Thread by @knows_med

BIOCHEMISTRY ---- A THREAD 📚

author: marieb (ninth edition)

Biochemistry- is the study of the chemical compisition and actions of living matter. All chemicals in the body fall into one of two major classes: organic or inorganic compounds.

Organic compounds
- contain carbon.
-All organic compounds are covalently bonded molecules, and many are large.

Inorganic compounds
-All other chemicals in the body
-These include water, salts, many acids and bases.

Example of Inorganic Compounds are:
• Water
Importance of water:
-high heat capacity
-high heat of vaporization
-polar solvent properties
-reactivity
-cushioning

Salts
A salt is an ionic compound containing cations other than H+ and anions other than the hydroxyl ion (OH-).

Acids and Bases
Acids- have a sour taste, can react with (dissolve) many metals, and "burn" a hole in your rug.
Bases- have a bitter taste, feel slippery

Carbohydrates
-A group of molecules that includes sugars and tarches, represent 1-2% of cell mass.
-It contanins carbon, hydrogen, oxygen.
-It can classified according to size and solubility as a monosaccharide (one sugar), disaccharide (two sugars) or polysaccharide (many sugar)

Monosaccharides
-simple sugars
-single-chain /single-ring structures containing from three to seven carbon atoms.

Disaccharide
-double sugar
-formed when two monosaccharides are joined by dehydration synthesis.

Polysaccharides
-polymers of simple sugars linked together.

Lipids
- are insoluble in water but dissolve readily in other lipids and in organic solvents such as alcohol and ether.
-all lipids contain carbon, hydrogen, and oxygen but the proportion of oxygen in lipids is much lower.

Proteins
-composes 10-30% of cell mass and is the basic structural material of the body.
-proteins which include enzymes (biological catalyst), hemoglobin of the blood etc.
-all proteins contain carbon, oxygen, hydrogen, and nitrogen, and many contain sulfur as well.

Amino Acids and Peptide Bonds

Amino acid structures
a. Generalized structure of all amino acids.

b. Glycine- simplest amino acids

c. Aspartic acid- has an acid group (---COOH) in the R group.

d. Lysine-( a basic amino acid) has an amine group. (--NH2) in the R group.

e. Cysteine- (a basic amino acid) has a sulfhydry (--SH) group in the R group, which suggests that this amino acid is likely to participate in intramolecular bonding.

Structural Levels of Proteins
a. Primary structure- the sequence of amino acids forms the polypeptide chain.

b. Secondary syructure- The primary chain forms spirals and sheets.

c. Tertiary structure- Superimposed on secondary structure. Helicates and sheets are folded up to form a compact globular molecule held together by intramolecular bonds.

.

d. Quaternary Structure- Two or more polypeptide chains, each with its own tertiary structure, combine to form a functional protein.

Enzymes and Enzyme Activity
Enzymes are globular proteins that act as a biological catalysts.

Three basic steps appear to be involved in enzyme action.

1. Substrate(s) bind to the enzyme's active site, temporarily forming an enzyme-substrate complex.

2. The enzyme-substrate complex undergoes internal rearrangements that form the product(s).

3. The enzyme releases the product(s) of the reaction.

Nucleic Acids (DNA and RNA)

Nucleic acids-composed of caebon, oxygen, hydrogen, nitrogen and phosphorous, are the largest molecules in the body.

The nucleic acids include two major classes of molecules:

1. deoxyribonucleic acid (DNA)
2. ribonucleic acid (RNA)

The structural units of nucleic acids, called nucleotides, are quite complex. Each nucleotide consists of three componets: a nitrogen-containing base, a pentose sugar, and phosphate group.

Five major varieties of nitrogen-containing bases can contribute to nucleotide structure:

1. adenine
2. guanine
3. cytosine
4. thymine
5. uracil

Comparison of DNA and RNA
DNA
Major cellular site: Nucleus
Major functions: Is the genetic material; directs protein synthesis; replicates itself before cell division.
Sugar: Deoxyribose
Bases: denine, guanine, cytosine, thymine.
Structure:Double strand coiled into a double helix

RNA
Major cellular site: Cytoplasm (cell area outside the nucleus)
Major functions: carries out the genetic instructions for protein synthesis
Sugar: Ribose
Bases: Adenine, guanine, cytosine, uracil.
Structure: Single strand, straight or folded.

Adenosine Triphosphate (ATP)

-ATP is the primary energy-transferring molecule in cells and it provides a form of energy that is immediately usable by all body cells.
-ATP can be compared to a tightly coiled spring ready to uncoil with tremendous energy when the catch is released

-ATP is a very unstable energy-stroring molecule because its three negatively charged phosphate groups are closed packed and repel each other.

for illustration

(c) Marieb (ninth edition)

for illustration

(c) Marieb (ninth edition)

for illustration

(c) Marieb (ninth edition)