Download Midterm 1b Key

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Midterm I: Chapters 19-21
Section I: Chapter 19: Carbohydrates (65 pts)
1. a) What is the primary energy storage molecule in animals (the energy storage molecule that
is used up first) (4pts)?
GLYCOGEN
b) Where is this molecule primarily stored (4pts)?
LIVER
2. Draw a !1"4 glycosidic linkage between two of the following molecules (8pts):
O
H
C
H
HO
C
C
H
C
OH
H
OH
H
C
OH
CH2OH
H
3. What is the circulating sugar in the blood (4pts)?
GLUCOSE
4. Why are artificial sweeteners sweet but non-caloric (6pts)?
THEY CAN NOT BE BROKEN DOWN AND THERFORE, WE DO NOT GET
ENERGY FROM CONSUMING THEM
5. What is the main cause of lactose intolerance (6pts)?
LACK OF THE ENZYME LACTASE
6. a) What organisms synthesize the carbohydrates we eat (3pts)?
PLANTS
b) What do they use from our environment to produce carbohydrates (6pts)?
CO2, H2O AND SOLAR ENERGY (SUN LIGHT)
7. a) Name a source of maltose (3pts)
BEER
b) Name a source of lactose (3pts)
MILK
c) Name a source of sucrose (3pts)
CANDY
8. a) What would happen if I added a pure anomer of glucose to water (6pts)?
THE PURE ANOMER WOULD OPEN AND CLOSE UNTIL AN EQUILIBRUIM
MIXTURE OF ALPHA (#
# ), BETA (!
! ), AND OPEN CHAIN IS ACHIEVED
b) What property of glucose allows this process to occur (4pts)?
IT IS A REDUCING SUGAR
9. What important functions do polysaccharides perform and name an example polysaccharide
molecule for each function you list (6pts).
POYSACCHARIDES SERVE AS STRUCTURAL MOLECULES (EX. CELLULOSE)
AND THEY SERVE AS A SOURCE OF ENERGY (EX. STARCH)
10. Name one important reason why diabetics should consume lots of fiber (6pts).
FIBER SLOWS THE RELEASE OF SUGARS FROM FOOD, LOWERING A
GLUCOSE SPIKE IN THEIR BLOOD AFTER EATING
Section II: Chapter 20: Lipids (69 pts)
11. a) What is the long-term energy source in animals (4pts)?
FAT
b) Why is it advantageous for our long-term energy to be stored in this way (4pts)?
ANIMALS CAN PACK MORE ENERGY IN A SMALLER SPACE. IF OUR LONG
TERM STORAGE MOLECULE WERE CARBOHYDRATES (LIKE IN PLANTS)
WE WOULD WEIGH TWICE AS MUCH.
12. Name an important function lipids perform in animals (4pts).
LIPIDS ARE ESSENTIAL COMPONENTS OF CELL MEMBRANES
13. a) What is the difference between saturated and unsaturated fatty acids (4pts)?
SATURATED FATTY ACIDS NAVE NO DOUBLE BONDS, WHILE
UNSATURATED HAVE ONE OR MORE DOUBLE BONDS (C=C)
b) What kind of fatty acids should people avoid eating in their diet (3pts)?
TRANS AND/OR SATURATED FATTY ACIDS
14. a) Which of the following will form a fat and which will form an oil and why (6pts)?
O
H2C-O-
O
H2C-O-
O
HC-O-C
O
O
HC-O-C
O
H2C-O-
H2C-O-
FAT- THIS MOLECULE HAS A
OIL-THIS MOLECULE HAS
GREATER ABILITY TO STACK
LESS ABILITY TO STACK A
A GROUP OF THESE MOLECULES
GROUP OF THESE MOLECULES
WOULD PACK INTO A SOLID
WOULD FORM A LIQUID
b) What are these types of lipids called (think of what their components are) (3pts)?
TRIACYLGLYECEROLS OR TRIGLYCERIDES
O
15. What products are formed when the molecule below is hydrolyzed (6pts)?
O
H2C-O-C-R1
O
HC-O-C-R2
O
H2C-O-C-R1
HO-C-
H2C-OH
+
HCl
HC-OH
H2C-OH
GLYCEROL
O
+
HO-C-R2
O
HO-C3 FATTY ACIDS
16. What role do waxes play in living organisms? Give an example of such a role in action
(4pts).
WAXES PLAY A PROTECTIVE ROLE. THE WAX ON A DUCK’S FEATHERS
PROTECTS THE FEATHERS FROM ABSORBING WATER, AND THEREFORE
PROTECTS THE DUCKS FROM DROWNING.
17. a) Name the main type of lipid in cell membranes (4pts).
