Chemical Basis of Life

Basic Chemistry

All matter on Earth is made from approx. 100 elements!!

Element-a substance that cannot be broken down by chemical processes into simpler substances– Atom-smallest form of an element

Compounds

A substance that is made of two or more elements chemically combined in definite proportions– Ex: H2O (water) Always two hydrogen molecules for every one Oxygen molecule

Organic Compounds

Generally associated with living things

All contain Carbon!!

Structure of an Atom

Protons: positively charged particles

Electrons: negatively charged particles

Neutrons: neutral particles

Periodic Table: Atomic Number = the number of protons

H = 1, O = 8

Atom: Just the facts

Atoms of the same element have the same number of protons and electrons

Atoms of the same element can have different numbers of neutrons = Isotopes

Radioactive: nucleus splits apart spontaneously (gives off energy)– Releases charged particles and radiation

Electrons

Orbit around the nucleus in specific energy levels– First energy level requires 2 electrons

– other energy levels require 8 electrons

Electrons (cont’d)

Atoms are most stable when their outer energy levels are “full”

Atoms will gain or lose electrons in order to fill the outermost level

The remaining atom is called an ion

Ions

Atoms with a positive or negative charge

Losing electrons = positiveGaining electrons = negative

Chemical bonds

Attractions that hold two or more atoms together– Whenever a chemical bond is formed or broken energy is absorbed or released (heat)

Three types: Ionic, Covalent, Hydrogen

1. Ionic Bonds

Formed between ions with opposite charges resulting in a compound that has no electrical charge

IMPORTANT—electrons are lost by one element and gained by another

EX: NaCl (table salt)

2. Covalent Bonds

Electrons are not gained or lost… they are shared (ex: water)

Covalent bonds create molecules!

See pages 40 & 41

Polar Molecules

Molecules in which electrons are not shared equally between atoms

This causes the molecules to have one slightly positive end and one slightly negative endO

H HFigure 2.12+ +

Hydrogen Bonds

Bonds that occur between molecules containing hydrogen

Important—properties of water and the chemistry of living things!

O

H+ +

Opposites attract

H+

+

Chemical formulas

Shows what type of atoms are in a compound or molecule– Empirical formula: shows simplest

proportions of atoms in compounds– Structural: shows number and type of

atoms as well as how they are bonded– Molecular: Shows number and types

of atoms (most common)

Simple Variety

Not all living things are as complex as humans

Most living things are made up of only four kinds of chemicals…

1. Carbohydrates

“chemical energy”– Sugars, starches, and cellulose

– Store energy and provide shape

Carbohydrates (cont’d)

Three types of sugars1. Monosaccharides 2. Disaccharides

3. Polysaccharides

Complex Carbohydrates

What do we use them for???Energy storage! In the form of

glycogen (in muscles and liver)

Plants store energy also! In the form of starch! (potatoes, wheat, grains)

Cellulose

Most abundant molecule on Earth

Storage for simple sugarsFound in desks, paper, pencils,

etc.

2. Lipids

“long term energy storage”Fats, oils, waxes, steroidsLipids are converted into fat

when too many are consumed

Lipids are important!!

Cell membranes are made of phospholipids

Waxes repel water– Fruits and leaves retain water– Ducks are waterproof

3. Proteins

Main control system in your bodyLarge complex molecules

composed of amino acids– Only 20 amino acids combine to make up the countless numbers of proteins that make up all living things!

The Importance of Protein!

Important for movement, structure, regulation, transport, nutrition, defense

Insects use proteins called pheromones to communicate

4. Nucleic Acid

Makes you who you are!Large, complex molecules that

contain genetic information

DNA

Deoxyribonucleic acid– Carries all of the instructions needed to make an organism

Heredity: the passing of genetic information from parent to offspring

RNA

Ribonucleic Acid– Uses DNA’s instructions to make proteins

Chemical Reactions

The breaking of bonds to change one or more substancesEx: remember the cracker, as the saliva broke down the starch the cracker began to have a sweet taste!

How did it do that????

Remember starch is a polysaccharide (carbohydrate)– The saliva breaks down the polysaccharide into simple sugars!

You were a part of a chemical reaction!!

Chemical Reaction

One or more substances is changed into a new substance by the breaking or forming of chemical bonds

Chemical Equation

Describes what happens in a chemical reaction

(reactants) (products)C6H12O6 + 6O2 6H2O + 6CO2 +

energy(Glucose)

Chemical Reactions & Energy

All chemical reactions are either…

1. Absorb energy = endothermic2. Release energy = exothermic

-The energy that is given off when a substance is formed is equal to the energy needed to break it down!!

