Transcript Cell Membrane

Cell Membrane
Passive Vs Active Transport
Cell Unit Outline
• Diffusion and osmosis
• Active vs Passive transport
• Mitosis and meiosis
ACOS # 2
• Describe cell processes necessary for achieving
homeostasis, including active and passive
transport, osmosis, diffusion, exocytosis and
endosytosis
– Identify functions of carbohydrates, lipids, proteins,
and nucleic acids
– Compare reactions of plant and animal cells in
isotonic, hypotonic and hypertonic solutions
ACOS # 2
– Explain how surface area, cell size,
temperature, light an pH affect cellular
activities
– Apply the concept of fluid pressure to
biological systems; examples – blood pressure,
turgor pressure, bends, strokes
ACOS # 2 – Terms
• Active transport – when the cell must use
energy to move substances in or out
• Bends – decompression sickness; caused by
nitrogen gas under pressure
• Concentration gradient – when there is a greater
amount (of molecules) in one place than there is
in another
ACOS # 2 – Terms
• Endocytosis – type of active transport when
a cell brings large materials inside
• Exocytosis – type of active transport when
cells move materials to the outside
• Diffusion – type of passive transport when
molecule ‘spread out’
• Homeostasis – steady state; the process of
maintaining correct conditions for life
ACOS # 2 – Terms
• Hypertonic – a concentrated solution
• Hypotonic – a less concentrated solution
• Isotonic – two solutions are in equal
concentration
• Osmosis – type of passive transport; when
water diffuses down its concentration gradient
ACOS # 2 – Terms
• Passive transport – when the cell can use
the energy of the molecules to move
materials in or out and not its own energy
• pH – unit measuring acidity (blood)
• Surface area – the ratio of outside of a cell
compared to the total volume of the cell
ACOS # 2 – Terms
• Stroke – rupture of a blood vessel (usually
from high blood pressure)
• Turgor – pressure created by water in the
water vacuole of plant cells
Cell Membrane
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Cell have to move materials in or out
What do they move in - ?
What do they move out - ?
What structure controls what gets in or out?
Cell Membrane
• Controls what materials enter or exit the cell
Passive Transport
• PASSIVE TRANSPORT – the cell does not
have to spend its energy for molecules to get
in/out
• Molecules are in constant motion
• The energy from the motion may be enough to
let some molecules ‘leak’ through the
membrane
• Molecules ‘want’ to ‘spread out’
Concentration Gradient
• Molecules may be closer together in one area
than they are in another
• The difference between the concentration of
molecules in one area vs the other area is called
a:
• CONCENTRATION GRADIENT
Diffusion
• Diffusion – when molecules move from where
they are close together to spread apart
• Whenever there is a CONCENTRATION
GRADIENT, molecules will diffuse
• The molecules will try to spread out
• Molecules move from an area of high
concentration to an area of low concentration
Diffusion
Types of Passive Transport
• Diffusion – molecules ‘spread out’; move
from an area of high concentration to an
area of lower concentration
• Small molecules diffuse through the membrane
easily;
– Gases like oxygen and carbon dioxide
Diffusion
• Molecules move from an area of high
concentration into the area of lower
concentration “down the CONCENTRATION
GRADIENT”
• Oxygen diffuses into blood cells from the lungs
• Carbon dioxide diffuses from blood to the
lungs
Alveoli
ALVEOLUS
Oxygen
CO2
Oxygen
Lots of
CO2
No O2
Oxygen
CO2
CO2
CO2 CO2 CO2 CO2
Oxygen
Lots of
CO2
No O2
Oxygen
CO2
CO2 CO CO2
2
Oxygen
Lots of
O 2;
No CO2
CO2 CO2
Lots of
CO2
No O2
Diffusion In Your Lungs
• Carbon dioxide (CO2) DIFFUSES down its
CONCENTRATION GRADIENT out of the
red blood cells
• Oxygen DIFFUSES down its
CONCENTRATION GRADIENT into the
red blood cells
Diffusion In Your Body
• In your body, all your body cells (muscles,
skin, stomach, nerves) produce carbon
dioxide and use up oxygen
• Carbon dioxide DIFFUSES out of the body
cells and into the blood cells
• Oxygen DIFFUSES from blood cells into
body cells
Oxygen
CO2 CO CO2
2
CO2 CO2
Oxygen
Smoking prevents diffusion
Passive Transport - Diffusion
• The movement of molecules down a
concentration gradient from an area of high
concentration to an area of low concentration
– A type of PASSIVE TRANSPORT because the
molecules have enough energy to move across the
membrane
Passive Transport - Osmosis
• A type of diffusion
• Water molecules move down their
concentration gradient from an area where there
is more water to the area where there is less
water
Osmosis
• Cells are a solution of sugars, proteins,
minerals, salts, etc.
