Chemical Compounds in Cellsand

The Cell in its Environment

Elements and Compounds What is an element?

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

The smallest unit of an element is an atom.

All living things include carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur.

What is a compound? A compound is made up of two or more

elements. Carbon dioxide is a compound. What

elements make up carbon dioxide? Carbon and oxygen

Organic and Inorganic Compounds

o Organic compounds contain carbon, inorganic compounds do not.

o Carbohydrates, lipids, proteins and nucleic acids all contain carbon. oThese are common compounds in

the food we eat.

Organic Compounds• Carbohydrates-

energy rich– Sugars are

produced during the food making process in plants

– Fruits and some vegetables have high sugar content

• Lipids- energy rich– Fats, oils and

waxes are lipids– Cell membranes

are made of lipids

More Organic Compounds• What do bird’s

feather, a spider’s web and your finger nail have in common?– They are all made

of protein.– Proteins are made

up of amino acids – There are 20

common ones that combine to form thousands of different proteins.

• Much of the structure and many of the organelles of cells are made up of proteins.

Water• Most chemical reactions within

cells could not take place without water.–Water helps cells keep their size

and shape.–Water helps keep the temperature

of the cell from changing rapidly.

The Cell in Its Environment• The cell membrane separates the

cell from the outside environment.• The cell membrane is selectively

permeable.– This means some substances can

pass through while others cannot.

Diffusion• Diffusion is the main method by

which molecules move across the cell membrane.– In diffusion, molecules ALWAYS

move from an area of higher concentration to an area of lower concentration.

Osmosis

• Osmosis is the diffusion of water through a semipermeable membrane.

• Cells depend on osmosis because, they cannot function properly without water.

• Why can’t people drink large amounts of salt water?

Active Transport• Passive transport if the movement

of dissolved material through the cell membrane without using cellular energy (high to low).

• Active transport requires cellular energy (low to high). This can be done in 2 ways.– Transport proteins “pick-up” method– Engulfing