5.1 How is the Structure of the Cell Membrane Related to it's Function

- Function of plasma membrane

1. Isoloates cells contents from external environment

2. regulates the exchange of essential substances

3. allows communication between cells

4. creates attachments within and between cells

5. regulates biochemical reactions

“ Fluid Mosaic” Model

• Membranes are “fluid mosaic” in which proteins move within layers of lipids

• The “Fluid mosaic” model of a membrane was proposed in 1972 by Singer & Nicolson

• Mosaic or 'a patch work of different proteins

• Allows materials to move in and out of the cell

Phospholipid Bilayer

1. Is the fluid portion of the membrane

2. Plasma Membrane/double layer where the water loving heads face both inside and outside watery environments.

3. Outside of the cell= is surrounded by watery fluids

4. Inside of the cell (cytoplasm) is also a watery environment

Polar Hydrophilic Heads

• water loving

• These heads face outside and inside the cell

Non-polar hydrophobic Tails

• “” water fearing

• Tails face the inside of the membrane staying away from water

Unsaturated Fatty Acids

that causes “kink'“ into the tails

The “ kinks” make the membrane fluid

Double/Triple Bonds

1. LESS FLUID= Bonds are mostly straight not as connected

2. the bends pushes neighbor phospholipids apart

3. MORE FLUID= bonds are kinky and connected together ( more flexible/runny, like vegetable oil)

Single Bonds

Straight tails pack tightly together causing membrane to be stiffer ( less fluid)

Passes Directly Through the Lipid Bilayer

Oxygen O2,

Carbon Dioxide

Co2,

small nonpolar molecules,

some water molecules

Simple Diffusion

Small non-polar molecule that has access to go right through the lipid bilayer

1. Non-polar molecules

2. some water molecules

3. oxygen gas o2

4. carbon dioxide ( Co2

Facilitated Diffusion

Large molecules that needs assistance passing through the lipid bilayer

1. Glucose ( large polar molecules)

2. ions ( CI-, Na+)

3. water molecules

High Temperature

Membranes become more fluid = more movement

Less Temperature

becomes less fluid= less movement

Cholesterol

Helps stabilize membranes , affecting fluidity and reducing permeability

Membrane Proteins & Their Functions

1. Receptor proteins- trigger cellular responses upon binding of specific molecules receives chemical signs such as hormones and sends response to inside the cells

2. Recognition proteins “ Name tag”- glycoproteins that act as identification tags so cells can recognize one another

3. Connection proteins- Anchor membrane to cells internal skeleton ( cytoskeleton) or neighboring cells

Receptor Protein Activation

1. A hormone binds to the receptor

2. Hormones binding activates the receptor, changing it’s shape

3. The activated receptor stimulated a response in the cell

Enzymatic proteins

are proteins that promote chemical reactions that synthesize or break apart biological molecules

Connection Proteins

anchor the cell membranes to the inner cytoskeleton. to proteins outside and other cells

Transport protein

Regulate the movement of hydrophilic molecules through the plasma membrane

Channel Proteins

Form channels to allow specific ions or water molecules to pass through the membranes

Carrier Proteins

having binding sites that can temporarily attach to specific molecules one side to the other side of the membrane.

5:2 Which Physical Processes Move Molecule in Fluids?

Molecules in fluids move in response to gradients

A fluid is a substance whose molecules can flow past one another

Solute

The substance that gets dissolved ( salt, sugar, or glucose atoms, ions, molecules) in the cell

Solvent

The liquid that’s dissolving the substance ( water)

Concentration

how much solute(the stuff) is dissolved in the specific given amount of solvent( liquid)

Gradient

is a physical different in temp, pressure, charge, or concentration between two adjoining regions

Diffusion

net movement of molecules or particles from regions of high concentration to regions of low concentration

Diffusion of a Dye In Water (Exam Question)

1. A drop of dye is place inside the water

2. Dye molecules diffuse into the water molecules diffuse into the dye

3. Both dye molecules and water are evenly mixed/dispersed

Passive Transport

Passive Transport is the movement of substance across cell membranes down concentration gradients, NO ENERGY REQUIRED

1. Simple diffusion- water, carbon, small molecules, non polar molecules dissolves gas, through the phospholipid bilayer

2. Facilitated diffusion water ions, water soluble molecules through a membrane channel or carrier of protein

3. Osmosis diffusion of water across the permeable membrane from a region high water concentration to low water concentration

Passive Transport ( HIGH TO LOW) (exam question)

(a) simple diffusion: Simple diffusion through the phosphlipid bilayer

water, dissolved gases, lipid soluble molecules through phospholipid bilayer

(b) facilitated diffusion: Facilitated diffusion through channel proteins (CI)

Large molecules that needs assistance passing through the lipid bilayer

(C) Osmosis: Osmosis through aquaporins or the bilayer phospholipid bilayer

The passive flow of water across a cell membrane toward where there is more solute ( salt/sugar ) high concentration- low concentration

(D) Facilitated diffusion through carrier proteins ( glucose)

Energy-requiring transport requires the use of cellular ENERGY (LOW TO HIGH (Exam question)

Any transport that spends ATP energy to move molecules uphill (low to high or carry big stuff in vesicles

(A) A ballon in an Isotonic Solution ( no net flow of water)

Isotonic solution- Equal solute inside and outside-water floes in and out equally both cell and balloon stays the exact same size

(B) A ballon in a hypertonic solution (water flows out the balloon= shrinks) Solution:-High solute=low water Ballon: High Water=low solute

