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Flashcards by milicevic.marija, updated more than 1 year ago
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Created by milicevic.marija
about 9 years ago
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| Question | Answer |
| Four most common elements found in living organisms | Carbon, hydrogen, oxygen and nitrogen |
| Where are they found? | Carbon, hydrogen and oxygen - found in all key organic molecules/organisms (protein, carbohydrates, nucleic acids and lipids) Inorganic - compounds that dont contain carbon |
| Where are inorganic substances found? | Living organisms. Vital to structure and functioning of different organisms. Sulphur, calcium, phosphorus, iron and sodium |
| Give the roles in prokaryotes, plants and animals for sulphur, calcium, phosphorus, iron and sodium | 3.1.3 Teddy's table |
| Draw and label the diagram of the structure and bonding of water molecules | |
| Discuss the polarity of water | Oxygen pole is slightly negative, hydrogen pole is slightly positive |
| Outline the thermal properties of water | Water has a high heat capacity. Large amounts of energy are needed to break hydrogen bonds and change its temp. The temp. of organisms tends to change slowly. Fluids such as blood can transport heat round their bodies |
| Outline the solvent properties of water | The polar molecules of water can interact with other polar molecules Ions dissolve easily. Large molecules with polar side groups, such as carbohydrates and proteins can also dissolve. So water acts as an excellent transport medium and as a medium for metabolic reactions |
| Outline the cohesive properties of water | Hydrogen bonds hold water molecules together. Water can travel in continuous columns, such as in the stem of plants, and act as transport mediums |
| What is cohesion? | When hydrogen bonds form between water molecules. Giving waster many biologically important properties: enable water to be drawn up through the xylem of stem. Surface tensions allow small organisms to walk on water |
| Why are thermal properties important to organisms? | Range of temp in which biological reactions can occur is quite narrow. Help an organisms body temp stay fairly constant and water is temp regulator. Evaporation requires lot of energy as H bonds between molecules must be broken (sweating) |
| Why are solvent properties important to organisms? | Inorganic substances dissolve well as their opposite charges are attracted to the charges of water molecules. These include sodium, potassium and chloride ion. Polar organic molecules are also soluble (amino acids and sugars) Protein synthesis and most of the photosynthesis take place in a water solution. Excellent medium for transporting substances round the body of all organisms. Plants->xylem->dissolved minerals to leaves Plants->phloem->soluble sugars go up and down the plant Animals->blood->transport medium or blood plasma carries dissolves sugars, amino acids and CO2 |
| What do organic compounds include? | all complex compounds of carbon found in living organisms but not simple carbon containing compounds such as carbon dioxide, carbonates and hydrogencarbonates |
| Draw glucose and ribose | |
| List three examples each of monosaccharides, disaccharides and polysaccharides | Monosaccharides: Glucose, galactose, fructose Disaccharides: Lactose, maltose, sucrose Polysaccharides: Cellulose, glycogen, starch |
| State one function of glucose, lactose and glycogen in animals and of fructose, sucrose and cellulose in plants | Animals Glucose: A source of energy which can be broken down to form ATP via cellular respiration Lactose: A sugar found in the milk of mammals, providing energy for suckling infants Glycogen: Used by animals for short term energy storage (between meals) in the liver Plants Fructose: Found in honey and onions, it is very sweet and a good source of energy Sucrose: Used primarily as a transportable energy form (e.g. sugar beets and sugar cane) Cellulose: Used by plant cells as a strengthening component of the cell wall |
| Outline the role of condensation and hydrolysis in the relationship between monosaccharides, disaccharides and polysaccharides | Condensation (dehydration) reactions occur when molecules are covalently joined together and water is formed as a by-product In carbohydrates, the bond that is formed is called a glycosidic linkage The opposite of a condensation reaction is a hydrolysis reaction, which requires a water molecule to break a covalent bond between two subunits Monosaccharides are single monomers that are joined to form disaccharides, while sugars containing multiple subunits (more than 10) are called polysaccharides |
| Draw a A Condensation Reaction between Two Monosaccharides | |
| What are lipids? | Lipids are a group of organic molecules that are insoluble in water but soluble in non-polar organic solvents Common lipids include triglycerides (fats and oils), phospholipids and steroids |
| Draw the General Structure of fatty acids Saturated (no double bonds) Unsaturated (double bonds) | go over |
