Exam 😈 Flashcards
what are prokaryotic cells
cells within prokaryotes that lack a membrane-bound nucleus
what are eukaryotic cells
cells within eukaryotes that have a membrane-bound nucleus and other membrane-bound organelles
what is nucleic acid made up of?
sub-units / monomers called nucleotides
what are nucleotides?
basic building blocks or sub-units of DNA and RNA consisting of a phosphate group, a base and a five-carbon sugar.
what are the types of sugar in RNA and DNA nucleotides?
DNA = deoxyribose, RNA = ribose
what are the 5 types of bases?
adenine, thymine, uracil, cytosine and guanine
what are the (main) 3 types of RNA?
transfer RNA (tRNA), messenger RNA (mRNA) and ribosomal RNA (rRNA)
what does mRNA do?
Carries the genetic message from the DNA from the nucleus to the ribosomes (to be translated)
what does rRNA do?
together with particular proteins, makes the ribosomes found in cytosol
what does tRNA do?
carry amino acids to ribosomes that are free in the cytoplasm, where they are used to construct proteins
what is it meant by the genetic code is degenerate
the property of the genetic code in which more than codon of bases can code or one amino acid
what are the steps of gene expression
Transcription
RNA processing
Translation
transcription definition
process of copying the genetic instructions present in DNA to messenger RNA
RNA processing definition
occurs after transcription and involves modifying pre-mRNA to form mature mRNA
translation definition
process of decoding the genetic instructions in mRNA into a protein (polypeptide chain) built of amino acids
what are the 3 steps of transcription
- The DNA is unwound by the RNA polymerase binding to the promoter region as well as DNA helicase assisting
- This base sequence of DNA gained acts as a template for a mRNA strand to be made by RNA polymerase continuing moving along (3’ to 5’) bring complimentary nucleotides as it goes
- A pre mRNA strand is made and released from the templated.
what are the 3 main steps in RNA processing?
Capping
Adding a tail
splicing
What happens during capping? (RNA processing)
The 5’ end of the pre-RNA has its G’s modified with a methyl cap (methyl guanosine). This capping protects the pre-RNA from enzyme attack and assists with stability, allowing it to attach to the ribosome.
what happens during adding a tail? (RNA processing)
A poly-adenine (A) tail with up to 250 A’s is also added to the 3’ end. The tail contributes to the stability of the mRNA and facilitates mRNA export from the nucleus
what happens during splicing (RNA processing)
the introns from the pre-RNA are spliced out allowing the exons to join together. This is done by spliceosomes which recognise the base sequences at the 5’ (GU) and 3’ (AG) that are the end of the introns.
what is alternate splicing?
exons can be removed enabling one gene to produce a multitude of proteins if required.
where does translation take place?
cytosol
what are the 4 steps of translation
- mRNA moves to the ribosome where it is read in codons.
- the amino acids are then brought to the mRNA by the tRNA. At one end of the tRNA it makes an anticodon, and at the other end it attaches to a specific amino acid.
- The ribosome then continues to make more amino acids and they are joined by peptide bonds.
- A codon that tells the ribosome to stop production is reached and the polypeptide is released from the ribosome.
what is the start codon
AUG
what are the 3 stop codons
UAA, UAG or UGA
what is the coding region?
the part of the gene that gives the information for making proteins
what is the flanking regions?
parts of the gene that isn’t the coding region
what is the coding region made up off?
exons and introns
what are the 2 flanking regions known as?
upstream and downstream
what are exons?
the part that contain the instructions for the synthesis of the protein and are both transcribed and translated
what are introns?
parts in the coding region that are transcribed but are cut out during RNA processing and therefore are not translated
what are the 3 sections of the upstream region?
promoter
operator
leader
what happens in the promoter region?
The promoter is where transcription factors and RNA polymerase binds to initiate transcription
what happens in the operator region?
It is a binding site for repressor proteins, which are proteins that prevents RNA polymerase binding to a promoter, and thus transcription cannot be initiated
what are the 4 parts of the leader region?
