1/13/20151. put HW(PM picture) into the bin.2. Current science x33. videos!Presentation: Cell TransportPreLab4.2 back & reviewHW: Quiz 4.1-4.2 AND WS on cell transport

NEW DATE: ReassessmentDUE TO THE SCHOOL CANCELLATIONS THE

DATE HAS BEEN CHANGED to JANUARY 21stRe-assessment for Unit 3 Test

BEFORE SCHOOL (7:00- 7:50) W/ MR. MAHONDURING Ac-Lab WITH YOUR BIO TEACHER.

You can split the sections between morning and ac lab If needed. EX: 3.1 in the morning & 3.2 in aclab or all of them in the morning or all in AcLab

Make sure to sign up w/ YOUR biology teacher and specify the time & the sections.

Current science

videos

Crossing the Membrane

Membranes Keeps Cells SeparateMost things are either too big to cross the membrane

OR they are polar and won’t mix with the membrane

Creates an internal environment different from the outside world(e.g. it has enzymes, proteins, sugars, ATP, NADH, FADH etc. floating around)

Called a semi-permeable membrane

What does this have to do with cells?Lots of things must enter and exit

the cellThey must be able to somehow cross

the membrane.Called Cell TransportCytosol

Vocab reminder!A. Solution: mixture of 2 or more components

1. Ex: seawaterB. Solvent: present in the largest amount, what

something is dissolving in.1. Ex: water

C. Solute: what dissolves into the solvent1. Ex: salt

D. Concentration gradient: difference in the solute concentration across space or across a membrane

E. Molecular Motion: the random movement of

atoms resulting in their collision with other atoms.

1. Simple DiffusionVery small hydrophobic (non-polar) molecules

can simply slip between the membranes and cross the hydrophobic layer

Some small polar molecules can slowly cross

2. Facilitated DiffusionOther small molecules need to move

through a protein channel (small polar or ionic compounds)

Concentration GradientMolecules on the top are likely to collide and

knock each other towards the bottom

High Concentration

Zero Concentration

More collisions

No collisions

Diffusion

High Concentration

Low Concentration

More collisions

Fewer collisions

Some will still get knocked back, but more will come to this side

Equilibrium / No Concentration GradientNo net change in concentration. Molecules

still move but on average the concentrations stay the same

Molecules on either side are equally likely to collide and be knocked to the other side

Medium Concentration

Medium Concentration

OsmosisSpecial name for

diffusion of waterWhen molecules can’t

diffuse, water doesWater diffuses

towards the more concentrated side until the concentrations are balanced*

*or another force is applied

What if We Want to Move Things Against the Gradient?Active Transport!We must invest energy to “pump”

molecules

ReviewSmall, non-charged

molecules can simply diffuse

Small, polar or charged molecules can pass through a protein

Energy must be invested to move things against the gradient

Diffusion, osmosis & facilitated diffusion: With the concentration gradient = No Energy

Active Transport: Againstthe concentration gradient = Uses Energy!

Big ThingsE.g. macromoleculesToo large to fit through membrane or

proteinsMembrane folds in

Endo/ExocytosisBig things must

enter through endocytosis and form a vesicle

Big things must exit by exocytosis, where the vesicle becomes part of the plasma membrane

Pre-LabWith your new table partners.Everyone answers on their worksheet.Do 1-5, then check in with me before #6When you are done you can grab the Cell

transport WS.Remind me to return 4.2 when there’s 5

minutes left.

HW reminder: cell transport ws and quiz 4.1-4.2