Pack 5 - DNA, ATP, Mitosis Flashcards
What are the three components of an individual nucleotide?
- A pentose sugar
- A phosphate group
- A nitrogen containing organic base.
Which 4 bases does DNA contain?
- Adenine
- Thymine
- Guanine
- Cytosine
Which 4 bases does RNA contain?
- Adenine
- Uracil
- Guanine
- Cytosine
What type of reaction joins a pentose sugar to a phosphate group and an organic base in a nucleotide?
Condensation reaction.
What is the monomer of DNA and RNA?
Nucleotide
What type of REACTION joins two mono nucleotides and what BOND is formed?
What is the name of the PRODUCT?
- Condensation
- Phosphodiester Bond
- Dinucleotide
What is the name for a long chain of nucleotides?
Polynucleotide
What sugar is found in RNA?
Ribose
What sugar is found in DNA?
Deoxyribose
Briefly describe three roles of RNA.
- Ribosomes are made of rRNA
- mRNA transfers genetic information from DNA to the ribosomes.
- tRNA is involved in protein synthesis
What type of bonds form between complementary bases on opposite strands of DNA.
Hydrogen bonds.
How many strands does DNA have?
2
How many strands does RNA have?
1
Which base pairs with Adenine in DNA?
Thymine
Which base pairs with Thymine in DNA?
Adenine
Which base pairs with Cytosine in DNA?
Guanine
Which base pairs with Guanine in DNA?
Cytosine
If a molecule of DNA contains 20% Adenine, what is the percentage of Cytosine in this molecule?
30%
What word is used to describe the direction in which each strand of DNA runs?
Antiparallel - one strand runs in one direction the other is ‘upside down’ running in the other direction.
Give two ways that DNA is a chemically stable molecule.
- Phosphodiester backbone protects the more chemically reactive bases.
- H-bonds link base pairs. As there are 3 h-bonds between C and G , the higher the proportion of C-G pairings, the more stable the molecule of DNA.
What is the function of DNA?
It is responsible for storing and passing on genetic information about an organism from cell to cell and generation to generation.
Give 5 ways in which DNA is adapted to carry out its function.
- Stable - information does not change/rarely mutates.
- Two strands joined by h-bonds - allows them to separate during DNA replication and protein synthesis.
- Large - carries a large amount of genetic information.
- Base pairs within helical cylinder - protects genetic information from outside chemical and physical forces.
- Base pairing - DNA can be replicated and transfer information as mRNA.
Describe the steps (5) of the semi-conservative replication of DNA.
- DNA helices breaks the hydrogen bonds between base pairs.
- The double helix separates into two strands and unwinds.
- Each exposed polynucleotide acts as a template to which free nucleotides bind to their respective complementary base pair, forming hydrogen bonds.
- DNA polymerase forms phosphodiester bonds between adjacent nucleotides, forming a polynucleotide.
- Each new molecule contains one strand from the original molecule.
Describe the Meselsohn Stahl experiment on bacteria.
- ¹⁵N ¹⁴N
- Bacteria grown in medium ¹⁴N as a control collected at the top of the centrifuge tube.
- Bacteria grown in medium ¹⁵N collected at the bottom of the centrifuge tube.
- They then placed the ¹⁵N bacteria into a ¹⁴N medium for one generation.
- Its DNA was in the middle of the centrifuge tube as it had 1 strand of light and one strand of heavy.
- After two generations 50% was a mixture of the isotopes DNA and and 50% was lights.
- This is because the light strands of the mixed DNA formed new DNA with a light strand and so did the light side>
What are the three components of ATP and what does ATP stand for?
- Adenine, ribose, 3 phosphate groups
* Adenosine triphosphate.
What is useful about the bonds between phosphate groups in ATP? (3 points)
- Unstable
- ⇒ Low activation energy
- Considerable amount of energy released when broken.
State the word equation of the hydrolysis of ATP.
ATP + H₂O → ADP + Pᵢ + Energy
What enzyme catalyses the hydrolysis of ATP?