TrpL (1), then three attenuator regions (2, 3, 4)
what happens in the leader region?
further regulation of transcription
what is an operon?
group of linked structural genes with a common promoter and operator that is transcribed as a single unit
what are the two types of regulation of the trp operon?
repression and attenuation
what happens when trp is present in repression (3 steps)
- trp binds to the repressor protein causing a configurational change in its shape, allowing it to be active
- This allows the repressor to bind at the operator
- RNA polymerase is unable to bind to the promoter and transcription does not occur. Thus the operon is OFF
what happens when trp isn’t present in repression (2 steps)
- the repressor is unable to bind to the operator (as it is still in an inactive form)
- RNA polymerase can bind to the promoter and start transcription of the structural genes; thus, the operon is ON
when there is trp present what happens in attenuation (4 steps)
- trpL can be quickly translated. When the ribosome translates this region quickly (to the leader peptide), it will quickly detach from the mRNA
- This allows a hairpin loop to form between the mRNA produced in regions 1 and 2.
- A terminator hairpin loop between the mRNA in regions 3 and 4 is also able to form.
- the RNA polymerase detaches from the DNA, transcription is stopped
when there isn’t trp present what happens in attenuation (5 steps)
- trpL is translated slowly
- As the ribosome translates the gene, the ribosome pauses at the trp codon to wait for enough tryptophan to be available to produce the leader polypeptide
- the ribosome stays attached to region 1, and therefore no hairpin loop can form between the mRNA in regions 1 and 2, but one will form between 2 and 3
- this hairpin loop does not cause the RNA polymerase to detach and prevents the terminator hairpin of regions 3 and 4 forming
- RNA polymerase continue remains attached to the trp operon, transcription and translation can occur
what are polypeptides?
large molecules made up of amino acids
what are amino acids made up of
an amino group and a carboxyl group. The difference between amino acids are the R group
what are the 4 levels of protein structure?
primary, secondary, tertiary, quaternary
what is a primary protein structure?
linear sequence of amino acids, each protein has a different primary structure and therefore different functions
what is a secondary protein structure?
folded amino acid sequences depending on the R group
what are the 3 types of secondary protein structures
- Alpha helix
- Beta-pleated sheet
- Random coiling
what is an alpha helix (protein)
secondary structure in proteins that appears as a tight twist
what is a beta-pleated sheet? (protein)
secondary structure in proteins that appears as folded sheets, with a change in direction of the polypeptide chain
what is random coiling? (protein)
secondary structure in proteins that does not fit in as either a alpha helix or beta-pleated sheet
what are tertiary structures?
total irregular 3D folding held together by ionic or hydrogen bonds forming a complex shape
what is a quaternary structure?
A structure in which two or more polypeptide chains interact to form a protein
what is the basic function of enzymes?
increase the rate of almost all the chemical reactions and to do this within the prevailing conditions of temperature and pH within cells
What is a proteome
The complete array of proteins produced by a single cell or an organism in a particular environment.
what happens at the ribosome?
translation (in cytosol ribosomes)
what happens in the rough endoplasmic reticulum?
transporting some of the proteins to various sites within a cell
what does the Golgi apparatus (complex) do?
packages proteins into vesicles for export from the cell through exocytosis
what do vesicles outside of the golgi apparatus do?
move to the plasma membrane of the cell, where they fuse with it and discharge their protein contents to the exterior through exocytosis
What is reverse transcription?
the process in cells by which an enzyme makes a copy of DNA from RNA
when is reverse transcription used?
when only specific genes or small sections of DNA are required to be synthesised, we use mRNA instead of DNA
what are the 5 steps in reverse transcription
- mRNA is isolated from cytosol
- Poly-A tail is added to the mRNA
- a primer is added and binds to this tail, then the DNA lengthens from nucleotides being added
- polymerase is added, catalysing the building of the complementary DNA strand
- the double stranded DNA is produced
what enzyme is used to use mRNA as the template to build the single stranded DNA in reverse transcription?
reverse transcriptase
what are restriction enzymes?
