CELL TRANSPORTObjectives1. Identify the main functions of the

cell membrane2. Describe what happens during

diffusion3. Explain the processes of osmosis,

facilitated diffusion, and active transport.

Membrane Structure1. Cell membranes are

composed of a double- layered sheet called a phospholipid bilayer.

2. Membrane Proteins• Proteins run through the lipid

bilayer and form channels and pumps to move material across the cell membrane.

3. Carbohydrate Molecules• They form chains that are

attached to the outer surfaces of these proteins.

• Many carbohydrates act like chemical identification cards, allowing cells to identify one another.

What does a Cell Membrane DO?• The cell membrane regulates what

enters and leaves the cell and also provides protection and support.

• The cell takes in food, water and ions and eliminates wastes through its membrane.

• Some molecules, like water moves freely through the membrane, other molecules must be carried/pumped through channels.

Passive Transport – does NOT use energy to move substances across a cell membrane.

the movement of molecules and ions with the concentration gradient.

(High concentration to Low concentration)

How do things get in and out of cells?

• Diffusion is the process by which substances spread through a liquid or gas.

• Substances move from regions of high concentration to regions of low concentration

• NO energy required

• Substances such as non-charged molecules, alcohol, water, and small lipids easily diffuse across the lipid bilayer.

Concentration Gradient

• A difference in number of molecules (or ions) of a substance between two adjacent regions.

Equilibrium• After the substances move from

high to low concentration,then the concentration of the substance on both sides of the membrane will be the same (equal). –Even after equilibrium is reached,

individual molecules continue to move rapidly across the membrane in both directions.

How do things get in and out of cells?• Osmosis – the diffusion of water through a

selectively permeable membrane. (molecules move from high to low concentrations)– Since water molecules are small, they can slip through

the gaps between phospholipids in the cell membrane.– As a result, water molecules constantly move back and

forth through the cell membrane.

How do things get in and out of cells?• Permeable- if a substance is able to

diffuse across a membrane• Impermeable- if things cannot pass

across the membrane• Selectively Permeable –some

substances can pass across, others cannot.

• Example-Osmosis• Example shows a

membrane that is permeable to water but is not permeable to sugar.

• On one side of membrane is a sugar solution, other side is pure water.

• As a result, there is a net movement of water into the sugar solution. This is due to diffusion (movement from high concentration to regions of low concentration).

Facilitated Diffusion- uses carrier proteins to shuttle molecules across the lipid bilayer. (high to low conc.)

This movement of a substance across a membrane occurs without the input of the cell’s energy. ex: transports large glucose

molecules from the blood into body cells.

How do things get in and out of cells?

PASSIVE TRANSPORT

Why do water molecules move with osmosis?• Osmoregulation- the control of water movement

across the cell membrane.– Water “follows” solute.

• Solute- a substance dissolved in solvent• Tonic- term used to refer to solvent

– Hypertonic- more solute in solvent outside of cell– Hypotonic- less solute in solvent outside of the cell– Isotonic- equal amount of solute outside of cell and

inside of cell.• Solute is usually charged and does not move through

membrane

• Hypertonic solution– Solute concentration

outside the cell is HIGHER than solute concentration inside the cell.

– Water is moving OUTSIDE the cell to follow solute

• Cell shrinks– plasmolysis

Why do water molecules move with osmosis?

• Hypotonic solution– Solute concentration outside

the cell is LOWER than solute concentration inside the cell.

– Water is moving INSIDE the cell to follow solute

• Animal cell swells and will possibly burst

– Cytolysis

• Plant cell swells until cell walls restrict further swelling

– Turgor pressure

Why do water molecules move with osmosis?

• Isotonic solution– Solute

concentration is the same inside and outside the cell.

– Water moves equally into and out of the cell.

• Normal Cell

Why do water molecules move with osmosis?

3. Active Transport – uses energy to move substances across a cell membrane.

the movement of molecules and ions against the concentration gradient.

(Low to High concentration)• Active Transport: http://www.youtube.com/watch?v=9XfVl6_R7_k

ACTIVE TRANSPORT

Example of Active Transport• Plant nutrients (solutes) are more

concentrated inside the roots than in the surrounding soil. (this is good!)

• Without active transport, these nutrients would diffuse out of the roots.

Examples of Active Transport• Sodium-potassium pump- concentration

gradients of sodium and potassium allow for cellular communication.

Bulk Movement (huge molecules)• Transporting very large molecules

such as polysaccharides or large proteins across the membrane.

• Materials all move across the cell membrane packaged in membrane-bound sacs called vesicles. The vesicle merges with the cell membrane.

Endocytosis• During endocytosis

materials are brought INTO the cell. a portion of the cell

membrane surrounds desirable macromolecules that are outside the cell. The cell pinches off and the new vesicle moves into the cell.

Example: when white blood cells engulf foreign particles like bacteria and viruses.

Types of Endocytosis

• Pinocytosis- fluid transported into cell• Phagocytosis- food particles transported into

cell• http://www.youtube.com/watch?

v=pvOz4V699gk

Exocytosis• During exocytosis

materials EXIT the cell• wastes and cell

products are packaged by the Golgi Apparatus in sacs called vesicles. They then fuse with the cell membrane and the materials in the vesicles are secreted out of cell.

