Biological Molecules

Question 1

what is the meaning of a monosaccharide, disaccharide, and polysaccharide?

Answer 1

monosaccharides - simplest carbohydrates consisting of only one sugar molecule
disaccharides - formed by joining two monosaccharides together in a condensation reaction
polysaccharides- are carbohydrate polymers made up of many monosaccharides

Question 2

combining alpha glucose with alpha glucose gets you which sugar? and where is it found in?

Answer 2

maltose - found in germinating seeds as more complex carbohydrates are broken down for energy

Question 3

combining alpha glucose with fructose gets you which sugar? and where is it found?

Answer 3

sucrose - mostly found in plants because sucrose is transported in the phloem to provide sugars to other parts of the plants

Question 4

combining alpha glucose with galactose gets you which sugar? and where is it found?

Answer 4

lactose - found in mammalian milk to provide energy for infant mammals

Question 5

how is a condensation reaction formed? and what bond is formed

Answer 5

condensation reaction forms water as one oxygen and two hydrogen atoms are removed from the monosaccharides. This bonds the monosaccharides together, forming a disaccharide.
this bond is known as glycosidic bond

Question 6

what is a glycosidic bond?

Answer 6

glycosidic bond is a covalent bond formed between two monosaccharides by a condensation reaction

Question 7

why is water a good solvent?

Answer 7

due to the unequal distribution of electrons, it’s a polar molecules, so many ions and covalently bonded polar substances will dissolve in it. Leads to chemical reaction to occur

Question 8

properties of water and its functions

Answer 8

• high specific heat capacity because many hydrogen bonds present in water - takes a lot of thermal energy to break and can maintain stable temp in environments
• cohesion : attraction of water molecules to each other —> surface tension
• adhesion : attraction of water molecules to other objects —> capillary action + transpiration

Question 9

how is a disaccharide broken down?

Answer 9

disaccharides are broken down through a hydrolysis reaction to form two monosaccharides

Question 10

structure of amylose

Answer 10

amylose is a long chain of a-glucose molecules joined together by 1,4 glycosidic bonds. It coils into a helix shape that makes it more compact so more energy can be stored

Question 11

structure of amylopectin

Answer 11

a long chain of a-glucose joined together with 1,4 and 1,6 glycosidic bonds. 1,6 glycosidic bonds cause amylopectin to have side branches, this is good due to terminal glucose molecules that can be easily hydrolyzed for use during cell respiration

Question 12

what are the two types of starch

Answer 12

amylose and amylopectin

Question 13

what is glycogen and where is it normally found?

Answer 13

Glycogen is found in cells with a high metabolic rate (liver cells and muscle cells)

Question 14

structure of glycogen?

Answer 14

many alpha glucose molecules joined together by 1,4 and 1,6 glycosidic bonds, resulting in a highly branched structure. Therefore has a very high number of accessible ends

Question 15

difference between monosaccharides, disaccharides, and polysaccharides?

Answer 15

mono and di are both sugars that are sweet tasting and soluble while poly does not taste sweet and is not soluble, its not a sugar

Question 16

what is the role of a-glucose?

Answer 16

alpha glucose is the main source of energy in respiration.
excess chemical energy is stored in cells by forming polysaccharides of alpha glucose

Question 17

how is a-glucose well suited for energy storage?

Answer 17

1. they are compact so a lot of energy can be stored in a small space
2. they are insoluble in water so they do not impact the water potential of a cell, so does not affect the osmotic effect of the cells
3. they are large so they do not diffuse out of the cell unlike monosaccharides that can leave by carrier protein
4. can easily be hydrolyzed to
   a-glucose when energy is needed

Question 18

where is starch normally found?

Answer 18

• found in photosynthesizing cells in leaves and storage cells in seeds and storage organs.
• compacted into dense, insoluble grains stored in special organelles called amyloplasts

Question 19

differences between amylose and amylopectin

Answer 19

amylose = only 1,4 glycosidic bonds
amylopectin = 1,4 and 1,6 glycosidic bonds, and amylopectin has more accessible ends meaning that it releases energy quicker than amylose which is better suited for respiration

Question 20

where is amylose, amylopectin, and glycogen found?

