B2.1

Question 1

phospholipids naturally form continuous _________ in water.

Answer 1

sheet-like bilayers

Question 2

The nucleus, chloroplasts, and mitochondria are ______________.

Answer 2

double membrane bound

Question 3

Double membrane bound means ___________.

Answer 3

the structure is enclosed by 2 phospholipid bilayers

Question 4

Give examples of structure that are single membrane bound.

Answer 4

Rough ER, lysosomes, golgi apparatus

Question 5

What is the primary function of the cell membrane.

Answer 5

The membrane serves as a barrier to separate the outside environment from the internal organelles.

Question 6

Explain why the hydrophobic core of a lipid bilayer forms a barrier to hydrophilic particles.

Answer 6

water and other polar or charged substances cannot easily cross the hydrophobic core of the membrane.

Question 7

List advantages of membranes forming barriers within and between cells.

Answer 7

• Cells can accumulate nutrients in higher concentrations than exist in the environment.
• Accumulate charged ions to create an electrical potential across the cell membrane.

Question 8

Describe simple diffusion.

Answer 8

Simple diffusion is the movement of particles from an area of higher concentration to a area of lower contraction.

Question 9

What molecules can easily pass through the membrane?

Answer 9

Small nonpolar

Question 10

What is the impact of concentration gradient on the rate of diffusion?

Answer 10

The higher the concentration gradient, the faster the rate of diffusion.

Question 11

Name an example of simple diffusion:

Answer 11

Nonpolar steroid hormones can diffuse across the lipid bilayer

Question 12

Compare the location of integral and peripheral proteins in the membrane.

Answer 12

Integral proteins pass through the core of the lipid bilayer while peripheral proteins do not pass through the core.

Question 13

Outline how the hydrophobic and hydrophilic structures of proteins impact their anchoring to the membrane.

Answer 13

hold cells in place give cells and tissues their structure, regulate intercellular communication

Question 14

Outline six functions (with example) of membrane bound proteins.​

Answer 14

• Pump proteins help move solute against the concentration gradient (Sodium/potassium pump)
• Channel proteins help molecules move with the concentration gradient passively
• Recognition proteins allow cells to identify each other/interact
• transport proteins enable specific hydrophilic solutes to cross through the hydrophobic interior.

Question 15

What is osmosis?

Answer 15

It is the diffusion of water from high to low concentration.

Question 16

Predict the direction of water movement based upon differences in solute concentration.

Answer 16

Water will always move down its concentration gradient from areas of high to low concentration.

Question 17

Outline the structure and function of aquaporin proteins.​

Answer 17

Aquaporins are made of six transmembrane helical segments. Aquaporin greatly increases membrane permeability to water since it function in moving large amounts of water.

Question 18

Describe the structure and function of channel proteins.

Answer 18

A channel protein, a type of transport protein, acts like a pore in the membrane that lets water molecules or small ions through quickly. It is highly selective and moves passively.

Question 19

Define facilitated diffusion.

Answer 19

A type of passive transport that uses specialized proteins, such as channel proteins and carrier proteins, to help molecules move across a cell membrane.

Question 20

Outline the specificity of channel proteins for ions.

Answer 20

Ion specificity means that the ion channel only allows the movement of a specific type of ion and prevents the movement of all other ions. Channel proteins are highly specific in that they can only transport a specific particle.

Question 21

List types of gates on channel proteins.

Answer 21

Electrically gated channel - changes based on the electrical potential of a cell membrane
Ligand gated channel - channel proteins allow ions to pass through the membrane only when a chemical messenger (ligand) has also bound to the channel.

Question 22

Describe one example of facilitated diffusion through a protein channel.

Answer 22

Calcium channels in cell membranes are used for facilitated diffusion during synaptic transmission between neurons and to control muscle contractions.

Question 23

Compare active transport using a pump protein to facilitated diffusion using a channel protein.

Answer 23

• They are both integral proteins that transport specific particle in regards to shape and charges.
• Channel proteins do NOT require energy and transport WITH concentration gradient
• Pump proteins DO require energy and transport particles AGAINST concentration gradient
• Channel proteins are bidirectional (move molecules in Both directions)
• Pump proteins are unidirectional (particles can be moved in one direction)

Question 24

Explain one example of active transport of molecules into and out of cells through a protein pump.

Answer 24

The sodium-potassium pump system moves sodium and potassium ions against large concentration gradients. It moves two potassium ions into the cell where potassium levels are high, and pumps three sodium ions out of the cell and into the extracellular fluid.

Question 25

Define selective permeability.

Answer 25

The phospholipid bilayer is selectively permeable which means it only allows some particles to pass through it

Question 26

Simple diffusion through the membrane is _________ and depends only on the __________.

Answer 26

not selective, concentration gradient

Question 27

Summarize the effect of particle size on ability to pass through the lipid bilayer.

Answer 27

Large molecules are unable to pass through the membrane, small molecules can pass through

Question 28

Summarize the effect of hydrophobic/hydrophilic properties of a particle on its ability to pass through the lipid bilayer.

Answer 28

• The membrane is permeable to hydrophobic particles such as gases and lipid molecules.
• Membrane has variable permeability to small, hydrophilic polar molecules (such as water)
• The plasma membrane is not permeable to any hydrophilic molecule with a charge (these particles cannot diffuse through the core of the membrane bilayer)

Question 29

List examples of particles with low and high membrane permeability.

Answer 29

-High permeability: Oxygen and carbon dioxide can pass through
-Low permeability: Glucose and sucrose cannot pass

Question 30

Outline how channels and pumps in the membrane allow for selective permeability.

Answer 30

Channel proteins - facilitated diffusion WITH concentration gradient
Pump proteins - Use ATP energy to move targeted ions AGAINST concentration gradient

Question 31

Outline the structure of glycoproteins and glycolipids.

Answer 31

Glycolipids are lipids with carbohydrate molecules attached. Like glycoproteins (which are proteins with carbohydrate molecules attached to their surface), they are for recognition purposes. They may also act as receptors for other chemicals. The structure of glycoproteins and glycolipids allow for it to function in cell adhesion and recognition.

Question 32

Outline the role of glycoproteins and glycolipids in cell adhesion and cell recognition.

Answer 32

-The glycoprotein on the surface on one cell is recognized by the receptors of another cell. This allows immune system cells to recognize other cells within its own body, versus foreign invaders, like bacteria, that may cause disease.
- Glycoprotein/glycolipids can form a layer on the outside of the plasma membrane called the glycocalyx. This adheres cells together so that tissues do not fall apart.

Question 33

Draw and label the fluid mosaic model of the membrane structure.

Answer 33

The fluid mosaic model represents cellular structure as dynamic, flexible structure made up of different components. Google docs.

Question 34

Compare and contrast the structure, melting point and relative fluidity of saturated and unsaturated fatty acids in lipid bilayers.

Answer 34

• Saturated fatty acids pack closely together (straight chain), which result in stronger intermolecular forces; higher melting points (decrease membrane fluidity/permeability)
• Unsaturated fatty acids with a bend in the molecule do not pack neatly (kinked chain), have weaker intermolecular forces; lower melting points (increase membrane fluidity/permeability)

Question 35

Outline an example of adaptation in membrane composition in relation to habitat.

Answer 35

Adaptation in lower temperatures results in an increase of unsaturated fatty acids in membranes. Antarctic notothenioid fish live in the freezing ice-laden waters of the Southern Ocean. Their cells possess an increased proportion of unsaturated fatty acids relative to species adapted to warmer habitats.