Cells

Section 3-3: Cell Processes

Metabolism

The sum of all building-up and breaking-down activities that occur in a living cell

Respiration

The process in which simple food substances such as glucose are broken down and the energy they contain captured in high energy molecules that can be used as fuel by the cell

Aerobic Respiration

Requires oxygen Occurs in the mitochondria C6H12O6 + 6O2 6CO2+ 6H2O +energy

(glucose) (ATP)

Aerobic Respiration

Although the equation is simple the process is complicated, involving many different molecules and many steps

Anaerobic Respiration

Does not use oxygen Provides much less energy Fermentation (such as the process used to

make wine) is a form of anaerobic respiration

Used by yeast that produce alcohol and carbon dioxide

Photosynthesis

Occurs in chloroplasts Also a very complex process 6CO2+ 6H2O + energy C6H12O6 + 6O2

(glucose) The energy is captured from light by

chlorophyll

Diffusion

The process by which molecules of a substance move from an area of higher concentration of that substance to areas of lower concentration of that substance

Occurs because of the constant motion of molecules that causes them to spread out until they are evenly distributed in the available volume

Diffusion

Is a physical process that does not require the input of energy from a living organism

A B C

Diffusion into a Cell

Diagram by Mariana Ruiz Villarreal, released to public domain

Osmosis

The diffusion of water into or out of a cell Many single-celled organisms that live in

fresh water use contractile vacuoles to pump excess water out of the cell. The water enters the cell by osmosis.

Semi-permeable Membranes

Cell membranes are semi-permeable or selectively permeable

This means that only certain molecules can diffuse through them including:

Water Oxygen Carbon dioxide Small food molecules

Osmosis

Of Salt

Of Salt

Higher Concentration of Water Molecules

Lower Concentration of Water Molecules

Active Transport

The process by which a cell moves molecules into and out of the cell that cannot diffuse through the membrane

Requires energy to work

Active Transport

One method uses special transport molecules (proteins) that pick up a specific substance on one side of the membrane and moves it to the other side

This is how ions of calcium (Ca), potassium (K) and sodium (Na) move

Active Transport

Diagram by Mariana Ruiz Villarreal, released to public domain

Active Transport

A second type of active transport is called phagocytosis.

A cell surrounds a food particle with a pocket of cell membrane which pinches off into the cell to form a food vacuole

Active Transport-Phagocytosis

Drawing of an ameba engulfing a bacterium