Chapter 2

Chemistry Comes Alive

Objectives

• Describe the important structural characteristics of monosaccharides, disaccharides, and polysaccharides.

• Explain the functions of carbohydrates in living things.

Organic Compounds

• What is an organic compound?– A molecule

made of carbon

What kinds of organic compounds are there, and

how do they work?

Carbohydrates

• Carbohydrates– Organic compounds

– Made of C, H, and O (1:2:1)

• Functions– Energy source (FUEL!)

• Where they are found– Most foods

– Fruits, vegetables, grains

Carbohydrates

• Monosaccharides– Building blocks of

carbohydrates

– Single sugars

– Between 3-7 C atoms

• Ex:– Glucose (C6H12O6)

– Fructose

Carbohydrates

• Disaccharides– Double sugars

– Formed when 2 monosaccharidesjoin

• Ex:– Sucrose (made of

fructose and glucose)

Carbohydrates

• Polysaccharides– Chains of 3 or more

monosaccharides

• Ex:– starch

Objectives

• Describe the structures of fatty acids, triglycerides, phospholipids, and steroids.

• Explain the functions of lipids in living organisms.

• Identify some reactions that fatty acids undergo.

• Relate the structure and function of the cell membrane.

Lipids

• Functions:– Energy storage

– Structure of membranes

• Ex:– Hydrophobic molecues:

• Fats, oils, waxes

• Structure:– C and H atoms

Fatty Acids

• Saturated Fatty Acid– All C atoms are fully

bonded with H atoms

• Unsaturated Fatty Acid– Not all C atoms are full

– Double bonds

– Causes “kinks” in the structure

Triglycerides

• 3 fatty acid tails attached to a glycerol molecule

• Fat storage molecule

Phospholipids

• Have hydrophilic heads and hydrophobic tails

• Structural, make up the cell membrane

Steroids

• Cholesterol:– Component of cell membrane

• Estrogens and testosterone:– Sex hormones

• Corticosteroids and calcitrol:– Metabolic regulation

• Bile salts– Derived from steroids

Steroids

• Structure– 4 carbon rings

Review!!

1. All organic compounds in the human body contain all of the following except _____.a. Hydrogen

b. Oxygen

c. Carbon

d. Calcium

e. Both a and d

2. A food contains organic molecules with the elements C, H, and O in a ratio of 1:2:1. What class of compounds do these molecules belong to?

a. Carbohydrates

b. Lipids

c. Proteins

d. Nucleic acids

3. What type of molecule is formed when two monosaccharides are joined?a. Glucose

b. Fructose

c. Disacccharide

d. Steroid

e. Corticosteroid

Objectives

• Describe the structures of proteins and amino acids.

• Explain the functions of proteins in living organisms.

• Identify some reactions that amino acids undergo.

• Relate the structure and function of enzymes.

Proteins

• The most abundant and important organic molecules

• Structure:– C, H, O, and N

• Building blocks– Amino acids

– 20 AA found in proteins

Proteins

• Functions:– Support

– Movement

– Transport

– Buffering (regulating pH)

– Metabolic regulation (enzymes)

– Coordination and control (hormones)

– Defense (antibodies)

KEY CONCEPT!!

• Proteins:– Control anatomical structure and

physiological function

– Determine cell shape and tissue properties

– Perform almost all cell functions

Nucleic Acids

• Large organic molecules

• Found in the nucleus

• Store and process information at the molecular level

• Ex:– DNA

– RNA

Nucleic Acids

• Building blocks:– Made up of nucleotides

• Nucleotides– Made up of 3 parts:

• Sugar

• Base

• Phosphate group

Bases

• A-T• G-C

Deoxyribonucleic Acid (DNA)

• Double-stranded

• Determines inherited characteristics

• Directs protein synthesis

• Controls enzyme production

• Controls metabolism

Ribonucleic Acid (RNA)

• Single-stranded

• Codes intermediate steps in protein synthesis

KEY CONCEPT!!!

• DNA in the cell nucleus contains the information needed to construct all of the proteins in the body

ATP

• Adenosine triphosphate– Single nucleotide

– Energy storing molecule

Objectives

• Explain the role of enzymes as catalysts that lower the activation energy of biochemical reactions.

• Identify factors, such as pH and temperature, and their effect on enzyme activity.

How do enzymes control metabolism?

Materials in Reactions

• Reactants: – materials going into a reaction

• Products: – materials coming out of a reaction

• Enzymes: – proteins that lower the activation energy of a reaction

Energy In, Energy Out

• Exergonicreactions: – produce more

energy than they use

• Endergonicreactions: – use more energy

than they produce

Enzymes, Energy, and Chemical Reactions

Most rxns do not occur spontaneously They need energy to start

(activation energy) Enzymes lower the activation

energy, start rxns Also called catalysts Most rxns necessary for life

require enzymes Exergonic rxns release

energy Endergonic rxns absorb

energy

What is pH and why do we need buffers?

pH

• pH: – the concentration of hydrogen ions (H+) in

a solution

• Neutral pH: – a balance of H+ and OH—

– pure water = 7.0

Acids and Bases

• Acid (acidic): pH lower than 7.0 – high H+ concentration,

low OH— concentration

• Base (basic): pH higher than 7.0– low H+ concentration,

high OH— concentration

pH Scale

• Has an inverse relationship with H+ concentration: – more H+ ions mean lower pH, less H+ ions

mean higher pH

KEY CONCEPT

• pH of body fluids measures free H+ ions in solution

• Excess H+ ions (low pH): – damages cells and tissues– alters proteins– interferes with normal physiological

functions

• Excess OH— ions (high pH) also cause problems, but rarely

Controlling pH

• Buffers: – weak acid/salt compounds

– neutralizes either strong acid or strong base