cleave (cut) DNA at specific recognition sequences known as restriction sites, splitting DNA into smaller fragments
what is a restriction site
a particular order of nucleotides
what do restriction enzymes create when cutting? (ends)
blunt and sticky ends
how are blunt ends cut?
at points directly opposite each other
how are blunt ends rejoined together (ligated)
the DNA fragments are joined directly together through the use of DNA ligase
how are sticky ends cut?
cut one strand at one point but cut the second strand at a point that is not directly opposite, leaving over hanging ends.
how are sticky ends joined together (ligated)
The DNA ligase enzyme connects the single-stranded DNA together via the sugar-phosphate backbones
where does ligase join DNA together?
sugar–phosphate backbones
what is polymerase chain reaction (PCR)
is a technique used to amplify a segment of DNA accurately and quickly
what is the main enzyme used in PCR and why is it used over others
Taq polymerase, because it can withstand great heat needed for the breakdown of DNA (heat resistant)
what are the 3 main steps in PCR?
- Denaturing
- Annealing
- Extension
what are the 2 steps involved in denaturing (PCR)
- DNA is heated to 94 degrees
- separation happens by raising the temperature of the PCR mixture, the hydrogen bonds between the complementary DNA strands break
what is the optimal temperature for denaturing to occur at and for how long
around 94 for a minute
What happens in annealing (PCR)
Short segments of single-stranded DNA, known as primers, are added, binding to the 3’ ends (target DNa sequences) initiating DNA synthesis. These primers bind to their complementary sequences on the single-stranded template DNA
what is the optimal temperature for annealing to happen and for how long
55 for 2 mins
What happens in extension (PCR)
The polymerase (Taq polymerase) uses the primers as a starting point and extending the primers, synthesising the new strands of DNA by adding nucleotides
what is the optimal temperature for extension to happen and for how long
72 for one minute
what is the difference between DNA and RNA polymerase
DNA polymerases synthesise DNA strands by adding (DNA) nucleotides (deoxyribose, ACTG)
RNA polymerases synthesise RNA strands by adding (RNA) nucleotides (ribose, AUCG)
what is gel electrophoresis
a technique for sorting a mixture of DNA fragments through an electric field on the basis of different fragment lengths
what are the 6 steps in gel electrophoresis
1.The DNA sample (fragments) is combined with DNA loading dye
2. it is then placed in a well at one end of a slab of aragose gel
3. This agarose gel is immersed in a buffer (salt) solution
4.The gel is then exposed to an electric field with the positive (+) pole (anode) at the far end and the negative (−) pole (cathode) at the starting origin. The DNA is attracted to the positive pole
5. Smaller fragments move through the agarose gel faster compared to larger fragments
6. fragments appear as bands on a gel which can be interpreted in various ways
why do smaller fragments move further in gel electrophoresis
the smaller fragments are able to better move and weave through the porous agarose gel compared to larger fragments
what is DNA profiling
a technique for identifying DNA from different individuals based on variable regions known as short tandem repeats (STRs)
what are STRs
short tandem repeats, sequences of just two to seven base pairs are repeated over and over
how are STRs used in DNA profiling
The number of repeats of an STR marker can vary between people and each variation is a distinct allele, so people with the same amount of repeats will match with certain DNA that is found
what is a plasmid
a small, circular, double-stranded DNA molecule, separate from the cell’s chromosomal DNA that exist naturally in bacterial cells
what is a recombinant plasmid
plasmids that carry foreign DNA
what are the 4 steps in making recombinant plasmids
- DNA of the plasmid is cut using a specific cutting enzyme in order to create sticky ends
- foreign DNA fragments are prepared using the same endonuclease so that the foreign DNA has sticky ends complementary to the cut plasmid (mostly done through reverse transcription)
- foreign DNA fragments and the plasmids are mixed, and, in some cases, their ‘sticky ends’ pair by using weak hydrogen bonds. A recombinant plasmid has been created
