Bio Chem Test Pt 2

Question 1

“Fluid mosaic” model and Importance

Answer 1

A Semi fluid phospholipid bilayer with a mosaic of proteins where lipids and proteins can move laterally due to weak intermolecular forces
between the membrane lipids.

Importance:
● If the cell membrane is punctured, the molecules
will rearrange themselves to seal the rupture

● Fluidity allows the cell to pinch pieces of the
membrane off creating vesicles

Question 2

Properties of Cell membrane

Answer 2

Selective Permeability: Allows certain substances to pass while blocking others.

Fluidity: Lipid molecules can move, allowing for flexibility and the ability to change shape.

Self-Healing: Can reseal if torn due to the fluid nature of the lipid bilayer.

Dynamic: Components can move laterally, which facilitates cell communication and transport processes.

Question 3

Functions of proteins within the cell membrane

Answer 3

Membrane Proteins:

Integral proteins: penetrate lipid bilayer, span the membrane; involved in transport and communication.

Peripheral proteins: Located on the surface; involved in signaling and maintaining the cell’s shape.

Glycoproteins: Glycoproteins function in cell recognition, immune response, structural support, transport and storage, enzymatic activity, signaling, and development and differentiation.

Question 4

Passive Transport

What are the types of

Answer 4

Passive Transport - Transport of molecules without the help of energy, goes along the concentration gradient.

-(Simple) Diffusion
-Osmosis
-Facilitated diffusion

Question 5

Active Transport

Answer 5

Active transport:

Moves molecules AGAINST the concentration gradient

From low concentration to high concentration with the use of ATP (energy)

• Conformational change in shape allows solute to be transferred across membrane
• Uses protein “pump”
• “Costs” energy

Examples: Ions (Na, K, etc), Nutrients (glucose amino acids, etc), metabolites.

Question 6

Simple Diffusion

What is rate of diffusion dependent on

Examples

Answer 6

Simple diffusion - Passive transport, no energy is needed, depends on the concentration of the substance on either side of the membrane

Rate of diffusion is dependent on:
-Size
-Polarity
-Charge

Examples:
Water, oxygen and carbon dioxide, non-polar molecules.

Question 7

Facilitated diffusion

Answer 7

Diffusion through protein channels

-Channels move specific molecules across the cell membrane
-No energy is needed to transport molecules

Examples: Ions, sugars, Amino acids, water (aquaporin)

2 Types
-Channel proteins
-Carrier proteins

Question 8

Carrier proteins

Answer 8

Carrier Proteins

-Bind to specific molecules

-They then undergo conformational changes that allow the molecule to pass through the membrane and be released on the other side

-Compared to channel proteins, carrier proteins can:

○ Transport larger molecules
○ Have lower diffusion rates

Question 9

Channel proteins

Answer 9

-Specific molecules freely pass through

• The shape and size of the channel determines
  the shape and size of particles that can pass
  through it

-Some remain open all the time, others have
Gates

Question 10

Osmosis

Answer 10

• Diffusion of water from high concentration of WATER to low concentration of WATER
• Movement of water occurs because the membrane is impermeable to the solute
• The direction of osmosis is determined by comparing total
  solute concentrations
• Cells survival depends on balancing water uptake and loss

Question 11

Na+/K+ pump

Answer 11

Membrane transport proteins pump Na+ out of the cell and K+ into the cell against the concentration gradient. Uses ATP (energy)!

Nerve cells must maintain a higher concentration of Na+ outside the cell and K+ inside the cell to function

Question 12

Bulk transport - Large molecules

Answer 12

Moving large molecules into & out of the cell
Through vesicles & vacuoles

TWO PROCESSES

Endocytosis - moving materials INTO the cell

• Phagocytosis = “cellular eating”
• Pinocytosis = “cellular drinking”
• Receptor-mediated endocytosis - molecules bind to receptors on the outside of the cell membrane.

Exocytosis - moving materials out of the cell

Question 13

How the membrane maintains fluidity and why this is important to cell transport

Answer 13

Cholesterol: Stabilizes membrane fluidity; helps maintain membrane integrity across temperatures.

At low temperatures, maintains fluidity

At high temperatures, maintains structure

Importance to cell transport
Fluidity allows the cell to pinch pieces of the
membrane off creating vesicles

Question 14

Endocytosis

Answer 14

Moving materials into the cell using energy

3 TYPES
Phagocytosis: certain living cells called phagocytes ingest or engulf other cells

Pinocytosis: cell takes in the fluids along with dissolved small molecules

Receptor-mediated endocytosis: a form of endocytosis where receptor proteins on cell surface are used to capture target molecule

Question 15

Exocytosis

Answer 15

• Cell products/waste that needs to leave the cell
• Transport molecules out of the cell
• Requires energy to transport material

Question 16

Hypertonic Solution

Answer 16

More solute

Less water

Animal Cell - Shriveled

Plant Cell - Phasmolysis

Question 17

Hypotonic Solution

Answer 17

Less solute

More water

Animal Cell - lysed

Plant cell - turgid

Question 18

Isotonic Solution

Answer 18

equal

equal

Animal Cell - normal

Plant Cell - flaccid

Question 19

Be able to compare and contrast the different types of transport (passive vs active;

Answer 19

Passive transport goes along the concentration gradient and requires no energy, while active transport goes against the concentration gradient and requires energy (ATP) to be able to do this.

Question 20

Be able to compare and contrast the different types of transport ( facilitated vs active)

Answer 20

Facilitated diffusion is a type of passive transport that uses protein channels to transport molecules that are large, polar, charged, etc. along the concentration gradient, while active transport goes against the concentration gradient and requires energy (ATP) to be able to do this.