Y12 Summer Exam revision Flashcards
To consolidate knowledge and understanding for the whole class.
Define Transpiration.
The inevitable consequences of gas exchange in the leaf.
What was the purpose of the experiment by Hershey and Chase?
To investigate whether genes where made of DNA or protein.
how does non-competitive inhibition work?
a molecule binds to the allosteric site (not the active site)
this causes a conformational change to the enzymes’s active site
the substrate cannot bind because the enzyme shape changed; substrate concentration increases
What are nucleosomes?
A structural unit of eukaryotic chromosomes, consisting of DNA coiled around 8 histones
What links histones?
A linker histone
What are the stages of mitosis?
There are four stages in mitosis: Prophase, Metaphase, Anaphase and Telophase.
what is metabolism
Metabolism is the web of all the enzyme-catalysed reactions in a cell or organism
DNA Replication
Occurs from 5’ to 3’ direction
DNA Helicase unwinds and separates the DNA double helix into 2 parent strands
DNA Gyrase binds at the replication fork to stabilize the DNA
At the leading strand (3’ to 5’):
DNA Primase attaches an RNA primer in the 3’ direction to the strand to begin replication at the 5’ end
As DNA continues to unwind and separate, more primers attach to the replication fork
DNA Polymerase 3 adds free nucleotides
DNA Polymerase 1 replaces the RNA primer with DNA nucleotides
DNA Ligase joins Okazaki Fragments together
At the lagging strand (5’ to 3’):
DNA Primase attaches RNA primers in the 5’ direction to begin DNA replication at the 3’ end
DNA Polymerase 3 adds all the free nucleotides
DNA Polymerase 1 replaces the RNA primer with DNA nucleotides
How is genetic information stored in prokaryotes?
There is one chromosome consisting of a circular DNA molecule. It is naked (no associated proteins). Some have plasmids, which are small extra loops of DNA.
What happens during Prophase?
During EARLY prophase the DNA in the cell supercoils, allowing it to be visible. That is when we get the X-shape we usually draw or imagine.
During LATE prophase, the MTOCs or centrioles (same thing) move to the north and south pole, from where the spindle fibers will form.
The nuclear envelope breaks down.
How do new alleles form?
Alleles form from other alleles by genetic mutation
What is the difference between Anaphase and Telophase?
In anaphase, the chromosomes split chromatids as the spindle fibres retract to the opposite sides of the cell.
In Telophase, two new nuclear membranes form around the two sets of DNA that have been separated, creating two new, identical cells.
What are homologous chromosomes?
All chromosomes of one particular type. They have the same genes in the same sequence, although not necessarily the same alleles.
what is metabolism
the totality of chemical processes that occur within a living organism in order to maintain life
What are autosomes?
Any chromosome, excluding sex chromosomes.
Describe the 3 stages by which binary fission occurs
The prokaryotic cells do divide in their own special way; instead of dividing through mitosis as eukaryotic cells do, they divide by binary fission, and is used for asexual reproduction.
The single circular chromosome is first replicated- these two copies of the chromosome then move to the opposite ends of the cell. After they reach the edge of the cell, the cell quickly divides, leaving each daughter cell with one copy of the chromosome, making them genetically identical.
What phenomena causes down syndrome?
Non-disjunction
DNA Structure
Antiparallel strands, each consisting of a sugar-phosphate backbone and one of 4 nitrogenous bases
DNA bases
Adenine
Thymine
Guanine
Cytosine
What bases bond together?
Adenine with Thymine
Guanine with Cytosine
DNA Replication
Occurs from 5’ to 3’
What happens during Metaphase?
The chromosomes move to the EQUATOR and attach to the spindle fibres that have reached out from the MTOCs.
What is a karyogram?
A photograph or diagram in which all the chromosomes of an organism are shown in homologous pairs in order of decreasing length.
What is a genome?
The whole of the genetic information of an organism.
Why can a diploid cell not have an odd number of chromosomes?
Because the chromosomes exist in homologous pairs, so that the number of chromosomes is always a multiple of 2. Exception: non-disjunction.
What properties of DNA and proteins did Hershey and Chase make use of in their experiment?
The fact that DNA contains phosphorus but not sulphur and proteins contain sulphur but not phosphorus.
The genetic material from both parents are called diploid and haploid. How many chromosomes do Diploid and haploid copy?
Diploid- two copies of each chromosome
Haploid- one copy of each chromosomes.
what are the four stages of glycolysis?
