Cell Transport: Moving molecules in and out of the cell

Label the following parts of your diagram

Plasma membrane (about 6-7 nm wide)

A. Phospholipids (A1 is the phosphate head, A2 is the fatty acid tail)

F, G. Proteins Some have channels (G)

D. Carbohydrate Glycoproteins (C)

– this is a molecule where a carb is attached to a protein Glycolipids (B)

The is a molecule where a carb is attached to a phospholipid

E. Cholesterol

Plasma membrane

Phospholipid bilayer that surrounds all cells and certain organelles within the cell

Phospholipids

Hydrophilic Phosphate head

Hydrophobic Fatty acid Tails

In water what will happen?

Water on outside of cell

Water on outside of cell

Also Water on Inside of cell

Double Layer Allows:

All hydrophobic parts to be away from water

All hydrophilic parts to be near water

Membranes are MORE than just phospholipids

Key components

The role of four key membrane components

Phospholipids allow only small non-polar molecules to enter

Proteins Act as transport for some larger molecules All transport of polar or charged molecules Increase contact with the water

Cholesterol Fluidity control (not too rigid, not too loose (more cholesterol =

more rigid.

The role of membrane components

Carbohydrates Chains act as “ID” tags help the body to

recognize whether a cell is “self” or “foreign”

Review of vocabulary

Homeostasis Maintenance of the cells internal conditions (pH, water,

temperature, size, etc)

The main job of the cell membrane is to maintain internal conditions!

Review of Vocabulary

SolutionHomogeneous mixture

Solute: what is dissolved (in living things this can be glucose, amino acids, salts, etc)

Solvent: What is the dissolver (in living things, this is water)

What needs to enter and leave the cell

What needs to enter the cell (what goes IN)? Gases like O2, N2, CO2 Ions Small polar molecules (water) Polar molecules (glucose, amino acids, fatty acids,

nucleotides)What needs to leave the cell (OUT)?

excess H2O, CO2, other waste products, glucose (in a leaf cell or in an intestinal cell), ions, large polar molecules (proteins) , N2, O2 (in the case of plant cells)

Selective Permeability

The membrane allows some, but not all molecules into the cell

The membrane DOES NOT necessarily protect the cell from “Bad things”!

http://www.youtube.com/watch?v=Pt4Ch-YW-xs

Not everything that passes through the phospholipids of the membrane are good!

Polar molecules like Glucose and water

What passes through the phospholipid bilayer?

GasesOxygen (O2) and nitrogen (N2) and CO2

http://education.seattlepi.com/kinds-molecules-can-pass-through-plasma-membrane-through-simple-diffusion-4587.html

Sometimes things that aren’t good for us!!!!

What types require a membrane protein

Look at the diagram (slide 25)…what cannot go through the membrane but is required by cells?

What do cells need that CAN’T pass through the phospholipid bilayer?

Small polar molecules (H2O) Ions

(Na+, Cl-, K+, Ca++) Large polar molecules

(Sugars, Amino Acids)

How do these things get into the cell????

These must go through proteins to get in

Need the proteins to “help” (facilitate) moving the molecule into the cell or out of the cell

http://www.d.umn.edu/~sdowning/Membranes/diffusionanimation.html

http://www.youtube.com/watch?v=NC8pIzNzqrc

Passive Transport

Requires no energy; molecules move from an area of high concentration to an area of low concentration.

Molecules “roll down the hill” to spread out

Three types of Passive Transport

DiffusionFacilitated DiffusionOsmosis

Diffusion

Movement of solutes from areas of high concentration to areas of low concentration until concentrations are equal

Move due to a concentration gradient.

Concentration Gradient = differences in Concentration

Diffusion – Do we need a membrane?

High Conc. Low Conc.

Can occur without a membrane

Think of it as “spreading out”

Progression of Liquid Diffusion

http://www.youtube.com/watch?v=aVc_LEuiZ-4

?

High Conc. Low Conc.

