Cell Membrane Notes

(1)

Cell Membrane Notes

(2)

About Cell Membranes

• All cells have a cell membrane

• Functions:

a. Controls what enters and exits the cell to maintain an internal balance called homeostasis

b. Provides protection and support for the cell

(3)

About Cell Membranes

• The cell membrane is constantly moving

• Proteins, and other structures move about the cell

membrane (like a fluid)

(4)

What is the purpose of cellular transport?

• The cell membrane regulates the passage of materials into and out of the cell

– Needed materials move in

• Glucose, oxygen, amino acids, etc.

– Excess materials move out

• Carbon dioxide, digested materials, etc.

(5)

How?

• A cell membrane is semipermeable (selectively

permeable), meaning that some substances can pass directly through the cell membrane while other

substances cannot.

• Materials can enter or exit through the cell membrane by passive transport or active transport.

Membrane movemen t animat ion

aa H₂O

sugar lipids salt waste

So what needs to get across the membrane?

O₂

(6)

Types of Cellular Transport

• Passive Transport

*cell does not use energy

1. Diffusion

2. Facilitated Diffusion 3. Osmosis

• Active Transport

*cell does use energy

1. Protein Pumps 2. Endocytosis 3. Exocytosis

hig h

low

This is gonna

be hard work!!

hig h

low Weeee!

!!

•Animations of Active Transport &

Passive Transport

(7)

Passive Transport

• cell uses no energy

• molecules move randomly

• The random motion of molecules occurs along the concentration gradient meaning molecules spread out from an area of high concentration to an area of low

concentration.

• (HighLow)

• Three types:

(8)

3 Types of Passive Transport

1. Diffusion – is the spreading out of molecules across a cell membrane until they are

equally concentrated.

2. Facilitative Diffusion – diffusion with the help of transport proteins

3. Osmosis – diffusion of water

(9)

Passive Transport:

1. Diffusion

• Diffusion: random movement of particles from an area of high concentration to an area of low

concentration.

• Diffusion continues until all molecules are evenly spaced (equilibrium is reached)

• Note: molecules will still move around but stay spread out.

(10)

inside cell

outside cell

fat

fat fat

fat

fat fat

fat

fat fat

LOW

HIGH

1. Diffusion

Simple Diffu sion Animati on

(11)

Facilitated diffusion:

•diffusion of specific particles from high to low concentration

•Help from transport proteins found in the membrane

2. Facilitated Diffusion

• http://bio.winona.edu/berg/Free.

htm

HIGH

LOW Glucose is an example of a

molecule that is transported through proteins

(12)

inside cell

outside cell

sugar

sugar sugar

sugar

sugar sugar

LOW

HIGH

• Channel Protei ns animations

(13)

• Osmosis: diffusion of water through a selectively

permeable membrane

• Water moves from a high

concentration of water to a low concentration of water

• More on this soon***

Osmosis

animation

Passive Transport:

3. Osmosis

(14)

Active Transport

• Requires the cell to use energy

• Actively moves molecules to where they are needed

• Molecules move against the concentration gradient - from an area of low concentration to an area of high concentration

• (Low  High)

• Three Types:

(15)

Types of Active Transport

1. Protein Pumps -transport proteins that require energy to do work

Sodium Potassi um Pumps

(Active

Transport using proteins)

Protein

changes shape to move

molecules: this requires

energy!

(16)

Types of Active Transport

2. Endocytosis: taking bulky material into a cell by forming a vesicle

• Uses energy

• Cell membrane in-folds around food particle

• “cell eating”

• forms food vacuole &

digests food

• This is how white blood cells eat bacteria!

(17)

3. Exocytosis: Forces material out of cell in bulk

• Membrane surrounding

the material fuses with cell membrane

• Cell changes shape – requires energy

• Ex: Hormones or wastes released from cell

Endocytosis & E xocytosis

animations

(18)

permeable membrane

• Because water is so small and in such abundance, the cell cannot control its movement through the cell membrane.

Osmosis

animation

Revisited:

Passive Transport: Osmosis

(19)

Effects of Osmosis on Life

• Water moves freely through through pores

(blue and white molecules)

• Solute (green) too large to move across.

• Reminder:

–Solute: what is being dissolved

–Solvent: what dissolves the solute

• In salt water, the solute is the salt and the solvent is the water

(20)

Hypotonic Solution

Hypotonic: The solution has a lower concentration of solutes and a higher

concentration of water than inside the cell.

(Low solute; High water)

Result: Water moves from the solution to inside the cell): Cell Swells and bursts open

(lyse)!

• Osmosis Animations for

isotonic, hypertonic, and

hypotonic solutions

(21)

Hypertonic Solution

Hypertonic: The solution has a higher concentration of solutes and a lower

(High solute; Low water)

Result: Water moves out of the cell into the solution: Cell shrivels!

hypotonic solutions

shrink s

(22)

Isotonic Solution

Isotonic: The concentration of solutes in the solution is equal to the concentration of

solutes inside the cell.

Result: Water moves equally in both directions and the cell remains same size!

hypotonic solutions

(23)

In what type of solution are these cells?

