Human Biochemistry Flashcards
Product of the condensation reaction of 2-amino acids to form polypeptides
dipeptide
a substituted amide made up of two amino acids joined by a peptide bond or a peptide linkage
Describe the characteristic properties of 2-amino acids
amino acids are colorless, crystalline solids that exist as zwitterions (dipolar ions)
explains their relatively high melting points for organic compounds and why they are generally more soluble in water than in organic solvents
Amphoteric
When R is not H, the 2-Carbon atom is chiral, the molecule is asymmetric and gives rise to two possible stereoisomers (enantiomers)
Explain primary structure of proteins
Simply the sequence of amino acid residues that form the protein
Indicated by using three-letter codes for the amino acids
Explain the secondary structure of proteins
manner in which the polypeptide chain folds itself due to intramolecular hydrogen bonding
Affects arrangement in space of the polypeptide chain
alpha helix and beta pleated sheets
Explain alpha helix
Resembles a right handed spiral staircase or coiled spring
Can make the protein elastic or sponge-like in fibrous proteins such as hair and wool
Maintains its shape through regular intramolecular hydrogen bonds
hydrogen bond between negative polar side O of the carbonyl group (C=O) and the positive polar side of the -NH2 group of the third peptide bond down the chain
Explain beta-pleated sheet
Different polypeptide chains are bound together by hydrogen bonds to create an orderly alignment of protein chains in which the direction of H-bonding is perpendicular to the sheet structure giving rise to a repeating, pleated pattern.
Explain tertiary structure of proteins
Folding or curling due to the interaction between the sequence of amino acids that maintains the three dimensional shape of the protein.
Amino acid chains interact in 4 ways to stabilize their shapes
1) covalent bonding (disulfide bridges)
2) H-Bonding between NH2 and COOH
3) salt bridges (electrostatic attraction) between NH3 and COO- groups
4) R group side chain depending on its polarity
Explain Quaternary Structure
How the polypeptide subunits are held together in a precise, more complex 3-D structural arrangement
Occurs only in proteins that are composed of more than one polypeptide chain which are held together by non-covalent bonds
Consist of hydrophobic interactions, H-bonding and ionic bonds
What is a subunit?
When a protein consists of more than one polypeptide chain, each polypeptide chain is a subunit
What is denaturation?
When proteins lose their 3-D structure and hence biological activity
Why does denaturing affect the functioning of a protein
The exact shape is the key to the function of each of the numerous proteins in the body.
Most common cause of denaturing is heat, as in the case when an egg is fried or boiled
Explain analysis of proteins through chromatography
Used for analyzing separation of mixtures of substances which are otherwise not easily separated
Paper chromatography - relative solubility of different amino acids varies in the stationary phase (water, which is absorbed on the cellulose paper) and in the mobile phase (solvent)
Amino acids with greater solubility in the eluting solvent will travel further in the direction of the solvent flow
Ratio of fronts = distance travelled by compound/distance travelled by solvent
Electrophoresis
Method of separating molecules on the basis of their electric charges
In order to analyze a protein using electrophoresis, the peptide bonds in the protein must first by hydrolyzed to release the individual amino acids
List the major functions of proteins in the body
Proteins carry out many important functions in the body
Structural - collagen (skin) keratin (hair)
biological catalysts - enzymes
hormones - insulin
antibodies - proteins that are produced as a result of the presence of foreign materials in the body
transport - hemoglobin
energy - proteins in the human body can be used to provide energy
carbohydrates
Main energy source for our bodies and are vital to the synthesis of cells.
Serve as food sources for living organisms and provide the structural support for plants.
Most carbohydrates are changed to glucose through digestion
Cellulose is the major component of plant cells that cannot be digested by humans; it does provide fiber
Describe the structural features of monosaccharides
Smallest molecular units of carbohydrates with the general formula (CH2O)n where n=3 to 9
Aldehydes or ketones containing a carbonyl group and at least 2 hydroxyl groups
(glucose, galactose)
List the major functions of carbohydrates in the human body
energy source - potatoes, bread, corn, rice contain carbohydrates
energy reserve - animals use glycogen stored in the liver as their energy storage polysaccharide; can be broken down by enzymes into glucose
precursor of other biologically important molecules - found as components of nucleic acids
Describe the importance of a diet high in fiber
Water insoluble fiber - provide bulk and move food through digestive system
water soluble fiber - includes pectins which undergo fermentation in the large intestine by bacteria to produce short-chain fatty acids (propanoic and butanoic acids) both help stabilize lipid and blood glucose levels
help prevent constipation and diverticulosis
IBS - refers to symptoms arising from the bowel not working as it should
Obesity - excess body mass; high fiber leads to feeling full on a diet with reduced carbohydrates and fats
Crohn’s Disease - inflammatory bowel disease; dietary fiber may help prevent
Haemorrhoids - enlarged blood vessels in and around the rectum that are swollen and can cause bleeding; caused by pressure in the abdomen due to constipation
Define lipids
substances found in living organisms that are defined in terms of their solubility: in general these are poorly soluble in water, but soluble in organic solvents which are non-polar or of low polarity
Due to large non-polar hydrophobic hydrocarbon chains
What are the groups that lipids are divided into?
triglycerides (fats and oils)
phospholipids (complex lipids containing phosphorus)
steroids (cholesterol)
Why are linoleic and linoeic acids vital?
They cannot be synthesized in our bodies, but are necessary for its correct functioning
Define the term iodine number
Number of grams of iodine that react with 100g of lipid/fat/oil
How to find iodine number of linoleum acid
100 g/ Mr
100/280.4
Describe how oral contraceptives function in the female body
Changes release of hormones (FSH and LH) from hypothalamus/ pituitary gland
Prevents ovulation/egg release
Prevents attachment of egg to uterus/ endometrium
Prevents sperm from reaching the egg by thickening the cervical mucus
