Phospholipid

phosphate head and 2 fatty acid tails

Cell Membrane

Is selectively permeable and is made of a phospholipid bilayer

Fluid Mosaic Model

• Describes the cell membrane
• A mosaic because of the proteins, carbs, sterols embedded in the membrane
• Fluid because it is flexable and moves

What are the 7 types of proteins?

1. Channel Proteins
2. Transport Proteins
3. Carrier Proteins
4. Aquaporins
5. Receptor Proteins
6. Recognition Proteins
7. Adhesion Proteins

Channel Proteins

Open passages through the membrane for hydrophilic substances

Transport Proteins

Span the bilayer and use ATP to move substances from low to high concentration

Carrier Protein

Bind to specific molecules and transfer them across the membrane

Aquaporins

Found in certain cells and greatly increase the passage of water

Receptor Proteins

Bind substances such as hormones, that trigger changes in cell activities

Recognition Protein

Identify cells as being a specific type

Adhesion Protein

Attach cells to neighboring cells and provides stability

Concentration Gradient

A difference in the number of molecules of a substance between two areas

Diffusion

• A form of passive transport
• Movement of molecules from high to low concentration

5 Factors that affect the rate of diffusion...

1. Gradient steepness
2. Molecular size
3. Temperature
4. electric gradient
5. Pressure gradient

Selectively Permeable

Permits some substances but not others to cross membrane

What molecules can simply diffuse across the bilayer?

CO₂, O₂, H₂O and small nonpolar molecules

Passive Transport

• Movement of substances from high to low concentration
• Does not require energy

3 Types of Passive Transport

1. Diffusion
2. Osmosis
3. Facilitated Diffusion

Osmosis

• Movement of water from high to low concentration
• No energy required
• A form of passive transport

Facilitated Diffusion

• Diffusion of solutes through channel proteins from high to low concentration
• No energy required
• A type of passive transport

Active Transport

• Solutes cross the membrane from low to high concentration
• Requires ATP

Calcium Pump

Helps keep the calcium concentration in a cell at least a thousand times lower than outside

Sodium-Potassium Pump

Moves potassium ions, K+, across the plasma membrane

Exocytosis

• A cell releases large amounts of materials
• Requires energy
• A type of active transport

Endocytosis

• A cell takes in substances
• Requires energy
• A type of active transport

3 Types of Endocytosis

1. Receptor-Mediated Endocytosis
2. Pinocytosis
3. Phagocytosis

Receptor-Mediated Endocytosis

Specific molecules bind to receptor proteins.  The receptor protein folds inward and the formation of a vesicle follows

Pinocytosis

• Cell takes in liquids
• A type of endocytosis

Phagocytosis

• Cell takes in solids
• A type of endocytosis

Bulk Flow

The mass movement of one or nmore substances in response to pressure, gravity, or some other external force

Tonicity

Refers to the relative solute concentration of two fluids

Hypotonic Solution

The solution having less solutes and more water

Hypertonic Solution

The solution having more solutes and less water

Isotonic Solution

The concentration of solutes is equal between two areas

Hydrostatic Pressure

A force directed against a wall, membrane or some other structure that encloses the fluid

Osmotic Pressure

The amount of force that prevents further increase in a solution's volume

Plasmolysis

Cell shrinks

Cytolysis

Cell swelling