cell membrane

What is the Fluid Mosaic Model?

→biological membranes consists of a fluid phospholipid bilayers in which proteins are embedded and freely move

What are the components (4) of this model?

1. phospholipids

2. sterols

3. carbohydrates

4. proteins

What are phospholipids?

→ double layer of phospholipid molecules arranged with the lipid tails in the middle

→ lipid molecules may vibrate, flex back and forth, spin around, move sideways and exchange places

fluidity is influenced by two factors:

1. composition of lipid molecules

2. temperature

What are sterols?

→ membrane stabilizers (ex. cholosterol in animals)

• HIGH temps → restrain movement thus reducing fluidity

• LOW temps → occupy space between preventing fatty acids from forming non-fluid gel

What are carbohydrates?

→ chains attach to lipids and proteins forming glycolipids and glycoproteins

→ located on exterior of cell ex. ABO blood type

→ role: recognition and cell-cell interactions

What are proteins?

• Several different types of proteins determine function and uniqueness

Types of proteins (4)

a) 🚚 Transport proteins

• use cell energy to pick up and transport molecules across

• control the movement of substances in and out of the cell (ex. ions)

b) 🧬 Enzymatic activity

• some are enzymes like those in respiration

c) 📡 Triggering signals

• receive hormone messages for cell communication

d) 👯 Attachment and Recognition

• used as cell surface identification (ex. Rh factor)

• attachment points for a range of cytoskeleton elements as well as cell-cell recognition

Two groups of proteins:

• Peripheral Proteins

• Intergral Proteins

Peripheral proteins:

• on surface held by hydrogen bonds and ionic bonds

Integral proteins

• Embedded in lipid bilayer

• Have one region that interacts with hydrophobic core

• Transmembrane → span entire bilayer

Label the following diagram

A. Lipid Bilayer

B. Phospholipids

C. Hydrophilic polar head

D. Hydrophobic non-polar tail

E. Cholesterol Molecule

F. Integral proteins

G. Peripheral Protein

H. Cytoskeleton Filaments

I. Alpha Helix Protein

J. Glycoprotein

K. Carbohydrate

How does the fluid mosaic model work?

→ The fluid mosaic model has four crucial components: phospholipid bilayer , sterols, carbohydrates & proteins

1. Phospholipid bilayer acts like a ‘semi-permeable’ membrane, blocking water-soluble substances while letting in small non-polar molecules like oxygen to enter

2. Sterols are sandwhcihed between the lipid tails and ensures that the membrane isn’t closely packed in cold temps & keeps it stable in warm temps

3. Carbohydrates acts as ‘identiification tags, allowing the immune system and other cells to recognize body’s own cells versus foreign invaders

4. Proteins scattered among the bilayer, integral protein acts as channels for larger molecules & peripheral protein attach to outer or inner surfaces to perform signalling