lipids l2 biology. as biology. foundation. cell membranes and transport 2 do now: key words to look...

LIPIDSL2 BIOLOGY

AS Biology. Foundation. Cell membranes and Transport

2

Do Now: Key words to look up Phospholipids

Hydrophilic Hydrophobic Cholesterol Proteins (in

cell membrane)

Selectively permeable

Phospholipid bilayer

Fluid mosaic model

What are Lipids?

Lipids include substances like fats, oils and waxes

Typical formula C51H98O6

What can you tell me about lipids from looking at this formula?

Lipid Structure

one glycerol three fatty acids(also called a triglyceride)

GLYCEROL

FATTY ACIDS

LIPID=Glycerol +3 fatty acids

Two Types of Fatty Acids

SATURATED– The fatty acids are completely full of

hydrogen atoms (no double bonds!)

UNSATURATED– There are one or more double bonds

Cont…

SATURATED FATS – Usually solid, fully hydrogenated –

animal sources

Cont…

UNSATURATED FAT– Usually a liquid; not fully

hydrogenated - plant sources

SATURATED OR UNSATURATED?

Trans Fats: Bad in your diet!

Trans fats–Unsaturated, but the double bond between carbons is turned so they are now SOLID at room temperature

–Considered “bad” fats (we create them artificially from liquid oils)

–Margarine, creams in snacks foods

3 functions of Lipids

Major component of cell membranes.

Long term energy storage. Protection.

1. What types of substances are lipids?

2. What are the four parts that make up a lipid?

3. What is the difference between a saturated fat, unsaturated fat, trans fat?

4. How are lipids like proteins?

5. How are lipids different from proteins?

Cell Membranes: Question: Can We live totally fat Free ?

Every cell is enclosed by a double layer of lipids: that is the cell membrane

-Called a phospholipid bi-layer-What does this mean?

AS Biology. Foundation. Cell membranes and Transport

16

Cell (plasma) Membrane Encloses the cell’s

contents Function:

Regulates which particles (nutrients, wastes) can enter and exit the cell.

Also is way cells “communicate”

Selectively permeable

AS Biology. Foundation. Cell membranes and Transport

17

A Phospholipid BilayerPhospholipids can

form:

BILAYERS

-2 layers of phospholipids with hydrophilic heads (on outside) and hydrophobic (fatty acid) tails protected inside.

The PHOSPHOLIPIDBILAYER is the basicstructure of

membranes.

AS Biology. Foundation. Cell membranes and Transport

18

Properties of Cell Membranes

Basic structure is Phospholipid

Bilayer.

Phospholipids have HYDROPHOBIC

(non-polar) tails and HYDROPHILIC

(polar) heads.

The fatty acid tails of phospholipids

can be SATURATED (straight) or

UNSATURATED (bent)

AS Biology. Foundation. Cell membranes and Transport

19

Plasma Membrane Structure Building blocks are phospholipids…

– Lipid with a polar phosphate group attached to one end.

AS Biology. Foundation. Cell membranes and Transport

20

Properties of Cell Membranes Phospholipids act as a barrier to

most water soluble substances

BUT, Phospholipids are only PART of the story…………

AS Biology. Foundation. Cell membranes and Transport

21

Fluid mosaic model

Cell membranes also contain cholesterol and proteins within the phospholipid bilayer.

This ‘model’ for the structure of the membrane is called the: FLUID MOSAIC MODEL

AS Biology. Foundation. Cell membranes and Transport

22

Why call it a Fluid Mosaic Model?

FLUID- because phospholipids and some proteins move around freely within the layer, like it’s a liquid.

MOSAIC- because of the pattern produced by scattered protein molecules in the membrane when viewed from above.

AS Biology. Foundation. Cell membranes and Transport

23

Visualizing structure and function membrane animation

AS Biology. Foundation. Cell membranes and Transport

24

Functions of Proteins/Cholesterol in Cell Membrane 1. Proteins act as channels for substances

to move in or out of cell.

2. Some act as membrane enzymes in

chemical reactions.

3. Proteins help to stabilize the membrane.

Cholesterol stabilizes and prevents ions

from entering.

4. glycoproteins act as markers for cell

communication or receptors that

hormones & other proteins can bind.

AS Biology. Foundation. Cell membranes and Transport

25

Functions of components of cell membranes

Use the following headings to produce a table summarizing the functions of the different types of molecules found in the cell membrane. Use your notes to find the information.

Component Description Function

1. Phospholipids

2. Proteins

3. Cholesterol

AS Biology. Foundation. Cell membranes and Transport

26

Quick Quiz:

1. What is the main component of the cell membrane?

2. a. What does the word “hydrophobic” mean? b. What does the word “hydrophilic” mean?

AS Biology. Foundation. Cell membranes and Transport

27

3. Name 1 function for proteins in the cell membrane.

4. What is the function of cholesterol in the cell membrane?

5 a. What do we call a protein with a carbohydrate (sugar) attached?b. Name 1 function for these molecules in the membrane.