The dye moves from an area of HIGH CONCENTRATION to an area of LOW concentration (of the dye)

Facilitation

Facilitated Diffusion

movement of solute from high concentration to low concentration

…………..BUT requires transport protein

…………..WHY? to move molecule that are too big or polar to get through the phospholipid bilayer

EXAMPLE: GLUCOSE too big for the PL membrane

Facilitated Diffusion compared to Diffusion

One requires “help” or facilitation to get through the membrane

Osmosis

A Passive Process where water moves across a cell membrane from an area that is hypotonic (lots of water, little solute) to an area that is hypertonic (little water, lots of solute). THE SOLUTE DOES NOT MOVE!!!!

PICTURE: Think of water as trying to dilute the concentrated side to make the concentrations equal (it can only do this if water moves, but not the solute!). Eventually both sides are “medium”

Weak Iced Tea Strong Iced Tea

Osmosis

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Osmosis and Tonicity

Water will move from an area of high concentration of WATER (low solute) to low concentration of water ( high solute)

Tonicity is concerned with the concentration of solute

Water moves from LOW tonicity (high water) to HIGH tonicity (low water)

A B A B

TONICITY

Term used to compare the concentrations (of solute) of two solutions

The tonicity will determine in WHICH DIRECTION the water flows

3 ConditionsHypotonic

IsotonicHypertonic

Terms used to describe tonicity

The solution with the higher concentration is called Hypertonic.

The solution with the lower concentration is called Hypotonic

If the concentrations are equal, they are called Isotonic

20% Salt Solution

10% Salt Solution

Assume the yellow circle is a cell. Is the salt solution outside the cell hypotonic, hypertonic or isotonic to the cell?

Outside is Hypertonic

Animal cells swell andCould break open (CYTOLYSIS)

Plant cells exhibit HIGH TURGORPRESSURE (they like this)

10% Salt Solution

20% Salt Solution

Is the solution hypotonic or hypertonic to the cell?

?Outside is Hypertonic

Animal cells shrivel. This iscalled CRENATION

The cell membraneof plant cells pulls Away from the cell wallPLASMOLYSIS

20% Salt Solution

20% Salt Solution

Isotonic:

Isotonic

Animal cells like thisenvironment(Isotonic cell)

While the PlantCell is at equilibrium, It prefers that theenvironment is hypotonic)

CrenationC

ytol

ysis

Comparing animal cells at different

PlasmolysisVs.

Turgidity in Plant cells

- Turgor pressure: Pressure that the water INSIDE the cell puts on

the cell wall. Supports plant

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter38/animation_-_osmosis.html

A B A B

Active Transport

Cell must use energy to force molecules to move across the membrane from a low concentration to a high concentration.

Usually used to move ion and since ions can not go through the phospholipids requires a transport protein . Usually moving from a low to high concentration

Active Transport:

Vesicle transport: when molecules are too big for the proteins!

EXOCYTOSIS – moves molecules OUT of the cell

ENDOCYTOSIS – moves molecules INTO the cell.

Vesicle Transport

Vesicle transport is different from Diffusion, Osmosis, facilitated diffusion and active transport

HOW IS IT DIFFERENT? Moves large quantities

(many molecules) at a time.

Requires energy

Must package the molecules in a vesicle (efficient transport)

Vesicle Transport

Making a vesicle requires the cell to exert energy in the form of ATP.

Concentration differences don’t matter

Vesicle transport is named based on the direction the vesicle is moving (into or out of the cell)

Moving materials out of a cell in a vesicle is called exocytosis. Moving materials into the cell is called endocytosis.

Exocytosis – Bulk Transport out of cell

Way of releasing large quantities of stuff from the cell including : Hormones, mucus and cell wastes

NEEDS ATP

Bulk transport into cell

Endocytosis

PHAGOCYTOSIS

PINOCYTOSIS

(SOLIDS)

(LIQUIDS)

PHAGOCYTOSIS: “CELL EATING” PROTEINS, BACTERIA, DEAD CELLS ARE ENCLOSED IN A PL. MEMB. SAC.

NEEDS ATP

PINOCYTOSIS: “Cell Drinking”

Plasma membrane “sinks” below a liquid containing small solutes and the sides “fuse” creating a vesicle

OCCURS IN MOST CELLS, EXP: KIDNEYS AND INTESTINES

REVIEW of CELL STRUCTURES AND FUNCTIONS (Eukaryotes)

Hperlink for Cell Structure and Function