Week 3 Recall Questions

Question 1

A) Polymerization

How are polymers synthesized?

What is the reaction?

What happens to the water molecule?

Is this reaction endergonic or exergonic?

Spontaneous?

What is the role of the enzymes?

Answer 1

• covalent bond between 2 monomers
• dehydration reaction
• it is lost
• end –> takes long time for natural depolymerization
• No
• catalyzes rxns

Question 2

B) Carbohydrates

What function do carbohydrates have in the cell?

Answer 2

• source of energy
• source of carbon to make other molecules
• structural components of the cell

Question 3

B) Carbohydrates
Chemical structure of monosaccharides:

What are the most common lengths of monosaccharides that exist in living organisms?

Answer 3

Those that contain 3 carbon (trioses, 5 carbon (pentoses, 6 carbon (hexoses)

Question 4

B) Carbohydrates
Chemical structure of monosaccharides:

What are the functional groups are found in monosaccharides?

How many of each functional group are present?

Answer 4

• hydroxyl (-OH)
• carbonyl (-CO)

-1 each?

Question 5

B) Carbohydrates
Chemical structure of monosaccharides:

All monosaccharides exist in a linear form (with the carbons in a straight chain).

For longer monosaccharides, what other form can occur?

Which form is more common in the cell?

Answer 5

• fold back on themselves to form a ring.
—> Folding occurs through a rxn between 2 functional groups in the same monosaccharide

• ring form of 5-,6- C sugars

Question 6

B) Carbohydrates
Monosaccharides:

When glucose (a 6-carbon monosaccharide) forms a ring, α (alpha) and β (beta) isomers are formed.

Describe the structural difference between these two isomers.

Answer 6

• if ring forms that the hydroxyl on carbon 1 is pointing down we get alpha glucose

• if ring forms that the hydroxyl group on carbon forms is pointing up we get beta glucose

Question 7

B) Carbohydrates
Monosaccharides:

Some monosaccharides can exist as enantiomers (aka optical isomers), with a D and an L form.

Describe the special type of carbon that allows enantiomers to form.

Describe the structural difference between the D and L enantiomers.

Explain why the D form of a
monosaccharide is usually the form found in cells

Answer 7

• linkages are designated as alpha or beta, depending on orientation of -OH group at 1 carbon that forms in the bond.

• L isomers have the hydroxy group attached to the left side, while D isomers have the hydroxy group on the right side.

• most enzymes catalyze biochemical rxns of monosaccharides react exclusively with d-form. B/c they fit readily into that form.
- higher stability than other monosaccharides
- the L-glucose is not produced naturally.

Question 8

B) Carbohydrates
Monosaccharides:

Another type of isomer that can exist in monosaccharides are structural isomers, where two molecules have the same chemical formula but a different order of atoms.

Explain the difference between aldehyde and ketone sugars, and how this difference creates structural isomers.

Answer 8

• molecules with same chemical formula but atoms arranged in diff order = structural isomers

• Aldoses contain the aldehydic functional group
— functional groups attached to the end carbons
• ketoses have the ketonic functional group
— functional groups attached to the middle carbons

Question 9

B) Carbohydrates
Disaccharides

What is the name of the chemical covalent bond that attaches the monomers together in a disaccharide?

What type of chemical reaction forms this bond?

Answer 9

• bonds of this type are glycosidic
• dehydration synthesis rxn

Question 10

B) Carbohydrates
Disaccharides

If a disaccharide is described as having an α(1→4) linkage, what does this mean?

Answer 10

A glycosidic bond between a 1 carbon and a 4 carbon is written in chemical shorthand as a 1 → 4 linkage.

Question 11

B) Carbohydrates
Polysaccharides:

What are the important storage polysaccharides?

Answer 11

• Glycogen
• Starch

Question 12

B) Carbohydrates
Polysaccharides:

How is starch characterized?
What is its function?
Where is it found?

Answer 12

*
*storage

• only found in plants

Question 13

B) Carbohydrates
Polysaccharides:

How is glycogen characterized?
What is its function?
Where is it found?

Answer 13

*
*storage

• found in animal livers, muscle cells, and bacteria

Question 14

B) Carbohydrates
Polysaccharides:

How is cellulose characterized?
What is its function?
Where is it found?

Answer 14

*
* structural component for the cell
* - found in plant cell walls
–> found in all plants, therefore one of most abundant biological substances on earth
- Fiber

Question 15

C) Lipids

What are important lipids found in cells?
What are their characteristics?
What are their functions?

Answer 15

• fats, phospholipids, or steroids.
• Functions:
• energy source (can store twice as much E as the same weight as carbohydrates. = really good at e storage)
• insulation
• protection

Question 16

C) Lipids

What are the main chemical properties common to all lipids?
How do they differ from other types of macromolecules?

Answer 16

• Properties of all:
• partially hydrophobic (contain a lot of non-polar c-c and c-h bonds)
• low water solubility
• more solid
• not polymers ( but still macromolecules)
• are not water-soluble and do not form lengthy sequences of comparable or repeating smaller units

Question 17

C) Lipids

Are lipids polymers? Explain why or why not.

