Topic 2 - Molecular Biology Flashcards
What is molecular biology?
Explaining biological processes in terms of the chemicals involved.
What are the four carbon compounds?
Carbohydrates, Lipids, Nucleic Acids, Proteins
What are the two types of enzyme-catalysed reactions?
Anabolism, Catabolism
Anabolism?
Forming macromolecules from monomers by condensation.
Catabolism?
Breaking complex macromolecules into simpler molecules by hydrolysis.
Example of biological compounds that can be synthesized outside of living things?
Urea
Falsification of vitalism?
Vitalism as a theory has since been disproven with the discovery that organic molecules can be artificially synthesised
Theory of vitalism?
doctrine that dictated that organic molecules could only be synthesised by living systems
How was the vitalism theory disapproved?
Frederick Woehler heated an inorganic salt (ammonium cyanate) and produced urea
Why was the theory of vitalism disapproved?
- Urea is a waste product of nitrogen metabolism and is eliminated by the kidneys in mammals
- The artificial synthesis of urea demonstrates that organic molecules are not fundamentally different to inorganic molecules
How many covalent bonds can carbon form?
4
Carbohydrates?
- Most abundant organic compound found in nature, composed primarily of C,H and O atoms in a common ratio – (CH2O)n
- Principally function as a source of energy (and as a short-term energy storage option)
- Also important as a recognition molecule (e.g. glycoproteins) and as a structural component (part of DNA / RNA)
Lipids?
- Non-polar, hydrophobic molecules which may come in a variety of forms (simple, complex or derived)
- Lipids serve as a major component of cell membranes (phospholipids and cholesterol)
- They may be utilised as a long-term energy storage molecule (fats and oils)
- Also may function as a signalling molecule (steroids)
Proteins?
- Make over 50% of the dry weight of cells; are composed of C, H, O and N atoms (some may include S)
- Major regulatory molecules involved in catalysis (all enzymes are proteins)
- May also function as structural molecules or play a role in cellular signalling (transduction pathways)
Nucleic Acids?
- Genetic material of all cells and determines the inherited features of an organism
- DNA functions as a master code for protein assembly, while RNA plays an active role in the manufacturing of proteins
3 Properties of carbon?
- Carbon has several allotropes, or different forms in which it can exist. These allotropes include graphite and diamond, which have very different properties.
- Despite carbon’s ability to make 4 bonds and its presence in many compounds, it is highly unreactive under normal conditions.
- Carbon exists in 3 main isotopes: 12C, 13C, 14C. 14C is radioactive and used in dating carbon-containing samples (radiometric dating).
Metabolism?
The sum of the chemical reactions that take place within each cell of a living organism and that provide energy for vital processes and for synthesizing new organic material.
Catabolism?
Breaking complex macromolecules into simpler molecules by hydrolysis.
Anabolism?
Forming macromolecules from monomers by condensation.
Why do hydrogen bonds occur in water?
Hydrogen atoms of one water molecule are attracted towards the oxygen atom of a neighboring water molecule
What are the 4 properties of water?
Adhesive
Thermal
Cohesive
Solvent
Solvent?
Water dissolves polar and ionic substances (forms competing polar associations to draw materials apart)
Cohesive?
Cohesion is the ability of like molecules to stick together
Thermal?
Water has the capacity to absorb significant amounts of heat before changing state (requires breaking of hydrogen bonds)
What does the di-polarity of a water molecule enable?
Enables it to form polar associations with other charged molecules (polar or ionic)
Why does water have the capacity to absorb significant amounts of heat before changing state?
Due to the extensive hydrogen bonding between water molecules – the H-bonds need to be broken before a change in state can occur and this requires the absorption of energy (heat)
Adhesive?
Adhesion is the ability of dissimilar molecules to stick together
What do the adhesive properties of water explain?
Capillary action
What do the cohesive properties of water explain?
Surface tension
How does dissolving occur in water?
The polar attraction of large quantities of water molecules can sufficiently weaken intramolecular forces (such as ionic bonds) and result in the dissociation of the atoms
Hydrophobic?
Substances that do not freely associate or dissolve in water are characterised as hydrophobic (‘water-hating’)
Hydrophobic substances include large, non-polar molecules (such as fats and oils)
Hydrophilic?
Substances that freely associate and readily dissolve in water are characterised as hydrophilic (‘water loving’)
Hydrophilic substances include all polar molecules and ions
Which are hydrophilic and hydrophobic? Glucose, amino acids, salts, cholesterol, fats.