| Outline the role of condensation and hydrolysis in the relationship between fatty acids, glycerol and triglycerides | A condensation reaction occurs between the three hydroxyl groups of glycerol and the carboxyl groups of three fatty acids This reaction forms a triglyceride (and three molecules of water) The bond between the glycerol and the fatty acids is an ester linkage When one of the fatty acids is replaced by a phosphate group and phospholipid is formed Hydrolysis reactions will, in the presence of water, break these molecules down into their constituent subunits |
| Draw formation of a tricglyceride | |
| State three functions of lipids | Structure: Phospholipids are a main component of cell membranes Hormonal signalling: Steroids are involved in hormonal signalling (e.g. estrogen, progesterone, testosterone) Insulation: Fats in animals can serve as heat insulators while sphingolipids in the myelin sheath (of neurons) can serve as electrical insulators Protection: Triglycerides may form a tissue layer around many key internal organs and provide protection against physical injury Storage of energy: Triglycerides can be used as a long-term energy storage source |
| similarities in use of carbohydrates and lipids in energy storage | Complex carbohydrates (e.g. polysaccharides) and lipids both contain a lot of chemical energy and can be used for energy storage Complex carbohydrates and lipids are both insoluble in water - they are not easily transported Carbohydrates and lipids both burn cleaner than proteins (they do not yield nitrogenous wastes) |
| contrast in use of carbohydrates and lipids in energy storage | Lipid molecules contain more energy per gram than carbohydrates (about twice as much) Carbohydrates are more readily digested than lipids and release their energy more rapidly Monosaccharides and disaccharides are water soluble and easier to transport to and from storage sites than lipids Animals tend to use carbohydrates primarily for short-term energy storage, while lipids are used more for long-term energy storage Carbohydrates are stored as glycogen in animals while lipids are stored as fats (in plants carbohydrates are stored as cellulose and lipids as oils) Lipids have less effect on osmotic pressure within a cell than complex carbohydrates |
| Draw amino acid | |
| Outline the role of condensation and hydrolysis in the relationship between amino acids and polypeptides | A condensation reaction occurs between the amino group (NH2) of one amino acid and the carboxylic acid group (COOH) of another amino acid This reaction forms a dipeptide (plus a molecule of water) that is held together by a peptide bond Multiple amino acids can be joined together to form a polypeptide chain In the presence of water, polypeptides can be broken down into individual amino acids via hydrolysis reactions |
| Draw formation of a dipeptide | |
| Outline DNA nucleotide structure in terms of a sugar (deoxyribose), base and phosphate | |
| State the names of the four bases in DNA and their types | Adenine and guanine are purines (double ring bases) Thymine and cytosine are pyrimidines (single ring bases) |
| Outline how the DNA nucleotides are linked together by covalent bonds into a single strand | Nucleotides a linked into a single strand via a condensation reaction The phosphate group (attached to the 5'-C of the sugar) joins with the hydroxyl (OH) group attached to the 3'-C of the sugar This results in a phosphodiester bond between the two nucleotides and the formation of a water molecule Successive condensation reactions between nucleotides results in the formation of a long single strand |
| Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds | Adenine pairs with thymine (A=T) via two hydrogen bonds Guanine pairs with cytosine (G=C) via three hydrogen In order for bases to be facing each other and thus able to pair, the two strands must run in opposite directions (i.e. they are anti-parallel) As the polynucleotide chain lengthens, the atoms that make up the molecule will arrange themselves in an optimal energy configuration This position of least resistance results in the double-stranded DNA twisting to form a double helix with approximately 10 - 15 bases per twist |
| Draw diagram of complementary base pairing | Thymine and adenine the cytosine and guanine |
| Draw and label a simple diagram of the molecular structure of DNA | |
| What does DNA helicase do? | Unwinds the DNA and separates the two polynucleotide strands by breaking the hydrogen bonds between complementary base pairs The two separated polynucleotide strands act as templates for the synthesis of new polynucleotide strands |
| What does DNA polymerase do? | DNA Polymerase Synthesises new strands from the two parental template strands Free deoxynucleoside triphosphates (nucleotides with three phosphate groups) are aligned opposite their complementary base partner and are covalently bonded together by DNA polymerase to form a complementary nucleotide chain The energy for this reaction comes from the cleavage of the two extra phosphate groups |
| Explain the significance of complementary base pairing in the conservation of the base sequence of DNA | Each of the nitrogenous bases can only pair with its complementary partner (A=T ; G=C) Consequently, when DNA is replicated by the combined action of helicase and DNA polymerase: The new strands formed will be identical to the original strands separated from the template The two DNA molecules formed will be identical to the original molecule |
