Chapter 2 Microbiology

Atom

smallest unit of matter

contains a nucleus and an electron cloud

composed of subatomic particles

join together to form molecules

Ionic Bonds

attractions between cations (electron donor) and anions (electron acceptor)

Cation

positively charged ion

anion

negatively charged ion

covalent bonds

involves sharing electrons

Hydrogen bonds

weak polar bonds based on partial electrical attractions

Decomposition reactions

breaks down chemical bonds

AB→ A + B

Hydrolysis

“water loosening or breaking”

ABCDE + H2O→ABC -- H + HO -- DE

Catabolism

breakdown of complex molecules withing body cells that produces energy

\--CD → C + D + energy

Synthesis Reaction

Forms chemical bonds

A + B → AB

Dehydration Synthesis (condensation)

* formations of a water molecule
* ABC-- H + OH -- DE → ABCDE + H20

Anabolism

synthesis of new molecules within body cells that uses energy

\-- C + D + energy → CD

Exchange Reaction

involves decomposition of first, then synthesis

\-- AB + CD → AD + CB

Reversible Reaction

occurs simultaneously in both directions

* AB

Enzymes

protein catalysts that lower the activation energy of reactions

not changed or used up in a reaction

Activation energy

amount of energy needed to get a reaction started

chemical reactions in cells cannot start without help

Exergonic (exothermic) reactions

produce more energy than they use

generates body heat

Endergonic (endothermic) reactions

use more energy than they produce

uses body heat

solution

mixture of 2 or more substances

solvent

medium (liquid, air)

solute

atoms, ions, or molecules which are dispersed (or dissolved) in solvent

solubility

water’s ability to dissolve a solute in a solvent to make a solution

ionization (dissociation)

ionic bonds broken in water due to polarity of water

hydration sphere

sheath of water molecules around an ion in solution

hydrophilic

water loving

molecules that interact readily with water molecules

ions, polar molecules

H+

extremely reactive in solution

pH

concentration of hydrogen ions (H+) in solution

concentration

the amount of solute in a solvent (mg/mL)

Neutral pH

balance of H+ and OH-

\-pH of human blood -- from 7.35 to 7.45

Acidic

pH lower than 7.0

high H+ concentration

Basic (alkaline)

pH higher than 7.0

low H+ concentration

pH scale

inverse relationship with \[H+\]

ranged from 0-14

acid

a solute that dissociates in solution & releases H+

proton donor

strong acids dissociates completely in solution (HCI)

HCI → H+ Cl-

Base

a solute that removes hydrogen ions from a solution

proton acceptor

strong bases dissociate completely in solution (NaOH)

NaOH → Na+ OH-

weak acids & weak bases

fail to dissociate completely (carbonic acid → bicarbonate)

H2CO3 → H+ + HCO3

help balance the pH

salts

solution that dissociate into cations and anions (except hydrogen ions and hydroxide ions)

NaCl → Na+ + Cl-

buffers

stabilize pH by removing or replacing H+

neutralizes either a strong acid or strong base

sodium bicarbonate is very important in humans

buffers carbonic acid

antacids

a basic compound that neutralizes acid and forms a salt

tums, rolaids

inorganic compounds

molecules not based on carbon or hydrogen

oxygen, water, inorganic acids, bases and salts, carbon dioxide

usually small and structurally simple

organic compounds

molecules based on carbon or hydrogen

carbohydrates, proteins, lipids, nucleic acids

functional group

an arrangement of atoms in an organic molecule that is responsible for most of the chemical properties of that molecule

organic molecules

contain H, C and usually O

covalently bonded

contain functional groups that determine chemistry

macromolecules

polymers consisting of many small repeating molecules called monomers

monomers join by dehydration synthesis reactions

carbohydrates

contain C, H, O in a 1:2:1 ratio

monosaccharides

simple sugars with 3 to 7 carbon atoms

disaccharides

two simple sugars condensed by dehydration synthesis

polysaccharides (starches)

many monosaccharides condensed by dehydration synthesis

hydrolysis breaks disaccharides → monosaccharides

structure of glucose

(picture)

structure of polysaccharide glycogen

(picture)

lipids

* carbon: hydrogen ration is 1:2
* contain much less O than carbs
* nonpolar & insoluble in water
* hydrophobic molecules: fats, oils, waxes
* need transporter in blood
* fatty acids, eicosanoids, glycerides, steroids, phospholipids, glycolipids
* primary components of cell membranes

simple lipids

* fats or triglycerides
* contain glycerol and fatty acids
* formed by dehydration synthesis
* broken by hydrolysis
* chains of hydrocarbons

saturated

with hydrogen (no double bonds)

Unsaturated

( one or more double bonds between carbons)

complex lipids

contains C, H, and O & P, N, or S

phospholipids that make up membranes

hydrophilic

* water loving
* interacts with water
* ions and polar molecules

hydrophobic

* water fearing
* does not interact with water
* nonpolar molecules, fats, oils

steroids

* four carbon rings with OH- group attached to one ring
* part of membranes; keeps membranes fluid

proteins

* most abundant and important organic molecules
* contains C, H, O, N
* 20 amino acids - building blocks
* amino acid structure
* central carbon atom
* hydrogen atom
* amino group (--NH2)
* carboxylic acid group (--COOH)
* variable side chain or R group

amino acids

* exist in either of two stereoisomers: D or L
* L- forms are most often found in nature

connecting amino acids

requires dehydration synthesis between amino group and carboxylic group producing a peptide bond

7 major protein functions

* support- structural proteins
* movement- contractile proteins
* transport- transport (carrier) proteins
* buffering- regulation of pH
* metabolic regulation- enzymes
* coordination and control- hormones
* defense- antibodies

protein structure

* conjugated proteins- consists of amino acids combined with other organic molecules
* glycoproteins
* nucleoproteins
* lipoproteins

primary structure

the sequence of amino acids along a polypeptide

secondary structure

hydrogen bonds form spirals or pleats

tertiary structure

secondary structure folds into a unique shape

quaternary structure

final protein shape - several tertiary structures together

denaturation

change in structure

due to temp, pH changes

protein becomes nonfunctional

fibrous proteins

extended sheets or strands

globular proteins

soluble spheres with active functions

protein function based on shape

shape based on sequence of amino acids

denaturation

proteins can undergo this

occurs when proteins encounter hostile environments such as temperature and pH

causes proteins to lose their shapes and functions

nucleic acids

* large organic molecules found in nucleus
* store & process information at molecular level

deoxyribonucleic acid (DNA)

* determines inherited characteristics
* directs protein synthesis
* controls enzyme production
* controls metabolism

ribonucleic acid (RNA)

controls and performs intermediate steps in protein synthesis

nucleotides

building blocks of DNA, RNA

3 molecular parts:


1. sugar (deoxyribose or ribose)
2. phosphate groups
3. nitrogenous base

(A, G, T, C, or U)

DNA

double stranded

* bases form hydrogen bonds to hold together
* twisting double- helix
* purines pair with pyrimidines
* adenine (A) to thymine (T)
* cytosine (C) to guanine (G)

RNA

usually single stranded

* uracil (U) replaces thymine; binds to adenine
* messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA)

high energy compounds

nucleotides can be used to store energy

adenosine diphosphate (ADP)

two phosphate groups; di- = 2

adenosine triphosphate (ATP)

3 phosphate groups; tri- = 3