Biological molecules - spec.

?
  • Created by: rachel
  • Created on: 18-03-13 13:15
Describe how hydrogen bonding occurs between water molecules.
Water is a polar molecule. This is because the O2 atom pulls the shared e- towards it, making it slightly negatively charged at the oxygen & positively charged at the hydrogen ends, so they can form hydrogen bonds with each other.
1 of 53
Explain the importance of water being solvent in relation to living organisms
Metabolic processes in all organisms rely on chemicals being able react together in solution.
2 of 53
Give an example of the importance of water being solvent in relation to living organisms.
70-95% of cytoplasm is water. Dissolved chemicals take part in processes such as respiration & photosynthesis in living organisms.
3 of 53
Describe how the hydrogen bonds make water a solvent.
If the solute is slightly charged/ionic, they will interact with water molecules. The water molecules will cluster around the charged parts, keeping solute molecules apart.
4 of 53
Explain the importance of water being liquid in relation to living organisms.
The movement of materials around organisms, both in cells & on a large scale in multicellular organisms requires a liquid transport medium.
5 of 53
GIve an example of the importance of water being liquid in relation to living organisms.
Blood in animals & the vascular tissue in plants use water as a liquid transport medium.
6 of 53
Describe how the hydrogen bonds make water a liquid.
Water remains a liquid over a range of large temperatures & can act as a solvent for many chemicals.
7 of 53
Explain the importance of water being able to create cohesion in relation to living organisms.
Water molecules stick to each other creating surface tension at the water surface. Cohesion also makes very ling, thi water columns very strong & difficult to break.
8 of 53
Give an example of the importance of water being able to create cohesion in relation to living organisms.
Transport of water in xylem relies on water molecules sticking to each other as they are pulled up the xylem in the transpiration stream. Some small animals make use of surface tension to 'walk on water'.
9 of 53
Describe how the hydrogen bonds make water create cohesion.
A drop of water on the waxy surface of the leaf looks almost spherical - it hardly wets the leaf at all. This is because hydrogen bonds pull the water in at the surface. This is cohesion, which also results in surface tension.
10 of 53
Explain the importance of water being frozen in relation to living organisms.
Water freezes, forming ice on the surface. Water beneath the surface becomes insulated & less likely to freeze.
11 of 53
GIve an example of the importance of water being frozen in relation to living organisms.
Organisms such as polar bears live in an environment on floating ice packs. lakes tend not to freeze completely, so aquatic organisms aren't killed as the temperatures fall.
12 of 53
Describe the hydrogen bonds in frozen water (why ice floats on water).
Water is unusual because its solid form is less dense than its liquid form. As water cools, its density increases until the temperature drops to 4oc, the density increases again, so ice floats on water
13 of 53
Explain the importance of water having thermal stability in relation to living organisms.
Large bodies of water have fairly constant temperatures. Evaporation of water can cool surfaces by removing heat.
14 of 53
Give an example of the importance of the water having thermal stability in living organisms.
Oceans provide a relatively stable environment in terms of temperature. Many land-based organisms use evaporation as a cooling mechanism, for example in panting or sweating.
15 of 53
Describe the hydrogen bonds in thermally stable water.
H bonds in liquified water restrict movement of water mol so a relatively large amount of H2O is needed to > the temperature of it. The evaporation of water uses large amount of energy, so water evaporating from surface removes heat from surface.
16 of 53
Explain the importance of water being metabolic in relation to living organisms.
Water takes part as a reactant in some chemical processes.
17 of 53
Give an example of water being metabolic in relation to living organisms.
Water molecules are used in hydrolysis reactions & in the process of photosynthesis.
18 of 53
Describe the structure of an amino acid.
It has an amino group, a carboxyl acid group, a side chain & an alpha carbon.
19 of 53
Describe the formation & breakage of peptide bonds in the synthesis of dipeptides & polypeptides. What type of reaction is this?
