Grade breakdowns—Period 5

A=4B=5C=13F=3 (Mandatory tutoring)

Build a cell membrane

Aka lipid bilayer Aka plasma membrane

LABEL 5 components

Label outside and inside cell

Pick up 2 different scripts from demo table (1 per 2 people)

Practice with a partner

What is the role of:-nucleus-RNA-ribosomes-rough ER-Golgi-transport vessicles

Draw diagram

Danish Review

Make 4 higher level questions from

1) Ecology2) Evolution3) Chemistry4) Cells

how does ... compare/contrast with ...? what evidence can you list for ...?

SYNTHESIS creating a unique, original product that may be in verbal form or may be a physical object combination of ideas to form a new whole

what would you predict/infer from ...? what ideas can you add to ...? how would you create/design a new ...? what might happen if you combined ...? what solutions would you suggest for ...?

EVALUATION making value decisions about issues resolving controversies or differences of opinion development of opinions, judgements or decisions

do you agree that ...? what do you think about ...? what is the most important ...? place the following in order of priority ... how would you decide about ...? what criteria would you use to assess ...?

Announcements

Cells test moved to Thursday, Dec 1 Lab report due tomorrow

Keep your Chapters 8 + 9 notes

Answer a flashcard for 0.5 points

Ch.7~MembraneStructure&Function

Fluid mosaic model

Exit Quiz: Membrane

1) Draw a membrane and label 5 components

2) Describe the role of 6 of the 6 membrane proteins

Bonus: Explain the 4 levels of a protein

Membrane structure, I

Selective permeability Amphipathic~

hydrophobic & hydrophilic regions

1935 Davson Danielli sandwich model

Singer-Nicolson: 1972 fluid mosaic model

Cell membrane must be more than lipids… In 1972, S.J. Singer & G. Nicolson proposed

that membrane proteins are inserted into the phospholipid bilayer

It’s like a fluid…It’s like a mosaic…It’s the Fluid Mosaic Model!

Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer

Extracellular fluid

Cholesterol

Cytoplasm

Glycolipid

Transmembraneproteins

Filaments ofcytoskeleton

Peripheralprotein

Glycoprotein

Phospholipids

1972, S.J. Singer & G. Nicolson proposed Fluid Mosaic Model

Phospholipids

Fatty acid

Phosphate

Phosphate head hydrophilic

Fatty acid tails hydrophobic

Arranged as a bilayer

Aaaah, one of thosestructure–functionexamples

“repelled by water”

“attracted to water”

Arranged as a Phospholipid bilayer

polarhydrophilicheads

nonpolarhydrophobictails

polarhydrophilicheads

Serves as a cellular barrier / border

H2Osugar

lipids

salt

waste

impermeable to polar molecules

Cell membrane defines cell Cell membrane separates living cell from

aqueous environment thin barrier = 8nm thick

Controls traffic in & out of the cell allows some substances to cross more easily than

others• hydrophobic (nonpolar) vs. hydrophilic (polar)

Permeability to polar molecules? Membrane becomes semi-permeable via

protein channels specific channels allow specific material across

cell membrane

inside cell

outside cell

sugaraaH2O

saltNH3

Cell membrane is more than lipids… Transmembrane proteins embedded in

phospholipid bilayer create semi-permeabe channels lipid bilayermembrane

protein channelsin lipid bilyer membrane

2007-2008

Why areproteins the perfect molecule to build structures in the cell membrane?

Proteins domains anchor molecule Within membrane

nonpolar amino acids • hydrophobic • anchors protein

into membrane

On outer surfaces of membrane in fluid polar amino acids

• hydrophilic

• extend into extracellular fluid & into cytosol

Polar areasof protein

Nonpolar areas of protein

NH2

H+

COOH

Cytoplasm

Retinalchromophore

Nonpolar(hydrophobic)-helices in thecell membrane H+

Porin monomer

-pleated sheets

Bacterialoutermembrane

proton pump channel in photosynthetic bacteria

aquaporin = water channel in bacteria

function through conformational change = protein changes shape

function through conformational change = protein changes shape

Examples

H2O

H2O

H+

H+

Many Functions of Membrane ProteinsOutside

Plasmamembrane

InsideTransporter Cell surface

receptorEnzymeactivity

Cell surface identity marker

Attachment to thecytoskeleton

Cell adhesion

“Antigen”

“Channel”

Membrane Proteins Proteins determine membrane’s specific functions

cell membrane & organelle membranes each have unique collections of proteins

Classes of membrane proteins: peripheral proteins

• loosely bound to surface of membrane

• ex: cell surface identity marker (antigens) integral proteins

• penetrate lipid bilayer, usually across whole membrane

• transmembrane protein

• ex: transport proteins– channels, permeases (pumps)

Membrane carbohydrates Play a key role in cell-cell recognition

ability of a cell to distinguish one cell from another

• antigens important in organ &

tissue development basis for rejection of

foreign cells by immune system