Hydrophilic: Glucose, amino acids, salts
Hydrophobic: Cholesterol, fats
Which are hydrophilic and hydrophobic? Glucose, amino acids, salts, cholesterol, fats.
Hydrophilic: Glucose, amino acids, salts
Hydrophobic: Cholesterol, fats
What does the transport of essential molecules within the bloodstream will depend on?
Solubility of water
Water soluble substances will usually be able to travel freely in the blood plasma, whereas water insoluble substances cannot
4 Water soluble substances?
Sodium chloride (NaCl)
Oxygen
Glucose
Amino acids
2 Water insoluble substances?
Lipids
Hydrophilic portions of proteins, cholesterol and phospholipids
3 Similarities between methane and water?
Structure
Comparable size and weight
Differences in thermal properties between methane and water?
Water is polar and methane is non polar Water has higher melting and boiling point Water has higher specific heat capacity Water has higher heat of vaporisation Water has higher heat of fusion
Why is water important for cooling (sweating)?
The evaporation of water as sweat is a fundamental mechanism employed by humans as a means of cooling down
How does cooling work?
- The change of water from liquid to vapour (evaporation) requires an input of energy
- This energy comes from the surface of the skin when it is hot, therefore when the sweat evaporates the skin is cooled
- Because water has a high specific heat capacity, it absorbs a lot of thermal energy before it evaporates
- Thus water functions as a highly effective coolant, making it the principal component of sweat
How does cooling work?
- The change of water from liquid to vapour (evaporation) requires an input of energy
- This energy comes from the surface of the skin when it is hot, therefore when the sweat evaporates the skin is cooled
- Because water has a high specific heat capacity, it absorbs a lot of thermal energy before it evaporates
- Thus water functions as a highly effective coolant, making it the principal component of sweat
How do monosaccharide monomers link together?
Condensation reactions
What happens when condensation reactions link together monosaccharide monomers?
They form disaccharide and polysaccharides
3 Examples of disaccharides?
Sucrose
Lactose
Maltose
3 examples of polysaccharides?
Cellulose
Starch
Glycogen
How are disaccharides formed?
From monosaccharides
What are carbohydrates made of?
Carbon
Hydrogen
Oxygen
What are carbohydrates composed of?
Carbohydrates are composed of recurring monomers called monosaccharides (which typically form ring structures)
3 examples of carbohydrates?
Monosaccharides
Polysaccharides
Disaccharides
3 examples of monosaccharides?
Glucose, Galactose, Fructose
What are monosaccharides?
Monosaccharides (one sugar unit) are typically sweet-tasting and function as an immediate energy source for cells
What are polysaccharides?
Polysaccharides (many sugar units) may be used for energy storage or cell structure, and also play a role in cell recognition
What are Disaccharides?
Disaccharides (two sugar units) are small enough to be soluble in water and commonly function as a transport form
Polysaccharides are carbohydrate polymers, what are they comprised of?
Hundreds to thousands of monosaccharides monomers.
How is the type of polysaccharide polymer formed determined?
Depends on the monosaccharide subunits involved and the bonding arrangement between them
What are the three key polysaccharides polymers that can be made from glucose monosaccharides ?
Cellulose
Starch
Glycogen
What is cellulose? (3)
Cellulose is a structural polysaccharide that is found in the cell wall of plants
It is a linear molecule composed of β-glucose subunits (bound in a 1-4 arrangement)
Because it is composed of β-glucose, it is indigestible for most animals (lack the enzyme required to break it down)
What is starch? (2)
Starch is an energy storage polysaccharide found in plants
It is composed of α-glucose subunits (bound in a 1-4 arrangement) and exists in one of two forms – amylose or amylopectin
What is amylose? (2)
Amylose is a linear (helical) molecule
Amylose is harder to digest and less soluble, however, as it takes up less space, is the preferred storage form in plants
What is amylopectin? (1)
Amylopectin is branched (contains additional 1-6 linkages)
What is glycogen? (20
Glycogen is an energy storage polysaccharide formed in the liver in animals
It is composed of α-glucose subunits linked together by both 1-4 linkages and 1-6 linkages (branching)
Are Fatty acids saturated, monounsaturated or polyunsaturated?
Can be all three
What are fatty acids? (1)
Fatty acids are long hydrocarbon chains that are found in certain types of lipids.
Where are fatty acids found?
Triglycerides and phospholipids
What are fatty acids that posses no double bonds?
Saturated meaning that they have a maximum number of H atoms.
What is the structure of a saturated fatty acid?
