CARBOHYDRATES, LIPIDS, AND PROTEINS

Question 1

monomers and polymers

Answer 1

• Monomers are individual molecules that make up a polymer.
• Polymers are long chains that are composed of many individual
  monomers that have been bonded together in a repeating pattern.
• Condensation Reactions occurs when two
  molecules combine to form a more complex
  molecule with the removal of water.
• Hydrolysis Reactions occurs when larger
  molecules are broken down into smaller
  molecules with the addition of water.

Question 2

carbohydrates

Answer 2

• Monosaccharides are the simplest carbohydrates, consisting of
  only one sugar molecule (e.g. Glucose, Fructose &
  Galactose).
• Ribose sugars (pentose) are found in many important
  biological molecules such as ribonucleic acid (RNA),
  ATP, NAD
• Glucose is a hexose sugar with 2 isomers
• Disaccharides are sugars that are composed
  of two monosaccharides joined together in a
  condensation reaction, forming a glycosidic bond
  Maltose - 2 × α-glucose
  Sucrose - α-glucose and fructose
  Lactose - β-glucose and galactose
• Polysaccharides are formed by many monosaccharides joined
  together.
  ◦ Amylose, amylopectin (starch) is the main polysaccharide
  energy store in plants, is composed of ž-glucose.
  ◦ In animals, the polysaccharide energy store is called
  glycogen, composed of ž-glucose.
  ◦ Cellulose is a structural component of plant cell walls

Question 3

lipids

Answer 3

Fatty acids can be:
◦ Saturated – there are no C=C bonds and the molecule has as
many hydrogen atoms as possible.
◦ Unsaturated – there is at least one C=C bond, therefore the
molecule contains fewer hydrogen atoms than is maximally
possible.
* A triglyceride molecule is formed by joining one molecule
of glycerol to three fatty acids through three condensation
reactions, forming ester bonds.
* Triglycerides have key
roles in respiration and
energy storage due to
its insolubility and high
carbon to hydrogen ratio.
* Phospholipids replace one of the fatty acid chains in
triglycerides with a phosphate molecule.
* The hydrophobic tails
and hydrophilic heads of
phospholipids allow them to
form phospholipid bilayers.

Question 4

proteins

Answer 4

• Amino acids are the monomer units used to make proteins.
• The 20 naturally occurring amino acids only diff er in their R groups.
• Dipeptides are formed when two
  amino acids are joined together
  by a condensation reaction,
  forming a peptide bond.
• A polypeptide is a polymer
  made of many amino acids
  joined together by peptide
  bonds.
• A protein may contain one or more polypeptide chains

Question 5

globular proteins

Answer 5

• A globular protein is protein with a spherical shape that is
  soluble in water; they typically have metabolic roles
• Globular proteins have a few important properties:
  ◦ They are roughly spherical in shape, with hydrophobic R
  groups on the inside and hydrophilic R groups on the outside.
  They are therefore soluble in water
  ◦ They have very specifi c shapes; this allows them to carry out
  very specifi c functions
• Haemoglobin is a conjugated globular protein, made of 4
  polypeptide chains and 4 haem prosthetic groups which contain Fe2+.
• Insulin is composed of two polypeptide chains, joined together
  by disulphide links. The specifi city of the shape allows binding
  to cell membrane receptors.
• Pepsin has hydrogen bonds, disulphide link and few basic R
  groups to keep it functional in low pH stomach acid.

Question 6

fibrous proteins

Answer 6

• Fibrous proteins have some similar properties to each other:
  ◦ They contain long polypeptide chains with repeating
  sequences of amino acids
  ◦ The amino acids have non-polar R groups, so the proteins are
  insoluble in water
  ◦ The polypeptide chains are able to form fi bres which make
  the proteins stronger
• Collagen is used to make bones, tendons and are found in
  artery walls to help resist the high pressure
• Keratin contains high amounts of cysteine, resulting in disulphide
  links forming between the two polypeptide chains, which makes
  the molecule very hard and strong. It is found in fi ngernails,
  hooves and horns.
• Elastin has the ability to stretch and recoil. Elastin is stretchy
  due to coiling of the elastin molecules and cross-links that keep
  the molecules together. It is found in the lungs, bladder and
  blood vessel walls.

Question 7

inorganic ions

Answer 7

• Inorganic ions are atoms or molecules with an electric charge,
  containing no carbon.
• Cations are positively charged ions
• Anions are negatively charged ions
• Inorganic ions occur in solution in the cytoplasm and body
  fl uids of organisms, some in high concentrations and others in
  very low concentrations
• Each type of ion has a specifi c role, depending on its properties
  ◦ Hydrogen ions determine the pH of bodily fl uids. The higher
  the concentration, the lower the pH
  ◦ Sodium ions are used in the co-transport of glucose and amino
  acids across cell membranes and transmission of nervous impulses
  ◦ Phosphate ions are essential components of DNA, RNA,
  nucleotides & ATP
  ◦ Calcium ions regulate protein channels, impulse transmission
  and harden body parts like teeth.
  ◦ Potassium ions play a role in muscle contraction, nervous transmission. active transport and maintaining turgidity in plant cells.
  ◦ Ammonium ions and Nitrate ions are part of the nitrogen
  cycle and a source of nitrogen for biological molecules
  ◦ Hydrogencarbonate ions are formed when carbon dioxide
  dissolves in blood. They are important in the transport of
  carbon dioxide in the blood and the regulation of blood pH
  CO2 + H2O ⇌ HCO3
  –
  + H+

Question 9

levels of protein structure

Answer 9

1. Primary
   - The specific sequence of amino acids in a polypeptide chain
   - Peptide bonds
2. Secondary
   - The curling or folding of the
   polypeptide chain into α-helices
   and β-pleated sheets due to the
   formation of hydrogen bonds
   - Hydrogen bonds
3. Tertiary
   - The overall specific 3-D shape of
   a protein, which is determined by
   interactions between R groups
   and the properties of R groups
   - Hydrogen bonds
   - Ionic bonds
   - Disulphide bridges
4. Quaternary
   - The specific 3-D shape of a
   protein that is determined by the
   multiple polypeptide chains and/or
   prosthetic groups bonded together
   - Hydrogen bonds
   - Ionic bonds
   - Disulphide bridges

Answer 10

1.Reducing sugars
- Benedict’s reagent → Heat Red/orange precipitate
- Reagent test strip
- Compare with calibration card

2. Nonreducing sugars
   - Hydrochloric acid → Heat Sodium hydrogencarbonate
   - Benedict’s reagent → Heat
   - Red/orange precipitate
3. Starch
   - Iodine in potassium iodide solution
   - Blue/black
4. Proteins
   - Sodium hydroxide
   - Copper (II) sulphate
   - Purple
5. Lipids
   - Ethanol
   - Water → Shake
   - Cloudy white