Homeostasis and TransportAnd Cell Structure

Types of Transport Cells move molecules using different types

of passive and active transport These differ from each other by whether or

not cells must use energy.◦ Passive= no energy◦ Active = use energy

Passive Transport Passive transport —movement of

substances through a membrane that requires NO ENERGY

Types:◦ Diffusion —movement of molecules from high to

low concentration◦ Osmosis —movement of WATER from high to low

concentration◦ Facilitated Diffusion —assisted diffusion of large

or insoluble molecules through a cell membrane.◦ Ion Channel Diffusion —movement of ions from

high to low concentration.

Molecules move from high to low concentration.◦ Move down their concentration gradient◦ Molecules can move through semi-permeable membranes◦ Continues until equilibrium is reached.

Diffusion

Molecules to large to diffuse through the membrane must find a channel pore to travel through

Osmosis is the movement of WATER from high to low concentration.

Depends on the concentration of solutes inside and outside of the cell.◦ Hypotonic Solution—solution outside the cell has a

lower concentration of solute molecules than inside. Water moves into the cell. (Oh NO! She’s gonna blow!)

◦ Hypertonic Solution —a solution outside the cell has a higher concentration of solute molecules than inside. Water moves out of the cell. (Cell shrinks!)

◦ Isotonic Solution —a solution in which the concentrations of solute molecules are equal on both sides of the membrane.

Osmosis

Control of osmosis◦ Contractile

vacuoles◦ Solute pumps◦ Cell Walls

Cytolysis —bursting of a cell due to osmosis.

Identify the pictures as a cell in an isotonic solution, hypertonic solution and hypotonic solution

IsotonicHypotonic Hypertonic

Facilitated Diffusion Assisted diffusion of large or insoluble

molecules through a cell membrane. Carrier Proteins help the molecules to move

from high to low concentration. Glucose is transported to cells in this way.

http://www.ncbi.nlm.nih.gov/books/NBK9847/

Ion Channel Diffusion Several ions are vital to cells but cannot

pass through the cell membrane because they are not soluble in lipids. They are:◦ Sodium (Na+) ◦ Potassium (K+ ) ◦ Calcium (Ca2+ ) ◦ Chlorine (Cl-)

They require specific ion channels to pass through membranes

http://tantalusprime.blogspot.com/2008_02_01_archive.html

Many ion channels have gates that close or open in response to three stimuli: 1. stretching of cell membrane

2. electrical signals3. chemical signals

Active Transport Active Transport —movement of

substances through a cell membrane that REQUIRES ENERGY.

Molecules move from low to high concentration ( “up” their concentration gradient).

The Carrier Proteins involved require energy from ATP and are called Cell Membrane Pumps.

Example: Sodium-potassium pump

Endocytosis Movement of VERY LARGE PARTICLES into a

cell. The cell membrane pinches off to trap the particle inside a vesicle which can then transport the particle throughout the cell.

Two types of endocytosis:

Phagocytosis—movement of large particles or whole cells

Pinocytosis—movement of fluids

Exocytosis Movement of VERY LARGE PARTICLES out of a cell. Vesicles

bring particles to the cell membrane to be released.

Cell—smallest unit of life All living things are made of one or many cells.

◦ Unicellular◦ Colonies◦ Multicellular

Cells come only from other cells. Levels of organization are:

Cell Theory

Cells Tissues Organ Organ System Organism

Cell Types (two basic types) Prokaryotes —cells without a

nucleus or membrane-bound organelles◦ Include bacteria and archaebacteria

Eukaryotes —cells with a nucleus and membrane-bound organelles◦ Include cells from plants, animals, fungi

and protists

http://www.phschool.com/science/biology_place/biocoach/cells/common.html

Features common to both prokaryotic and eukaryotic cells include:◦ DNA —genetic material located in the nucleus of

eukaryotic cells and in the nucleoid region of prokaryotic cells

◦ Plasma Membrane —outer boundary of cell◦ Cytoplasm —all the material inside the plasma

membrane, (not including the nucleoid region or nucleus). It includes a fluid part called the cytosol and many organelles and other particules floating in it.

◦ Ribosomes —site of protein synthesis

http://www.phschool.com/science/biology_place/biocoach/cells/common.html

Plasma Membrane —Phospholipid bilayer that surrounds a cell. Controls what gets in and out.

Cell Organelles

Phospholipids have hydrophilic heads and hydrophobic tails

Embedded in the phospholipid bilayer are different types of proteins for transport, identification and binding.

Cytoplasm —gel like substance that fills the cell. Organelles float in cytoplasm.

Nucleus —control center of cell. Contains DNA.

Mitochondria —powerhouse of cell. Site of cellular respiration (where ATP is made). Contains its own DNA.

Ribosomes —protein factories of cell. Can float in cytoplasm or be attached to ER.

Cell Organelles

Endoplasmic Reticulum —transport system of cell. Make up a large part of the endomembrane system. Rough (with ribosomes attached) and Smooth (with no ribosomes)

Golgi Apparatus —packaging center. Receives proteins and lipids; modifies and packages them into vesicles.

Vesicles —transport vehicles. Types: Lysosomes, peroxisomes, glyoxysomes, endosomes.

Cell Organelles

Plant cells have all of the same structures plus:◦ Cell wall —made of cellulose◦ Central Vacuole —to store water◦ Plastids —including chloroplasts (contain their

own DNA), chromoplasts and amyloplasts.

Cell Organelles

Compare them all

http://gmgmesjwk.pbworks.com/f/ksjakja.bmp

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