biological molecules B

Question 1

What are important molecules that carry information?-

Answer 1

~ Deoxyribonucleic acid(DNA)
~ Ribonucleic acid(RNA)

Question 2

what does a nucleotide consist of?

Answer 2

-phosphate
-pentose sugar
-base ( nitrogen containing)

Question 3

What bond does a condensation reaction between two nucleotides form?

Answer 3

Phosphodiester bond

Question 4

how do polynucleotides form?

Answer 4

condensation reactions between nucleotides which form strong phosphodiester bonds

Question 5

state the role of DNA in living organisms

Answer 5

-base sequence of genes codes for functional RNA and amino acid sequence of polypeptides
-genetic information determines inherited characteristics

Question 6

relate the structure of DNA to its functions

Answer 6

-sugar phosphate backbone and many H-bonds provide stability
-long molecule stores lots of genetic information
-helix is compact for storage in nucleus
-base sequence of triplets codes for amino acids
-double stranded for semi-conservative replication
-complementary base pairing for accurate replication
-weak H-bonds break so strands separate for semi-conservative replication

Question 7

what is the DNA nucleotide structure ?

Answer 7

-phosphate
-deoxyribose sugar
-base

Question 8

what are the bases in DNA?

Answer 8

A-adenine
T- thymine
C- cytosine
G- guanine

Question 9

What bond is between bases when two DNA polynucleotides strands join together?

Answer 9

hydrogen bonds

Question 10

What are the complementary base pairings in DNA?

Answer 10

-adenine+thymine
-cytosine+ guanine

Question 11

If there was 33% of adenine, how much of thymine would there be and why?

Answer 11

-33%
-there are always equal amounts of a+t and c+g

Question 12

how many hydrogen bonds are there between A and T?

Answer 12

two

Question 13

how many hydrogen bonds are there between C and G?

Answer 13

three

Question 14

What is the RNA nucleotide structure?

Answer 14

-phosphate
-ribose sugar
-base

Question 15

what are the bases in RNA?

Answer 15

A-adenine
U- uracil
C-cytosine
G-guanine

Question 16

What are the complementary base pairings in RNA?

Answer 16

• adenine+uracil
  -cytosine+guanine

Question 17

what is the difference between DNA and RNA?

Answer 17

DNA
-double stranded
-deoxyribose sugar
-bases: A,T,C,G
-long
RNA
-single stranded
-ribose sugar
-bases: A,U,C,G
-relatively short

Question 18

what does mRNA do?

Answer 18

-transfers genetic information from DNA to the ribosomes

Question 19

what does tRNA do?

Answer 19

brings amino acids to the ribosomes

Question 20

who were the two scientists who discovered the structure of DNA and their model of DNA double helix

Answer 20

watson and crick

Question 21

why is DNA replication describes as semiconservative ?

Answer 21

-strands from original DNA molecule act as a template
-new DNA molecule contains 1 old strand and 1 new strand

Question 22

outline the process of semiconservative DNA replication.

Answer 22

1.DNA helicase breaks H-bonds between pairs
2.each strand acts as a template
3. free nucleotides from nuclear sap attach to exposed bases by complementary base pairing
4. DNA polymerase catalyses condensation reactions that join adjacent nucleotides on new strand
5.H-bonds reform

Question 23

Use your knowledge of enzyme action to suggest why DNA polymerase
moves in opposite directions along DNA strands

Answer 23

-DNA has antiparallel strands
-So shapes / arrangements of nucleotides on two ends are different
-DNA polymerase is an enzyme with a specific shaped active site
-So can only bind to substrate with complementary shape (phosphate end of developing strand

Question 24

describe the Medellin-Stahl experiment (semi-conservative replication)

Answer 24

1. Bacteria were grown in a medium containing heavy isotope 15N for many generations.
2. Some bacteria were moved to a medium containing light isotope 14N. Samples were extracted after 1 & 2 cycles of DNA replication.
3. Centrifugation formed a pellet. Heavier DNA (bases made from 15N) settled closer to bottom of tube.

Question 25

Describe the structure of adenosine triphosphate (ATP)

Answer 25

-adenine
-ribose
-3 phosphate groups

Question 26

word equation for use of ATP

Answer 26

ATP + H20 —> ADP+ Pi

Question 27

explain how ATP is used in cells

Answer 27

-ATP is broken down to ADP and Pi
-this is a hydrolysis reaction
-phosphate bond is broken and energy is released
-reaction is catalysed by enzyme ATP hydrolase
-energy released is coupled to metabolic reactions
-phosphate group phosphorylates compounds to make them more reactive

Question 28

How is ATP resynthesised in cells ?

Answer 28

-ATP synthase catalyses condensation reaction between ADP and Pi
-during photosynthesis and respiration

Question 29

explain why ATP is suitable as the “energy currency” of cells

Answer 29

-High energy bonds between phosphate groups.
-Small amounts of energy released at a time = less energy wasted as heat.
-Single-step hydrolysis = energy available quickly.
-Readily resynthesised

Question 30

why is water a polar molecule?

Answer 30

-O is more electronegative than H, so attracts the electron density in the covalent bond more strongly
-forms o- and H+

Question 31

name the properties of water

Answer 31

-COHESIVE helps water to flow making it greater for transporting substances
-SPECIFIC HEAT CAPACITY means water doesn’t experience rapid temperature changes
-HIGH HEAT OF VAPORISATION means living organisms can use water loss through evaporation to cool down without losing too much water
-METABOLITE for metabolic reactions
-GOOD SOLVENT meaning some substances can dissolve in it

Question 32

how is water an important metabolite?

Answer 32

-used in lots of important condensation/hydrolysis reactions

Question 33

why is water a good solvent ?

Answer 33

-polar water molecules surround and are attracted to ions or other polar molecules ,so these substances can dissolve and be transported

Question 34

state and explain the property of water that can help to buffer changes in temperature

Answer 34

-water has a relatively high specific heat capacity
-can gain/lose a lot of heat/energy without changing temperature

Question 35

give two properties of water that are important in the cytoplasm of cells

Answer 35

-solvent so that metabolic reactions occur faster in solution
-reactive so takes place in hydrolysis/condensation

Question 36

what bonds form between water molecules ?

Answer 36

hydrogen bonds

Question 37

explain the role of hydrogen ions in the body

Answer 37

-The concentration of H+ in a solution determines the pH
-high conc of H+= lower pH
-H+ ions interact with H-bonds and ionic bonds in tertiary structure of proteins, which cause them to denature

Question 38

describe the roles of iron ions,sodium ions and phosphate ions in cells

Answer 38

IRON IONS
1.haemoglobin binds with oxygen

SODIUM IONS
2.co-transport of glucose/amino acids
3.because sodium moved out by active transport
4.creates a sodium concentration/diffusion gradient
5. affects osmosis/water potential

PHOSPHATE IONS
6.affects osmosis/ water potential
7.joins nucleotides
8.used in/ to produce ATP
9.phosphorylates other compounds making them more reactive
10.hyprophillic part of phospholipid bilayer

Question 39

recall the uses of ATP

Answer 39

provides energy for:
-synthesis of macromolecules
-muscle contraction
-active transport
-secretion

phosphate released:
-phosphorylation of molecules
-can active other key bio molecules

Question 40

where are inorganic ions found?

Answer 40

-in cell cytoplasm
-in bodily fluids of organisms
-the role of the ion determine the required concentrations of the ions