L06: Biomolecules: Carbohydrates and Lipids

Question 1

Which elements comprise carbohydrates? What are examples of carbohydrates? What roles do carbohydrates play in biota?

Answer 1

Carbohydrates (C, H, O) = sugars, starch, glycogen,
cellulose, chitin, etc.
- energy to make ATP
- short-term energy storage
- cellular/molecular tags
- structural roles (some biota)

Question 2

Which elements comprise lipids? What are examples of lipids? What roles do lipids play in biota?

Answer 2

Lipids (C, H, O) = Fats, oils, phospholipids, steroids, etc.
- energy to make ATP
- long-term energy storage
- cellular membrane structure
- hormones
- insulation
- cushion

Question 3

What are saccharides?

Answer 3

Saccharides are sugars typically used for immediate energy or metabolized into larger biomolecules (e.g., DNA)

Question 4

What are monosaccharides? How are monosaccharides classified?

Answer 4

Monosaccharides (monomer for carbs) (e.g., glucose) are sugars whose carbon skeletons routinely assume a single ring conformation (shape).

Monosaccharides are classified as aldoses or ketoses by their functional group (=O) (e.g., glucose is an aldose).
Monosaccharides are also classified by the number of sugars in their carbon skeleton (e.g., glucose is a hexose).

Question 5

How is glucose classified? Can you give examples of aldose and ketose monosaccharides?

Answer 5

Glucose is an aldose (carbonyl is end of carbon skeleton) and a hexose.
Fructose is a ketone (carbonyl is in middle) and hexose.

Question 6

What is the difference between a triose, pentose, and a hexose?

Answer 6

Trioses: 3-carbon sugars (C3H6O3)
Pentoses: 5-carbon sugars (C5H10O5)
Hexoses: 6-carbon sugars (C6H12O6)

based off carbon atoms

Question 7

Monosaccharides routinely assume ring conformations. What does this allow them to do?

Answer 7

Monosaccharides now serve as a monomer.
Ring conformations permit monosaccharides to polymerize
via dehydration reactions into disaccharides (e.g., maltose,
sucrose) and polysaccharides (e.g., starch, glycogen).

Question 8

What are disaccharides?

Answer 8

the sugar formed when two monosaccharides are joined by glycosidic linkage (covalent bond).

Question 9

Which monomers form maltose and sucrose? Which enzymes hydrolyze these disaccharides? Do humans have these enzymes? Which suffix is used to indicate an enzyme?

Answer 9

Two glucose monomers polymerize into maltose whereas glucose and fructose form sucrose.

We hydrolyze maltose with maltase and sucrose with sucrase. (enzymes tend to end with -ase).

Question 10

What is a polysaccharide?

Answer 10

a carbohydrate (e.g. starch, cellulose, or glycogen) whose molecules consist of a number of sugar molecules bonded together. (amylo prefix for polysaccharides starches)

Question 11

Which polysaccharides do plants make and for what purpose?

Answer 11

Plants make/store starch for a source of glucose when photosynthesis rate is low and/or energy needs are high (e.g., reproduction).

Plant makes storage molecules (starch) to tap into when doesn’t have access to light or has large energy demands like reproduction

Question 12

Which plant polysaccharide can humans digest/hydrolyze? Which enzyme hydrolyzes it? Do humans have cellulosases? What role does cellulose play in humans?

Answer 12

We eat starch (potatoes) and hydrolyze it with amylase (enzyme to break down starch) made from salivary glands and pancreas.

Plants also make cellulose to strengthen cell walls but animals DONT have cellulases.
We can absorb small amounts of cellulose that serve as insoluble fiber that stimulates mucus production and bulks feces.

Question 13

What is glycogen? How is it made? Which group of biota make glycogen? Which human tissues make/store glycogen?

Answer 13

Glycogen is polysaccharide of glucose. Animals polymerize glucose into glycogen; larger and more branched than starch. Glycogen is stored in energy-demanding tissues; e.g., muscle and liver.

Question 14

Which conditions favor glucose polymerization into glycogen and glycogen depolymerization into glucose? What do humans do with extra glucose when glycogen levels are maximized?

Answer 14

Glycogen is replenished when energy demands is low/glucose is high (sleeping, eating, relaxing). The liver breaks it down to maintain blood glucose levels and muscles break down glycogen to maintain energy for contractions.
Excess glucose gets shunted into fat production for long term storage. Glycogen is longer term storage than glucose but it really isn’t considered to be long term.

Question 15

What are fatty acids? How do fatty acids vary?

Answer 15

Fatty acids are hydrocarbon chains with a terminal carbonyl group (lipid basic building blocks). They vary in carbon chain length.

Question 16

What is glycerol?

Answer 16

(short helper molecule) Glycerol is a precursor for synthesis of triacylglycerols and of phospholipids in the liver and adipose tissue.

