Cellular Transport

An Overview

How does the polarity of water make hydrogen bonding possible?

• Water is a polar molecule– slightly positive end (H) and slightly negative end

(O) because electrons spend more time in orbit around larger O molecule

– H’s of one water molecule are attracted to O’s of another• Form Hydrogen bonds• H-bonds are usually weak, but are unusually strong in

water• Gives water several important properties

Hydrogen Bonding• http://www.classzone.com/cz/bo

oks/bio_09/resources/htmls/animated_biology/unit1/bio_ch02_0041_ab_bonding.html

How are the 3 properties important in cells and organisms?

• 3 important properties:– Cohesion• Water molecules stick together• Surface tension, blood

– Adhesion• Water molecules stick to other things• Capillary action

– High Specific Heat• Water resists changes in temperature• Chemical reactions produce a lot of heat• Maintains homeostasis

What is blood?

• Liquid part is called plasma– About 95% water

• Also includes red blood cells, white blood cells, platelets, sugars, proteins, etc.

Water as a Solvent

• Water is an excellent solvent, but not the “universal solvent” as commonly called

• Water readily dissolves polar substances and ionic compounds– Sugars, proteins, salts

• Water does not dissolve nonpolar substances– Fats, oils

Double Layer of Phospholipids

Other components of the Cell Membrane

• Proteins– Aid in transport of materials in and out of cell– Anchor cell membrane to cytoskeleton

• Carbohydrate chains– Identify cells

• Cholesterol– Strengthen membrane

How is the cell membrane like a window screen?

• Selective Permeability– It allows some molecules

to pass through it but not others

– Some molecules need an opening, like a transport protein

Cellular Transport

• Two types– Passive transport• Particles move from higher concentration to lower

concentration, requires no cellular energy• Diffusion, facilitated diffusion, osmosis

– Active Transport• Particles move from lower concentration to higher

concentration, requires cellular energy• Pumps, endocytosis, exocytosis

Passive Transport

Passive Transport: Osmosis

Tonicity Animation

Active Transport

Active Transport Passive Transport

Active transport in the body

• Sodium-Potassium Pumps– Help your nerve cells to function– Pump sodium ions out of and potassium ions into

cell• Endocytosis– Cell eating and drinking (single-celled organisms)

• Exocytosis– Cell secretions, waste disposal

Endo/Exocytosis

Cellular Transport Review

• http://www.classzone.com/cz/books/bio_09/resources/htmls/animated_biology/unit2/bio_ch03_0093_ab_cellmem.html