CELL MEMBRANE & CELL MEMBRANE & TRANSPORTTRANSPORT

PRE-AP BIOLOGYPRE-AP BIOLOGY

CELL MEMBRANECELL MEMBRANE

Separates cell contents from the environmentSeparates cell contents from the environmentComposed of 2 groupsComposed of 2 groups

1.1. PhospholipidsPhospholipidsa.a. Head with 2 tailsHead with 2 tailsb.b. Phosphate group & lipidPhosphate group & lipidc.c. HEAD: polar, attracts hydrogen molecules (hydrophilic)HEAD: polar, attracts hydrogen molecules (hydrophilic)d.d. TAIL: non-polar; repels water (hydrophobic)TAIL: non-polar; repels water (hydrophobic)

*Grease on hands (need soap)*Grease on hands (need soap)-The pushing & pulling (repelling/attracting water) forms a layer -The pushing & pulling (repelling/attracting water) forms a layer

of phospholipids: LIPID BILAYERof phospholipids: LIPID BILAYER

2.2. ProteinsProteinsa.a. Located within the layer & act as passageways for some Located within the layer & act as passageways for some

things to passthings to passb.b. Example: food, wastesExample: food, wastes

LIPID BILAYERLIPID BILAYER

Not firm or continuousNot firm or continuous

More fluidMore fluid

Non-polar zone keeps particles from Non-polar zone keeps particles from getting into the cell: “barrier”getting into the cell: “barrier”

Phospholipids float within bilayerPhospholipids float within bilayer

Example: light oil or a soap bubbleExample: light oil or a soap bubble

FLUID MOSAIC MODELFLUID MOSAIC MODEL

Components of membrane are fluid or Components of membrane are fluid or constantly movingconstantly moving

Fluid property allows it to seal itself if Fluid property allows it to seal itself if brokenbroken

Arrangement of phospholipid & protein Arrangement of phospholipid & protein molecules resemble the tiles of a mosaic molecules resemble the tiles of a mosaic artart

CELL MEMBRANE IS SIMILAR TO CELL MEMBRANE IS SIMILAR TO A DOORA DOOR

PROTEIN=LOCKPROTEIN=LOCK

THINGS THAT CAN CROSS=KEYTHINGS THAT CAN CROSS=KEY

EVERYTHING MOVES FROM HIGH EVERYTHING MOVES FROM HIGH CONCENTRATION TO LOW CONCENTRATION TO LOW CONCENTRATIONCONCENTRATION

CELL MEMBRANE: LIPID CELL MEMBRANE: LIPID BILAYERBILAYER

PASSIVE TRANSPORTPASSIVE TRANSPORT

Movement of substances through a cell’s Movement of substances through a cell’s membrane without using energymembrane without using energy

1.1. DiffusionDiffusiona. Water molecules move quickly & randomlya. Water molecules move quickly & randomlyb. Movement from high # to low # water moleculesb. Movement from high # to low # water moleculesc. CONCENTRATION GRADIENTc. CONCENTRATION GRADIENTd. Once all molecules have diffused throughout the d. Once all molecules have diffused throughout the

solution, equilibrium is reachedsolution, equilibrium is reached1. Solute: dissolved substances1. Solute: dissolved substances2. Solvent: dissolves solute2. Solvent: dissolves solute3. Solution: mixture of solutes & solvents3. Solution: mixture of solutes & solvents

**Oxygen in, Carbon dioxide out; Kidney dialysis**Oxygen in, Carbon dioxide out; Kidney dialysis

PASSIVE TRANSPORTPASSIVE TRANSPORT

2. Osmosis2. Osmosisa. Diffusion of water molecules across a a. Diffusion of water molecules across a selectively permeable membrane from high to selectively permeable membrane from high to low concentration of soluteslow concentration of solutesb. Water molecules accumulate on one side & b. Water molecules accumulate on one side & create pressure, can be great enough to burst create pressure, can be great enough to burst cellcellc. c. Osmotic pressureOsmotic pressure

1. increased water pressure resulting from 1. increased water pressure resulting from

osmosisosmosis2. strong cell wall can withstand pressure2. strong cell wall can withstand pressure

PASSIVE TRANSPORTPASSIVE TRANSPORT

3. 3. Facilitated DiffusionFacilitated Diffusiona. Diffusion through selective poresa. Diffusion through selective poresb. No energy usedb. No energy usedc. Example: glucose moves into most cells by facilitated c. Example: glucose moves into most cells by facilitated diffusiondiffusion

HOW?HOW?-Glucose is not lipid soluble, too large for membrane -Glucose is not lipid soluble, too large for membrane channelschannels-Channels do NOT change-Channels do NOT change-Carrier molecules change shape so that glucose can be -Carrier molecules change shape so that glucose can be ‘carried’ across membrane‘carried’ across membrane-Once released, glucose’s original shape returns-Once released, glucose’s original shape returns-Insulin facilitates glucose movement-Insulin facilitates glucose movement

P.T. (cont.)P.T. (cont.)

