Module 5

Question 1

What are sucrose, lactose, and maltose composed of?

Answer 1

All three are made up of glucose. Specifically:
Sucrose= Glucose (C1)+Fructose(C2)– linked via 1,2 linkages– both are non-reducing
Lactose= Galactose (non reducing end)+Glucose (reducing end) linked by Beta-1,4 linkages
Maltose= 2 glucoses linked by Beta-1,4 linkages

Question 2

For animals that must react with sudden action that requires rapid energy, what two things are needed in terms of glucose?

Answer 2

..???? (many non reducing ends and alpha-1,4 linkages between glucoses)

Question 3

How is cellulose different from glycogen?

Answer 3

Glycogen has ALPHA-1,4 linkages while cellulose has BETA-1,4 linkages

Question 4

Under what conditions do the melting temperature of fatty acids increase?

Answer 4

The melting temperatures of fatty acids increase when there is more saturated/ non-kinked FA’s present and increase in length

• decreases when there is an increase in unsaturated length and double bonds

Question 5

Outline the different ways molecules are transported across a membrane. – just list for now

Answer 5

1. Non-mediated
2. Mediated
3. Passive mediated
4. Active

Question 6

What is non-mediated transport?

Answer 6

Non-mediated transport is simple diffusion driven by chemical potential gradients across membrane.

• non-polar molecules diffuses in the direction that eliminates the gradient
• the rate will depend on the solubility in the membrane’s nonpolar core

Question 7

What is mediated transport?

Answer 7

Mediated transport via permeases, channels, ionophores, and transporters

Question 8

What is passive mediated transport?

Answer 8

Passive-mediated transport from high to low concentration

- this form of transport eliminates the gradient

Question 9

What is active transport?

Answer 9

Active transport is from low to high concentration/ against the gradient, coupled to an exergonic process (i.e. ATP hydrolysis)

Question 10

What is the difference between D-Glucose and D-Fructose?

Answer 10

D-glucose is an aldose where C1 is an aldehyde
D-fructose is a ketose where C2 is a ketone
-Both have and OH to the right at C5

Question 11

How do monosaccharides form cyclic rings?

Answer 11

The C5 OH attacks the C1 carbonyl to form the ring. This carbon carbonyl now becomes an anomeric carbon

Question 12

What is the difference between cyclic glucose, mannose, and galactose?
- Note: these are all monosaccharides

Answer 12

Mannose and galactose are all EPIMERS of glucose. So the only difference between them is the positions of their OH groups where (from C1-C4):

• Glucose: up, down, up, down
• Mannose: up, up, down, up
• Galactose: down, up, up, up

Question 13

What is considered the reducing ends and non-reducing ends of a sugar?

Answer 13

Reducing end= the anomeric carbon with no OR group attached to it
- it is called the reducing end b/c it can reduce copper
Non-reducing end= the end that can form a glycosidic bond

Question 14

Name the 4 major polysaccharides that we discussed in class?

Answer 14

1. Cellulose
2. Amylose
3. Chitin
4. Glycogen

Question 15

What is cellulose?

Answer 15

Cellulose is a polymer made up of 50,000 glucoses linked by B-1,4 glycosidic linkages

• insoluble in H2O
• linkages position each glucose in alternating positions to prevent H-bonding with H2O

Question 16

What is amylose?

Answer 16

Amylose is a component of starch that unlike cellulose IS H2O soluble.

• has alpha-1,4 linkages
• Amylose dissolves in water because its alpha 1,4 glycosidic bond causes the formation of a helical structure that does not form inter-strand hydrogen bonds like cellulose

Question 17

What is chitin?

Answer 17

Chitin is made up of GLUNAc (aka glucose-N-acetyl or N-acetylglucosamine) where the N-acetyl group is on C2

• this is a linear unbranched polysaccharide
• chitin is found in insect exoskeleton, shell of shrimps and crabs

Question 18

What is glycogen?

Answer 18

Glycogen is a branched energy storage carbohydrate found in animals with many non-reducing ends (branched every 7-11 sugars)
- has ALPHA-1,4 linkages

Question 19

Why does amylose and cellulose have differences in linkages?

Answer 19

This differences arise in a change in chirality (i.e. celulose= Beta-1,4; while amylose= Alpha-1,4)

Question 20

What is amylopectin and how does it differ from glycogen?

Answer 20

Amylopectin is the storage carbohydrate for PLANTS and forms ALPHA-1,6 linkage, branching every 30-50 sugars

• this differs from glycogen because it has less reducing ends that can be cleaved for release of glucose
• Also, glycogen has ALPHA- 1,4 linkages and branches more frequently (every 7-11 sugars) than amylopectin.
• However, they BOTH have alpha 1,6 linkages at their branch points!*

Question 21

What enzyme is used to cleave glycogen and where does the cleaving occur in the molecule?