- The joining enzyme, ligase, is added and this makes the joins permanent through covalent bonding
what needs to happen after making a recombinant plasmid
needs to be transferred into a bacterial cell (bacterial transformation)
what is bacterial transformation
process in which bacterial cells take up segments of foreign DNA that become part of their genetic make-up
what are selectable markers
genes carried by plasmids for certain traits, often for antibiotic resistance
what are screening markers
A marker inserted into a plasmid that will change colour based on if the DNA has been taken up by the bacteria, lacZ is an example
what is a main thing we create using recombinant plasmids
insulin
what type of protein structure is insulin, therefore what does that mean
quaternary, meaning multiple peptide chains
how is insulin prepared before undergoing recombinant plasmid construction
reverse transcription, because don’t have to splice out introns
what are the 5 simple steps in creating insulin separately
- cut with endonucleases
- add insulin genes using ligase
- transformations of bacteria with plasmids and expression of proteins
- extract protein (insulin + B-galactosidase) from bacteria
- purify both A and B and combine each to each other
how can the success rate of bacterial transformation be increased
by heat shock or electroporation
why is heat shock and electroporation used
to increase the chance of bacteria to take up the recombinant plasmid as chances are low
what happens in electroporation
Cells are briefly placed in an electric field that shocks them and appears to create holes in their plasma membranes, allowing the plasmid entry
what is a vector
an agent or vehicle used to transfer pathogens or genes between cells and organisms
what happens in heat shock
The bacterial cells are suspended in an ice-cold salt solution and then transferred to 42 °C for less than one minute. This treatment appears to increase the fluidity of the plasma membranes of the bacterial cells and increases the chance of uptake of plasmids
what is gene cloning
the process which a gene of interest is located and cloned to produce multiple copies
what is recombinant DNA
DNA that is formed by combining DNA from different sources, often from different kinds of organisms
what are recombinant proteins
proteins that are expressed by recombinant DNA present in an organism
CRISPR Cas9 definition
a tool for precise and targeted genome editing that uses specific RNA sequences to guide an endonuclease
what is Cas9
a restriction enzyme, that will cut at the right positions based on the gRNA (guide) also known as sgRNA (synthetic/single guide RNA)
what is CRISPR
short, repeated segments of DNA, with each repeated segment being separated by a length of spacer DNA.
what are spacers?
a region of non-coding DNA between genes
what are the 4 main steps that CRISPR Cas9 uses when cutting DNA
- Targeting
- binding
- cleaving
- DNA repair
What happens in the targeting step? (CRISPR-Cas9)
Cas9 will locate and bind to a common sequence in the genome known as the PAM sequence
what is the PAM sequence
a sequence of bases (NGG, N is any nucleotide) that is in the genome
what happens in the binding step (CRISPR-Cas9)
Cas9 unwinds the DNA, and if the DNA at that location matches with the 20 strands of gRNA then it will bind together with complimentary base pairing
what happens in the cleaving step? (CRISPR-Cas9)
Binding triggers Cas9 to change shape and gives the signal to cleave both strands of DNA upstream of PAM.
This disables the viral DNA
what happens in the DNA repair step? (CRISPR-Cas9)
the cell will try and repair the DNA, leading to mutation (error prone). Disabling the gene
Or scientists will add another sequence or modify the specific sequence allowing for knocking out genes or replacing faulty ones with healthy ones
what are GMOs (genetically modified organisms)
are organisms that has had their genome altered using genetic engineering technology
what are transgenic organisms
sub-group of GMOs, that contain genetic material from different species
what may GMOs involve (2)
- addition of gene segment
- silencing of gene
what are some uses for GMOs for plants (3)
- increased photosynthesis efficiency
- greater crop yield
- faster growth rates
what are biomechanical reactions
reactions occurring in cells that lead to the formation of a product from a reactant.