Linear and are typically solid in room temperature
What are fatty acids with double bonds are?
Unsaturated
Are unsaturated fatty acids monounsaturated or polyunsaturated?
Either one
What is the structure of a unsaturated fatty acids?
Bent in structure and are typically liquid in room temperature.
Are unsaturated fatty acids cis or trans isomers?
Either one
What are cis isomers?
The hydrogen atoms attached to the carbon double bond are on the same side
What are trans isomers?
The hydrogen atoms attached to the carbon double bond are on different sides
Structure of trans fatty acids?
Linear in structure
How are triglycerides formed?
Triglycerides are formed by condensation from three fatty acids and one glycerol
What do plants store triglyceride for?
Plants tend to store triglycerides as oils (liquid)
What do animals store triglycerides for?
Animals tend to store triglycerides as fats (solid)
What is the largest class of lipids?
Triglycerides
What do triglycerides usually function for?
Function primarily as long-term energy storage molecules
Health risks of trans fats?
Trans fats raise your bad (LDL) cholesterol levels and lower your good (HDL) cholesterol levels.
Health risks of saturated fatty acids?
Can cause cholesterol to build up in your arteries (blood vessels). Saturated fats raise your LDL (bad) cholesterol. High LDL cholesterol increases your risk for heart disease and stroke.
Can cholesterol dissolve in blood or water?
No
What are the two main health claims made about lipids in the diet?
Diets rich in saturated fats and trans fats increase the risk of CHD
Diets rich in monounsaturated and polyunsaturated (cis) fats decrease the risk of CHD
Are carbohydrates or lipids a better long term energy storage?
Lipids
Why are lipids a better long term energy storage? SODAS
Storage: More suitable for long-term energy storage
Osmolarity: Less effect on the osmotic pressure of a cell
Digestion: Easier to digest
ATP yield: Store more energy per gram
What is ATP?
The energy currency of the cell – in this respect it is akin to cash
How is BMI calculated?
Body Mass Index = Mass in KG/ (height in m)^2
What is BMI usually used for?
It is commonly used as a screening tool to identify potential weight problems in sedentary adults
What is BMI?
The body mass index (BMI) provides a measure of relative mass based on the weight and height of the individual
What is the range of BMI?
From underweight to obese.
What are nomograms?
An alternative way of calculating body mass index is by using an alignment chart (nomogram)
What do nomograms display?
Nomograms display height and weight on perpendicular axes and then assign BMI values to colour coded regions
How are amino acids linked together?
Condensation to form polypeptides
How many different amino acids in polypeptides synthesised on ribosomes are there?
20
Structure of proteins?
Comprised of long chains of recurring monomers called amino acids
Structure of amino acids?
Amino acids all share a common basic structure, with a central carbon atom bound to.
What 4 things do amino acid structure have?
An amine group (NH2)
A carboxylic acid group (COOH)
A hydrogen atom (H)
A variable side chain (R)
Where are amino acids joined together and to form what?
On the ribosomes to form long chains called polypeptides which make up proteins.
What is the covalent bond between amino acids called?
Peptide bond
What do covalently joined together amino acids form?
Dipeptide and water
How are polypeptide chains broken down?
Hydrolysis reactions
What is required for polypeptide chains to be broken down via hydrolysis reaction?
Water to reverse the process.
What are peptide bonds formed between?
The amine and carboxylic acid groups of adjacent amino acids
What happens when the peptide bond forms?
The amine group loses a hydrogen atom (H) and the carboxylic acid loses a hydroxyl (OH) – this forms water (H2O)
What is the order of an Amino acid sequence called and what does it determine?
Primary Structure
Determines the way the chain will fold
What is it called when the amino acid sequences commonly fold into two stable configurations?
Secondary structures
When do Alpha helices occur?
When the amino acid sequence folds into a coil / spiral arrangement
When do Beta-pleated sheets occur?
Occur when the amino acid sequence adopts a directionally-oriented staggered strand conformation
What do α-helices and β-pleated sheets result from?
Hydrogen bonds forming between non-adjacent amine and carboxyl groups
What is the overall three-dimensional configuration of the protein is referred to as
Tertiary structure of the protein
What is the tertiary structure of the protein determined by? and what do they include?
The interactions between the variable side chains.
These interactions may include hydrogen bonds, disulphide bridges, ionic interactions, polar associations, etc.
Are proteins capable of a fourth level of structural organisation?
Yes, the quaternary structure
Where are the quaternary structure of a protein found?