| What does it mean by: DNA replication is semi-conservative | DNA replication is a semi-conservative process because when a new double-stranded DNA molecule is formed: One strand will be from the original molecule One strand will be newly synthesised |
| Compare the structure of DNA and RNA | |
| Outline DNA transcription | Transcription is the process by which an RNA sequence is produced from a DNA template: RNA polymerase separates the DNA strands and synthesises a complementary RNA copy from one of the DNA strands It does this by covalently bonding ribonucleoside triphosphates that align opposite their exposed complementary partner (using the energy from the cleavage of the additional phosphate groups to join them together) Once the RNA sequence has been synthesised, RNA polymerase will detach from the DNA molecule and the double helix will reform The sequence of DNA that is transcribed into RNA is called a gene Transcription occurs in the nucleus (where the DNA is) and, once made, the mRNA moves to the cytoplasm (where translation can occur) |
| Three main types of RNA are predominantly made: | Messenger RNA (mRNA): A transcript copy of a gene used to encode a polypeptide Transfer RNA (tRNA): A clover leaf shaped sequence that carries an amino acid Ribosomal RNA (rRNA): A primary component of ribosomes |
| Describe the genetic code in terms of codons comprised of triplets of bases | The genetic code is the set of rules by which information encoded in mRNA sequences is converted into proteins (amino acid sequences) by living cells Codons are a triplet of bases which encodes a particular amino acid As there are four bases, there are 64 different codon combinations (4 x 4 x 4 = 64) The order of the codons determines the amino acid sequence for a protein The coding region always starts with a START codon (AUG) and terminates with a STOP codon |
| The genetic code has the following features: | It is universal - every living thing uses the same code (there are only a few rare and minor exceptions) It is degenerate - there are only 20 amino acids but 64 codons, so more than one codon may code for the same amino acid (this allows for silent mutations whereby a change in the DNA sequence does not affect the polypeptide sequence) |
| Explain the process of translation, leading to polypeptide formation | Translation is the process of protein synthesis in which the genetic information encoded in mRNA is translated into a sequence of amino acids in a polypeptide chain Ribosomes bind to mRNA in the cell's cytoplasm and move along the mRNA 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. UAC will align with AUG) 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 a condensation reaction) The ribosome moves along the mRNA molecule synthesising a polypeptide chain until it reaches a stop codon, at this point translation stops and the polypeptide chain is released |
| Explain the relationship between one gene and one polypeptide | A gene is a sequence of DNA which encodes a polypeptide sequence A gene sequence is converted into a polypeptide sequence via the processes of transcription (making an mRNA transcript) and translation (polypeptide synthesis) Translation uses tRNA molecules and ribosomes to join amino acids into a polypeptide chain according to the mRNA sequence (as read in codons) The universality of the genetic code means all organisms show the same relationship between genes and polypeptides (indicating a common ancestry and allowing for transgenic techniques to be employed) Some proteins may consist of a number of polypeptide chains and thus need multiple genes (e.g. haemoglobin consists of four polypeptide subunits encoded by two different genes) When a gene is mutated it may lead to the synthesis of a defective polypeptide, hence affecting protein function |
| There are two exceptions to the 'one gene - one polypeptide' rule: | Genes encoding for tRNA and rRNA do not code for polypeptide sequences (only mRNA sequences code for polypeptides) A single gene may code for multiple polypeptides if alternative splicing occurs (the removal of exons as well as introns) |
| Define enzyme and active site | Enzyme: A globular protein that increases the rate of a biochemical reaction by lowering the activation energy threshold (i.e. a biological catalyst) Active Site: The site on the surface of an enzyme which binds to the substrate molecule |
| Explain enzyme-substrate specificity | Active site and substrate complement each other in terms of both shape and chemical properties (e.g. opposite charges) Binding to the active site brings the substrate into close physical proximity, creating an enzyme-substrate complex The enzyme catalyses the conversion of the substrate into a product (or products), creating an enzyme-product complex As the enzyme is not consumed in the reaction, it can continue to work once the product dissociates (hence only low concentrations are needed) |
| Describe lock and key model | Enzymes and substrates share specificity (a given enzyme will only interact with a small number of specific substrates that complement the active site) This explanation of enzyme-substrate interaction is described as the 'lock and key' model (a lock only opens in response to a specific key) |