A B C

Hyperto nic

Isoton ic

Hypotoni c

(24)

Cell Membrane Notes

(25)

About Cell Membranes

• All cells have a _____

__________________

• Functions:

a. Controls what enters and exits the cell to maintain an internal balance called _________________

b. Provides protection and support for the cell

(26)

About Cell Membranes

• The cell membrane is constantly _______________

• Proteins, and other structures move about the cell membrane (like a __________)

(27)

What is the purpose of cellular transport?

• The cell membrane regulates the

passage of materials __________ and _______ of the cell

– Needed materials move _____

• Glucose, oxygen, amino acids, etc.

– Excess materials move _______

• Carbon dioxide, digested materials, etc.

(28)

How?

• A cell membrane is _____________________

(selectively permeable), meaning that __________

substances can pass directly through the cell

membrane while other substances ___________

• Materials can enter or exit through the cell membrane by __________ transport or _________ transport.

Membrane movemen t animat ion

aa H₂O

sugar lipids salt waste

So what needs to get across the membrane?

O₂

(29)

Types of Cellular Transport

• Passive Transport

*cell does ______ use energy

1. _______________

2. Facilitated Diffusion 3. ______________

• Active Transport

*cell does use _________

1. Protein Pumps 2. Endocytosis

3. _______________

hig h

low

This is gonna

be hard work!!

hig h

low Weeee!

!!

•Animations of Active Transport &

Passive Transport

(30)

Passive Transport

• cell uses no energy

• molecules move __________________

• The random motion of molecules occurs along the concentration gradient meaning molecules spread out from an area of

_________ concentration to an area of __________ concentration.

• (HighLow)

• Three types:

(31)

3 Types of Passive Transport

1. Diffusion – is the spreading out of molecules across a cell membrane until they are

equally concentrated.

2. Facilitative Diffusion – diffusion with the help of _______________ _______________

3. Osmosis – diffusion of ___________

(32)

1. Diffusion

• Diffusion: ____________ movement of particles from an area of high concentration to an area of low concentration.

• Diffusion continues until all molecules are evenly spaced (___________________ is reached)

• Note: molecules will still ____________ around but stay spread out.

(33)

inside cell

outside cell

fat

fat fat

fat

fat fat

fat

fat fat

LOW

HIGH

1. Diffusion

Simple Diffu sion Animati on

(34)

Facilitated diffusion:

•diffusion of specific particles from high to low concentration

•Help from _____________ ______________found in the membrane

•These molecules cannot pass through the membrane alone

• http://bio.winona.edu/berg/Free.

htm

HIGH

LOW Glucose is an example of a

molecule that is transported through proteins

(35)

inside cell

outside cell

sugar

sugar sugar

sugar

sugar sugar

LOW

HIGH

• Channel Protei ns animations

(36)

• Osmosis: diffusion of

_____________ through a

selectively permeable membrane

• Water moves from a _________

concentration of water to a __________ concentration of water

• More on this soon***

Osmosis

animation

Passive Transport:

3. Osmosis

(37)

Active Transport

• Requires the cell to use ________________

• Actively moves molecules to where they are needed

• Molecules move against the concentration gradient - from an area of __________

concentration to an area of __________

concentration

• (Low  High)

• Three Types:

(38)

Types of Active Transport

1. ____________ Pumps -transport proteins

that require energy to do work

Sodium Potassium Pumps (Active Transport using

proteins)

Protein

changes shape to move

molecules: this requires

energy!

(39)

2. __________________: taking bulky material into a cell by

forming a vesicle

• Uses energy

• Cell membrane in-folds around food particle

• “_____________________”

• forms food vacuole & digests food

• This is how white blood cells eat bacteria!

(40)

3. Exocytosis: Forces material out of cell in bulk

• Membrane surrounding

the material ____________

with cell membrane

• Cell changes shape – requires energy

• Ex: Hormones or wastes released from cell

Endocytosis &

Exocytosis animations

(41)

• Osmosis: diffusion of water

through a selectively permeable membrane

• Because water is

so___________and in such abundance, the cell

__________control its movement through the cell membrane.

Osmosis

animation

Revisited:

(42)

permeable membrane

• Because water is so small and in such abundance, the cell cannot control its movement through the cell membrane.

Osmosis

animation

Revisited:

(43)

Effects of Osmosis on Life

• Water moves_________

through pores

(blue and white molecules)

• Solute (green) too __________

to move across.

• Reminder:

–Solute: what is being dissolved

–Solvent: what dissolves the solute

• In salt water, the solute is the salt and the solvent is the water

(44)

Hypotonic Solution

Hypotonic: The solution has a ____________

concentration of solutes and a higher

(Low solute; High water)

Result: Water moves from the solution to ___________ the cell): Cell ____________ and

bursts open (lyse)!

hypotonic solutions

(45)

Hypertonic Solution

Hypertonic: The solution has a _____________

concentration of solutes and a ___________

(High solute; Low water)

Result: Water moves ___________the cell into the solution: Cell

_____________!

hypotonic solutions

shrink s

(46)

Isotonic Solution

Isotonic: The concentration of solutes in the solution is ___________ to the concentration of

solutes inside the cell.

Result: Water moves _____________ in both directions and the cell remains same size!

hypotonic solutions

(47)

In what type of solution are these cells?

A B C

_____________ _____________ _____________

(48)

How Organisms Deal with Osmotic Pressure

• Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure.

• A protist like the paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.

• Salt water fish pump salt out of their specialized gills so they do not dehydrate.

• Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.

• Paramecium (protist)

removing excess water video