Biological molecules pt 2 Flashcards
(43 cards)
DNA stands for and structure
Deoxyribose Nucleic Acid
Two strands twisted in a double helix structure with hydrogen bonds between complementary base pairs
Phosphate group, deoxyribose,nitrogenous base of adenine thymine cytosine guanine
Phosphate group has a negative charge
Covalent bonds
C1 of deoxyribose to nitrogenous base
Monomer to polymer of nucleotides
Nucleotides form phosphodiester bonds in condensation reactions and are broken thriugh hydrolysis
DNA VS RNA formula and relate to stability
C5O4H10 is DNA loss of oxygen is more stable than C5O5H10
DNA vs RNA differences
Two strands (antiparallel) vs one strand Nucleus vs nucleus and cytoplasm Thymine vs uracil Replicates and stores in for vs converts to a format acceptable for protein synthesis One type vs three types
How/why is dna stable
Phosphodiester backbone protests the bases inside the double helix which fairies the genetic code so is protected from outside chemical and physical forces
Bases on each strand are linked by hydrogen bonds forming bridges between the sugar phosphate backbone
Many hydrogen bonds are string together
DNA function and properties
Very stable allowing it to pass from generation to generation without changing - rare mutations
Two strands that can be separated during replication and protein synthesis
Large so carry huge amounts of genetic info
Base sequence of a gene determines structure and function of protein
Semi conservative replication
DNA helicase enzyme breaks the hydrogen bonds between the complementary base pairs leaving them exposed and individual strands can act as a template for the new strand to be formed. Free activated nucleotides with two extra phosphate groups (which helps lower the activation energy and increase the likelihood of a reaction) binds to the complementary base pairs. DNA polymerase enzyme catalysts the synthesis of phosphodiester bonds starting on the strand ending on 3’ hence in the 5’ to 3’ direction. The new molecule formed retains half of the original DNA and half of the new.
2 features of DNA and explain how each one is important in semi conservative replication (2 marks)
Hydrogen bonds between complementary base pairs are important because DNA helicase needs to break them in order to separate the strands leaving the bases exposed, allowing each strand to act as a template. Complementary base pairing allows for accurate replication.
Dispersive model of DNA
Two molecules with old and new DNA dispersed between the strands
Watson and crick used other scientists results but pieced it all together
All DNA bases contain nitrogen 14…..when bacteria is grown in a medium they will absorb nitrogen from the medium and incorporate it into the new nucleotides and ultimately DNA. All bacteria grown in a heavy medium then spun in a centrifuge which allows the heavy and light DNA to separate. Results showed only one line in the middle hence ruling out the conservative model. The second generation showed 14N and 15N line hence ruling out dispersive because that would only be one line.
Why did many scientists not agree that nuclei acid contained the molecule of heritage
Proteins have 20 amino acids hence have numerous possibilities which seemed more suited to explain the genetic variation present in humans whereas there are only four nitrogenous bases.
Explain why new nucleotides can only be added in the 5’ to 3’ direction
The enzyme DNA polymerase is specific and has an active site of a complementary shape to the 3 OH group of 5’ strand and phosphate of growing strand hence can only work on substrate in that direction.
ATP stands for and is an…with an extra… which makes it …..
Adenosinetriphosphate
Activated nucleotide - extra phosphate bond makes it more reactive so easily broken down
Function of ATP
Stores chemical energy from glucose as chemical energy in ATP
ATP hydrolysis
Energy stored in ATP is released (exothermic) by breaking off third phosphate and small amounts of energy are steadily related to drive energy requiring process in the cell.
ATP hydrolyse catalyses the hydrolysis
ATP hydrolysis is exergonic meaning
Energy is released
Condensation of ATP
Adds phosphate group, ATP synthase catalyses the synthesis and is endergonic hence energy is required.
3 ways to make ATP
Phosphorylation in chloroplasts uses light energy in a condensation reaction
Oxidative phosphorylation uses glucose and other fuels in a condensation reaction
Substrate level phosphorylation is when the phosphate group is in a high energy bond with sugar substrate instead of dissolved in cytoplasm .
Base reaction is ADP plus Pi = ATP plus water with arrows for light or fuels upwards
Last reaction is sugar substrate plus ADP gives sugar substrate plus ATP
Functions ATP examples
Anabolism so protein synthesis
Muscle contraction - needed for filaments to slide past one and other
Active transport
Secretion of substances from cells - needed to form lysosomes
Activation if Molecules - glycolysis - add phosphate toe glucose molecules so can be broken into TP
Explain how the hydrolysis of ATP for energy requiring reactions (endergonic) is useful
ATP is an immediate source of energy for cells (better than glucose) and can be rapidly synthesised after hydrolysis and transfers small manageable amounts of energy for reactions that require it
What are enzymes
Enzymes are globular proteins that act as biological catalysts that speed up a reaction by lowering the activation energy without getting used up.
How is the function of enzyme reliant on its primary protein structure?
The primary protein structure is the sequence of amino acids that then fold in on each other forming a 3D molecule. An enzyme has a specific shape that will fit the substrate the enzyme is meant to work upon. A change to the primary structure would cause a difference in bonds formed during folding hence changing the shape rendering the active site useless and unable to form an enzyme - substrate complex.
What is the induced fit model of action?
Proposes that the decreased proximity of substrate is a change in the environment of the enzyme causes the shape of the enzyme to change , like a glove does to a hand, to accommodate the substrate. As the enzyme changes shape, strain is applied on the substrate molecule which distorts the bonds in the substrate, consequently lowering the activation energy.
Locke and Key model limitations
Older model than induced fit
Too rigid as enzymes are extremely specific hence does not explain scientists observing enzymes accommodating similarly shaped molecules to that of the intended substrate.