Answer 17

No. b/c they are not built with a monomer unit (units with similar composition)

Question 18

C) Lipids
Fats:

What are the components of fats?
How are fats formed?
How many reactions are necessary?
What kind of linkages do they establish?

Answer 18

• three fatty acid chains linked to a single molecule of glycerol.
  –> also often referred to as triacylglycerols or triglycerides
• hydroxyl group on glycerol backbone react with carboxyl groups of fatty acids.
• 1? dehydration
• ester linkages

Question 19

C) Lipids
Fats:

What are the characteristics of phospholipids?
What is their function in a cell?

Answer 19

•

• Function:
• are primary lipids of cell membranes.
• most common phospholipids, glycerol forms the backbone for the molecule, as in triglycerides.
• acts as boundary between cell and environment

Question 20

C) Lipids
Phospholipids:

What are the components of phospholipids?
How are phospholipids formed?
How many reactions are necessary?
What kind of linkages do they establish?

Answer 20

• 1 Polar unit/additional unit, 1 phosphate group, 1 glycerol, 2 fatty acid chains
• phosphate group attached to C3 and a polar unit binded to that
• 1? dehydration
• attached by ester bonds, formed by dehydration rxn.

Question 21

C) Lipids
Phospholipids:

What are the characteristics of phospholipids?
What is their function in a cell?

Answer 21

• are amphipathic (part hydrophobic, part hydrophilic)
  —> hydrophilic head, interacts with H2O
  —> hydrophobic tails, interacts with other hydrophobic tails
• Function: main component of cell membranes

Question 22

C) Lipids
Sterols:

What are the characteristics or properties of sterols?
What are their functions in a cell?

Answer 22

• characteristics
• non polar
• carbon skeleton of 4 fused rings
  —> C-C & C-H bonds, therefore non polar and hydrophobic
• Function: cell membrane, chemical signalling in molecules

Question 23

C) Lipids
Sterols:

What is an example of a sterol?

Answer 23

Cholesterol

Question 24

C) Lipids
Sterols:

Why is cholesterol important?
What is its function and where is it synthesized?

Answer 24

• Cholesterol is an important component of the plasma membrane surrounding animal cells

Question 25

C) Lipids
Variation is fatty acids:

What are the parts of a fatty acid’s structure?
How can they vary?

Answer 25

• straight chain of carbon atoms, and at 1 end have Carboxyl group (-COOH)
• can vary by:
  1. Length of H-C chain
  2. #, location, and type of DB (double bond)

Question 26

C) Lipids
Variation is fatty acids:

Describe how the length of the fatty acid changes its physical properties (such as solubility and viscosity).

Answer 26

• Range from 14 C to 22 C

• Generally become less fluid (more solid) as the length of their fatty acid chains increases;
– shorter chains remain liquid
– longer chains solidify.

• length of chain increases, viscosity increases.

• chain length is shorter, melting point is lower.

• solubility in water decreases with the length of the carbon chain

Question 27

C) Lipids
Variation is fatty acids:

Describe how the number and type of double bonds changes its physical properties (such as solubility and viscosity)

Answer 27

• Adding DBs increases fluidity. (viscosity increases)
  –> b/c lead to an inefficient packing of the fatty acid molecules compared to saturated fatty acids
• Weaker interaction will give a lower boiling point and lower melting point for the fatty acid

Question 28

C) Lipids
Variation is fatty acids:

Some fatty acids are ‘saturated’ and some are ‘unsaturated’.

What is the difference in the chemical structure between these two types of fatty acids?

How are they characterized (shape, viscosity, density)?

Answer 28

• saturated:
- no DBs
- angles of the bonds makes it linear (straight molecule)
- can pack close together
- solid at room temp
- when in membranes, phospholipids compact tightly and it is more solid
- high melting points
- highest number of hydrogens
Ex: sat fats, red meat, butter

• unsaturated:
- 1 or more DBs
- bend b/c of DBs
- can’t pack tightly together
-liquid at room temp
- when in membranes, phospholipids can’t pack tightly together, making it more fluid. = more movement of molecules & membrane
- low water solubility, dissolve completely in nonpolar organic solvents
- lower melting points
- lowest number of hydrogens
Exs: unsat fat, oils, fish, plants

Question 29

C) Lipids
Variation is fatty acids:

What are the differences between cis – and trans unsaturated fatty acids?

Answer 29

• cis
- naturally occurring
- C found on same side of DB
- bent molecule

• Trans
- not naturally occurring
- C found on opposite sides of DB
- straight molecule
- behave more like saturated fatty acids (b/c straight)

• Comparing
- angle of DB between 2 is different.
—> cis causes bend at DB, trans does not.
—> being straight causes a more solid fatty acid

Question 30

C) Lipids
Variation in sterols:

How do sterols differ?

Answer 30

• variation due to attachment of different functional groups on the 4 carbon ring.
  —> allows cell to produce a lot of different types of sterols based on a common carbon skeleton.