Answer 20

amylose + amylopectin are both found in plants while glycogen is found in animals

Question 21

what is cellulose and its function?

Answer 21

cellulose is a polysaccharide that makes up the cell wall, it is very strong and stops plant cells from bursting when too much water enters by osmosis - it makes the cells turgid

Question 22

structure of cellulose

Answer 22

cellulose is composed of many thousands of B-glucose molecules joined together by 1,4 glycosidic bonds

Question 23

how are cellulose fibers formed?

Answer 23

hydrogen bonds that cross-link the cellulose chains allow the chains to form stronger fibers

Question 24

what are microfibrils?

Answer 24

strong threads made of long cellulose chains, parallel to one another, joined by hydrogen bonds forming strong cross linkages

Question 25

where is chitin found, and what is it used for?

Answer 25

in fungi, chitin is used to strengthen the cell wall

Question 26

the function of chitin in insects

Answer 26

give strength to insects' exoskeleton waterproof - helps insects prevent water loss from their body

Question 27

structure of chitin?

Answer 27

B-glucose joined together with 1,4 glycosidic bonds, similar to cellulose

Question 28

difference in structure of chitin and cellulose

Answer 28

chitin contains acetylamine groups bonded to carbon 2 of the B-glucose monosaccharides

Question 29

difference between fats and oil and what causes the difference in state?

Answer 29

fats are solid at rtp oils are liquid at rtp difference in the state is due to the presence of double bonds between carbon atoms and fatty acids

Question 30

what are saturated hydrocarbon chains

Answer 30

fatty acids with hydrocarbon chains that have no double bond between carbon atoms

Question 31

what are unsaturated lipids

Question 32

how is a triglyceride synthesized

Answer 32

the formation of ester bonds during condensation reactions between glycerol and three fatty acids

Question 33

why are unsaturated hydrocarbon chains liquid at rtp

Answer 33

because the fatty acid tails bend due to the presence of the c=c bond, the bent tail pushes the molecules further apart. This then weakens the intermolecular forces between the unsaturated triglyceride molecules so they form liquid at rtp

Question 34

how do triglycerides play a role in respiration

Answer 34

triglycerides can be broken down into glycerol and fatty acids, used in respiration

Question 35

asides from glycerol and fatty acids, what molecule is released when triglycerides are broken down during respiration

Answer 35

water, it is a good source of metabolic reactions

Question 36

why are triglycerides good energy storer

Answer 36

- provide the most energy per unit of mass, useful for animals as it reduces the mass that must be carried around

Question 37

uses of fats by animals

Answer 37

- protect internal organs - thermal insulation - aquatic animals produce oil to waterproof their fur

Question 38

how is the structure of a phospholipid different from triglyceride

Answer 38

the difference is that one of the fatty acids is replaced by a phosphate molecule, which occurs through condensation reactions

Question 39

what happens to phospholipids when they are in water

Answer 39

hydrogen ions dissociate from the phosphoric acid, forming a phosphate group that has a negative charge

Question 40

which part of the phospholipid is hydrophilic

Answer 40

heads

Question 41

which part of the phospholipid is hydrophobic

Answer 41

tails

Question 42

what is a monolayer of phospholipids called

Answer 42

micelles

Question 43

structure of a phospholipids bilayer

Answer 43

the hydrophilic heads form two rows on the outside while the hydrophobic tails are sheltered in the middle where there is no water

Question 44

unique structure of the phospholipid bilayer

Answer 44

will never expose the hydrophobic tails to the water keeping the membrane stable

Question 45

importance of the phospholipid bilayer

Answer 45

- a barrier, that controls substance that goes in and out of the cell - electrical insulation - the area in the middle is a non-aqueous environment so this creates a barrier to charged molecules which are dissolved in water

Question 46

what molecules can pass through the membrane?

Answer 46

oxygen: enter cells for respiration carbon dioxide: leaves the cell as a waste product both are small and non-polar