Quaternary structures are found in proteins that consist of more than one polypeptide chain linked together
How many polypeptide chains is the haemoglobin composed of and what are they?
Haemoglobin is composed of four polypeptide chains.
Two alpha chains and two beta chains.
What is denaturation of proteins? Because of?
A structural change in a protein that results in the loss (usually permanent) of its biological properties
Because the way a protein folds determines its function, any change or abrogation of the tertiary structure will alter its activity
What are the 2 reasons why there would be denaturation of proteins?
Temperature and pH
Why would temperature cause denaturation of proteins?
High levels of thermal energy may disrupt the hydrogen bonds
Why would pH cause denaturation of proteins?
Changing the pH will alter the charge of the protein
What is a gene?
A sequence of DNA which encodes a polypeptide sequence
What are the two process ad gene sequences is converted into a polypeptide?
Transcription
Translation
Transcription?
Making an mRNA transcript based on a DNA template (occurs within the nucleus)
Translation?
Using the instructions of the mRNA transcript to link amino acids together (occurs at the ribosome)
What are the rules for one gene to code for one polypeptide? (3)
Genes may be alternatively spliced to generate multiple polypeptide variants
Genes encoding tRNA sequences are transcribed but never translated
Genes may be mutated (their base sequence is changed) and consequently produce an alternative polypeptide sequence
What is a proteome?
The totality of proteins expressed within a cell, tissue or organism at a certain time
Why is each individuals proteome unique?
As protein expression patterns are determined by an individual’s genes
What are the 2 factors to why the proteome is significantly larger than the number of genes in an individual?
- Gene sequences may be alternatively spliced following transcription to generate multiple protein variants from a single gene
- Proteins may be modified (e.g. glycosylated, phosphorylated, etc.) following translation to promote further variations
What roles do proteins play in a cell and examples? (SHITSME)
Structure - collagen, spider silk Hormones - insulin, glucagon Immunity - immunoglobulins Transport - haemoglobin Sensation - Rhodopsin Movement - actin, myosin Enzymes - Rubisco, catalase
What does pH stand for?
Power of hydrogen
What does the pH scale represent?
The concentration of hydrogen ions in a water-based solution
What does the pH scaled range from and what measures acidic and base?
1-14
1-7: Acidic
7: Neutral
8-14: Base/alkaline
What are the two main classes of a protein tertiary structure? and their structure?
Fibrous proteins are generally composed of long and narrow strands and have a structural role (they are something)
Globular proteins generally have a more compact and rounded shape and have functional roles (they do something)
What is an enzyme?
A globular protein which acts as a biological catalyst by speeding up the rate of a chemical reaction
What is the active site?
The region on the surface of the enzyme which binds to the substrate molecule
How does the active site work?
The active site and the substrate complement each other in terms of both shape and chemical properties
What does enzyme catalyse require from the substrate?
be brought into close physical proximity with the active site
Process of enzyme catalyse?
- When a substrate binds to the enzyme’s active site, an enzyme-substrate complex is formed
- The enzyme catalyses the conversion of the substrate into product, creating an enzyme-product complex
- The enzyme and product then dissociate – as the enzyme was not consumed, it can continue to catalyse further reactions
What 3 external factors can modify the enzyme structure?
High temperatures, substrate concentration, and extreme pH
What is lactose?
Lactose is a disaccharide of glucose and galactose which can be broken down by the enzyme lactase
How is lactose-free milk produced?
- The lactase is purified from yeast or bacteria and then bound to an inert substance (such as alginate beads)
- Milk is then repeatedly passed over this immobilised enzyme, becoming lactose-free
What is the lock and key model?
According to the lock and key model, the enzyme’s active site complements the substrate precisely
The substrate fits a particular active site like a key fits into a particular lock
This theory of enzyme-substrate interaction explains how enzymes exhibit specificity for a particular substrate
What is the induced fit model?
According to the induced fit model, the enzyme’s active site is not a completely rigid fit for the substrate
Instead, the active site will undergo a conformational change when exposed to a substrate to improve binding
This theory of enzyme-substrate interactions has two advantages compared to the lock and key model
What are nucleic acids?
The genetic material of the cell and are composed of recurring monomeric units called nucleotides
Each nucleotide is comprised of what three principal components?
- 5-carbon pentose sugar (pentagon)
- Phosphate group (circle)
- Nitrogenous base (rectangle)
What are the two types of nucleic acids present in cells?
DNA and RNA
What is DNA?
DNA (deoxyribonucleic acid) is a more stable double stranded form that stores the genetic blueprint for cells
What is RNA?