| Explain the effects of temperature | Low temperatures result in insufficient thermal energy for the activation of a given enzyme-catalysed reaction to be achieved Increasing the temperature will increase the speed and motion of both enzyme and substrate, resulting in higher enzyme activity This is because a higher kinetic energy will result in more frequent collisions between enzyme and substrate At an optimal temperature (may differ for different enzymes), the rate of enzyme activity will be at its peak Higher temperatures will cause enzyme stability to decrease, as the thermal energy disrupts the hydrogen bonds holding the enzyme together This causes the enzyme (particularly the active site) to lose its shape, resulting in a loss of enzyme activity (denaturation) |
| Explain the effects of pH | Changing the pH will alter the charge of the enzyme, which in turn will protein solubility and may change the shape of the molecule Changing the shape or charge of the active site will diminish its ability to bind to the substrate, abrogating enzyme function Enzymes have an optimum pH (may differ between enzymes) and moving outside of this range will always result in a diminished rate of reaction |
| Explain the effects of substrate concentration | Increasing substrate concentration will increase the activity of a particular enzyme More substrate means there is an increased likelihood of enzyme and substrate colliding and reacting, such that more reactions will occur and more products will be formed in a given time period After a certain point, the rate of reaction will cease to rise regardless of further increases to substrate concentration, as the environment has become saturated with substrate and all enzymes are bound and reacting (Vmax) |
| Define denaturation | Denaturation is a structural change in a protein that results in the loss (usually permanent) of its biological properties Heat and pH are two agents which may cause denaturation of an enzyme |
| Explain the use of lactase in the production of lactose-free milk | Lactose is a disaccharide of glucose and galactose which can be broken down by the enzyme lactase Historically, mammals exhibit a marked decrease in lactase production after weaning - leading to lactose intolerance (incidence is particularly high in Asian / African / Native American / Aboriginal populations) Lactose-free milk can be produced by purifying lactase (e.g. from yeast or bacteria) and binding it to an inert substance (such as alginate beads) Milk passed over this immobilised enzyme will become lactose-free |
| The generation of lactose-free milk can be used in a number of ways: | As a source of milk for lactose-intolerant individuals As a means to increase the sweetness of milk (glucose and galactose are sweeter in flavour), thus negating the need for artificial sweeteners As a way of reducing the crystallisation of ice-creams (glucose and galactose are more soluble than lactose) As a means of shortening the production time for yogurts or cheese (bacteria ferment glucose and galactose more readily than lactose) |
| Define cell respiration | Cell respiration is the controlled release of energy from organic compounds in cells to form ATP (adenosine triphosphate) |
| What happens in cell respiration? | Glycolysis is the breakdown of one molecule of glucose (6C) into two molecules of pyruvate (2 x 3C) with a small net yield of ATP (2 molecules of ATP) This process also results in the reduction of two hydrogen acceptors (NAD+) to form 2 molecules of NADH + H+ |
| plain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP | Anaerobic respiration occurs in the absence of a ready supply of oxygen (e.g. during intense physical activity, when oxygen reserves are depleted) In order to generate the small amounts of energy provided by glycolysis, the end product (pyruvate) must be converted into another substance before more glucose can be used This is because the conversion of pyruvate replenishes the levels of the hydrogen acceptor (NAD+) needed for glycolysis to occur |
| The conversion of pyruvate occurs in the cytoplasm of the cell and the products are: | Lactate (3C) in animal cells Ethanol (2C) and carbon dioxide (CO2) in plants, fungi (e.g. yeast) and bacteria The conversion of pyruvate into ethanol and CO2 is also known as fermentation |
| Explain that, during aerobic cell respiration, pyuvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP | Aerobic respiration occurs in the presence of oxygen and takes place in the mitochondrion Pyruvate is broken down into carbon dioxide and water and a large amount of ATP is formed (34 - 36 molecules) Although this process begins with glycolysis (to break down glucose into pyruvate), glycolysis does not require oxygen and is an anaerobic process |
| What is photosynthesis? | Photosynthesis is the process by which plants synthesise organic compounds (e.g. glucose) from inorganic compounds (CO2 and H2O) in the presence of sunlight Photosynthesis is a two step process: 1. The light dependent reactions convert the light energy into chemical energy (ATP) 2. The light independent reactions use the chemical energy to synthesise organic compounds (e.g. glucose) The organic molecules produced in photosynthesis can be used in cellular respiration to provide the energy needed by the organism |