A covalent peptide bond forms between the H of the amine group of one amino acid & the OH from the carboxyl group of another. This is a condensation reaction where water is lost.
20 of 53
Describe the formation & breakage of peptide bonds in the hydrolysis of dipeptides & polypeptides. What type of reaction is this?
A water molecule is used to break the peptide bond. The -H joins back to the N, and the -OH back to the C. This is a hydrolysis reaction.
21 of 53
Explain the term primary structure.
The sequence of amino acids found in a protein molecule.
22 of 53
Explain the secondary structure with reference to hydrogen bonding.
The coiling or folding of parts of a protein molecule (localised folding) due to the formation of hydrogen bonds as the protein is synthesised. The main forms are the alpha-helix & the beta-pleated sheet.
23 of 53
Explain the term tertiary structure, with reference to hydrophobic & hydrophilic interactions, disulphide bonds & ionic interactions.
Overall 3-D structure of protein mol. Result of interactions between: R groups of different aa's in parts protein molecule such as: H b. between 2 R groups. f of disulphide bridges between 2 cysteine aa's. Hydrophobic & phillic & ionic interactions.
24 of 53
Explain the term quaternary structure, with reference to the structure of haemoglobin.
Protein structure where a protein consists of more than one polypeptide chain. Haemoglobin has a quaternary structure as it is made up of 4 polypeptide chains. Not all proteins have a quaternary structure.
25 of 53
Describe the structure of a collagen molecule.
Made up of 3 helical polypeptide chains, each about 1000 amino acids long, wound around each other. H & covalent bonds (cross links) from between chains. Cross links are staggered to make molecule stronger. Collagen is strong & doesn't stretch.
26 of 53
Describe the structure & function of haemoglobin.
Hb: Globular. Soluble in H2O. Much of mol wound into alpha helix structures. Wide range of a.a constituents in primary structure. 4 polypeptides subunits. 2 alpha chains & 2 beta chains. prosthetic group is haem, 1 haem per poly. 4 haems per molecule
27 of 53
Describe the structure & function of Collagen.
Collagen: fibrous protein, insoluble in water, 35% of molecules primary structure is glycine. Doesn't have prosthetic group. Much of mol consists of left-handed helix structures.
28 of 53
State the structural difference between alpha & beta glucose.
alpha glucose- OH on carbon 1 is below the chain of ring. Beta glucose- Above the chain or the ring.
29 of 53
Describe the formation of glycosidic bonds in the synthesis & hydrolysis of a disaccharide (maltose) & a polysaccharide (amylose).
Formation: water is eliminated as the -OH from one glucose and the -H from an -OH from the other leave. This means that the remaining O joins to the C on the other glucose making a disaccharide.
30 of 53
Describe the breakage of glycosidic bonds in the synthesis & hydrolysis of a disaccharide (maltose) & a polysaccharide (amylose).
Water is used to break the glycosidic bond between the subunits. The -H returns to the O & the -OH returns to C4. In polysaccharides, there are many glucose subunits joined together by 1,4-glycosidic bonds.
31 of 53
Describe the structure & functions of starch (amylose).
Amylose: Made of alpha glucose. Straight chain, tends to coil up, plant storage polysaccharide.
32 of 53
Describe the structure & functions of cellulose?
Made of b-glucose joined by 1,4 bonds in chain, no branches. Alternate glucose subunits = inverted. Forms straight chains that form fibres with H bonding between chains. Beta-glycosidic bond only broken down by cellulose enzyme. Forms plant cell wall
33 of 53
Describe the structure of glycogen.
Made up of alpha-glucose joined by 1-4 glycosidic bonds & also 1-6 glycosidic bonds which form branches. Forms granules.
34 of 53
Explain how the structure of glucose relate to their functions in living organisms.
Glucose is used in respiration to release energy & cause formation of ATP. Easily converted into glycogen for storage. Soluble in water, lowers water potential & causes osmotic problems.
35 of 53
Explain how the structure of amylose relate to their functions in living organisms.
Amylose is insoluble in water do doesn't affect the water potential of the cell so excellent for storage.
36 of 53
Explain how the structure of glycogen relate to their functions in living organisms.
Glycogen is highly branched so can be hydrolysed into glucose quickly due to lots of branches for enzymes to attach. Insoluble so doesn't affect the water potential of the cell. The compact molecule therefore has high energy content for its mass.
