Transcript Powerpoint: Cell Membranes

Homework:
 Graphs & Analysis Q’s for Lab 1B
 Do Now:
1. New Seats! Pick a place to sit.
2. Remember back to chemistry…

a) What is a mole?
b) What does the unit “molarity” measure? How is it
calculated?
Write this in your notebook.

After discussing the Do Now:
 Read the intro and complete Pre-Lab #1-3 on Lab 1B

Homework:
 Graphs & Analysis Q’s for Lab 1B

Goal for Today:
 Design and carry out an experiment to measure the rate of osmosis
into model cells of varying concentrations

Agenda:
 Pre-Lab Discussion
 Hypotheses
 Procedure
 Set up & start experiment
 30 min. wait time – discuss & hand in Lab 1A; set up graphs &
start analysis for 1B
 Collect results & record them on the class Excel sheet
 Graphs must be done by hand for this lab!
Homework:
 Work on Prob Set 8!
 Do Now:

Take out the Lab and be ready to discuss the results and analysis
questions.

Goals for Today:
 Analyze the results of the osmosis lab
 Explain how the structure of the cell membrane allows it to regulate
the movement of substances into and out of the cell

Results:
 We deleted Group 3’s data… do all the other
groups’ data seem okay?
 What conclusion can we draw about the rate of
osmosis in the 30 minute period of the expt?



AQ #1: What does explain mean?
AQ #3: Why % change?
Other questions?

Forms the boundary of the cell (act as a
barrier between the cell and its environment)

Selectively allows certain molecules to pass
into/out of cells (selective permeability)

[Also has various signaling & recognition
functions, but we’ll leave those for later…]
4 Main Structural Components:
Phospholipids
II. Proteins
III. Glycolipids & Glycoproteins – Carbohydrates
IV. Cholesterol
Plus the ExtraCellular Matrix
I.
Phospholipids


Amphipathic Structure
(polar on one end, nonpolar
on the other end)
In water: Assemble into a
micelle or a lipid bilayer

Phospholipid Bilayer w/ embedded protein
channels (pores)

Also contains various other proteins,
glycoproteins, and glycolipids for various
signaling and recognition functions
Two main types:
Peripheral – on the
surface of the
membrane
Integral/Transmembrane –
passing all the way
through the
membrane

Function primarily as
signaling/recognition
molecules
 Ex: ABO Blood Types on
Red Blood Cells
How do proteins and
carbs get attached to
the membrane?


A lipid (steroid) embedded between the
phospholipid tails
Function: moderates the fluidity of the
membrane (the Goldilocks molecule)

Protein and glycoprotein fibers outside the
cell, anchored to the membrane
Functions:
• Connect and stabilize
cells within tissues
• Communicate between
cells
• Regulate cell activity by
influencing gene
expression (which genes
turned on/off)
EXPERIMENT:

Small Molecules
 Passive transport – down the concentration gradient
(high to low)
▪ Simple diffusion – straight through phospholipids
▪ Facilitated diffusion – through a transport protein
SIMPLE DIFFUSION
FACILITATED DIFFUSION
What kinds of molecule would use each type of diffusion?

Small Molecules
 Passive transport – down the concentration gradient (high to low)
▪ Simple diffusion – straight through phospholipids
▪ Facilitated diffusion – through a transport protein
 Active transport – requires ATP, goes from low to high conc.
▪ Ex: Na/K pump

Large Molecules
 Endocytosis – entrance via vesicle pinching off from cell
membrane
▪ Phagocytosis – cell eating (big chunks)
▪ Pinocytosis – cell drinking (water and small nutrients)
 Exocytosis – exiting via vesicle merging into cell
membrane

Turgid –
 Firm and sturdy due to being filled with water
 Turgid cells have turgor pressure – pressure of water pushing outward on
cell wall
 Keeps plants upright when in a hypotonic environment

Flaccid –
 Limp, un-sturdy due to lack of turgor pressure
 Plant cells are flaccid when in isotonic environments
 Think wilted plant

Plasmolysis –
 The shrinking of the cytoplasm and plasma membrane away from the cell
wall
 Caused by osmosis out of the cell due to a hypertonic environment

Marine: not enough water, too much salt!
 Protozoa: Osmoconformers (cytoplasm has same
solute concentration as ocean water)
 Fish: Drink a lot, really concentrated urine, pump
salt out through gills

Freshwater: too much water! (danger of cells
exploding)
 Protozoa: Contractile vacuoles
 Fish: Really dilute urine

Go to Ch. 7 videos on CD
 http://highered.mcgraw-
hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::
/sites/dl/free/0072437316/120068/bio02.swf::Endoc
ytosis%20and%20Exocytosis
 Paramecium (watch closely for contractile vacuole)
 Phagocytosis (Amoeba [green] consuming yeast
cells [red])