonds) so:

  * compact

  * doesn't affect osmotic potential

  * good storage molecule

  (starch found in plants)
• what are the properties of the other polysaccharides of starch ?

  amylopectin

  -branched chains (makes it compact, it takes up little space in the cell) of α-glucose monomers joined by 1,4-glycosidic bonds and 1,6-glycosidic bonds

  -The 1,6-glycosidic bonds form the links which make branches -->

  -the branches mean there are many glucose molecules accessible on the end of chains which can be easily broken off by hydrolysis for use in respiration.
• what are the properties glycogen ?

  Highly branched => Can be broken down faster

  Shorter than starch (No alpha-helices)

  Stored in muscle/liver cells

  Readily hydrolysed bcs of SIDE CHAINS
• how do glycosidic bonds form in beta glucose molecule ?

  -every alternate beta glucose orientate itself 180 degrees

  -beta glucose is monomer for cellulose

  
• what are the properties of cellulose ?

  -several beta glucose molecules bond together make long chain aka a polymer in condensation reaction

  -they form beta pleated sheets between which hydrogen bonds can form cross links form bundles called microfibrils. (Larger bundles called macrofibrils)

  -these provide high tensile strength and make up plant cell walls

  -allow water pass through, prevents cell from bursting, determines shape
• how does an ester bond form ?

  
• what is the difference between saturated fatty acid and unsaturated fatty acid ?

  -saturated fatty acids have unkinked (straight) fatty acids whereas unsaturated triglyceride double bond created kink in chain therefore fatty acids can't lie close to another so creates less dense substance such as oil

  
• Why are triglycerides goo at storing energy ?

  -used as respiratory substrate and they release water when broken down

  - are insoluble so won't affect water potential

  - used make hormones

  -water proofing

  - buoyancy

  -good at forming layers insulation for warmth or protective layers around organs or on nerves e.g myelin sheath

  -also fat absorption, fat soluble molecules e.g vitamin A
• What does cholesterol do to membrane ?

  -regulates fluidity as their small size and flattened shape allow them fit between phospholipids and bind their hydrophobic tails making membrane more rigid

  -regulates fluidity membranes by keeping them fluid at low temp but stopping them becoming too fluid at high temp
• what are the properties of fibrous proteins ?

  -flexible

  -insoluble water (lots amino acids with hydrophobic R groups)

  -very strong (high tensile strength) and tough ( many cross bridges between polypeptide chains)
• what are examples of fibrous proteins and their function

  - keratin (hair and nails) = lot of disulphide bridges for strength

  - Elastin (alveoli) = recoils after being deformed

  -Collagen (skin) = flexible but doesn't stretch
• what are the properties of globular proteins ?

  - soluble in water (amino acids with hydrophilic R groups in centre protein)

  -provide metabolic role (enzymes or hormones)

  - compact, 3D

  -conjugated proteins have prosthetic groups
• what are examples of globular proteins and their function

  -Insulin = specific fixed shape

  -Haemoglobin (conjugated protein) = can change shape

  - Catalase (conjugated protein) = specific fixed shape
• what are examples of reducing suagars ?

  glucose, lactose, galactose and fructose
• how would you test for an non-reducing sugar ?

  e.g sucrose

  - heat sample with benedicts and if no change, then heat with acid/HCl

  - add excess NaOH

  -heat sample with benedicts in water bath

  -non-reducing sugar present if brick red colour appears
• how would you do a serial dilution ?

  
• why must you be careful when handling thin layer chromatography ?

  handle with gloves so amino acids on hands don't contaminate results
• why do lighter amino acids travel further up chromatogram ?

  as they have smaller R group and have will have less resistance between that amino acid and chromatogram (silica gel it's moving through)