• Cells are surrounded by a solution
• The amount of water in the cell compared to the
amount of water outside of the cell is the
concentration gradient
Solutions
• Made of two parts:
• Solute = substance that gets dissolved; ex.
Sugar, salts, minerals; tea, kool-aid
• Solvent = substance that does the dissolving,
usually water
• The amount of sugar (solute) in the water is the
CONCENTRATION
Osmosis
• Three terms are used to describe the solution
inside the cell compared to the solution outside
the cell:
– Hypertonic
– Hypotonic
– Isotonic
Osmosis
• Hypertonic = a solution that has MORE solutes
than the other solution. Hyper = higher
• Hypotonic = a solution that has LESS solutes
than the other solution. Hypo - low
• Isotonic = solutions that have EQUAL amounts
of solutes
ISOTONIC
1%
1%
Water moves from the lower number into the higher number
The solution is
HYPOTONIC
0%
1%
The cell is
HYPERTONIC
Water moves from the lower number into the higher number
The cell is
HYPOTONIC
1%
3%
The solution is
HYPERTONIC
1%
Equilibrium
1%
Water always
moves from the
area of high
WATER
concentration into
the area of low
WATER
concentration
Solution is____________
Cell = 1% salts
1%
99% water
Solution = 3% salts
3%
Size of the cell will…
97% water
Solution is ______________
Cell = 1% salts
1%
99% water
Solution – 0% salts
0%
Cell will ………
100 % water
Osmosis
• Water will move from HYPOtonic into
HYPERtonic
1%
3%
1%
2%
Hypertonic solution
Plasmolysis
Hypotonic solution
Turgor pressure =
water pressure
placed on plant cell
walls
1%
0%
1%
1%
1%
3%
Osmosis
Salt water fish
3%
1%
salt
Fresh water fish
0%
1%
0% -freshwater
1%
salt
0%
0%
salt
3% salt water
1%
3% salt water
3%
Osmosis
Passive Transport- Facilitated
Diffusion
• Some molecules are too big and need ‘help’ to
fit through the membrane
– Ex. Glucose
• A special molecule embedded in the membrane
acts as a ‘channel’ to let glucose in
• INSULIN
Glucose
Glucose
Glucose
Insulin
Transport protein Insulin
Glucose
Insulin
Insulin
Insulin
Passive Transport: Review
• Cell spends no energy for molecules to
move inside
• 3 types:
– Diffusion
– Osmosis
– Facilitated diffusion
Active Transport
Cell Has to Use Energy To Move
Substances Across The
Membrane
Active Transport
•
Why does the Cell have to use its own
energy?
1. Must move particles AGAINST the
concentration gradient
2. Particles are too LARGE
Types of Active Transport
• Endocytosis
• Exocytosis
Endocytosis
• Large particles brought into the cell
• TOO BIG
• Cell membrane ‘pinches’ in
Endocytosis/Exocytosis
Phagocytosis
Amoeba
Endocytosis
Endocytosis
Endocytosis
Endocytosis
Phagocytosis
Exocytosis
•
Large particles are moved to outside of the
cell
• Opposite of endocytosis
• Two reasons:
1. Excretion – removal of wastes
2. Secretion – substance used by another cell
(INSULIN)
Exocytosis
Cell Transport: Review
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Passive
Diffusion
Osmosis
Facilitated
diffusion
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Active
Pumps
Endocytosis
Exocytosis