what are biomechanical pathways
a series of linked biomechanical reactions
what are the types of biomechanical pathways
- anabolic pathways
- catabolic pathways
what is metabolism
The total activity of the reactions of all biochemical pathways in a living organism
what are substrates
a compound on which an enzyme acts
what happens to the energy levels in the anabolic pathways
anabolic pathways are energy-requiring or endergonic
what are anabolic pathways (anabolism)
These pathways turn simple molecules into more complex ones
what are catabolic pathways (catabolism)
These pathways break down complex molecules into more simple ones
what happens to the energy levels in catabolic pathways
Catabolic pathways are energy-releasing or exergonic
example of anabolic pathway
Photosynthesis, where glucose molecules are synthesised from carbon dioxide and water using radiant energy from the Sun
example of catabolic pathway
Aerobic cellular respiration, where glucose molecules are broken down into carbon dioxide and water molecules
what are catalysts
factors that increase rate of reaction
are enzymes specific to reaction?
yes, each different reaction will be catalysed by a specific enzyme
are all catalysts enzymes?
no, enzymes are all catalysts but not all catalysts are enzymes
what is activation energy
minimum amount of energy required to initiate a chemical reaction
what is the active site
region of an enzyme that binds temporarily with the specific substrate of the enzyme
how do enzymes lower activation levels (2)
- Influence the stability of bonds in the reactants
- Providing an alternative reaction pathway;
what do enzymes do to speed up a reaction
lower activation levels
how do enzymes bind to substrates (2 steps)
- the enzyme and substrate with join to form the E-S complex (when it binds to the active site)
- the substrate forms weak bonds with particular amino acid residues (in the protein) at the active site.
what are coenzymes
an organic molecule that acts with an enzyme to alter the rate of a reaction
what are cofactors
a non-protein molecule or ion that is essential for the normal functioning of some enzymes
are cofactors and coenzymes the same
no, coenzymes are cofactors but not all cofactors and coenzymes
what are inorganic cofactors
cofactors that do not contain carbon and include metal ions such as magnesium or copper
what are organic cofactors
small non-protein organic molecules that are essential for the function of particular enzymes
what are the 2 types of organic cofactors
- prosthetic groups
- coenzymes
prosthetic groups are ……
cofactors that are tightly bound to an enzyme and are essential for it to function as a catalyst.
what is the difference between prosthetic groups and coenzymes
prosthetic groups are tightly bound to an enzyme, whereas, coenzymes are loosely bound
what are the 5 main coenzymes we focus on
- NAD
- NADP
- FAD
- ATP
- CoA (coenzyme A)
what are the 2 roles of coenzymes to assist enzymes
- transfers of atoms or groups of atoms, such as hydrogens, phosphate groups and acetyl groups
- energy transfers
loaded coenzymes main info
they are high in energy and have a group that can be transferred. In simple they are electron donors
unloaded coenzymes main info
they have low energy, and accept groups. In simple they are electron acceptors
what are the 3 factors that impact enzyme activity
- temperature
- pH
- substrate concentration
why does a temperature that it close to an enzymes (or reactions) optimum have an increased reaction rate
there is more movement of particles, therefore more collisions possible with substrate and enzyme
summary of what happen with varied pH for enzyme activity (rate of reaction)
As pH increases or decreases from optimum pH, the rate of reaction and the activity of an enzyme decreases.
summary of what happen with varied substrate concentration for enzyme activity (rate of reaction)
the rate of reaction increases with increasing substrate concentration — but only up to a point. Beyond this, any further increase in substrate concentration produces no significant change in reaction rate (active sites are all occupied)
what are enzyme inhibitors
substances that prevent the normal action of an enzyme and therefore slow the rate of enzymes-controlled reactions
what are the 2 types of inhibition
reversible inhibition
irreversible inhibition
what are the 2 types of reversible inhibition
- competitive inhibition
- non-competitive inhibition
what is competitive inhibition
inhibition in which a molecule binds to the active site of a molecule instead of the usual substrate
what is non-competitive inhibition
inhibition in which a molecule binds to the allosteric site of an enzyme causing a conformation change in the active site
why does competitive inhibition slow down reaction rate
inhibitor molecules prevent the formation of the E–S complexes (as active site is partially occupied)
why does non-competitive inhibition slow down reaction rate
as the binding of the inhibitor to the allosteric site changes the shape of the enzyme’s active site the E-S complex cannot form
what is irreversible inhibition
occurs when a specific molecule can form a strong covalent bond with an enzyme at its active site, so that the normal substrate is permanently blocked from accessing the active site
what are common irreversible inhibitors?