Answer 21

Glycogen phosphorylase breaks down glycogen by cleaving at the non reducing ends of glucose monomers

Question 22

What makes fats similar to lipids?

Answer 22

both fats and lipids have aliphatic hydrocarbon tails and polar head groups

Question 23

What are fatty acids?

Answer 23

FA’s are what make up fats and considered stored energy

• they include a carboxylic acid head group and hydrocarbon tail that can be either:
  1. Saturated
  2. Unsaturated

Question 24

What is the difference between unsaturated and saturated fatty acids?

Answer 24

Unsaturated= contains 30 degree cis double bonds/ “kinks”
- considered unsaturated b/c they have less hydrogens present
Saturated= contain only single bonds in hydrocarbon tail; therefore, having more hydrogen molecules

• I mention hydrogen here b/c saturation deals with being saturated or filled with hydrogen in the tail, the more H’s the more saturated

Question 25

How do you name fats?

Answer 25

delta naming= count from C1 carbonyl carbon omega naming= count from opposite end of carbonyl Naming- C(number of carbons): number of double bonds, delta/omega (location of double bonds) - Ex: C18:3delta3,6,9 - note double bonds will occur every 3 carbons b/c their structure will not allow double bonds to be direct neighbors (every 2 carbons)

Question 26

What are triacylglycerides?

Answer 26

These are fats that are made up of 3 acyglycerides formed via ester linkages between glycerol and FA at their carbonyl carbons Note: glycerol comes from fructose and glucose breakdown

Question 27

What is a membrane lipid?

Answer 27

Mmebrane lipid is similar to fat except there is a phosphate group on C3 of glycerol backbone instead of another acylglyceride - lipid is known as phosphotidic acid

Question 28

What are the types of phospholipids? (know structures)

Answer 28

1. Phosphatidyl-choline 2. Phosphatidyl-serine 3. Phosphatidyl- ethanolamine 4. Phosphatidyl- linositol-4,5 phosphate

Question 29

What is cholesterol and how does it affect the bilayer?

Answer 29

Cholesterol is considered a sterol, but is sometimes considered a lipid since it plays an integral part of the membrane as it embeds in the hydrophobic core, INCREASING rigidity of the bilayer. -It is able to do this b/c at high temperatures, it stabilizes the membrane and raises its melting point, whereas at low temperatures it help to retain fluidity and prevent it from stiffening.

Question 30

What is the difference between lateral and transverse diffusion in lipid membranes?

Answer 30

Lateral diffusion: individual lipid molecuels are allowed to move quicker in membrane (does not require crossing hydrophobic barrier) Transverse diffusion- is much slower since it involves moving the polar head group across this barrier (not favorable)

Question 31

What are some ways proteins interact with membrane?

Answer 31

1. transmembrane/integral proteins- can span entire lipid bilayer, some will allow polar molecules to cross the barrier 2. Peripheral proteins- are partially embedded or associate with the lipid head groups, some are modified with hydrophobic tails for anchoring

Question 32

What are ionophore?

Answer 32

Ionophores are small membrane soluble molecules/peptides that bind and transport specific ions or molecules across a membrane

Question 33

What is GLUT 4 and how does it allow transport in the lipid membrane?

Answer 33

GLUT 4 is a glucose transporter that transport glucose and 6 carbon sugars across the plasma membrane 10x faster than normal diffusion. - allows transport by conformational change in the protein structure. - when glucose binds to GLUT 4, GLUT 4 will flip to allow glucose to the inside of the cell

Question 34

What is an aquaporin and how is water transported through this?

Answer 34

Aquaporins transport H2O across the membrane allowing it to pass in a single file - it has polar and basic residues that orient water - it can regulate the amount of H2O in cell. - due to repulsion between positive charges on the residue of the channels, H3O+ will not be able to enter

Question 35

What is Valinomycin?

Answer 35

Valinomycin consists of 3 repeat tetra peptides, each with 3 valines - the structure positions hydrophobic side chains outward to be membrane soluble and the polar backbone carbonyl will form a channel that can bring in K+

Question 36

How does valinomycin only allow K+ and not Na+ into the cell?

Answer 36

- K+ that will bind will have a similar energy as solvated K+ ions, so the free energy bound by valinomycin is the same as water - Free energy of Na+ ions is much higher than its solvated form, so it remains in more energetically stable aqueous environment,so it will not be transported (i.e Na+ would rather remain solvated than be transported)

Question 37

How does ATP dependent active transporter work?

Answer 37

ATP dependent active transporters transport ions and molecules against the gradient, requiring ATP hydrolysis to DRIVE the reaction. - it will pump 3 Na+ ions out and 2 K+ ions into the cell - this form of transport is essential for energy neurons and muscle contractions

Question 38

What are the functions of carbohydrates?

Answer 38

Carbohydrates function as: 1. chemical energy 2. barrier on cell surface 3. for cell interactions 4. stabilizing plant structure 5. signaling molecules