4. FILTRATION4. FILTRATION-Separation of solids from liquids-Separation of solids from liquids-Molecules forced through a membrane-Molecules forced through a membranea. Filter Paper: water is forced through a porous a. Filter Paper: water is forced through a porous membrane (paper)membrane (paper)

-Example: coffee filter-Example: coffee filter-Capillaries release water & small dissolved -Capillaries release water & small dissolved

substances through poressubstances through pores-Larger particles (protein) not released-Larger particles (protein) not released-Movement driven by blood pressure-Movement driven by blood pressure-Proteins retain water=causing occasional edema -Proteins retain water=causing occasional edema

due to overproduction of tissue fluid (edema=swelling)due to overproduction of tissue fluid (edema=swelling)

RELATING TO OSMOSISRELATING TO OSMOSIS

Hypertonic: Osmostic pressure of solution is Hypertonic: Osmostic pressure of solution is greater than that of body fluid (more solutes)greater than that of body fluid (more solutes) Example: eating country ham, salt on a slugExample: eating country ham, salt on a slug

Isotonic: Osmostic pressure of solution is Isotonic: Osmostic pressure of solution is greater than that of body fluid (equal solutes)greater than that of body fluid (equal solutes) IV SolutionIV Solution

Hypotonic: Osmotic pressure of solution is lower Hypotonic: Osmotic pressure of solution is lower than that of body fluidthan that of body fluid Slug in example aboveSlug in example above

Hyper: cells lose water & shrinkHyper: cells lose water & shrinkHypo: cells gain water & swellHypo: cells gain water & swell

ACTIVE TRANSPORTACTIVE TRANSPORT

Uses energy to transport a particle through Uses energy to transport a particle through a membrane against a concentration a membrane against a concentration gradient (low to high)gradient (low to high)

Transports molecules that the cell needs Transports molecules that the cell needs to survive (very little on the outside of the to survive (very little on the outside of the cell)cell)

Needs energy to cross, cannot diffuseNeeds energy to cross, cannot diffuse

Example: food, moleculesExample: food, molecules

ACTIVE TRANSPORT (cont.)ACTIVE TRANSPORT (cont.)

1.1. Sodium-Potassium PumpSodium-Potassium Pumpa.a. Most important energy-using process in your Most important energy-using process in your

bodybody

b.b. Over 1/3 of energy used by a human cell, Over 1/3 of energy used by a human cell, that is not dividing, is used in this pumpthat is not dividing, is used in this pump

c.c. Nerves use this pump to send signals Nerves use this pump to send signals through the bodythrough the body

d.d. Also transports food moleculesAlso transports food molecules

ACTIVE TRANSPORT (cont.)ACTIVE TRANSPORT (cont.)2. Endocytosis2. Endocytosis

a. Larger meala. Larger mealb. Engulfs particleb. Engulfs particlec. Requires energyc. Requires energyd. Vesicle forms & transports foodd. Vesicle forms & transports foode. 2 typese. 2 types

-Phagocytosis-Phagocytosis *Cell eating*Cell eating *Cell takes in solids rather than liquids*Cell takes in solids rather than liquids *Ex: White blood cell engulfing bacteria (vesicle *Ex: White blood cell engulfing bacteria (vesicle

forms around bacteria & decomposes, which expels it)forms around bacteria & decomposes, which expels it)-Pinocytosis-Pinocytosis *Cell drinking*Cell drinking *Cell takes in liquid & a vesicle forms to hold the liquid*Cell takes in liquid & a vesicle forms to hold the liquid *Liquid eventually becomes part of the cytoplasm (supplying *Liquid eventually becomes part of the cytoplasm (supplying

proteins & proteins & nutrients)nutrients)Phagocytosis & Pinocytosis engulf molecules near cell membranePhagocytosis & Pinocytosis engulf molecules near cell membrane

A.T. (cont.)A.T. (cont.)

3. EXOCYTOSIS3. EXOCYTOSIS

a. Dumping of wastes out of the cell a. Dumping of wastes out of the cell (through the vesicle)(through the vesicle)

-Vesicle fuses with cell membrane & -Vesicle fuses with cell membrane &

expels wastesexpels wastes

-Example: Gland cells secrete -Example: Gland cells secrete

hormones into the bloodstreamhormones into the bloodstream