BASIC BIOCHEMISTRY

Chemical Bonding1. Covalent Bond - strong

bond, formed by sharing of 2 or more electrons

Example: C6H12O6 & any organic molecules

2. Ionic Bond – formed by the transfer of 1 or more electrons

Example: NaCl & MgCl2 Cation – positive Anion - negative

…

3. Hydrogen Bonding – weak bond formed by hydrogen w/i a molecule being attracted by oxygen & nitrogen w/i a molecule

Important in DNA and proteins

Macromolecules of Life

Abundance in a cell: Proteins (55%) Nucleic acids (24%) Lipids (9%) Carbohydrates (5%) Lipopolysacharides (3%) Other (4%) = inorganics

Question: How Are

Macromolecules Formed?

Answer: Dehydration Synthesis

Also called “condensation reaction”

Forms polymers by combining monomers by “removing water”.

HO H

HO HO HH

H2O

Question: How are

Macromolecules separated or

digested?

Answer: Hydrolysis

Separates monomers by “adding water”

HO HO HH

HO H

H2O

Lipids Any biological molecule that has low

solubility in water & high solubility in nonpolar organic solvents

Hydrophobic; thus they are good barriers for aqueous environments

6 major groups: Fatty acids Tricylglycerols Phopholipids Glycolipids Steroids Terpenes

Lipids … Fatty Acids Building blocks for most complex

lipids Long chains with a carboxylic acid at 1

end Can be saturated or unsaturated

Saturated only single C-C bonds Unsaturated has one or more C=C (double

bond) Oxidation gives huge amounts of

chemical energy for a cell

Lipids … Triacylglycerols

A.K.A. triglycerides, fats, or oils

Have a 3 Carbon backbone (glycerol) that’s attached to 3 fatty acids

Function is to store energy, thermal insulation, and padding to an organism

Adipocytes (fat cells) contain almost nothing but triglycerides

Lipids … Phospholipids Glycerol

backbone with one of the fatty acids replaced by a polar phosphate group

Major component of membranes

Amphipathic

Lipids … Glycolipids Phospholipid with

one or more carbohydrates attached to glycerol rather than phosphate

Also amphipathic Found in the

membranes of myelinated cells of the nervous system

Lipids … Steroids & TerpenesSteroids Terpenes 4-ringed structure Includes hormones,

vitamin D, & cholesterol

Includes vitamin A (important for vision)

Lipids are transported by lipoproteins in the blood

Classified by their density: (the greater the ratio of lipid to protein, the lower the density) Very low density lipoproteins (VLDL) Low density proteins (LDL) – ‘bad

cholesterol’ High density lipoproteins (HDL) – ‘good

cholesterol’

Proteins

Building block is amino acids linked together by a peptide bond

AKA polypeptides Nearly all protein in all species are

built from the same 20 amino acids 10 are essential (ingested rather

than manufactured by body) Side chains differ from amino acid to

amino acid

Protein StructurePrimary Structure Secondary Structure

Number and sequence of amino acids in a polypeptide

Single chain can twist into an α-helix or β-pleated sheets

Both are reinforced with H-bonds between amino acids

Protein Structure…Tertiary Structure Quaternary Structure

3-D shape formed when the peptide chain curls and folds

Created by 5 forces: Covalent disulfide

bonds b/w cysteine Electrostatic ionic

interactions (acidic & basic)

Hydrogen bond Van der Waals forces Hydrophobic side chains

push away from water toward center

Protein Structure…

Quaternary Structure 2 or more polypeptide

chains bond together Same 5 forces as

tertiary

A denatured protein has lost secondary, tertiary, and quaternary structure Protein can sometimes form back when

denaturing agent is removed 2 main functions of proteins:

Structural (cell wall) Functional (enzymes)

2 main types of proteins: Globular (functional)

Enzymes Hormones Membrane pumps & channels Membrane receptors Intercellular and intracellular transport and

storage Osmotic regulators Etc.

Structural – maintain and add strength to cells Ex. Collagen

…

Central Dogma

DNA → RNA → protein ↑ ↑

transcription translation

Genotype Phenotype

Carbohydrates AKA sugars or saccharides Glucose accounts for 80% of carbs

absorbed by humans Liver converts most carbs to glucose

Glucose turned to ATP during cellular respiration If cell has enough ATP, the glucose is turned to

glycogen (only animals) or fat Most cells absorb glucose via facilitated

diffusion – insulin increases absorption rate Plants form cellulose and starch from

glucose

Carbohydrates … Building blocks are simple sugars

(monosaccharides) glucose, ribose, etc

Cell wall constituents (peptidoglycan) Cell recognition factors in membranes

lipopolysaccharides Serves as high energy storage compounds

(glycogen) Serve as bacterial ‘food’

(chemoheterotrophs)

2 monosaccharides make a disaccharide

Monomer to disaccharide to polysaccharide

Nucleic Acids Building blocks are nucleotides:

5-C Sugar, phosphate group, & nitrogen base

Nitogen bases: adenine, cytosine, guanine, thymine, uracil (a=t) & (c=g) & (a=u)

Nucleotides joined by phosphodiester bonds

Examples of nucleic acids include DNA, RNA, ATP, NADH, FADH2

DNA is written 5’ to 3’

Functions – information storage RNA has multiple functions:

mRNA – RNA copy of DNA rRNA – part of ribosome, helps to make

proteins tRNA – carries amino acids to ribosome

Pop Quiz1. A molecule of DNA contains all of the

following except:a) Deoxyribose sugarsb) Polypeptide bondsc) Phophodiester bondsd) Nitrogenous bases

2. Which of the following is a carbohydrate polymer that is stored in plants and digestible by animals?

a) Starchb) Glycogenc) Cellulosed) Glucose

…cont.3. Excessive amounts of nitrogen are found in the

urine of an individual who has experienced a period of extended fasting. This is most likely due to:

a) Glycogenolysis of the liverb) The breakdown of body proteinsc) Lipolysis in adipose tissued) A tumor on the posterior pituitary causing excessive ADH

secretion4. Metabolism of carbohydrate and fat spare protein

tissue. All of the following are true of fats except:e) Fats may be used in cell structuref) Fats may be used as hormonesg) Fats are more efficient form of energy storage than

proteinsh) Fats are less efficient form of energy storage than proteins

… cont.

5. Which of the following is found in the RNA but not the DNA of a living cell?

a) Thymineb) Double helixc) An additional hydroxyl groupd) Hydrogen bonds

Answers

1. B2. A3. B4. C5. C