How to speed up a chemical reaction…

1. Temperature—an increase in temperature = an increase in chemical reaction rate (why??)

2. Catalyst—a substance that speeds up or slows down a reaction (it is not used or changed in the reaction)

Catalyst

All living organisms contain catalysts = enzymes!– An enzyme is a protein catalyst that speeds up the chemical reactions within an organism by reducing the amount of activation energy needed

Pg. 44 Figure 2.15

Enzyme Facts

Names usually end in –aseHave a specific shape so they only

fit one substrate (lock & key)They are never actually used up in

the reactionAllow reactions to occur in an

organisms without increasing the organism’s temperature.

Enzyme Specifics

A substrate bonds to an enzyme at the active site.

Once the enzyme and substrate are bonded together the enzyme changes shape to ensure the substrate will stay attached = induced fit

The enzyme + substrate = E-S complex

1. What are enzymes made out of?2. What do enzymes do?3. Molecules that can bind with

enzymes are called_________.4. Why does heating an enzyme

change its function?

1. What enzyme broke down H2O2?2. Where was the enzyme located?3. What were the products of the

reaction?4. What are enzymes made out of?

Chemistry in Life Processes

How does the food you eat keep you warm?– Food releases energy when it breaks

down chemically, some is in the form of heat

– energy is stored in the chemical bonds of the food we eat—it is released by chemical reactions (digestion)

Major life processes

MetabolismCommunicationReproductionHomeostasisGrowth and Repair

Metabolism

The combination of all of the chemical changes that takes place in an organism– Organisms break chemical bonds

(digestion) in compounds to release energy

– Plants and some organisms can use sunlight to make energy-rich compounds

– Products of chemical reactions = heat and wastes

– To grow and develop, cells of organisms must make new carbohydrates, proteins, and lipids—also to make repairs

– Regeneration-the process of growing back a lost body part

Homeostasis

Tendency of an organism to maintain stable internal conditions– Ex: sweat to cool body, panting

Communication

Internal – neurotransmittersFeedback loop- series of reactions

that help maintain homeostasis by controlling chemical reactions

Pheromones—insects use this protein to communicate(ants form a line to food)

Water and Solutions

Life processes depend on the properties of water and the characteristics of solutions– Solution: uniform mixture of 2 or more substances; cannot distinguish between the substances

Water and Solutions (cont’d)

– Solute: the dissolved substance in a solution

– Solvent: the dissolving substance Ex: Ice tea = solvent

Sugar = solute-Suspension: mixture that separates upon standing

Water-the universal solvent

Water will form a solution with most ionic compounds

Why????Because it is a polar

molecule!(partial charges)

Water

Cohesion—sticking togetherExpansion—water expands

when it freezes….allowing it to floatWhy is that important???

Allows pond-dwelling organisms to survive

Acids, Bases, and Salts

When ionic compounds form solutions the compound breaks apart and releases ions– Acid: releases H+ (hydrogen)ionsEx: orange juice, HCl, vinegar

HCl H + Cl

– Base: releases OH- (hydroxide)ionsEx: NaOH (sodium hydroxide), soaps, ammonia, baking soda

NaOH Na + OH

– Salt: releases ions other than H+ and OH-Ex: NaCl (table salt)

NaCl Na + Cl

When water breaks apart (disassociates) in a solution it releases both H+ and OH- ions= Neutralization reactionNaOH + HCl H2O + NaCl

(base) (acid) (water) (Salt)

pH scale

Measure of the concentration of H+ ions in a solution

So, what mechanism keeps our pH at 7.4?

1 2 3 4 5 6 7 8 9 10 11 12 13 14

ACID Neutral BASE

Why is this important???

Burning fuels such as coal, oil, and gasoline releases sulfur and nitrogen compounds into the air

What’s also in the air??Water!!

Acid Rain

When these things mix H+ ions are released…causing the rain to become acidic

Acid rain has a pH of less than 5.6Destroys minerals in the soil vital

to plants…no plants no peopleDecreases the Ph in lakes…killing

aquatic life

Page 54– Questions 1-5– Write the answers

Tell me all you know about enzymes and the liver lab.– What is an enzyme? Why does it have an active site? What enzyme did we use in the lab? What substrate did it break down? Etc…

Read “The Molecules of Life”– Answer post test questions 1-11