macromolecules

Question 1

what are organic molecules / hydrocarbons / functional groups

Answer 1

• compounds containing C, H, N, O, P and S
• often small
• organic molecules with C and H, non-polar, energy rich
• component of a molecule that retains distinctive chemical properties, chemical reactions results from transfer of functional group

Question 2

what are macromolecules

Answer 2

• large molecules (polymers) made up of repeating units (monomers)
• proteins, carbohydrates, lipids and nucleic acids
• built by covalently bonding two or more subunits
• condensation / dehydration: release molecule of water
• hydrolysis: releases energy, molecule of water added, to break apart polymer

Question 3

what do proteins do

Answer 3

• enzyme catalyst: chemical reactions
• defence: antibodies
• transport: membrane transport and blood cells
• support: cytoskeleton and collagen
• motion: muscle fibre contraction and cilia
• regulation: hormones

Question 4

what are amino acids

Answer 4

• comprised of central C atom bonded to an amino group (NH2), carboxyl group (COOH), H atom and R side chain (unique for each AA)
• R group: 20 amino acids, classified by shape, size, hydrophobicity, charge and chemical reactivity
• neutral / non-polar: hydrophobic AA, non-polar R groups inside
• neutral / polar: hydrophilic AA
• charged: acidic / basic

Question 5

describe the different structures of proteins

Answer 5

secondary: backbone folds, stabilised by h-bonds between ‘common’ AA components
- alpha helices or beta pleated sheets
tertiary: folded 3D shape, extended rigid rods or globular mass
- folds non-polar R groups into the interior (hydrophobic), polar face exterior (hydrophilic)
- stability determined by fit of internal portions (H, ionic, van der waals, disulphide)
quaternary: a proteins subunit arrangement, subunit (same or different polypeptide structure)

Question 6

what happens when unfolding / abnormal proteins occur

Answer 6

• unfolding: alteration of proteins environment (temp, pH, conc.), denaturation / loss of function, renders protein biologically inactive
• abnormal: denatured / mis-folded, marked for degradation, if elimination fails = aggregation (parkinsons, alzheimers)

Question 7

what are proteins

Answer 7

• polymers of amino acids in specific sequence
• peptide bonds link two or more amino acids
• polypeptide chain
• long AA chains folded into complex shapes

Question 8

what are protein chaperones

Answer 8

• help proteins fold, refold or disassemble proteins
• molecular: binds to unfolded proteins and prevents aggregation
• chaperonins: form ‘chambers’ which provide suitable environment and time to allow correct folding, deficiency = cystic fibrosis

Question 9

what is a carbohydrate

Answer 9

• fuels and building materials, contain energy rich C-H bonds (covalent), simple sugars and their monomers
• 1:2:1 - C:H:O (Cn(H2O)n)
• contain multiple OH and =C
• monomers joined together via glycosidic linkages (dehydration), covalent bond, to form polymers

Question 10

how are carbohydrates classified

Answer 10

• monosaccharide: simple sugar, ring in (aq), 3-7 C atoms, glucose / fructose (6)
• disaccharides: two monosaccharides joined, lactose (glucose + galactose)
• oligosaccharides: in-between di and poly, glycoprotein / glycolipid, raffinose
• polysaccharide: many monosaccharide units (100-1000’s), connective tissue, exoskeleton, cell wall, energy reserve (glucose as glycogen)

Question 11

what are isomers of monosaccharides

Answer 11

• isomer: two molecules with same chemical formula
• stereo: identical chemical groups bonded to same C atom, different arrangement
• structural: same chemical groups bonded to different C atoms

Question 12

what is cellulose

Answer 12

• carbohydrate of plants
• glucose can form two rings OH below (alpha, starch) or above (beta, cellulose)
• both produced by plants, chains of glucose
• cellulose cannot be digested by humans (unable to break beta linkages), passes through digestive tract untouched

Question 13

what are levo / dextro sugars and chirality

Answer 13

• levo: left handed, rare, mirror image of normal sugars (no energy value, tastes same, no calories)
• dextro: majority of sugars `

Question 14

what are nucleic acids

Answer 14

• amino acid sequence programmed by unit of inheritance (gene)
• gene: DNA = polymer of nucleic acid monomers
• information storage molecules
• ‘blueprint’ for proteins, act as template for copies of themselves
• DNA: hereditary material
• RNA: ‘read’ info encoded in DNA, direct protein synthesis

Question 15

what is the structure of nucleic acids

Answer 15

• nucleotide (monomers)
• pentose: 5 carbon sugar, DNA (deoxyribose), RNA (ribose), numbered 1-5 (5= hanging off), backbone (C2 bonded to H)
• P group: part of sugar phosphate backbone
• nitrogenous base: protrude from backbone, purines (5C, adenine, guanine) and pyrimidines (6C, cytosine, uracil, thymine)
• 3’ to 5’ prime directionality
• double helix ladder

Question 16

describe DNA structure (forces / bonds / joining nucleotides)

Answer 16

• P group binds to OH group of adjacent sugar (phosphodiestar bond)
• H bonds: hold two chains together (between bases)
• van der waals forces: between adjacent atoms, stability of entire molecule

Question 17

what is the function of DNA

Answer 17

• gene codes: nucleotide sequence of DNA = code
• genes: sections code for particular polypeptides
• order: of nucleotides = specifies AA order in protein, primary structure dictates 3D conformation / function of proteins

Question 18

what is RNA

Answer 18

• ribose sugar (C2 bonded to OH)
• uracil replaces thymine
• single stranded
• involved in protein synthesis
• mRNA = carries message from DNA
• rRNA = part of ribosomes, read mRNA
• tRNA = positions amino acids / complementary bases

Question 19

what are lipids

Answer 19

• highly vary in form and function
• little / no affinity for water (insoluble, hydrophobic)
• does not fold up like proteins (cluster - cell membrane)
• does not include polymers, common subunits
• triglycerides (3 fatty acid chain)
• string of C with H groups hanging off
• formed by dehydration of smaller molecules to form ester linkages

Question 20

what are simple lipids

Answer 20

• triglycerides
• fatty acid: hydrocarbon chain with carboxyl group (COOH)
• waxes: long fatty acid / fatty alcohol chain (sebum, cerumen, vernix caisson - pregnancy)

Question 21

what are fats

Answer 21

• glycerol molecule with 3 fatty acids = triglyceride

- C-H bonds = store energy, cushioning, insulation

Question 22

what are the types of fats

Answer 22

saturated:
- maximum number of C-H bonds (single), straight fatty acid (solid at room temp, very dense)
- increase LDL: plaques, decrease artery size, connective tissue growth in cardiovascular system (decrease elasticity)
- HDL: bind to left over cholesterol, return it to liver
- hydrogenated oil: H added to unsaturated fat (peanut butter, margarine)
unsaturated:
- double bonds, kinks at double bonds, liquid at room temp, less dense (oil)
- take up larger volume
- polyunsaturated: more than one double bond
- ‘healthy’ fats

Question 23

what are trans fats

Answer 23

• uncommon
• same molecular formula but different shape (hydrogenation)
• negative effects, straighter than -cis molecules
• risk of coronary heart disease due to increase LDL, removing double bond = susceptible to free radicals

Question 24

what are other types of lipids

Answer 24

• phospholipid: glycerol backbone (3 C 3 OH), fatty acid chain (16-18 C, end with COOH), P group (hence amphipathic)
• isoprenoids: diverse (chemical signalling, light reception), vitamins A, E, K
• steroid: cholesterol, hormones (testosterone / oestrogen), co-factors (vitamin D)