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

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 membrane components Proteins  Act as transport for some larger molecules  Increase contact with the water Cholesterol  Keeps the membrane “tight” and makes it less permeable to small molecules

The role of membrane components Carbohydrates  Chains act as “ID” tags (made in the SER (carbs) and attached to proteins and packaged in the Golgi)

Review of vocabulary Homeostasis  Maintenance of the cells internal conditions (pH, water, temperature, size, etc)

Review of Vocabulary Solution  Homogeneous 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”!

Not everything that passes through the phospholipids of the membrane are good! Polar molecules like Glucose and water

What passes through the phospholipid bilayer? Gases  Oxygen (O2) and nitrogen (N2) and CO2 Sometimes things that aren’t good for us!!!!

What types require a membrane protein Look at the diagram…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  

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 Diffusion Facilitated Diffusion Osmosis

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 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: GLUCOSEtoo 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 TeaStrong Iced Tea

Osmosis hill.com/sites/ /student_view0/chapter2/ani mation__how_osmosis_works.html hill.com/sites/ /student_view0/chapter2/ani mation__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 Conditions Hypotonic Isotonic Hypertonic

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 Which of the solutions is Hypertonic (as compared to the other)?

Inside is Hypertonic

10% Salt Solution 20% Salt Solution Which is hypertonic?

? Outside is Hypertonic

20% Salt Solution Isotonic:

Isotonic

Crenation Cytolysis Comparing Cell types chart

Plasmolysis Vs. Turgidity in Plant cells - Turgor pressure: Pressure that the water INSIDE the cell puts on the cell wall. Supports plant

hill.com/sites/ /student_view0/cha pter38/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 TransportActive 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, facilitate 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 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)

PHAGOCYTOSISPHAGOCYTOSIS: “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