- phosphorylation: hexose sugar (6C) + 2ATP -> less stable glucose molecule
- lysis: 6C split into two 3C sugars
- oxidation: hydrogen removed from 3C sugars, makes 2 NADH
- substrate level phosphorylation
- > 2ATPs per 3C sugars made
Outline the procedure of the experiment by Hershey and Chase.
1) They used a 🦠 that infected E.coli by injecting its genes into the cytoplasm.
2) Viral proteins start being made in the cytoplasm of E. coli soon after the virus comes into contact with it, showing that the viral genes have entered the bacterium.
3) Hershey and Chase prepared two strains of T2, one having its DNA radioactively labelled with 32-P and the other having its protein labelled with 35-S.
4) These two strains of labelled T2 were each mixed with E. coli.
5) the mixture was agitated in
a high-speed mixer and then centrifuged at 10,000 rpm to separate into a solid pellet containing the bacteria and a liquid supernatant.
6)A Geiger counter was used to locate the radioactivity.
per glucose molecule, how many of each product is created in the krebs cycle
4 × CO2
2 × ATP
6 × NADH + H+
2 × FADH2
How many chromosomes does each daughter cell have after meiosis?
23 chromosomes
what are competitive inhibitors?
Competitive inhibition involves a molecule, other than the substrate, binding to the enzyme’s active site
The molecule (inhibitor) is structurally and chemically similar to the substrate (hence able to bind to the active site)
The competitive inhibitor blocks the active site and thus prevents substrate binding
As the inhibitor is in competition with the substrate, its effects can be reduced by increasing substrate concentration
what are non-competitive inhibitors?
Non-competitive inhibition involves a molecule binding to a site other than the active site (an allosteric site)
The binding of the inhibitor to the allosteric site causes a conformational change to the enzyme’s active site
As a result of this change, the active site and substrate no longer share specificity, meaning the substrate cannot bind
As the inhibitor is not in direct competition with the substrate, increasing substrate levels cannot mitigate the inhibitor’s effect
Functions of Non-coding DNA
1) Regulation of gene expression
2) Introns
3) Telomeres
4) Genes for tRNA
What is telomeres?
They are distinctive structures found at the end of your chromosomes. Consist of short DNA sequences repeating over and over again.
What are the functions of introns?
Introns increase the gene length that leads to crossing over the sister chromosomes that lead to greater genetic variation and can result new gene.
What is the difference between diffusion and endo/exocytosis?
Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration (through a concentration gradient) through the cell’s semi-permeable membrane. This process does not require energy and transports particles rather than water.
Exocytosis and endocytosis are energy-driven processes where vesicles containing fluid enter or exit the cell through the membrane. A vesicle is a small sac of membrane with a droplet of fluid inside; they’re spherical and normally present in any eukaryotic cell. To form a vesicle, a small region of membrane is pulled from the rest of the membrane and is pinched off; proteins in the membrane carry out this process, and require energy from ATP. Vesicles are formed inside the cell after the cell accepts material from outside of the cell; this is endocytosis.
Vesicles taken in by endocytosis contain water and solutes from outside the cell, but also often contain larger molecules needed by the cell that cannot pass across the plasma membrane through diffusion. An example of this is in the placenta, whereby proteins from the mother’s blood are absorbed into the fetus by endocytosis.
On the other hand, exocytosis is then the release of vesicles from the cell into their surroundings. This happens when a vesicle fuses with the cell’s plasma membrane and the materials are released into the surrounding. Digestive enzymes are often released from the gland cells by exocytosis; the polypeptides in the enzyme are synthesized by the rER, processed in the Golgi apparatus and then carried to the membrane by vesicles for exocytosis. However, in this case, it is referred to as “secretion”, due to the fact that a useful substance was released, not a waste product.
what does cell respiration involve?
oxidation and reduction of electron carriers
What is transcription?
DNA is copied into RNA by DNA polymerase
Transcription Process
Initiation:
RNA polymerase binds to the promoter region of the gene
Elongation:
RNA polymerase simultaneously uncoils and transcribes the coding region in the 5’ to 3’ direction
Termination:
RNA polymerase detaches from the mRNA strand after reaching the termination sequence
The mRNA separates from the DNA template
What happens in during Interphase?
All cell contents duplicate.