• Ex: tear production

In Da Club- best review video https://www.youtube.com/watch?v=dPKvHrD1eS4

Cellular TransportMembrane

Structure consists of

1. Cell membranes are composed of a double- layered sheet called a ___

__________________________

2. Membrane Proteins• Proteins run through the lipid

bilayer and form ___________ and ___________ to move material across the cell membrane.

3. Carbohydrate Molecules• They form chains that are

attached to the outer surfaces of these proteins.

• Many carbohydrates act like chemical ___________ cards, allowing cells to identify one another.

What does a Cell Membrane DO?• The cell membrane ___________ what

enters and leaves the cell and also provides ___________ and ___________ .

• The cell takes in food, water and ions and eliminates ___________ through its membrane.

• Some molecules, like water moves freely through the membrane, other molecules must be carried/pumped through channels.

Passive Transport – does ______ use energy to move substances across a cell membrane.

the movement of molecules and ions with the concentration gradient.

(High concentration to Low concentration)

How do things get in and out of cells?

• Diffusion is the process by which substances __________ through a liquid or gas.

• Substances move from regions of high concentration to regions of low concentration

• NO energy required

• Substances such as non-charged molecules, alcohol, water, and small lipids easily ___________ across the lipid

bilayer.

Concentration Gradient• A ___________ in number of molecules (or

ions) of a substance between two adjacent regions.

Equilibrium• After the substances move from

high to low concentration,then the concentration of the substance on both sides of the membrane will be the same (___________ ). –Even after equilibrium is reached,

individual molecules continue to move rapidly across the membrane in ___________ directions.

How do things get in and out of cells?• Osmosis – the ___________ of water through

a selectively permeable membrane. (molecules move from high to low concentrations)– Since ___________ molecules are ___________ , they

can slip through the gaps between phospholipids in the cell membrane.

– As a result, water molecules constantly move back and forth through the cell membrane.

How do things get in and out of cells?• Permeable- if a substance is able to

diffuse across a membrane• Impermeable- if things ___________

pass across the membrane• Selectively Permeable –some

___________ can pass across, others cannot.

• Example-Osmosis• Example shows a

membrane that is permeable to water but is not permeable to ___________ .

• On one side of membrane is a sugar solution, other side is pure water.

• As a result, there is a ______ movement of water into the sugar solution. This is due to diffusion (movement from high concentration to regions of low concentration).

Facilitated Diffusion- uses carrier ___________ to shuttle molecules across the lipid bilayer. (high to low conc.)

This movement of a substance across a membrane occurs without the input of the cell’s energy. ex: transports large ___________

molecules from the blood into body cells.

How do things get in and out of cells?

Why do water molecules move with osmosis?• Osmoregulation- the ___________ of water

movement across the cell membrane.– Water “___________ ” solute.

• Solute- a substance dissolved in solvent• Tonic- term used to refer to solvent

– Hypertonic- __________ solute in solvent outside of cell– Hypotonic- _______ solute in solvent outside of the cell– Isotonic- ___________ amount of solute outside of cell

and inside of cell.• Solute is usually charged and therefore does not move through

membrane

• Hypertonic solution– Solute concentration

outside the cell is ___________ than solute concentration inside the cell.

– Water is moving OUTSIDE the cell to follow solute

• Cell ___________ – plasmolysis

Why do water molecules move with osmosis?

• Hypotonic solution– Solute concentration outside

the cell is ___________ than solute concentration inside the cell.

– Water is moving INSIDE the cell to follow solute

• Animal cell ___________ and will possibly burst

– Cytolysis

• Plant cell swells until cell walls restrict further swelling

– Turgor pressure

Why do water molecules move with osmosis?

• Isotonic solution– Solute

concentration is the ___________ inside and outside the cell.

– Water moves equally into and out of the cell.

• Normal Cell

Why do water molecules move with osmosis?

3. Active Transport – uses ___________ to move substances across a cell membrane.

the movement of molecules and ions against the concentration gradient.

(Low to High concentration)

Example of Active Transport• Plant nutrients (solutes) are more

concentrated inside the roots than in the surrounding soil. (this is good!)

• Without active transport, these nutrients would diffuse out of the roots.

Examples of Active Transport• Sodium-potassium pump- concentration

gradients of sodium and potassium allow for cellular communication.

Bulk Movement (huge molecules)• Transporting very ___________

molecules such as polysaccharides or large proteins across the membrane.

• Materials all move across the cell membrane packaged in membrane-bound sacs called ___________ . The vesicle merges with the cell membrane.

Endocytosis• During endocytosis

materials are brought ___________ the cell. a portion of the cell

membrane surrounds desirable macromolecules that are outside the cell. The cell pinches off and the new vesicle moves into the cell.

Example: when white blood cells ___________ foreign particles like bacteria and viruses.

Types of Endocytosis

• Pinocytosis- ___________ transported into cell

• Phagocytosis- ___________ particles transported into cell

Exocytosis• During exocytosis

materials ___________ the cell• wastes and cell

products are packaged by the Golgi Apparatus in sacs called vesicles. They then fuse with the cell membrane and the materials in the vesicles are secreted out of cell.

• Ex: tear production