Question 17

What are triglycerides (triacylglycerols)? How many fatty acids are found in triglycerides? Do they all have to be the same length? Which human cells make triglycerides? Which human cells store triglycerides? What roles do they play in humans? What can happen if one over-consumes triglycerides?

Answer 17

Fatty acids bond with glycerol to form triglycerides and phospholipids. Triglycerides are a type of fat (lipid) found in your blood.
triglycerides (triaclyglycerols) = 3 fatty acids + glycerol
They can vary in length.
They are made in liver cells and move through your blood to be stored in adipose cells where they insulate, cushion, and serve as long term storage.

High triglycerides may contribute to hardening of the arteries or thickening of the artery walls (arteriosclerosis) — which increases the risk of stroke, heart attack and heart disease.

Question 18

How are fats classified?

Answer 18

Fats are classified by how saturated their hydrocarbon chains are with H atoms.

Question 19

What is the relationship among hydrogen atom saturation of fatty acids, packing ability, and melting temperature?

Answer 19

Hydrogen saturation influences the melting point of fats.

Saturated fats have straight fatty acids that pack tightly.
They have high melting points and are solid at room temp.

Unsaturated fats have bent fatty acids that do not pack
tightly because of their cis double bonds. They have lower
melting points and are liquid at room temp.

Question 20

What is different between saturated and unsaturated fatty acids? Which fatty acid is solid?

Answer 20

Saturated fats (e.g., butter, lard) only have single C-C bonds.
Unsaturated fats (e.g., olive oil) have at least one cis C=C bond.

Saturated fats have straight fatty acids that pack tightly.
They have high melting points and are solid at room temp.

Question 21

How does a cis double carbon bond impact the overall shape of a fatty acid? Which fatty acids do trans fats most resemble and why?

Answer 21

Cis double bond makes it an unsaturated fatn
Trans fat most resemble saturated fats.

Question 22

What is LDL-C and HDL-C? Over-consumption of which two fats increases LDL-C?

Answer 22

HDL-C (‘good’ cholesterol) is high-density lipoproteins + total cholesterol
Excessive saturated fats and trans fats increases LDL-C (low density lipoproteins + total cholesterol) in the blood

Unsaturated fats ↓ LDL-C (low density lipoproteins + total
cholesterol) in the blood ↓ risk of antherosclerosis/CV disease.

Question 23

What happens to arteries when LDL-C are elevated in the blood? What are the likely consequences of maintaining high levels of LDL-C in the blood?

Answer 23

atherosclerosis (narrowing of arteries) & cardiovascular disease (heart attack and stroke)

Question 24

How do monounsaturated and polyunsaturated fats impact LDL-C, and HDL-C? Is elevated blood HDL-C good or bad for you?

Answer 24

monounsaturated fats:
- lower total cholesterol
- lower LDL
- raise HDL (reduce risk of atherosclerosis/CV disease)

polysaturated fats:
- lower total cholesterol
- lower LDL
- lower HDL

Question 25

What is a phospholipid? How is a phospholipid similar to/different from a triglyceride?

Answer 25

Biota polymerize fatty acids into phospholipids to make cellular membranes.

Like triglycerides, phospholipids have a glycerol backbone. But unlike triglycerides, phospholipids only have two fatty acid molecules attached to the glycerol backbone, while the third carbon of the glycerol backbone is bonded to a phosphate group

Question 26

Phospholipids are amphipathic - what does that mean? Which region of a phospholipid is polar and which region is non-polar?

Answer 26

They have polar and non-polar regions.
The head is polar; hydrophilic (love water will form hydrogen bonds with water molecules)
Tails are non-polar; hydrophobic (not gonna form bonds with water)

Question 27

How do phospholipids arrange themselves in liquid water? How do phospholipids arrange themselves within a cellular membrane? Why?

Answer 27

A surface films or droplets.

Phospholipids organize themselves in a bilayer within cellular membranes. Polar groups face H2O in the cytosol (aq. portion of the cell interior) and the cell exterior (body fluids) and the non-polar groups face each other

Question 28

What is a steroid?

Answer 28

Steroids are lipid molecules with a 4-ring carbon
skeleton that has various functional groups attached.

Question 29

What is cholesterol and which biota make it and where is it used?

Answer 29

Cholesterol is a steroid synthesized only by animals to help build their membranes.

Question 30

Which kinds of hormones are made using a steroid carbon skeleton? If these hormones are made with the same carbon skeleton, how do they differ from each other?

Answer 30

The steroid carbon skeleton is also used to synthesize sex
(testosterone and estradiol) and stress hormones (cortisol).
They differ in function groups.

Question 31

Can you discern among the following: polyunsaturated fats, monounsaturated fats, trans fats, and saturated fats?

Answer 31

Different fats impact human health differently.
Polyunsaturated fats have 2+ cis C=C bonds.
Monounsaturated fats have 1 cis C=C bond.
Trans fats have 1 trans C=C bond.
Unsaturated fats have cis C=C bond.
Saturated fats lack C=C bonds because they are saturated with H atoms.