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LB145 Sec 001-004. Today’s Outline. HAND IN StudyNotes – front of classroom. Homework Assignment due on Tuesday. Create a Classroom Code of Conduct. Protein review. Lipids + Membranes A human experiment Membrane transport. What is a protein?. What do proteins do?.

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LB145 Sec 001-004

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LB145Sec 001-004

Today’s Outline

  • HAND IN StudyNotes– front of classroom.

  • Homework Assignment due on Tuesday.

  • Create a Classroom Code of Conduct.

  • Protein review.

  • Lipids + Membranes

  • A human experiment

  • Membrane transport

What is a protein?

What do proteins do?

Where do you get proteins from?

  • Discuss with your neighbor:

    • What are some foods that are high in protein content?

    • What are some foods that contain no protein?

What is a protein?

  • A protein is a chain of amino acids.

  • ALL foods contain proteins – because all living cells contain proteins.

  • When we eat proteins, our body breaks them down into their composite amino acids. We use these amino acids to make our own proteins.

A Chain of Amino Acids


Clicker Question: What is a lipid?

  • Is a group of molecules that includes: fats, steroids and phospholipids.

  • Molecules that have fatty-acid side chains.

  • Carbon-containing compounds that are non-polar and hydrophobic.

  • A molecule with a hydrophilic head and a hydrophobic tail that is a major component in cell membranes.


  • A lipid is an organic compound, found in organisms, that is primarily non-polar and hydrophobic.

  • Three types to know

    • Fats (triacylglycerol)

    • Phospholipids

    • Steroids

Campbell 8e, Fig. 5.15

Campbell 8e, Fig. 5.13b

Fatty acids form ester bonds with glycerol

Fats consist of glycerol linked to three fatty acids

Biological Membranes are Composed of Phospholipids

Biological Membranes are Composed of Phospholipids

Campbell 8e, Fig. 5.13

What is a Membrane?

  • A phospholipid bilayer (a fluid mosaic).

Membrane Fluidity

The individual phospholipid molecules in lipid bilayer membranes are in constant motion

Membranes are dynamic structures

Membrane Fluidity

The Role of Steroids


Which is true?

  • Cholesterol reduces fluidity and reduces permeability of membranes.

  • Cholesterol increases fluidity and increases permeability of membranes.

  • Cholesterol increases fluidity and decreases permeability of membranes.

  • Cholesterol decreases fluidity and increases permeability of membranes.

Role of Cholesterol

Back to talking about things that have fatty acid side chains…

Saturated vs. Unsaturated(a fat question)

Which of the following statements about unsaturated fat is true?

  • They are more common in animals than plants.

  • They have double bonds in the carbon chains of their fatty acids.

  • They generally solidify at room temperature.

  • They contain more hydrogen that saturated fats having the same number of carbon atoms.

  • They have fewer fatty acid molecules per fat molecule.

The Shape of Phospholipids…

  • Why is one leg of the phospholipid bent?

Saturated vs. Unsaturated

Membrane Permeability

A human experiment…


Osmosis can cause the shrinking or swelling of cells

Building Mental Models

  • Think about a cell membrane – how would you draw one?




Cell exterior



Cell interior

Transmembrane Proteins and Transport

Transmembrane proteins are imperative for cellular transport.


Carrier proteins or transporters


Passive facilitated processes

Active facilitated process

Hydrophilic interior

Outside cell

Hydrophobic exterior


Inside cell

Gated Channels

Potassium ions enter

the channel

Outside cell

Inside cell


Positive charge triggers channel to open.

Electrochemical gradient.


Active Transport by Pumps

Molecules can be transported againstan electrochemical concentration gradient.

This requires energy.

Summary of Membrane Transport


Small, non-polar, uncharged

Facilitated diffusion

Channel Protein

Carrier Protein

Active transport

Requires Energy


This homework is worth 5 points. Once you hand it in, you will be asked to evaluate someone else’s homework – the quality of your evaluation will be worth an additional 2 points. All point-determinations will be made by the teaching team.


- Use a word-processor (12 pt. font) for your responses.

- You MUST upload a copy of your homework to the Angel TurnItInDropbox folder.


- When you upload your assignment to the Angel TurnItInDropbox folder it should have no identifying marks.

- When you bring a copy to hand in at class on January 15th (12:40pm), you should identify yourself using ONLY the last four digits of your PID #. If your name is on the assignment it will not be accepted.

The Question:

Compare and contrast simple diffusion, facilitated diffusion, and active transport across a biological lipid bilayer membrane.

- Define each process as applied to a biological lipid bilayer membrane.

- Provide a specific example of each process as applied to a biological lipid bilayer membrane.

- Describe each example (what’s going on? how does it work?).

REMEMBER – It’s OK to discuss ideas with friends, but YOU MUST TURN IN YOUR OWN UNIQUE WORK!!!

For Tuesday:

  • Homework #1 is due

    • Available on the website.

    • Be sure to follow instructions!!

    • TurnItIn + Paper Copy.

  • Register your clicker.

  • StudyNotes #2 is due onThursday. It’s a big one!7.0, 7.1, 7.2, 7.5

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