1.4. Carbohydrates

Question 1

Monossacharides exist in 2 forms: ____ (solid) and ___ (in water, to form polymers).

Answer 1

straight chain, ring form

Question 2

Two glucose molecules when joined are…

Answer 2

…joined between O (OH group bonded with 1st C) of the first and 4th C of the second mol. Water is released: H (from OH group of 1st C) of the first mol., and OH group of the 4th C of the second mol.).

Question 3

glycosidic bond

Answer 3

covalent bond between two monosaccharides

Question 4

1 -> 4 glycosidic bond

Answer 4

glycosidic bond connecting 1st C of one glucose molecule and 4th C of another

Question 5

using structural formulas, represent the creation of maltose

Answer 5

…

Question 6

glucose + glucose =
glucose + galactose =
glucose + fructose =

Answer 6

maltose
lactose
sucrose

Question 7

starch

Answer 7

• alpha glucose polymer (polysaccharide)
• short term E storage
• two types:
  1) amylose
  2) amylopectin
• they differ in structure (branching) and function

Question 8

pentamer

Answer 8

polymer with 5 monomers

Question 9

amylose

Answer 9

• 1->4 glycosidic bonds between alpha glucose molecules
• gluc. mol. oriented the same, developing a helical shape (spiral)
• non-neighboring mol. connected with H-bonds (strengthening and stabilizing the structure, decreasing the digestibility)
• no branches at all
• acts as a dietary fiber (indigestable but valuable in the dig. process) - keeps moisture in the bowels (no dehydration - maintaining the consistency of feces)

Question 10

amylopectin

Answer 10

• 1->4 glycosidic bonds between alpha glucose molecules + 1->6 g.b. (branching)
• easily digestible (gluc. mol. more easily loaded and unloaded at the branching sites)
• E rich form of starch (less healthy than amylose)

Question 11

natural starch = amylose (__%) + amylopectin (__%)

Answer 11

30, 70 (legumes and bananas have more than 30%)

Question 12

Plants store E in __&__, animals in __&__.

Answer 12

oil, starch, fat, glycogen (oil, fat longterm)

Question 13

glycogen

Answer 13

• alpha glucose oriented in the same direction
• connected by both 1->4 and 1->6 glycosidic bonds (more branched than amylopectin - even better E storage)
• short term E storage in animals (liver and muscles)
• insoluble in water (not osmotically active - no problems with osmosis (hepatocytes))

Question 14

glycogen in liver

Answer 14

glucose (from stomach) > blood vessels > liver (checking glucose levels) > too much? - content of blood modified before going to supply organs > dehydration reaction (glucose into glycogen) > stored in liver > if level of glucose is too low in blood > hydrolysis reaction (glycogen into glucose) > maintaining the homeostatic level of gl. in blood

Question 15

Why must glucose be converted into glycogen before storing it in the liver cells?

Answer 15

Glucose is soluble in water so it would dissolve in the cytoplasm, increase the cytoplasm concentration, make water enter the cell, and cell could burst (glycogen not soluble).

Question 16

cellulose

Answer 16

• beta glucose molecules
• orientation alternates (up-down-up)
• 1->4 glycosidic bonds (no branches, completely straight chains), H-bonds between different chains (3C(OH(H))-O)
• firm structure (structural function)
• straight, unbranched polymer; cellulose microfibrils run parallel and are interconnected by H-bonds (great tensile (elastic but firm) strength)

Question 17

celluolse is found in:

Answer 17

(basis for) plant cell wall, high trees (wind example)

Question 18

role of glycoproteins in cell-cell recognition

Answer 18

• glycoprotein = polypeptide + oligosaccharide
  (polypeptide = chain composed of many amino acids
  oligosaccharide = 3-10 monosaccharides)
• embeded into plasma membrane; used for cell recognition and cell-to-cell adhesion (marks the cell from the outside - antigens - e.g. blood groups)

Question 19

The ratio 1:2:1 (C:H:O) works for all hexoses and pentoses except…

Answer 19

…deoxyribose.

Question 20

1) monosaccharides
2) disaccharides
3) polysaccharides

Answer 20

1) glucose, fructose, galactose
2) lactose (glucose + galactose), maltose (glucose + glucose), sucrose (glucose + fructose)
3) cellulose, starch, glycogen (all just glucose)

Question 21

carbohydrates

Answer 21

energy-providing molecules (except cellulose)

Question 22

stable monosaccharide rings (in water):

Answer 22

1) hexoses
a) alpha glucose (down down up & down - OH) - starch uses only alpha
b) beta glucose (up down up & down - OH)
2) pentoses (C=5) - pentose sugars (constituent part of nucleotides (monomers of DNA and RNA))
a) ribose
b) deoxyribose (-1 oxygen)

Question 23

sketch ribose, deoxyribose, glucose (a and b) and how maltose is created

Answer 23

…