Cell Membrane

Passive Vs Active Transport

Cell Unit OutlineCell 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• 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 TRANSPORTPASSIVE 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 GRADIENTCONCENTRATION GRADIENT

DiffusionDiffusion

• Diffusion – when molecules move from where they are close together to spread apart

• Whenever there is a CONCENTRATION CONCENTRATION GRADIENTGRADIENT, 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

• DiffusionDiffusion – 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 oxygenoxygen and carbon dioxidecarbon dioxide

Diffusion

• Molecules move from an area of high concentration into the area of lower concentration “down the CONCENTRATION CONCENTRATION GRADIENTGRADIENT”

• OxygenOxygen diffuses into blood cells from the lungs

• Carbon dioxideCarbon dioxide diffuses from blood to the lungs

Alveoli

Lots of CO2 No O2

Oxygen

Oxygen

CO2

ALVEOLUS

Lots of CO2 No O2

Oxygen

Oxygen

CO2

CO2

CO2 CO2CO2

CO2

Lots of CO2 No O2

Oxygen

CO2

CO2

CO2 CO2CO2

CO2

Oxygen

Lots of O2; No CO2

Diffusion In Your Lungs• Carbon dioxideCarbon dioxide (CO2) DIFFUSESDIFFUSES down its

CONCENTRATION GRADIENTCONCENTRATION GRADIENT out of the red blood cells

• OxygenOxygen DIFFUSESDIFFUSES down its CONCENTRATION GRADIENTCONCENTRATION 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 dioxideCarbon dioxide DIFFUSES out of the body cells and into the blood cells

• OxygenOxygen DIFFUSES from blood cells into body cells

CO2CO2 CO2CO2

CO2

Oxygen

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 TRANSPORTPASSIVE TRANSPORT because the

molecules have enough energy to move across the membrane

Passive Transport - OsmosisPassive Transport - Osmosis

• A type of diffusion

• WaterWater molecules move down their concentration gradient from an area where there is more water to the area where there is less water

OsmosisOsmosis

• Cells are a solutionsolution 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

SolutionsSolutions• Made of two parts:• SoluteSolute = substance that gets dissolved; ex.

Sugar, salts, minerals; tea, kool-aid• SolventSolvent = substance that does the dissolving,

usually water• The amount of sugar (solute) in the water is the

CONCENTRATIONCONCENTRATION

OsmosisOsmosis• Three terms are used to describe the solution

inside the cell compared to the solution outside the cell:– HypertonicHypertonic– HypotonicHypotonic– IsotonicIsotonic

OsmosisOsmosis• HypertonicHypertonic = a solution that has MOREMORE solutes

than the other solution. Hyper = higher

• HypotonicHypotonic = a solution that has LESSLESS solutes than the other solution. Hypo - low

• IsotonicIsotonic = solutions that have EQUALEQUAL amounts of solutes

1%

1%

ISOTONICISOTONIC

1% 0%The cell isThe cell is

HYPERTONICHYPERTONIC

The solution is HYPOTONICHYPOTONIC

Water moves from the lower number into the higher numberWater moves from the lower number into the higher number

1%

3%

The cell is HYPOTONICHYPOTONIC

The solution is HYPERTONICHYPERTONIC

Water moves from the lower number into the higher numberWater moves from the lower number into the higher number

1% 1%

Water always moves from the

area of high WATER

concentration into the area of low

WATER concentration

Equilibrium

1%

3%

Solution is____________

Size of the cell will…

Cell = 1% salts

99% water

Solution = 3% salts

97% water

1%

0%

Solution is ______________

Cell = 1% salts

99% water

Solution – 0% salts

100 % water

Cell will ………

Osmosis

• Water will move from HYPOtonicHYPOtonic into HYPERtonicHYPERtonic

1%

3%

1%

2%

Hypertonic solution

Plasmolysis

Hypotonic solution Hypotonic solution

Turgor pressure = Turgor pressure = water pressure water pressure

placed on plant cell placed on plant cell walls walls

1%

0%

1%

1%

1%

3%

OsmosisOsmosis

3%

1%1%

salt

Salt water fishSalt water fish

0%1%

Fresh water fishFresh water fish

0% -freshwater

1%1%

salt

0%

salt

0%0%

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

• INSULININSULIN

Transport protein InsulinInsulin Transport protein InsulinInsulin

Glucose Glucose

Glucose

InsulinInsulin

GlucoseGlucose

InsulinInsulin

GlucoseGlucose

InsulinInsulin

Glucose

InsulinInsulin

Passive Transport: Review• Cell spends no energyno energy for molecules to

move inside

• 3 types:

– Diffusion

– Osmosis

– Facilitated diffusion

Active Transport

Cell Has to Use EnergyEnergy To Move Substances Across The

Membrane

Active Transport

• Why does the Cell have to use its own energy?

1. Must move particles AGAINSTAGAINST the concentration gradient

2. Particles are too LARGELARGE

Types of Active Transport

• EndocytosisEndocytosis

• ExocytosisExocytosis

Endocytosis • Large particles brought into the cell

• TOO BIGTOO BIG• Cell membrane ‘pinches’ in

Endocytosis/Exocytosis

Phagocytosis Amoeba

Endocytosis

Endocytosis

Endocytosis

Endocytosis

Phagocytosis

ExocytosisExocytosis • Large particles are moved to outsideoutside of the

cell• Opposite of endocytosis• Two reasons:1.1. ExcretionExcretion – removal of wastes2.2. SecretionSecretion – substance used by another cell

(INSULININSULIN)

Exocytosis

Cell Transport: ReviewCell Transport: Review

• PassivePassive

• Diffusion

• Osmosis

• Facilitated diffusion

• ActiveActive

• Pumps

• Endocytosis

• Exocytosis