4 Lesson: BIO.A.4.1 Cell Membrane and Diffusion

Cell Membrane

•Semipermeable: Regulates the passage of materials in and out of the cell

• Made up of proteins and lipids and contains molecular receptors

Cell Membrane Function

• A barrier keeping the constituents of the cell in and unwanted substances out

• A gate allowing transport into the cell of essential nutrients and movement from the cell of waste products

• Communication- intracellular

• Recognition - signalling, adhesion or proteins and other host cells

• Signal generation- stimulus response to changes

Structure

• Phospholipid Bilayer: Head group= hydrophilic polar and Tail = hydrophobic and non-polar

• Cholesterol (in phospholipid Bilayer) maintain cell membrane stability and fluidity at varying temperatures.

• Proteins: Catalyst - enzymes; Transporters - channels and pumps; Receptors - hormones

Membrane Transport

• Passive Transport - does not use energy

• ........Diffusion

• ........Facilitated Diffusion

• ........Osmosis

• Active Transport - uses energy

Passive Transport

• Diffusion: moving from areas of high concentration to areas of low concentration, down the concentration gradient.

• Osmosis by diffusion in which water molecules diffuse through a selectively permeable membrane

• ............hypotonic solution (more water, less solutes)

• ............hypertonic solution (less water, more solutes).

Osmosis is known as Tonicity

• Hypertonic solution, there will be a net flow of water out of the cell, and the cell will lose volume

• Hypotonic solution, there will be a net flow of water into the cell, and the cell will gain volume.

• Isotonic solution, there will be no net flow of water into or out of the cell, and the cell’s volume will remain stable

Facilitated Diffusion

• Passive movement (no energy) of molecules across the cell membrane via the aid of a membrane protein

• Channel Proteins

• Carrier Proteins

• ...........bind a specific molecule via an attachment similar to an enzyme-substrate interaction

• Note: Carrier proteins may move molecules against concentration gradients in the presence of ATP (energy)

Multiple Choice

Diffusion will occur until ________ is reached and concentrations on both sides of the membrane are the same.

• solution

• transport

• gravity

• equilibrium

Multiple Choice

Passive movement of substances from high to low concentration.

• hydrolysis

• active transport

• diffusion

• endocytosis

Multiple Choice

Passive transport does not require ______ input from the cell.

• energy

• matter

• reactant

• solute

Multiple Choice

What does G represent?

• phosphlipids

• carbohydrates

• membrane proteins

• cholesterol

Multiple Choice

The _________________ model describes the structure of the plasma membrane.

• fluid mosaic

• double helix

• Bohr

• distribution

Multiple Choice

Which statement best describes the cell membrane?

• The protective outer layer that controls what enters and leaves the cell.
  
• Stores information on DNA molecules / Directs and controls the activities of the cell.
  
• A folded membrane that moves materials around inside cells / Also acts as the site of manufacturing materials needed by the cell.
  
• The smallest organelle with a huge job / Makes proteins, which are the building blocks of the body.
  

Multiple Choice

What forms the channels and pumps in the phospholipid bilayer?

• Carbohydrates
• Proteins
• Hydrophilic heads 
• Lipids

Multiple Choice

Hydrophobic region of the cell membrane?

• E
• B
• C
• A 

Multiple Choice

Cell membrane is made up of 

• Polar heads, non-polar tails
• Non-polar heads, polar tails
• Polar heads, polar tails
• Non-polar heads, non-polar tails

Multiple Choice

Osmosis is the diffusion of __________.

• water
• glucose
• air
• passive transport

Multiple Choice

Describe the movement of molecules in the illustration.

• Molecules are moving from a lower concentration to a higher concentration.

• Molecules are moving from a high concentration to a lower concentration.

• Molecules are moving from a higher concentration to a lower concentration and then from a lower to higher concentration.

• Molecules are moving from a lower concentration to a higher concentration and then from a higher concentration to a lower concentration.

Multiple Choice

In passive transport, the concentration gradient goes from..

• Low to low

• High to low

• Low to high

• High to high