1/13/ put HW(PM picture) into the bin. 2. Current science x3 3. videos! Presentation: Cell Transport PreLab 4.2 back & review HW: Quiz AND WS on cell transport

NEW DATE: Reassessment DUE TO THE SCHOOL CANCELLATIONS THE DATE HAS BEEN CHANGED to JANUARY 21st Re-assessment for Unit 3 Test BEFORE SCHOOL (7:00- 7:50) W/ MR. MAHON DURING 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

Membranes Keeps Cells Separate Most 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 cell They must be able to somehow cross the membrane. Called Cell Transport Cytosol

Vocab reminder! A. Solution: mixture of 2 or more components 1. Ex: seawater B. Solvent: present in the largest amount, what something is dissolving in. 1. Ex: water C. Solute: what dissolves into the solvent 1. 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 Diffusion Very 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 Diffusion Other small molecules need to move through a protein channel (small polar or ionic compounds)

Concentration Gradient Molecules 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 Gradient No 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

Osmosis Special name for diffusion of water When molecules can’t diffuse, water does Water diffuses towards the more concentrated side until the concentrations are balanced* *or another force is applied

Why? More solute, means more water bound to the solute Less free water, so it’s like a low concentration of water

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

Review Small, 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: Against the concentration gradient = Uses Energy!

Big Things E.g. macromolecules Too large to fit through membrane or proteins Membrane folds in

Endo/Exocytosis Big 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-Lab With your new table partners. Everyone answers on their worksheet. Do 1-5, then check in with me before #6 When 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