37 of 53
Explain how the structure of cellulose relate to their functions in living organisms.
100's of polypeptide chains lie side by side forming H bond cross links with each other- forms very strong structure. Arrangement of macro-fibrils in cell walls allows: water to move though cell walls, & to move easily though. Prevents cells bursting
38 of 53
Describe the structure of a triglyceride.
Triglyceride: Glycerol + 3 fatty acids. Joined by 3 ester bonds between fatty acids & glycerol. In plants, fatty acids = unsaturated & triglycerides are oils. In animals fatty acids are saturated & triglycerides are more solid.
39 of 53
Describe the structure of a Phospholipid.
Glycerol + 2 fatty acids & a phosphate group. Joined by 2 ester bonds.
40 of 53
Explain how the structures of a triglyceride relates to its functions in living organisms.
Compact energy store. Insoluble in H2O. Stored as fat providing insulation & protection. Provides buoyancy. Waterproofing. Source of H2O (camel). Provides electrical insulation around neurones. Helps absorption of fat soul vitamins. Doesn't affect Ψ
41 of 53
Explain how the structures of a phospholipid relates to its functions in living organisms.
Part hydrophilic (head), part hydrophobic (tail), so ideal basis for cell surface membranes. Phosphate may have carbohydrate part attached forming glycolipids involved in cell signalling.
42 of 53
Explain how the structures of cholesterol relates to its functions in living organisms.
Small, thin molecules that can fit into the lipid bilayer giving strength & stability used to form steroid hormones.
43 of 53
Describe how to carry out chemical tests to identify the presence of a protein (biuret test)
Add biuret solution. If protein is present, turns from pale blue -> lilac.
44 of 53
Describe how to carry out chemical tests to identify the presence of reducing sugars (Benedicts test)
Add benedicts solution, heat to 80oc. If reducing sugars are present, turns from blue solution -> orange-red precipitate.
45 of 53
Describe how to carry out chemical tests to identify the presence of non-reducing sugars (Benedict's test)
If reducing sugars test is negative, boil fresh sample with HCl, cool & neutralise with Sodium hydrogencarbonate. Add benedict's solution, heat to 80oc, if non reducing sugars are present, turns from blue solution -> orange-red precipitate.
46 of 53
Describe how to carry out chemical tests to identify the presence of starch (iodine solution)
Add iodine solution. Turns from yellow -> blue-black if starch is present.
47 of 53
Describe how to carry out chemical tests to identify the presence of lipids (emulsion test)
Mix with ethanol. Pour into water. If a white emulsion forms, a lipid is present.
48 of 53
What's the first step in describing how the concentration of glucose in a solution may be determined using colorimetry.
1. Heat known concentrations of glucose with Benedict's solution (using the same volumes of glucose solutions each time & excess Benedict's)
49 of 53
What's the second step in describing how the concentration of glucose in a solution may be determined using colorimetry.
2. Benedict's changes to green/orange/yellow/brown/red colour.
50 of 53
What's the third & fourth step in describing how the concentration of glucose in a solution may be determined using colorimetry
3. Remove precipitate by filtering. 4. Zero the colorimeter using water (use filter)
51 of 53
What's the fifth & sixth step in describing how the concentration of glucose in a solution may be determined using colorimetry
5. Read the absorbance. 6. Less absorbance of filtrate = more sugar present.
52 of 53
What's the last step in describing how the concentration of glucose in a solution may be determined using colorimetry
7. Plot a calibration curve by plotting absorbance against glucose concentration. Use the reading of he unknown glucose solution & read off graph to find concern.
53 of 53

Other cards in this set

Card 2

Front

Explain the importance of water being solvent in relation to living organisms

Back

Metabolic processes in all organisms rely on chemicals being able react together in solution.

Card 3

Front

Give an example of the importance of water being solvent in relation to living organisms.

Back

Preview of the front of card 3

Card 4

Front

Describe how the hydrogen bonds make water a solvent.

Back

Preview of the front of card 4

Card 5

Front

Explain the importance of water being liquid in relation to living organisms.

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biological molecules, organic chemistry and biochemistry resources »