Chapter 2 Flashcards
What are 2 examples of nucleic acid?
DNA - in the nucleus carries genetic information
RNA - information carrying molecules - carry genetic information from DNA to ribosomes
Describe a nucleotide structure
Pentose sugar
Phosphate
Base
Describe the structure of a DNA nucleotide
Phosphate
Deoxyribose
cytosine, thymine, adenine, guanine
Describe the nucleotide structure of RNA
Phosphate
Ribose
cytosine adenine uracil and guanine
What bonds with cytosine?
Guanine
What bonds with adenine?
Thymine
Or uracil in RNA
What are bases joined together by?
Hydrogen bonds
How many hydrogen bonds are there between Cytosine and Guanine?
3
How many hydrogen bonds are between adenine and thymine?
2
What are the structural differences between DNA and RNA?
Deoxyribose in DNA ribose in RNA
DNA makes long chains RNA makes short chains
DNA is double stranded RNA is single stranded
DNA is ATCG and RNA is AUGG
Which bases are purines?
What does this mean?
Adenine and Guanine
2 ring carbon + nitrogen
What bases are pyramidines ?
What does this mean?
Thymine and cytosine
1 ring
What is semi conservative replication?
A type of replication which produces 2 chains each with one parental stand and one with a daughter strand
What enzyme is used to split the strands?
DNA helicase
What bonds do DNA helicase break ?
Hydrogen
What enzyme causes the nucleotides to bind together?
DNA polymerase
What bond does DNA polymerase make?
Phosphodiester bonds
As each strand contains ….. the original DNA the method is called …….
Half
Semi conservative replication
State to differences found between the nucleotides in RNA and DNA
RNA has a base of uracil whereas DNA had thymine
RNA had a ribose sugar whereas DNA has deoxyribose sugar
Nucleotides are joined by ….. reactions to form a ….. chain with a sugar ….. backbone and base …..
Condensation
Polynucleotide
Phosphate
Side arms
Describe how the proportion of DNA that contains 15N changes at each division when bacteria are grown on the 14N medium in the evidence for semi conservative replication
The proportion of 15N halves each time it was grown on the 14N medium
Why does the proportion of 15N change in the evidence of specific replication?
Because DNA replicates via semi conservative replication so each strand takes half the genetic information it had so the amount halves each time
What is meant by complimentary base pairing?
Bases that always pair with a specific bade because of their structure as they have shapes that fit together
What features make DNA a stable molecule?
Hydrogen bonds link the base pairs together
The phosphodiester backbone protects vulnerable bases
It is made of 2 strands
The helix shape protects the bases
Why is DNA helicase important to DNA replication ?
It breaks the hydrogen bonds which splits the strands so new nucleotides can attach to the original strand
What stage of the cell cycle does the DNA replication occur?
Interphase
Why is DNA polymerase important to DNA replication ?
It makes the phosphodiester bonds between nucleotides to make a new strand
Explain why scientists doubted that DNA container the genetic information
It is much simpler than many molecules, particularly proteins, as it has only 4 bases, unlike protein which has 20 amino acids
What is adenine?
A nitrogen containing organic base
What is ribose
A sugar molecule with a 5-carbon ring structure that acts as the backbone to which the other groups are attached
What is adenosine
A molecule of adenine bonded to a molecule of ribose
What is adenosine triphosphate?
A molecule of adenine bonded with a molecule of ribose and three phosphate molecules
What is the reaction for releasing energy from ATP? Is this hydrolysis or condensation?
ATP + (H2O) ———> ADP +Pi+ (E)
Hydrolysis
What is Pi?
What is this used for?
An inorganic phosphate group
To phosphorylate other molecules to make these molecules more reactive
What is the equation to make ATP? Is this hydrolysis or condensation?
What is this catalysed by ?
ADP + Pi ——-> ATP
Condensation
ATP synthase
Name 6 features of ATP
It cannot be stored
It is an unstable molecule
It has to be used immediately after its made
It releases energy in small manageable amounts
It is soluble in water
It is a simple, single step reaction
What is the advantage of ATP being an unstable molecule?
It can be easily broken down to release energy
What are the uses of ATP?
Secretion Activation of molecules Active transport Movement Metabolic processes
Explain how ATP is used for the activation of molecules
Activation of molecules- inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds to make them more reactive so less activation energy is required
Explain how ATP is used for active transport
ATP provides energy to change the shape of the carrier proteins in plasma membranes. This will allow molecules or ions to be moved against concentration gradients
Explain how ATP is used for metabolic processes
Provides energy needed to build up macromolecules from their basic units
How is ATP used for movement?
ATP provides the energy for muscle contraction. In the muscle contraction ATP provides the energy for the filaments of muscle to slide past one another and therefore shorten the overall length of a muscle fibre
Explain how ATP is used for secretion
ATP is needed to form the lysosomes necessary for the secretion of cell products
A water molecule is known to be —— because it has to be a positive and a negative pole as a result of the uneven distribution of —— within it. This creates attractive forces called ——- ——- between water molecules, causing them to stick together. This stickiness of water means that its molecules are pulled inwards at its surface which is called ———. Water is able to spilt large molecules into smaller ones by a process known as ———. Water is the raw material for the process of ———— in green plants
Polar Electrons Hydrogen bonds Cohesion Hydrolysis Photosynthesis
List some of the features of water
Major component of cells It is a very important solvent Relatively high heat capacity Relatively large latent heat of vaporisation Strong cohesion Has a large surface tension
What are hydrogen ions important for ?
Determining the pH of solutions and therefore the functions of enzymes
What are the use of phosphate ions?
Form a structural role in the DNA molecules and strong energy in ATP molecules
What are iron ions used for ?
Found in haemoglobin to transport oxygen
What are sodium ions used for?
Important in the transport of glucose and amino acids across plasma membranes
What are potassium ions used for ?
Nerve impulses - action potential
What are the biological importance of water as a solvent?
Oxygen and carbon dioxide for osmosis
Dissolves wastes such as urea and ammonia to be transported out of the body
What is the benefit of ice being less dense than water?
It provides an insulating layer for the animals
Forms icecaps and land masses so aquatic habitats arent lost
Why is it important that water has a high specific heat capacity?
It means that in extreme conditions organisms dont change temperature too much so enzymes can continue to work. It acts as a buffer for temperature changes
Why is it important that a large amount of heat energy is required to evaporate water?
It means that it takes a lot of energy to change water to a gas so not too much water is lost via evaporation
