Transcript The Cell and Its Environment POWER POINT

The Cell and Its Environment
Spring 2010
What is a cell?
A cell is the basic unit of living things.
Some living things are composed of only
one cell and are called UNICELLULAR
organsims.
Organisms that have many different cells
are called MULTICELLULAR organisms.
What is the function of a cell?
 For an organism to live, grow and reproduce an
organism must perform processes that allow
them to do so.
 An organism must be able to use energy to live.
 All living things use energy and different types of
organisms obtain energy different ways through
the processes of photosynthesis or respiration.
 Since organisms must use energy there are
certain things that have to get into and out of the
cell to enable the organism to use or convert
energy to a useable form.
Materials that must be able to move INTO
ANIMAL cells:
1. Oxygen
2. Water
3. Particles of food
Materials that must be able to move OUT
of ANIMAL cells:
1. Carbon dioxide
2. Waste materials
Materials that must move INTO PLANT
cells:
1. Sunlight
2. Water
3. Carbon dioxide
Materials that must be able to get OUT of
PLANT cells:
Oxygen
Waste products
What lets stuff in and out of the cell?
Cell Membrane
Definition- a membrane that controls how
materials move into or out of a cell. It acts
as a gatekeeper to allow things in and out
Cell
of the cell.
Membrane
What is a cell membrane?
Cell membranes are the outside covering
of a cell that allows things in and out of the
cell.
Cell membranes are composed of 3 things:
1. double layer of lipid molecules (fats)
2. transport proteins
3. carbohydrate chains
How does stuff get in and out of the cell?
The cell membrane is what allows stuff in
and out of the cell. The membrane is
selectively permeable.
Selectively permeableDefinition- means that some substances
can cross the membrane while others
cannot.
How does stuff get in and out of the cell?
CONT’D
Substances that move into and out of a
cell do so by means of one of two
processes: PASSIVE TRANSPORT or
ACTIVE TRANSPORT.
Passive Transport
Definition: is the movement of dissolved
materials across a cell membrane without
using the cells energy.
Energy required: NO
Type of Transport: PASSIVE
Passive Transport
Diffusion
 Definition: is the process by which molecules
move from an area of higher concentration to an
area of lower concentration.
 Ex: If a bacteria lives in a pond, the water in the
pond contains oxygen molecules. The area
inside the bacteria cell has a lower amount of
oxygen than the pond. So, the oxygen
molecules outside of the cell will freely move into
the cell.
Diffusion CONT’D
Energy required: NO
Type of Transport: PASSIVE
Osmosis
Definition: is the diffusion of water
molecules across a selectively permeable
membrane.
-Many life processes require water,
therefore; all cells must have the
appropriate amount of water in them to
function.
Energy Required: NO
Type of Transfer: PASSIVE
Click on link below to see the flow of
water during osmosis.
http://people.eku.edu/ritchisong/RITCHISO
/osmosis3.gif
What do cells look like when they have
too much or too little water?
Facilitated Diffusion
 Things like oxygen and carbon dioxide diffuse
freely across a cell membrane.
 Sugar and other molecules do not.
 Definition: is the process that sugar and other
molecules go through to make it easier for them
to pass through the cell membrane. The sugar
passes through the transport protein “down
spouts” into the cell.
 Energy Required: NO
 Type of Transfer: PASSIVE
Facilitated Diffusion CONT’D
Active Transport
 Sometimes cells need materials to flow the opposite
direction of the flow of diffusion. In this case the cell
would need to use ACTIVE TRANSPORT to carry these
materials in and out.
 DEFINITON: is the movement of materials a cross a cell
membrane using cellular energy.
 The cell uses its’ energy so the transport proteins “pick
up” materials and “carry” them across the membrane.
 Examples of substances that are carried in and out of
the cell this way are: calcium, potassium, and sodium.
 ENERGY REQUIRED: YES
TYPE OF TRANSPORT: ACTIVE
Active Transport