RNA (ribonucleic acid) is a more versatile single stranded form that transfers the genetic information for decoding
What are the DNA base pairs?
AT
GC
What are the RNA base pairs?
AU
GC
DNA and RNA are both polymers of nucleotides, however differ in a few key structural aspects, how?
Number of strands present
Composition of nitrogenous bases
Type of pentose sugar
What are nucleic acids composed of?
Nucleotide monomers which are linked into a single strand via condensation reactions
How are 2 polynucleotide chains of DNA are held together?
Hydrogen bonding between complementary nitrogenous bases
Who and when was the structural organisation of the DNA molecule correctly proposed?
1953 by James Watson and Francis Crick
What did James Watson and Francis Crick conclude?
- DNA is composed of nucleotides made up of a sugar, phosphate and base – Phoebus Levene, 1919
- DNA is composed of an equal number of purines (A + G) and pyrimidines (C + T) – Erwin Chargaff, 1950
- DNA is organised into a helical structure – Rosalind Franklin, 1953 (data shared without permission)
How many nitrogenous bases are nucleic acids composed of?
5
What are the 3 types of RNA?
Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)
Why is DNA replication is a semi-conservative process?
When a new double-stranded DNA molecule is formed:
- One strand will be from the original template molecule
- One strand will be newly synthesised
When and by who was the theory that DNA replication was semi-conservative confirmed?
Meselson-Stahl experiment in 1958
What 2 enzymes is DNA replication coordinated by?
Helicase and DNA polymerase
What does the helicase do in DNA replication?
- Helicase unwinds the double helix and separates the two polynucleotide strands
- It does this by breaking the hydrogen bonds that exist - between complementary base pairs
- The two separated polynucleotide strands will act as templates for the synthesis of new complementary strands
What does the DNA polymerase do in DNA replication?
- DNA polymerase synthesises new strands from the two parental template strands
- Free deoxynucleoside triphosphates (nucleotides with 3 phosphate groups) align opposite their complementary base partner
- DNA polymerase cleaves the two excess phosphates and uses the energy released to link the nucleotide to the new strand
What is polymerase chain reaction (PCR)?
- An artificial method of replicating DNA under laboratory conditions
- The PCR technique is used to amplify large quantities of a specific sequence of DNA from an initial minute sample
The reaction occurs in a thermal cycler and uses variations in temperature to control the replication process via three steps: What are they?
- Denaturation – DNA sample is heated (~90ºC) to separate the two strands
- Annealing – Sample is cooled (~55ºC) to allow primers to anneal (primers designate sequence to be copied)
- Elongation – Sample is heated to the optimal temperature for a heat-tolerant polymerase (Taq) to function (~75ºC)
What is Taq polymerase?
An enzyme isolated from the thermophilic bacterium Thermus aquaticus
Process of transcription?
- RNA polymerase separates the DNA strands and synthesises a complementary RNA copy from one of the DNA strands
- When the DNA strands are separated, ribonucleoside triphosphates align opposite their exposed complementary base partner
- RNA polymerase removes the additional phosphate groups and uses the energy from this cleavage to covalently join the nucleotide to the growing sequence
- Once the RNA sequence has been synthesised, RNA polymerase detaches from the DNA molecule and the double helix reforms
Where does the transcription of genes occur?
In the nucleus (where DNA is), before the RNA moves to the cytoplasm (for translation)
What is codons?
The mRNA sequence is read by the ribosome in triplets of bases called codons
What does the order of codons in an mRNA sequence determine?
The order of amino acids in a polypeptide chain
What is the genetic code?
The genetic code is the set of rules by which information encoded within mRNA sequences is converted into amino acid sequences (polypeptides) by living cells
What does the genetic code identify?
The corresponding amino acid for each codon combination
The coding region of an mRNA sequence always begins with? and ends with?
(AUG)
A STOP codon
What is translation?
Translation is the process of protein synthesis in which the genetic information encoded in mRNA is translated into a sequence of amino acids on a polypeptide chain
Process of translation?
