Cell Processes Notes
Cells perform 5 processes to keep them alive: metabolism, respiration, diffusion, osmosis, and active
transport.
METABOLISM – the sum total of all chemical changes that take place in living organisms. It includes
cell activities such as absorption of food, releasing energy from food, growth and repair of cells, making
protein, getting rid of waste, maintaining homeostasis, and carrying out cell division. All these things
require a lot of energy. The rate of an organism’s metabolism may vary. The rate of metabolism in a
young organism is higher than in an older organism and higher in an organism that is active than in
someone or something that sits around and doesn’t exercise.
Enzymes are proteins that control most chemical changes that occur in an organism. Enzymes
SPEED UP the rate of chemical changes. Nucleic acids form the code for making enzymes and thus
control cell activities. They are made in the nucleus of the cell and in the ribosomes.
Homeostasis is the tendency of a living organism to adjust itself to maintain a balanced state. For
example, when an organism needs more energy, the mitochondria will speed up their activity. An
organisms feedback system signals an increase or decrease in cell activity to permit homeostasis.
CELL TRANSPORT PROCESSES
Living cells need many kinds of
substances to remain alive, such as water,
sugar for energy, oxygen (animals), carbon
dioxide (plants), and amino acids for
proteins. Materials may pass through the
cell membrane when in water solution.
Transport processes control the amount of
each entering and leaving the cell.
Certain materials, like food
molecules, oxygen, carbon dioxide, water,
and waste, need to enter or leave your cells
by going through the cell membrane. The
cell membrane is selectively permeable.
That means that it will allow only certain
substances to enter or leave the cell.
Passive Transport Processes – use NO energy and go from where there is MORE to where there is LESS.
Molecules are in constant motion, trying to spread apart. Because of this the molecules move from a
higher concentration to a lower concentration.
DIFFUSION - the movement of particles in a liquid or gas from an area where there is more to where
there is less. Examples: gases (smells) – cookies baking, smelly bathroom, perfume, etc; liquids – iodine
on an onion slice enters the cell to stain the nucleus
OSMOSIS - a special type of diffusion where WATER
moves through a MEMBRANE. It is usually a cell membrane
but it can be any type of membrane. Example: drink glass of
water then the water enters your cells
ACTIVE TRANSPORT - takes lots of ENERGY. It is the
movement of materials from where there is LESS to where
there is MORE. It is also the movement of SOLIDS into or
out of the cell. Examples: getting waste out of your cells;
getting calcium, potassium, or sodium into the cells.
32 % freshwater
98 %
fresh
water
Where is there more freshwater, inside or outside the cell? inside
Which way will the water move? Out of the cell
What is the amount of freshwater inside and outside the cell when the water stops moving?
It will be the same amount inside and outside the cell – 65%
Will energy be needed for the freshwater to move? NO Active or passive transport? Passive transport
Is this osmosis or diffusion? Osmosis How do you know? Movement of water across a membrane
= carbon dioxide
Where is there more carbon dioxide? Outside the cell
Which way will the CO2 move? Into the cell
What is the amount of CO2 inside & outside the cell when it
stops moving? Same inside and outside – 10 particles
Use arrows to show the movement of CO2 in/out the cell.
Will energy be needed for the CO2 to move? NO
What process is this? diffusion
How do you know?
Movement of gas/liquid (not water) from where there is more to where there is less until it is even.