Explain the entire Cell respiration process, including glycolysis, Kreb cycle and chemiosmosis phosphorylation. simplified version
Interphase
The stage in the development of a cell between two successive divisions
This phase of the cell cycle is a continuum of three distinct stages:
G1 – First intermediate gap stage in which the cell grows and prepares for DNA replication
S – Synthesis stage in which DNA is replicated
G2 – Second intermediate gap stage in which the cell finishes growing and prepares for cell division
M phase
The period of the cell cycle in which the cell and contents divide to create two genetically identical daughter cells
This phase is comprised of two distinct stages:
Mitosis – Nuclear division, whereby DNA (as condensed chromosomes) is separated into two identical nuclei
Cytokinesis – Cytoplasmic division, whereby cellular contents are segregated and the cell splits into two
what is the difference between cyclical and non-cyclic photophosphorylation?
non-cyclic: involves both photosystems uses photolysis of water oxygen as byproduct NADPH synthesised
cyclic: involves photosystem 1 doesn't use water no oxygen produced no NADPH synthesised
Explain the entire Cell respiration process, including glycolysis, Kreb cycle and chemiosmosis phosphorylation. simplified version
Interphase
The stage in the development of a cell between two successive divisions
This phase of the cell cycle is a continuum of three distinct stages:
G1 – First intermediate gap stage in which the cell grows and prepares for DNA replication
S – Synthesis stage in which DNA is replicated
G2 – Second intermediate gap stage in which the cell finishes growing and prepares for cell division
M phase
The period of the cell cycle in which the cell and contents divide to create two genetically identical daughter cells
This phase is comprised of two distinct stages:
Mitosis – Nuclear division, whereby DNA (as condensed chromosomes) is separated into two identical nuclei
Cytokinesis – Cytoplasmic division, whereby cellular contents are segregated and the cell splits into two
The Cell Cycle
cell cycle
How does nucleosomes regulate gene expression?
Nucleosomes affect the accessibility of transcription factors to occupy their binding sites in chromatin of eukaryotic cells.
What is translation?
The process in which gene transcripts are converted into large polypeptide chains that can be folded and modified to create functional proteins
Translation Process
Initiation:
The tRNA molecule binds to the small subunit of the ribosome, which binds to the 5’ end of the mRNA strand and moves from the 5’ to 3’ direction until it finds the start codon of the mRNA strand
The large and small subunit of the ribosome bind together
The tRNA molecule with the anticodon complimentary to the next mRNA codon on the chain binds to the amino acid and ribosome site
Elongation:
The anticodon of incoming tRNA molecules pair with its complimentary mRNA codon at the amino acid of the ribosome
The amino acids in the tRNA and amino acid sites form a peptide bond
Translocation:
The tRNA on the peptide site moves to the exit site
The tRNA codon binds to the amino acid site, where the complimentary codon can bind
The process is repeated
What discovery suggested that Genes were made of DNA in Hershey and Chase experiment?
There was a high proportion of radioactivity within the protein in the pellet when 32-P was used.
What is the difference between 3’ and 5’ ends in DNA?
The 3’ end in DNA has a deoxyribose to which the phosphate of another nucleotide could be linked.
The 5’ end in DNA has a phosphate that is attached to C5 of deoxyribose.
Name three factors that influence the rate of transpiration.
Temperature
Humidity
Light Intensity
Wind
What is the problem of stomata opening for the plant to take in carbon dioxide?
Water vapour is lost.
How do plants minimise the water lost through stomata?
By using guard cells which can control the aperture of the stoma and can adjust it from wide open to fully closed.
Which group of land plants does not have any stomata?
The Liverworts.
Which properties of water help it move up the xylem?
Cohesion and adhesion
Define cohesion.
Water molecules are polar and the partial negative charge on the oxygen atom in one water molecule attracts the hydrogen atom in a neighbouring water molecule.
Define adhesion.
Water is attracted to hydrophilic parts of the cell walls of xylem.
Define transpiration pull.
The low pressure in the xylem, created by the water loss, generates a pulling force that is transmitted through the water in the xylem vessels down the stem and to the ends of the xylem in the roots.
what was the first molecule being synthesised that disproved vitalism?
Urea
what are the groups in a molecules present in a diagram of an amino acid?
an amine group
a carboxyl group
a hydrogen atom
the R group
what is metabolism?
the web of all enzymes catalysed reactions in a cell or organism
what is Anabolism?
the synthesis of of complex molecules from simpler molecules
what is Catabolism?
it is the breakdown of complex molecules into simpler molecules
Name 2 properties of Water and their advantages
- adhesive - water is attracted to there polar molecules - attracted to the polar xylem wall
- cohesive - water molecules are attracted toothier water molecules due to hydrogen bonding - they can be pulled up the xylem more easily
how body cool by sweat
the heat needed for the evaporation of water in sweat is taken from the tissues of the skin, reducing their temperature.
Give 3 examples of monosaccharides
Glucose, fructose ribose
