Chapter 3 - Biological Molecules (Module 2)

Question 1

3.1

when two or more atoms bond what is it called

Answer 1

molecule

Question 2

3.1

how does a covalent bond work and how many bonds can a carbon make

Answer 2

two atoms share a pair of electrons that are found on the outer shell
carbon can make 4 bonds as they have 4 unpaired electrons on their outer shell

Question 3

3.1

definition of an ion and an ionic bond

Answer 3

Ion = an atom or molecule that’s total number of electrons is not equal to the total number of protons
Ionic bond = one atom in the pair donates an electron and the other receives it causing positive and negative ions so the atoms are held together by the opposite charges.

Question 4

3.1

what happens when an atom/molecule loses and gains an electron

Answer 4

loses electron - net positive charge (cation)

gains electron - net negative charge (anion)

Question 5

3.1 
Important cations :
- calcium 2
- sodium 2
- potassium 1
- hydrogen 1
why are these important/function

Answer 5

calcium- muscle contraction and nerve impulse transmission
sodium - kidney function and nerve impulse transmission
potassium - nerve impulse transmission
hydrogen - catalyzes reactions

Question 6

3.1
Important anions 
- nitrate 1  
- hydrogen carbonate 1
- phosphate 3
- hydroxide 1

Answer 6

nitrate - nitrogen supply
hydrogen carbonate - maintenance of blood ph.
phosphate - cell membrane formation, atp and nucleic acid formation and bone formation
hydroxide - catalyzes reactions

Question 7

3.1

definition of polymer

Answer 7

long chain molecules made up by the linking of multiple individual molecules ( monomers ) in a repeating pattern .

Question 8

3.2

how do molecules become polar and what group of molecules are all slightly polar

Answer 8

• in covalent bonds some electrons spend more time closer to one of the atoms than the other which causes one to be slightly negative and one slightly positive
• hydroxyl

Question 9

3.2

definition of a hydrogen bond and two characteristics

Answer 9

hydrogen bonds = positive and negative regions of molecules attract each other and from bonds

• weak
• occur in high numbers

Question 10

3.2

definition of specific heat capacity, why is it important to living organisms that water has a large shc

Answer 10

shc - the heat needed to raise the temperature of 1kg of water by 1 degrees
- it is important because it means they can absorb large amounts of heat before temperature rising meaning the water around cells ‘buffers’ change

Question 11

3.2
definition of the latent heat of vaporization, why does it occur and why is it important to living organisms (animals and plants)

Answer 11

• energy lost due to evaporation of water molecules
• in a body of water some molecules have higher kinetic energy so escape the water and bring the energy with them
• animals sweat and when this evaporates it cools them, water evaporates of plant leaves

Question 12

3.2

why does water have strong cohesion (flow in a continuous stream), 2 reasons its important to living organisms

Answer 12

as they are polar water molecules are attracted to each other forming hydrogen bonds

• xylem in plants; water moves up from the roots
• causes surface tension - small animals can live on surface ( pond skater )

Question 13

3.2

how is water a solvent, what does it allow, why is it important for living organisms

Answer 13

• the positive and negative charges of water attract other molecules causing them to separate (dissolve)
• when substances are dissolved they are free to react with other molecules
• the metabolic reactions in living organisms can only happen when reactants are dissolved in water

Question 14

3.2

what two reactions are water molecules involved in, what do the two reactions do

Answer 14

• hydrolysis = digestion of large molecules ( adding water)

- condensation = synthesis of important molecules e.g. proteins ( removing water)

Question 15

3.2

Why does ice float, why is it important to living organisms

Answer 15

• less dense than liquid water

- in cold temperatures the top layers will freeze, leaving the aquatic environment still liquid - habitat intact

Question 16

3.3

what are single sugars, two sugars and multiple sugars known as

Answer 16

• monosaccharide
• disaccharide
• polysaccharide

Question 17

3.3

definition of glucose, the structure of alpha and beta glucose (what is the key difference)

Answer 17

glucose = basic monomer of all large carbohydrates

• structure = see book
• difference is beta glucose hydorxyl group is above the carbon 1 instead of below ( its flipped )

Question 18

3.3

what makes glucose soluble in water and why is this important

Answer 18

• hydrogen bonds at the hydroxyl groups and water molecules

- important because it means glucose is dissolved in the cytosol in the cell

Question 19

3.3
how do two alpha glucose molecules bond :
- what carbons does it occur
- what kind of reaction ( what is the product )
- how does it occur and what does it look like
- what does it form
- what is the covalent bond that occurs called

Answer 19

• carbon 1 and carbon 4
• condensation ( water )
• two hydrogens and one oxygen are removed leaving one oxygen
• disaccharide (maltose)
• glycosidic bond

Question 20

3.3
what are the other two hexose monosaccharides, what do they form when added with glucose and what are the two pentose monosaccharides

Answer 20

• fructose and galactose
• fructose + glucose = sucrose, galactose + glucose = lactose
• ribose and deoxyribose

Question 21

3.3

definition of starch, what are the name of the two polysaccharides that are known collectively as starch

Answer 21

• Starch = glucose made by photosynthesis in plant cells is stored as starch
• amylose and amylopectin

Question 22

3.3
amylose :
- where do the glycosidic bonds form between the alpha glucose 
- what does the angle of the bond cause 
- two advantages compared to glucose

Answer 22

• from at carbon 1 and carbon 4 on the alpha glucose
• angle of the bond causes the long chain to twist and form a helix which is stabilized by hydrogen bonding
• makes it compact so more can be stored, less soluble so will stay inside the plant and won’t dissolve into the system.

Question 23

3.3
Amylopectin : 
- how is this different to amylose with the glycosidic bond location 
( how often does it occur ) 
- what does this cause 
- two advantages of this

Answer 23

• 1-4 glycosidic bonds and a 1-6 glycosidic bond every 25 carbons
• this causes a branched structure
• they can quickly add energy to their storage, break energy down quicker when needed

Question 24

3.3
Definition of glycogen :
- what bonds does it have
- 3 advantages for animals

Answer 24

glycogen = how glucose is stored in animals

• 1-4 glycosidic and 1-6 glycosidic bonds
• lots of branches so very compact so lots can be stored, lots of branches means glucose molecules can easily be added or removed which speeds up the process of sotring or releasing glucose molecules, insoluble = wont dissolve into the bloodstream and will stay stored

Question 25

3.3

Definition of respiration, how are glucose released from starch of glycogen for respiration

Answer 25

respiration = process of biochemical energy in the stored nutrients is converted into useable energy source for the cell
- starch or glycogen undergo a hydrolysis reaction which requires additional water molecules, break down glycosidic bonds

Question 26

3.3
Cellulose :
- why can’t beta glucose molecules bond the same way as alpha glucose
- how do two beta glucose molecules bond with each other
- what does this then form
- 2 characteristics and what it is used for

Answer 26

• the hydroxyl groups on carbon 1 and carbon 4 are too far away to from a glycosidic bond
• one beta glucose molecule must be flipped upside down in order for them to form
• it creates a straight chain molecule as it can’t coil or form branches
• strong and insoluble so makes cell walls .

Question 27

3.3

3 structures of cellulose

Answer 27

• cellulose molecules make hydrogen bonds with each other forming microfibrils
• these microfibrils join together forming macrofibrils
• these combine to produce fibres