Hypertonic solution has more solute (higher concentration)- water rushes out of the cell towards the solution-ballon shrinks/blood cell shrivels

• Water moves across a membrane TOWARD the hypertonic solution

(C) A ballon in a hypotonic solution

Hypotonic solution has less solute(lower concentration)- water rushes into the cell away from solution-balloon swells/red blood cells expand and may purse

• Water moves across a membrane AWAY from the hypotonic solution

• Solution High (Water) low solute

• Ballon:: High solute-low water

The Effect of Solute Concentration on Osmosis ( balloon experiment)

(a) a ballon in an isotonic solution equal inside and outside

(b) a ballon in a hypertonic solution ( hyper=lots of red dots)water leaves ballon- shrinks

( C ) a ballon in a hypotonic solution water entering the balloon ( hypo = swell/hippo) burst

Osmosis across the plasma membrane plays an important rile in the lives of the cells (exam question)

When cells are place into a hypertonic solution they shrink due to water loss

When cells are placed into hypotonic solution, they swell because they are bringing in water

When cells are place into isotonic solution remains unaffected

The effects of Osmosis on Red Blood Cell (Exam Question)

(A) Red blood cells in an isotonic solution - remains the same shape

(B) Red blood cells in a hypertonic solution loses water -shrinks

(C) Red blood cells in a hypotonic solution gains water -swells

osmosis the flow of water from cytoplasm of plants( Exam question)

Water pressure within the central vacuole is called turgor pressure

1. Water going into the plant cell and out= isotonic solution(flaccid)

2. Water going out of the plant cell and shrinks away from cell wall = hypertonic( plasmolyze)

3. Water going into the cell membrane causes walls to expand= hypotonic=turgid

turgid=tight/swollen flaccid-flat droopy plasmolyze=plasma pulls away

Turgor Pressure in Plants Cells

Water pressure that builds up inside the plants cell’s central vacuole as water flows in through osmosis

Water in central vacuole-pushes against cell wall high turgor pressure

Pressure (firm plant) Water leaves vacuole-central vacuole

shrinks-loss of turgor pressure( wilted plant)

Energy required Transport

1. Active Transport - proteins use energy to move substance across plasma membrane ( protein pump) low to high concentration

2. Endocytosis cells engulf particles and transport them using vesicles( cell reaches out or sinks in like a pouch to scoop large molecules to bring inside.)

3. Exocytosis vesicle inside the cell that carries large molecules or particles to the membrane, fuses with it and dumps molecules out of the cell using energy

Endocytosis

The cell membrane reaches or sinks in like a pouch to scoop up large molecules and drags them inside using ATP energy

sinks in like a pouch reaches out scoops up drags inside (USING ATP)

Exocytosis

Vesicles inside the cell that carries large molecules or particles to the membranes fuses with it and dumps it out of the cell using energy

Vesicles EXIT and dumps the trash (USING ATP)

Osmosis

The passive movement of water across a membrane toward wherever there is more solute (salt/sugar) “water follows salt (solute)!” Water rushing across a membrane to dilute salt

High Concentration

High amount of salt with low water

Low Concentration

Low salt with a lot water

High water concentration

ALOT OF WATER WITH LOW SALT

Low WATer Concentration

low water with a lot of salt

Energy-requiring transport (exam question)

Moving things from low concentration to high concentration

1. The transport protein binds both ATO and CA²+

2. Energy from ATP changes the shape of the transport protein and moves ions across the membrane

3. The protein releases the ion and the remnants of ATP (ADP and P) and closes

Two different types of Endocytosis ( Exam question)

a. pinocytosis ( “cell drinking”) moves liquids into the cell

b. Phagocytosis (“ cell eating'“) move large particles into the cell

Exocytosis- (Exam Question)

Moves material out of the cell uses energy and vesicles to dispose of waste products

Exam- material is enclosed in a vesicle that fuses with the plasma membrane allowing it’s contents to diffuse out

Exo= wasting exiting the cell that has entered

Spherical Cell enlarges (Exam Question)

As a spherical cell enlarges, it’s innermost part get farther away from the plasma membrane

* Once the cell become to big diffusion ( which is slow) can take long to supply important process deep within the cell

ANSWER- Once the cell gets too large, the distance between the middle of the cell and the outside of the cell becomes to great and takes too much energy to get something

Should know surface area to volume is an important ratio within cells

Surface area- volume the radius increases

• Volumes increases. much faster than surface area as a cell gets larger

• BASKETBALL = IT CAUSES TOO MUCH ENERGY TO GET ENERGY FROM OUTSIDE OF THE CELL TO THE INSIDE OF THE CELL

Why does the distance from the center to the membrane limit maximum cell size /what happens to the ratio as a cell grows?

? ( Spherical Cell) Exam

Volume increases at a faster rate than surface area

As a cell grows the surface area-to volume ratio decreases (from 3.0 to 0.75

How does Specialized junctions Allow Cells to Connect and Communicate?

Desmosomes- attaches cells together

• Anchors that holds cells together so movement doesn’t tear them apart ( small intestine)

• (a) in desmosomes protein filaments hold cells together

Tight Junctions- Make cell attachment leak proof

• A continuous waterproof seam stitched between cells so liquid can’t seep through ( found in tubes, sacs, they must hold the liquid without leaking) Unitary bladder

• (b) tight junctions proteins seal cells together

Gap Junction ( animals)

allows direct communication between the cells

Plasmodesmata ( plants)

Allows direct communication between cells