ATP Hydrolase (ATPase)
What enzyme catalyses the synthesis of ATP?
ATP synthase
What is the equation of the synthesis of ATP?
ADP + Pᵢ + Energy → ATP + H₂O
What type of reaction is the synthesis of ATP?
Condensation reaction
In what three ways is ATP synthesised from ADP?
- in chlorophyll-containing plant cells during PHOTOSYNTHESIS.
- during RESPIRATION.
- in plant and animal cells when phosphate groups are transferred from donor molecules to ADP
Why is ATP a bad long term energy source ?
Unstable bonds between phosphate groups.
What kind of energy source is ATP?
Intermediate energy source.
Why is ATP a better intermediate energy source than glucose?
- Hydrolysis of ATP releases less energy. Energy for reactions is released in smaller more manageable quantities.
- Hydrolysis of ATP to ADP is a single reaction. Breakdown of glucose is a series of reactions.
Why does ATP have to be continuously made?
It cannot be stored in the cell.
Where is ATP made continuously in metabolically active cells?
Mitochondria
Name 5 processes where ATP is used?
- Metabolic processes - provides energy needed to build macro-molecules, e.g. starch.
- Movement - ATP provides energy for muscle contraction.
- Active transport - ATP provides energy to change the shape of carrier proteins.
- Secretion - ATP is used to form lysosomes necessary for secretion.
- Activation of molecules - phosphate released can be used to phosphorylate other compounds, thus lowering the activation energy in enzyme-catalysed reactions.
In what phase of the cell cycle does DNA divide?
S phase of interphase.
What connects the two strands of identical DNA after it replicates?
Centromere
Name the 4 stages of mitosis in order and the following process.
- Prophase
- Metaphase
- Anapahse
- Telophase
- Cytokinesis
Describe the stages of prophase. (5 steps)
- Chromosomes become visible and shorten and fatten.
- Centrioles move to poles of the cell.
- Spindle fibres develop (from centrioles)
- Nucleolus disappears; nuclear envelope breaks down.
- Spindle fibres draw chromosomes towards the equator. Attached at the centromere.
What is a centriole?
Cylindrical organelles found in animal cells from which spindle fibres develop.
What are spindle fibres collective known as?
Spindle apparatus
Describe the stages of metaphase. (3 steps)
- Chromosomes are seen to be made of two sister chromatids connected at the centromere (each chromatid is identical copy of each other).
- Microtubules attach to the centromere.
- Chromosomes are pulled along the spindle apparatus and line up at the equator.
Describe the stages of Anaphase. (3 steps)
- Centromeres divide into two.
- Spindle fibres pull individual chromatids apart towards the poles.
- Mitochondria provide energy for the process by gathering around the spindle fibres.
Describe the stages of Telophase. (4 steps)
- Chromosomes reach their poles.
- Chromosomes become longer and thinner and eventually visibly disappear.
- Spindle fibres disintegrate.
- Nuclear envelope and nucleolus reform.
What is cytokinesis.
Following telophase, the cytoplasm divides forming two separate cells.
What is the name of the process by which prokaryotic cells divide?
Binary fission
Describe in 5 steps binary fission.
- Circular DNA replicates.
- Both copies attach to the cell membrane.
- Plasmids replicate
- Cell membrane grows between the two molecules (dividing the cytoplasm in two).
- Cell wall forms between the two copies of DNA forming two daughter cells.
Describe how viruses replicate (4 steps).
- Virus attaches to host cell with attachment proteins on the surface of the cell.
- They inject their nucleic acid into the host cell.
- The host cells resources use the viruses genetic information to produce viral components. (e.g. nucleic acids and enzymes)
- These are assembled into new viruses.
If 10 out of 100 cells in view are undergoing metaphase, what proportion of the cell cycle is taken up by metaphase?
10%
Give 3 uses of mitosis.
- Growth
- Repair
- Asexual reproduction
What are the three stages of the cell cycle?
- Interphase
- Nuclear division
- Cytokinesis
What causes uncontrolled cell division?
Mutation of genes that control cell division.