Heavy metals
what are 3 things that the regulation of rates of reaction does
- prevent waste, such as would occur if pathway products were made in excess of cell requirements
- prevent the build-up in cells of products to potentially harmful levels
- prevent depletion of substrates
what are the 2 types of regulation
- allosteric regulation
- feedback regulation
what is allosteric regulation
control of the reaction rate of enzymes through conformational changes in enzymes. This occurs when a regulator molecule binds to the allosteric site
what can the regulator molecules be (allosteric regulation)
- allosteric inhibitors
- allosteric activators
what does allosteric inhibitors do
their binding produces a change of shape in the enzyme that stops enzyme activity; they act like an OFF switch
what does allosteric activators do
the shape change resulting from the binding produces an increase in enzyme activity; they act like an ON switch
what is feedback regulation
the end product of a metabolic pathway acts as an inhibitor of the key enzyme that catalyses the first step in a pathway.
what is photosynthesis
the process by which plants use the radiant energy of sunlight trapped by chlorophyll to build carbohydrates (glucose) from carbon dioxide and water.
what are the 2 stages of photosynthesis
- light-dependent stage
- light-independent stage
what is the photosynthesis equation
6 carbon dioxide + 6 water = glucose + 6 oxygen (gas)
what is the function of the light dependent stage
to transform sunlight energy that is captured by chlorophyll into the chemical energy of loaded coenzymes
what is the function of the light independent stage
to assemble simple inorganic carbon dioxide molecules into more complex organic glucose molecules
what is another name for the light independent stage
Calvin cycle
where does photosynthesis occur
chloroplasts, in the chlorophyll pigment inside (in the cytosol of plants)
what does chloroplasts enable a plant to do
capture the radiant energy of sunlight, bringing it into cells as the starting point of photosynthesis
what are the 3 main things inside the chloroplasts (not including chlorophyll)
thylakoids
grana
stroma
what are thylakoids
flattened membranous sacs in chloroplasts that contain chlorophyll
what is the grana
stacks of thylakoids are known as grana, where a singular stack is a granum
what is stroma
fluid inside the chloroplasts, containing the enzymes that are involved in calvin cycle
what does the light dependent stage involve
involved in the capture of sunlight and the transformation of its energy to the chemical energy of loaded coenzymes, NADPH and ATP.
where is the light dependent stage occur (c3)
thylakoid (within the grana)
what are the 3 inputs in the light dependent stage
- water
- ADP + Pi
- NADP+
what are the 3 outputs of the light dependent stage
- oxygen
- ATP
- NADPH
summary of what happens in light dependent stage
the energy caught by the chlorophylls make the electrons have high energy (excited) and the splitting of water molecules gives H+ ions (protons).
This then allows NADPH to form as well as ATP
what do the chloroplasts have after the light dependent stage
a supply of high-energy loaded ATP molecules
a supply of high-energy loaded NADPH coenzymes that can act as donors of hydrogen ions and electrons
light dependent equation
water + 18ADP + NADP into 6O2 + 18ATP + NADPH
what happens in the light independent stage
inorganic carbon dioxide molecules (CO2) are built into energy-rich reduced organic molecules, such as glucose (C6H12O6).
