biological molecules B Flashcards
What are important molecules that carry information?-
~ Deoxyribonucleic acid(DNA)
~ Ribonucleic acid(RNA)
what does a nucleotide consist of?
-phosphate
-pentose sugar
-base ( nitrogen containing)
What bond does a condensation reaction between two nucleotides form?
Phosphodiester bond
how do polynucleotides form?
condensation reactions between nucleotides which form strong phosphodiester bonds
state the role of DNA in living organisms
-base sequence of genes codes for functional RNA and amino acid sequence of polypeptides
-genetic information determines inherited characteristics
relate the structure of DNA to its functions
-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
what is the DNA nucleotide structure ?
-phosphate
-deoxyribose sugar
-base
what are the bases in DNA?
A-adenine
T- thymine
C- cytosine
G- guanine
What bond is between bases when two DNA polynucleotides strands join together?
hydrogen bonds
What are the complementary base pairings in DNA?
-adenine+thymine
-cytosine+ guanine
If there was 33% of adenine, how much of thymine would there be and why?
-33%
-there are always equal amounts of a+t and c+g
how many hydrogen bonds are there between A and T?
two
how many hydrogen bonds are there between C and G?
three
What is the RNA nucleotide structure?
-phosphate
-ribose sugar
-base
what are the bases in RNA?
A-adenine
U- uracil
C-cytosine
G-guanine
What are the complementary base pairings in RNA?
- adenine+uracil
-cytosine+guanine
what is the difference between DNA and RNA?
DNA
-double stranded
-deoxyribose sugar
-bases: A,T,C,G
-long
RNA
-single stranded
-ribose sugar
-bases: A,U,C,G
-relatively short
what does mRNA do?
-transfers genetic information from DNA to the ribosomes
what does tRNA do?
brings amino acids to the ribosomes
who were the two scientists who discovered the structure of DNA and their model of DNA double helix
watson and crick
why is DNA replication describes as semiconservative ?
-strands from original DNA molecule act as a template
-new DNA molecule contains 1 old strand and 1 new strand
outline the process of semiconservative DNA replication.
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
Use your knowledge of enzyme action to suggest why DNA polymerase
moves in opposite directions along DNA strands
-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
describe the Medellin-Stahl experiment (semi-conservative replication)
- Bacteria were grown in a medium containing heavy isotope 15N for many generations.
- Some bacteria were moved to a medium containing light isotope 14N. Samples were extracted after 1 & 2 cycles of DNA replication.
- Centrifugation formed a pellet. Heavier DNA (bases made from 15N) settled closer to bottom of tube.
Describe the structure of adenosine triphosphate (ATP)
-adenine
-ribose
-3 phosphate groups
word equation for use of ATP
ATP + H20 —> ADP+ Pi
explain how ATP is used in cells
-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
How is ATP resynthesised in cells ?
-ATP synthase catalyses condensation reaction between ADP and Pi
-during photosynthesis and respiration
explain why ATP is suitable as the “energy currency” of cells
-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
why is water a polar molecule?
-O is more electronegative than H, so attracts the electron density in the covalent bond more strongly
-forms o- and H+
name the properties of water
-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
how is water an important metabolite?
-used in lots of important condensation/hydrolysis reactions
why is water a good solvent ?
-polar water molecules surround and are attracted to ions or other polar molecules ,so these substances can dissolve and be transported
state and explain the property of water that can help to buffer changes in temperature
-water has a relatively high specific heat capacity
-can gain/lose a lot of heat/energy without changing temperature
give two properties of water that are important in the cytoplasm of cells
-solvent so that metabolic reactions occur faster in solution
-reactive so takes place in hydrolysis/condensation
what bonds form between water molecules ?
hydrogen bonds
explain the role of hydrogen ions in the body
-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
describe the roles of iron ions,sodium ions and phosphate ions in cells
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
recall the uses of ATP
provides energy for:
-synthesis of macromolecules
-muscle contraction
-active transport
-secretion
phosphate released:
-phosphorylation of molecules
-can active other key bio molecules
where are inorganic ions found?
-in cell cytoplasm
-in bodily fluids of organisms
-the role of the ion determine the required concentrations of the ions