PHOSPHOLIPIDS
b) What properties do these lipids have that make them ideal components of membranes
(4pts)?
THEY ARE AMPHIPATHIC, THEY HAVE A POLAR END (POLAR END CAN
INTERACT WITH THE INTRACELLULAR AND EXTRACELLULAR FLUID,
AQUEOUS MEDIUM) AND A NON-POLAR END (THAT IS EMBEDDED, FORMING
THE MEMBRANE)
18. Name two important functions of cell membranes (4pts)?
CONTROLS WHAT ENTERS AND EXITS THE CELLS, AND
COMPARTIMENTALIZES THE CELL AND ORGANELLES
19. a) How do polar molecules cross membranes (5pts)?
PASSIVE DIFFUSION
b) Name the process by which polar molecules cross a membrane, driven by a concentration
gradient (3pts).
FACILITATED DIFFUSION
20. a) What is the main difference between the four types of lipoproteins found in animals, in
terms of composition (5pts)?
HDL’S HAVE THE HIGHEST PROTEIN CONCENTRATION AND THE LOWEST
LIPID CONCENTRATION, WHILE CHYLOMICRONS HAVE THE HIGHEST LIPID
AND THE LOWEST PROTEIN.
HDL>LDL>VLDL>CHYLOMICRONS (IN TERMS OF PROTEIN CONCENTRATION)
b) Why are high LDL levels an indication of problems with a certain type of lipid (4pts)?
THEY TRANSPORT CHOLESTEROL, HENCE THEY ARE AN INDICATION OF
PROBLEMS WITH CHOLESTEROL LEVELS
Section III: Chapter 21: Proteins (68 pts)
21. Draw the zwitterion structure of glycine (4pts).
+
H3N-CHH
22. a) If you had a protein embedded in a membrane, what kind of amino acids would you find
on the exterior of the protein interacting with the membrane (4pts)?
NON-POLAR AMINO ACIDS
b) Name three amino acids you could find there (3pts)?
GLY, ALA, VAL, LEU, ILE, PHE, TRP, MET, PRO
23. Why are amino acids considered nature’s buffer (4pts)?
BECAUSE THEY CAN ACCEPT OR DONATE A PROTON
24. If the amino acid below is at pH 7.0, what will it look like at its isoelectric point (4pts)?
H3N-CH-COO-
+
H3N-CH-COO-
CH2
CH2
COO-
COOH
+
25. a) What important functional group do acidic amino acids have (2pts)?
-COOH, CARBOXYLIC ACID GROUP
b) What important functional group do basic amino acids have (2pts)?
-NH3, AMINO GROUPS
c) What important functional group does cys have (2pts)?
-SH, SULFHYDRIL
O
+
26. Draw a dipeptide of pure glycine (6pts)?
H3N-CH-C-N-CH-COOH
H
H
27. What are the possible peptide sequences formed from the following four amino acids: ser,
lys, ala, & glu please note that ala is at the C-terminus and glu is at the N-terminus (4pts).
GLU-LYS-SER-ALA
&
GLU-SER-LYS-ALA
28. What are the two main types of protein classes? (This type of classification is based on
solubility and structure) (4pts)
FIBROUS AND GLOBULAR
29. a) What are the two main types of secondary structure (4pts)?
ALPHA (#
# ) HELICES AND BETA (!
! ) PLEATED SHEETS
b) What main differences do you see between the two structures (4pts)?
ALPHA HELICES ARE COILED AND HAVE INTRA H-BONDING, WHILE BETA
SHEETS ARE FLATT AND HAVE INTER H-BONDS
30. Name four forces that stabilize the tertiary and quaternary structure of proteins (4pts).
H-BONDING, IONIC BONDS, VAN DER WAALS INTERACTIONS (OR
HYDROPHOBIC INTERACTION) & DISULFIDE BRIDGES
31. What kind of amino acids would you most likely see on the exterior of a protein that is
floating around in blood like Hemoglobin? Name three of those amino acids (6pts).
POLAR AMINO ACIDS, SUCH AS SER, THR, CYS, TYR, ASN, GLN, ASP, GLU, LYS,
ARG, AND HIS
32. Why are prions infectious (5pts)?
PRIONS ARE INFECTIOUS BECAUSE THEY ARE THE ROGUE OR INFECTIOUS
FORM OF A NORMAL PROTEIN AN ORGANISM ALREADY HAS. WHEN THE
ORGANISM IS INFECTED WITH THE ROGUE CONFOMER IT CAUSES A
CONFORMATIONAL CHANGE IN THE NORMAL PROTEIN, PROPAGATING THE
ROGUE CONFORMER.
33. Name two properties proteins loose, when they are denatured (4pts)?
STRUCTURE AND FUNCIONTION