where does the light independent stage occur
the stroma
what is required for the light independent stage
Rubisco, and the NADPH (donate H and e-) and ATP (energy source) from the previous stage
what are the 3 inputs of the light independent stage
- ATP
- NADPH
- CO2
what are the 3 outputs of the light independent stage
- ADP + Pi
- NADP+
- Glucose
summary of what happens in light independent stage
inorganic carbon is converted in organic CO2 thru carbon fixation
NADPH donate hydrogens and electrons as molecules are reduced to higher energy levels
ATP supplies energy for anabolic steps
why are there different types of plants
they are categorised into how they fix carbon into glucose
how do C3 plants carry out the Calvin Cycle
These plants carry out the original Calvin Cycle, using Rubisco, and are prone to photorespiration
what are optimal conditions for C3 plants
moist and cool conditions
how do C3 plants use RuBisco
use the Rubisco enzyme to fix inorganic carbon dioxide from the air and it enters the Calvin cycle joined to a carrier molecule (RuBP)
where does the Calvin Cycle take place in C3 plants
in the stroma of the leaf mesophyll cells
Photorespiration definition
a process in which plants take up oxygen rather than carbon dioxide in the light, resulting in photosynthesis being less efficient. (Rubisco takes up O2 instead of CO2)
what does rubisco normally do
the critical enzyme in C3 plants that brings carbon dioxide from the air into the Calvin cycle where the glucose is made
when does photorespiration occur
rubisco binds oxygen rather than carbon dioxide
why will Rubisco bind to oxygen instead of carbon dioxide
the active site can readily accommodate the oxygen molecules as well as the carbon dioxide molecules, so the two different molecules are in competition for the active site of Rubisco.
2 ways photorespiration arise in C3 plants (increase amount)
- temperature increases
- conditions dry out
why does photorespiration increase as temperature increases
the ability of the Rubisco enzyme to distinguish between carbon dioxide and oxygen decreases and, as a result, Rubisco will increasingly bind oxygen.
why does photorespiration increase as conditions dry out
C3 plants close their stomata to prevent water loss. This closure blocks the entry of carbon dioxide needed as input to the Calvin cycle and limits the exit of oxygen produced
creating a high oxygen low CO2 environment inside the mesophyll cells
how do C4 plants carry out the Calvin Cycle
carry out an adapted Calvin cycle, in which carbon fixation and glucose production occur in different cells
what are optimal conditions for C4 plants
These cells will thrive in warm and tropical regions
what anatomy changes are present in C4 plants (compared to C3 and CAM)
- bundle sheath cells have chloroplasts
- mesophyll cells that are arranged in a close association around the bundle sheath cells
where do the two processes (stages) occur in C4 plants
leaf mesophyll cells and bundle sheath cells
what happens in the first process in C4 plants (light dependent stage)
Carbon dioxide is converted into malic acid, in the mesophyll cells
PEP carboxylase catalyses the binding of carbon dioxide to an acceptor molecule (malic acid) (this is called carbon fixation)
what enzyme is used in the first step of C4 plants in photosynthesis
PEP carboxylase
what happens in the second process of the C4 plants (light independent stage)
Calvin cycle (glucose production) occurs in the bundle sheath cells
produce a steady supply of carbon dioxide from the breakdown of malic acid that raises the carbon dioxide concentration in their leaves. This allows the RuBisco in the bundle sheath cells to bind only to CO2
how do CAM plants carry out the Calvin Cycle
two stages of the Calvin cycle occurring at different times
what are optimal conditions for CAM plants
thrive in hot and arid environments, that are exposed to droughts
when does carbon fixation happen in CAM plants
at night (stomata are open)
when does the Calvin cycle happen in CAM plants
in the day (when the stomata are closed)
where do photosynthesis processes occur in the CAM plants
mesophyll cells
does CAM plants use PEP carboxylase or Rubisco initially
PEP carboxylase
what happens to the malic acid produced in CAM plants when it is night time
it is stored in vacuoles waiting for the stomata to close (day time)
what 3 things will make RuBisco work most efficiently
- carbon dioxide levels in leaves are high
- oxygen levels are low (as happens when water is freely available)
- when temperatures are moderate.
what are 2 examples of CAM plants
- cacti
- pineapples
what are 3 examples of C3 plants
- wheat
- rice
- potato
what are 2 examples of C4 plants
- maize/corn
- sugar cane
what are the 4 main factors that affect the rate of photosynthesis
- the amount of light reaching their leaves
- the temperature of the environment
- the availability of water
- the concentration of carbon dioxide
what is a limiting factor
any environmental condition that restricts the rate of biochemical reactions in an organism.
what happens to the rate of photosynthesis as light intensity increases
increases as light intensity increases, until it reaches a maximal point.