| State that light from the Sun is composed of a range of wavelengths (colours) | Sunlight is white light, made up of all the colours of the visible spectrum Colours are different wavelengths of light and range from ~ 400 nm - 700 nm |
| The colours of the visible spectrum are (from longer to shorter wavelength): | Red Orange Yellow Green Blue Indigo Violet (R.O.Y.G.B.I.V) |
| State that chlorophyll is the main photosynthetic pigment | Chlorophyll is the main site of light absorption in the light dependent stage of photosynthesis There are a number of different chlorophyll molecules, each with their own distinct absorption spectra (the spectrum of light absorbed by a substance) When chlorophyll absorbs light energy, they release electrons which are used to make ATP (chemical energy) |
| Outline the difference in absorption of red, green and blue light by chlorophyll | The main colours of light absorbed by chlorophyll are red and blue light The main colour of light not absorbed (it is reflected) by chlorophyll is green light This explains why leaves are green - excepting when the presence of other pigmented substances (e.g. anthocyanins) produces a different colour Deciduous trees stop producing high amounts of chlorophyll in the winter (due to insufficient sunlight), allowing other photosynthetic pigments (e.g. xanthophylls, carotenoids) to come to the fore, which changes the colour of the leaf |
| State that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen | The first part of photosynthesis is the light dependent reaction, which uses light energy to make ATP Light Dependent Reaction Light stimulates chlorophyll to release electrons, which results in the production of ATP Light energy also splits water molecules (photolysis), producing oxygen and hydrogen The hydrogen is taken up by a hydrogen carrier (NADP+) to form NADPH The splitting of water also releases electrons, which replace those lost by the chlorophyll The ATP and hydrogen (NADPH) are taken to the site of the light independent reactions |
| State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon molecules to make organic molecules | The second part of photosynthesis is the light independent reaction, which makes organic compounds from the products of the light dependent reactions Light Independent Reaction ATP and hydrogen (carried by NADPH) are products of the light dependent reactions They are used to fix carbon molecules together (add CO2 to basic carbon compounds) This allows for the production of more complex organic molecules (e.g. sugars) These organic molecules can then be stored to use in cellular respiration as required |
| How can rate of photosynthesis be measured | Measuring CO2 uptake Measuring O2 production Measuring biomass |
| Explain the first method of the previous flashcard | CO2 uptake can be measured by placing a plant in an enclosed space with water Carbon dioxide interacts with the water molecules, producing bicarbonate and hydrogen ions, which increases the acidity of the resulting solution The change in pH can therefore provide a measure of CO2 uptake by a plant (increased CO2 uptake = more alkaline pH) |
| second method | O2 production can be measured by submerging a plant in an enclosed space with water attached to a sealed gas syringe Any oxygen gas produced will bubble out of solution and can be measured by a change in water level (via the position of the meniscus) |
| Third method | Glucose production can be indirectly measured by a change in a plant's biomass (weight) This requires the plant to be completely dehydrated prior to weighing to ensure the change in biomass reflects a change in organic matter and not water content An alternative method for measuring glucose production is to determine the change in starch levels in a plant (glucose is stored as starch) Starch can be identified via iodine staining (resulting solution turns purple) and quantitated using a colorimeter |
| Outline the effect of temperature | Photosynthesis is controlled by enzymes, which are sensitive to temperature As temperature increases, the rate of photosynthesis will increase as reagents have greater kinetic energy and are more likely to react Above a certain temperature, the rate of photosynthesis will decrease as essential enzymes begin to denature |
| Effect of Light Intensity | As light intensity increases, the rate of photosynthesis will increase up until a certain point, when photosynthesis is proceeding at its maximum rate Further increases to light intensity will have no effect on photosynthesis (the rate will plateau), as chlorophyll are saturated by light Different wavelengths of light will have different effects on the rate of photosynthesis (e.g. green light will not be used) |
| Effect of CO2 conc | As the concentration of carbon dioxide increases, the rate of photosynthesis will increase up until a certain point, when photosynthesis is proceeding at its maximum rate Further increases to carbon dioxide concentration will have no effect on photosynthesis (the rate will plateau), as the enzymes responsible for carbon fixation become saturated |
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