The Biology of a Cell Membrane and Cellular Transport

Cell Membrane

Cell Membrane Components

• Protein channels

• Proteins- Peripheral Proteins

• Lipid- Phospholipid bilayer

• Carbohydrate chains- glycoproteins and glycolipids

• Cholesterol

• Internal proteins

• Channel

• Carrier

Four Major Biomolecules

• Carb

• Lipid

• Protein

• Nucleic acid

Monomers-  They are one small molecule

Polymers-  They are a long chain of many molecules

Lipids

• In terms of cell membranes, lipids are technically called phospholipids

• The parts of a phospholipid bilayer:

• The phosphate, (It is polar/hydrophilic, meaning it likes water)

• The glycerol

• The fatty acid chains (They are nonpolar/hydrophobic, meaning they don’t like water)

• Lipids make up the majority of the cell membrane

• The monomer of lipids: glycerol and 3 fatty acids

• The polymer of lipids: triglyceride

• They are made of carbon, hydrogen, and oxygen

• Examples of lipids include butter, oil, wax, and steroids

Carbohydrates

• Carbohydrates take up the external surface of a cells membrane

• Glyco is the prefix for protein

• For example glycoproteins and glycolipids

Proteins

• They span the cell membrane

• They help let molecules into the cell

• The types of protein that help with cellular transport:

• Channel protein- They form openings to let molecules pass through the cell membrane

• Carrier proteins- They act as a binding site that selects the molecules that are safe to enter through the cell membrane into the cell

• The types of proteins that help the cell with responses:

• Receptor proteins- They act as “receptors” in the cell and trigger responses that are sent to the cell

• Enzymatic proteins- They help to carry out the metabolic reactions that the receptor proteins caused

Biomolecules Chart (This is a more general chart, it isn’t specific to cell membranes)

Cellular Transport

The two types of transport:

1. Active transport (ATP is required)

• Endocytosis (entering)

• Exocytosis (exiting)

• Sodium-Potassium Pump

2. Passive Transport (ATP is not required)

• Diffusion- happens on its own, without the help of a channel or carrier protein

• Facilitated diffusion- needs a channel protein to help with the diffusion (carrier proteins require energy)

• Osmosis- The movement of water from high to low concentrations through the semipermeable membrane

• The three types of osmotic solutions:

• Hypertonic- water exists from the cell, causing the cell to shrink

• Isotonic- water simultaneously enters and exits the cell, creating equilibrium within the cell

• Hypotonic- water enters into the cell, causing the cell to grow

• Osmosis only applies to the diffusion of water

ATP

ATP is a nucleic acid that is needed in the movement of molecules from a low to a high concentration. This is needed because molecules need to against the concentration gradient.