Download Main concepts Carbohydrates Fats, Proteins and Enzymes

Main concepts Carbohydrates Fats, Proteins and Enzymes
1. Food performs three essential functions in our bodies: it supplies energy, provides raw materials for
growth and repair, and provides essential nutrients for the control of biochemical processes.
2. Carbohydrates are composed of the three elements carbon, hydrogen and oxygen.
3. Carbohydrates include monosaccharides, disaccharides and polysaccharides.
4. The molecular formulas for carbohydrates can be represented as Cx(H2O)y.
5. Monosaccharides form the basis of all other carbohydrates.
6. Disaccharides (two sugars), including sucrose, lactose and maltose, are formed from the condensation
reaction between two monosaccharide molecules.
7. Polysaccharides (many sugars), including starch, glycogen and cellulose, are formed from the
condensation reactions between many monosaccharide molecules.
8. Plants store starch in the cytoplasm of their cells.
9. Glycogen is the storage form of glucose for animals. It is primarily stored in the liver and skeletal muscles.
10. Fats and oils are the most abundant subgroup of a large group of compounds called lipids.
11. Fats and oils are made from the three elements carbon, hydrogen and oxygen.
12. The major function of fats in our bodies is as an energy source.
13. Fats are natural esters called triglycerides or triacylglycerols.
14. They are formed from 1,2,3-propanetriol, commonly known as glycerol, and fatty acids.
15. The general structure of a triacylglycerol is
16. Fats and oils usually contain several different acids ranging from 14 to 20 carbon atoms, but always with
an even number of carbon atoms.
17. Fatty acids are long chain alkanoic acids.
18. There are two main types of fatty acids, saturated fatty acids, eg stearic acid, and unsaturated fatty acids,
eg oleic acid.
19. Unsaturated fatty acids can be further subdivided into monounsaturated (contain one C=C double bond)
and polyunsaturated (contain two or more C=C double bonds) fatty acids.
20. Triacylglycerols are insoluble in water because the long hydrocarbon chains of the fatty acid sections are
non-polar and their hydrophobic properties are greater than the hydrophilic properties exhibited by the
ester links.
21. Proteins perform many roles in a healthy functioning body. Fibrous proteins provide structure for many
body components eg hair, skin, tendon and cartilage; globular proteins transport oxygen, function as
antibodies that fight disease and catalyse biochemical reactions.
22. Proteins are large biopolymers formed from the condensation polymerisation of amino acids.
23. There are twenty amino acids found in the human body including eight (for adults) and nine (for children)
essential amino acids.
24. Amino acids contain the elements carbon, hydrogen, oxygen and nitrogen. Some also contain sulfur.
25. Amino acids contain both the amine (–NH2) and carboxylic acid (–COOH) functional groups.
26. The general structure of an amino acid is:
27. The chemical structure of the –R side chain groups (non-polar, polar or charged) accounts for the differing
properties of amino acids.
28. Amino acids tend to exist as zwitterions (dipolar positively and negatively charged ions), because the
acidic and basic groups within an amino acid react with one another.
29. When amino acids join together, they form peptide bonds.
30. Proteins are polypeptides containing hundreds of amino acid molecules joined by peptide bonds.
31. The shape of a protein has four levels of organisation: primary, secondary, tertiary and quaternary.
32. Primary structure is the sequence of amino acids.
33. Secondary structure is the spatial arrangement of the polypeptide chain; generally produces a spiral
structure.
34. Tertiary structure or the overall folding pattern of the polypeptide chain may result in long elastic proteins
required for structural proteins or globular proteins.
35. Quaternary structure is the way in which individual polypeptide chains form an aggregated whole.
36. The forces and bonds which determine the final shape of protein molecules, apart from the peptide bonds
which link the amino acids, are electrostatic (ionic) forces, hydrogen bonds, hydrophobic (dispersion)
forces, and covalent disulfide bonds.
37. Protein denaturation is any process that disrupts the secondary, tertiary or quaternary structure of the
protein rendering it biologically inactive.
38. Various factors, including temperature, pH and some chemicals, can denature proteins, usually
irreversibly.
39. Enzymes are a group of proteins responsible for catalysing most reactions in living systems.
40. Enzymes are biochemical catalysts which:
dramatically increase reaction rates
are not consumed in a reaction
do not affect the position of equilibrium
are reaction-specific
operate under mild conditions (especially temperature and pH).
41. In an enzyme-catalysed reaction the enzyme forms specific bonds with the particular reactant or
(substrate) molecule(s) at the enzyme’s active site.
42. The formation of the enzyme–substrate complex provides a low energy pathway for
43. the substrate to undergo a particular reaction.
44. Enzyme action is often explained in terms of a ‘lock and key’ mechanism, because the active site of the
enzyme has a specific shape (similar to a key) and only the correct shaped substrate (similar to a lock) will
fit that site.
45. Lipase, ATP ase and Protease are three examples of important enzymes in the human body.