- Ribosomes bind to mRNA in the cytoplasm and move along the molecule in a 5’ – 3’ direction until it reaches a start codon (AUG)
- Anticodons on tRNA molecules align opposite appropriate codons according to complementary base pairing (e.g. AUG = UAC)
- Each tRNA molecule carries a specific amino acid (according to the genetic code)
- Ribosomes catalyse the formation of peptide bonds between adjacent amino acids (via condensation reactions)
- The ribosome moves along the mRNA molecule synthesising a polypeptide chain until it reaches a stop codon
- At this point translation ceases and the polypeptide chain is released
What are the key components of translation? MRCATAPP
Messenger RNA (goes to…) Ribosome (reads sequence in …) Codons (recognised by …) Anticodons (found on …) Transfer RNA (which carries …) Amino acids (which join via …) Peptide bonds (to form …) Polypeptides
What does it mean of the genetic code is universal?
Almost every living organism uses the same code (there are a few rare and minor exceptions)
Photosynthesis equation?
Glucose + oxygen —(sunlight, chlorophyll)—> Carbon dioxide + Water
What are the 2 main types of cell respiration?
Aerobic - utilises oxygen to completely break down glucose in the mitochondria for a larger ATP yield
Anaerobic - involves the partial breakdown of glucose in the cytosol for a small yield of ATP
Cell respiration is the controlled release of energy from organic compounds to produce?
ATP
The main organic compound used to produce ATP?
Carbohydrates (glucose)
What is ATP?
A high energy molecule that functions as an immediate source of power for cell processes
What does One molecule of ATP contain?
3 covalently linked phosphate groups – which store potential energy in their bonds
How do both anaerobic and aerobic respiration pathways begin?
With the anaerobic breakdown of glucose in the cytosol by glycolysis
What is glycolysis?
The breakdown of glucose by enzymes.
How does anaerobic respiration proceed to happen?
In the absence of oxygen and does not result in the production of any further ATP molecules
What is the purpose of anaerobic respiration?
To restore stocks of NAD+ – as this molecule is needed for glycolysis
What do muscle contractions require?
The expenditure of high amounts of energy and thus require high levels of ATP
What does the body do when exercising at high intensity and the cells’ energy demands exceed what the available levels of O2 can supply aerobically?
the body will begin breaking down glucose anaerobically to maximise ATP production.
Which can typically undergo anaerobic respiration? Carbohydrates, lipids and proteins.
Carbohydrates
What does aerobic respiration require?
The presence of oxygen and takes place within the mitochondrion
What does anaerobic respiration involve the breakdown of?
The breakdown of carbohydrates in the absence of oxygen
In yeasts, fermentation results in the production of?
Carbon dioxide, and ethanol
What is a respirometer?
A device that determines an organism’s respiration rate by measuring the rate of exchange of O2 and CO2
How does a respirometer work?
- The living specimen (e.g. germinating seeds or invertebrate organism) is enclosed in a sealed container
- Carbon dioxide production can be measured with a data logger or by pH changes if the specimen is immersed in water
- When an alkali is included to absorb CO2, oxygen consumption can be measured as a change in pressure within the system
- The pressure change can be detected with a data logger or via use of a U-tube manometer
What are the 5 factors that can affect respiration rates?
Temperature, hydration, light (plants), age and activity levels
What are 6 biochemical processes the utilise ATP? BANGME
Biosynthesis of macromolecules Active transport Nerve transmission Growth and repair Movement Emission of light
What is photosynthesis?
The process by which cells synthesise organic compounds (e.g. glucose) from inorganic molecules (CO2 and H2O) in the presence of sunlight.
What is the electromagnetic spectrum?
The range of all possible frequencies of electromagnetic radiation
What is chlorophyll?
A green pigment found in photosynthetic organisms that is responsible for light absorption.
What happens when chlorophyll absorbs light?
It releases electrons which are used to synthesise ATP (chemical energy)
What does the action spectrum indicate?
Indicates the overall rate of photosynthesis at each wavelength of light.
Photosynthesis is a 2 step process, what are the 2 steps?
- The light dependent reactions convert light energy from the Sun into chemical energy (ATP)
- The light independent reactions use the chemical energy to synthesise organic compounds (e.g. carbohydrates)
What is chromatography?
An experimental technique by which mixtures can be separated
Process of the chromatography experiment?
A mixture is dissolved in a fluid (called the mobile phase) and passed through a static material (called the stationary phase)
The different components of the mixture travel at different speeds, causing them to separate
A retardation factor can then be calculated (Rf value = distance component travels ÷ distance solvent travels)
What are the 2 most common techniques for separating photosynthetic pigments?
- Paper chromatography – uses paper (cellulose) as the stationary bed
- Thin layer chromatography – uses a thin layer of adsorbent (e.g. silica gel) which runs faster and has better separation
What are the 3 things photosynthesis is dependent on?
- Temperature
- Light intensity
- Carbon dioxide concentration
