Human Biochemistry

Amino Acids and Proteins

there are about 20 amino acids that occur naturally they are the basic “building blocks” of life/proteins

NH 2 CHRCOOH

condensation reactions will link amino acids together to form polypeptides that eventually fold up into proteins enzymes are necessary! water is formed and they link together with a peptide bond peptide bonds YouTube (1:14)

Primary Structure determined by the number, kind, and order of a.a. in the polypeptide held together by simple peptide bonds Proteins have a complex structure which can be explained by defining four levels of structure What is a protein video 3:38

Secondary Structure the polypeptide then spontaneously folds into regular, repeating structure because of hydrogen bonding

Tertiary Structure highly specific looping and folding of the polypeptide because of the following interactions between their R-groups: –covalent bonding –hydrogen bonding –ionic bonding –London dispersion forces this tertiary level is the final level of organization for proteins containing only a single polypeptide chain

Quaternary Structure linkage of two or more polypeptides to form a single protein in precise ratios and with a precise 3-D configuration. Protein folding

Quaternary Structure example

Carbohydrates most abundant class of biological molecules range from simple sugars (glucose) to complex carbohydrates (starch)

Monosaccharides simplest sugars (single sugars) – all contain the empirical formula (CH 2 O) can be straight chains or cyclic form two common isomers of monosaccharides (C 6 H 12 O 6 ) glucose fructose

Disaccharides two monosacharides bonded together by a condensation reaction that creates a glycosidic linkage water is formed

three common disaccharides (don’t need to know this) 1. sucrose - common table sugar glucose + fructose 2. lactose - major sugar in milk glucose + galactose 3. maltose - product of starch digestion glucose + glucose

Polysaccharides starch- condensation of many glucose molecules

condensation of many glucose molecules to form long chains serve principally as food storage and structural molecules in plants

three types of polysaccharides 1. Starches (plants) – serve as storage depots of glucose 2. Cellulose (plants) – most abundant polysaccharide on Earth – the major structural material of which plants are made (wood and plant fibers) – plant cell walls are among the strongest of biological structures 3.Glycogen – multi-branched that serves as a form of energy storage in animals and fungi

Lipids

3 Main Types of Lipids

‘lipid’ comes from lipos, the Greek word for fat all are hydrophobic (water-fearing/insoluble in water) greasy, oily

1. Triglycerides (fats and oils) found in adipocyte cells that are in fatty tissue a condensation reaction called ester linkage

types -saturated fat -do NOT contain C=C bonds -therefore straight chained and have high melting points -lard and butter -unsaturated fat -have double bonds between one (monounsaturated fats) or more (polyunsaturated fats) of the carbons in the chain -causes a kink in the carbon chain which prevents them from packing close together and therefore have low melting points (London dispersion forces are weaker) -vegetable oils

Saturated vs. Unsaturated fatty acids (2:51)

2. Phospholipids major structural components of cell membranes polar “heads” love water (hydrophilic) uncharged “tails” avoid water (hydrophobic) + _

+ _

3. Steroids cholesterol is the most abundant and important steroid

lipoproteins – molecules made of proteins and fat – transport cholesterol around the body – low density lipoproteins (LDL) “bad cholesterol” transport cholesterol to cells to be used however, can build up and cause cardiovascular disease – high density lipoproteins (HDL) “good cholesterol” doesn’t have much cholesterol, therefore, can absorb more cholesterol from the arteries and transports it back to the liver