what is the light saturation point
the point where further increases in light intensity have no effect and the rate of photosynthesis stays constant
why does increased light intensity increase the rate of photosynthesis
more chlorophylls are energised
what does too little or too much water do to the rate of photosynthesis
rate of photosynthesis declines and then stops because closed stomata prevent the uptake of carbon dioxide needed for the Calvin cycle
what does waterlogging do to the rate of photosynthesis
the rate of photosynthesis will also decline and stop because the lack of oxygen for cellular respiration in root cells stops water uptake
what happens to the rate of photosynthesis as temperature increases
As the ambient temperature is increased, the rate of photosynthesis also increases due to an increase in collisions between the reactants and the enzymes involved in photosynthesis. Eventually, as the heat passes a certain threshold, the enzymes start to denature, in which the tertiary structure of an enzyme is lost. This causes the rate to again decrease.
what happens to the rate of photosynthesis as CO2 concentration increases
the rate of photosynthesis will increase until it levels off due to limiting factors
does CO2 concentration impact the light dependent stage and why
no, because CO2 is not apart of the reaction
what is cellular respiration
the process of converting chemical energy into a useable form by cells, typically ATP.
what are the 2 types of cellular respiration
- aerobic
- anaerobic
what is the equation for aerobic cellular respiration (without coenzymes)
glucose + oxygen → carbon dioxide + water + ATP
how many ATP does aerobic respiration make
30-32, 36-38 in optimal conditions
what are the 3 steps of aerobic cellular respiration
- glycolysis
- Krebs cycle
- electron transport chain
what is the main (broad) thing that happens in glycolysis
glucose is broken down into pyruvate
what is the main (broad) thing that happens in Krebs cycle
makes a supply of energy-rich loaded coenzymes
what is the main (broad) thing that happens in the electron transport cycle
transfers energy from electrons supplied by loaded coenzymes to make ATP.
where does glycolysis occur
cytosol
how much ATP is produced from glycolysis
2
what are the 3 inputs in glycolysis
glucose, 2x (ADP + Pi) and 2x (NAD+)
what are the 4 outputs in glycolysis
2x (pyruvate), 2x ATP, 2x (NADH) and two hydrogen ions (protons)
where does the Krebs cycle and electron transport chain occur
mitochondria
where specifically does the Krebs cycle occur
the matrix
what is the matrix of the mitochondria
gel like solution within their inner membrane
where specifically does the electron transport chain happen
the cristae
what does cristae do
It folds in the inner membrane of the mitochondria, it holds enzyme
what happens in between glycolysis and Krebs cycle
pyruvate oxidation
what in summary happens in pyruvate oxidation
pyruvate loses a C and an H atom, forming a 2C acetyl group that is delivered to the Krebs cycle by coenzyme A.
what are the 2 coenzymes that are becoming high in energy in the Krebs cycle
FAD+ and NAD+
what are the 4 inputs in Krebs cycle and pyruvate oxidation
2 x (acetyl CoA (acetyl groups)), 6 x (NAD+), 2 x (FAD) and 2 x (ADP + Pi)
what are the 4 outputs in Krebs cycle and pyruvate oxidation
4 x (CO2), 6 x (NADH), 2 x (FADH2) and 2 x (ATP)
detailed electron transport chain info
Electrons are transferred along enzyme complexes
The first input of high-energy electrons to the ETC comes from loaded NADH coenzymes.
FADH2 also donates its high-energy electrons to an acceptor, but further down the chain.
Oxygen accepts electrons and hydrogen ions, forming water
how is so much ATP produced in the ETC
As electrons transfer from one enzyme complex to the next, the energy released is ultimately used to power the production of ATP from ADP and Pi.
what are the 4 inputs of ETC
- 6 (oxygen)
- 26-28 (ADP + Pi)
- 10 (NADH)
- 2 (FADH2)
which process of aerobic cellular respiration needs oxygen
electron transport chain
what is anaerobic respiration/fermentation
processes that occur without the presence of oxygen, producing a net of 2 ATP molecules
when does anaerobic fermentation occur in humans
occurs in human skeletal muscle cells when the supply of oxygen to the cells by aerobic cellular respiration cannot keep up with their demand for ATP.