Air is a mixture of gases, including oxygen and nitrogen

Oxygen and nitrogen are elements

An element is any substance that cannot be broken down into simpler substances

An atom An element

is made up of only one kind of atom

Carbon, oxygen, hydrogen, and nitrogen

A compound Example:

Water is a compound made up of the elements hydrogen and oxygen

A molecule A water

molecule is made up of two hydrogen atoms and one oxygen atom

Carbon Compounds

that contain carbon are called organic compounds

Carbohydrates, lipids, proteins, and nucleic acids

Many of these are found in food

Inorganic Compounds

Exception: Carbon dioxide is classified as inorganic even though it contains carbon

Examples: Water, and sodium chloride

An energy-rich organic compound made up of the elements carbon, hydrogen, and oxygen

Example: sugars and starches

During the food-making process that takes place in plants

Sugar molecules combine forming large molecules called starches

Plant cells store excess energy in molecules of starch

Examples of starchy foods: potatoes, noodles, rice, and bread

Our body breaks down the starch into glucose (a sugar) which our cells use to produce energy

Large organic molecules made of carbon, hydrogen, oxygen, nitrogen, and in some cases sulfur

Proteins make up our fingernails and spider webs

Examples of food high in protein: meat, eggs, fish, nuts, and beans

Smaller molecules called amino acids

Cells combine the 20 common amino acids to form thousands of different proteins

The type of protein formed depends on the kind of amino acid and the order with which they form, very much like how letters in the alphabet make different words; rice also spells mice

AlanineArginineAsparagineAspartic Acid

CysteineGlutamic Acid

GlutamineGlycineHistidineIsoleucineLeucineLysineMethioninePhenylalanine

ProlineSerineThreonineTryptophanTyrosineValine

A type of protein that speeds up a chemical reaction in a living thing

Example: Enzymes in your saliva speed up digestion by breaking down starches into sugar

Fats, oils, and waxes are all lipids

Like carbohydrates, lipids are energy-rich organic compounds made of carbon, hydrogen, and oxygen

Lipids contain more energy than carbohydrates

Cholesterol is a lipid that our bodies need – our liver produces enough

Excess cholesterol collects along blood vessels and blocks the flow of blood

Meat, cheese, and eggs are high in cholesterol

Very large organic molecules made of carbon, oxygen, hydrogen, nitrogen, and phosphorus

These contain the instructions that cells need to carry out all the functions of life

There are two kinds: DNA and RNA

Deoxyribonucleic acid The genetic material

that carries information about an organism that is passes from parent to offspring – directs all of the cell’s functions

Most of the DNA is found in the chromatin in the nucleus

Ribonucleic Acid

Plays a role in the production of proteins

Found in the cytoplasm, as well as in the nucleus

Water Without water,

most chemical reactions could not take place

Water helps the cells keep their size and shape and carries substances into and out of the cell

How is the cell membrane like a gatekeeper?

The cell membrane is selectively permeable – some substances can pass through while others cannot

Diffusion Osmosis Active Transport

The process by which molecules tend to move from an area of higher concentration to an area of lower concentration

Molecules are always moving, bumping into each other as they do

The more molecules in an area the more collisions – these collisions cause them to spread out eventually spreading evenly across an area

The diffusion of water molecules through a selectively permeable membrane

The movement of materials through a cell membrane without using energy

Diffusion and Osmosis

The movement of materials through a cell membrane using energy

Active transport requires the cell to use energy while passive transport does not

Transport proteins Transport by engulfing

Transport proteins in the cell membrane “pick up” molecules outside and inside the cell to move them like a bus moves people.

These substances include calcium, potassium, and sodium

The cell membrane engulfs (or surrounds) a particle

It would take much longer for a molecule to reach the center of a very large cell than it would in a small cell

When a cell reaches a certain size it divides into two new cells