12.3 Nucleic Acids, ATP and Water Flashcards
Nucleotide structure
Monomer of nucleic acid
- Phosphate group
- Nitrogenous base
- Pentose (deoxy/ribose) sugar
DNA
- Pentose sugar (deoxyribose)
- 4 bases ATCG
- Nucleotides link together via a condensation reaction to make a phosphodiester bond from 5’ to 3’ carbons
- 2 poly nucleic chains are held together via weak hydrogen bonds between specific complementary base pairing
- Double helical structure
Hydrogen bonds in A-T
TWO
Hydrogen bonds in C-G
THREE
Purine
A and G
Pyrimidine
C and T
RNA
- Pentose sugar (ribose)
- 4 bases AUCG
- Short polynucleotide chain which is single-stranded
- mRNA used to transfer genetic material to ribosomes
Describe the structure of DNA
- Sugar-phosphate (backbone)/double stranded/helix so provides strength/stability /protects bases/protects hydrogen bonds;
- Long/large molecule so can store lots of information;
- Helix/coiled so compact;
- Base sequence allows information to be stored/ base sequence codes for amino acids/protein;
- Double stranded so replication can occur semi-conservatively/ strands can act as templates;
- Complementary base pairing / A-T and G-C so accurate replication/identical copies can be made;
- (Weak) hydrogen bonds for replication/ unzipping/strand separation;
- Many weak hydrogen bonds so stable/strong molecule;
Describe Semi-conservative replication.
- Strands separate / H-bonds break;
- DNA helicase (involved);
- Both strands/each strand act(s) as (a) template(s);
- (Free) nucleotides attach;
- Complementary/specific base pairing due to H bonds forming between bases/ Adenine to Thymine and GC;
- DNA polymerase joins nucleotides (on new strand) forming phoshodiester bonds by condensation;
- Semi-conservative replication / new DNA molecules contain one old strand and one new strand;
Describe the role of DNA polymerase in the semi-conservative replication of DNA.
- Joins (adjacent DNA) nucleotides;
- (Catalyses) condensation (reactions);
- (Catalyses formation of) phosphodiester bonds (between adjacent nucleotides);
Name the two scientists who proposed models of the chemical structure of DNA and of DNA replication.
Crick and Watson;
Give two features of DNA and explain how each one is important in the semi-conservative replication of DNA.
- Weak / easily broken hydrogen bonds between bases allow two strands to separate / unzip;
- Two strands, so both can act as templates;
- Complementary base pairing allows accurate replication;
ATP
- Adenosine triphosphate
- ADP + inorganic phosphate in a condensation reaction by the enzyme ATP synthase
ATP uses
- Anabolic reactions (making complex molecules from small ones)
- Active transport
- Muscle contraction
- Cell growth
- Phosphorylation of molecules to lower Ea
ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use.
- Releases relatively small amount of energy/ little energy is lost as heat;
- Releases energy instantaneously;
- Phosphorylates other compounds, making them more reactive;
- Can be rapidly re-synthesised;
- Is not lost from/ does not leave cells;
Describe how an enzyme can be phosphorylated.
- Attachment/association of (inorganic) phosphate (to the enzyme);
- (Released from) hydrolysis of ATP OR (Released from) ATP to ADP + Pi;
Describe how an enzyme can be phosphorylated.
- Attachment/association of (inorganic) phosphate (to the enzyme);
- (Released from) hydrolysis of ATP OR (Released from) ATP to ADP + Pi;
Describe how ATP is resynthesized in cells (2)
- ADP + Pi
- By ATP synthase
- In respiration
Adenosine triphosphate (ATP) is a nucleotide derivative.
Contrast the structures of ATP and a nucleotide found in DNA to give TWO differences. (2)
- ATP has ribose and DNA nucleotide has deoxyribose
- ATP has 3 phosphate (groups) and DNA nucleotide has 1 phosphate (group);
- ATP- base always adenine and in DNA nucleotide base can be different varies;
Explain five properties that make water important for organisms.
- A metabolite in condensation/hydrolysis/ photosynthesis/respiration;
- A solvent so (metabolic) reactions can occur OR A solvent so allowing transport of substances;
- High heat capacity so buffers changes in temperature;
- Large latent heat of vaporisation so provides a cooling effect (through evaporation);
- Cohesion (between water molecules) so supports columns of water (in plants);
- Cohesion (between water molecules) so produces surface tension supporting (small) organisms;
Inorganic ions definition
- Ions found in solution in the cytoplasm and body fluids of an organism
- Each ion has its own role
Hydrogen and Hydroxide (H+)(OH-)
Affects pH
H+ used in photosynthesis to provide energy to make ATP
Iron (Fe2+)( Fe3+)
Structural component of haemoglobin to bind with O2
Sodium (Na+)
Used in the co-transport of glucose and amino acids into epithelial cells
Changes the water potential
Phophate (PO4 3-)
Components of phospholipids, DNA, RNA and ATP
Describe the roles of iron ions, sodium ions, and phosphate ions in cells.
Iron ions
1. Haemoglobin binds/associates with oxygen OR Haemoglobin transports/loads oxygen;
Sodium ions
2. Co-transport of glucose/amino acids (into cells);
3. (Because) sodium moved out by active transport/Na – K pump;
4. Creates a sodium concentration/diffusion gradient;
5. Affects osmosis/water potential;
Phosphate ions
6. Affects osmosis/water potential;
7. Joins nucleotides/in phosphodiester bond/in backbone of DNA/RNA/in nucleotides;
8. Used in/to produce ATP;
9. Phosphorylates other compounds (usually) making them more reactive;
10. Hydrophilic/water soluble part of phospholipid bilayer/membrane
