Section 1- biological molecules Flashcards
What molecules do the cells of all living organisms consist of?
Carbohydrates, Lipids, Proteins DNA/RNA and water
What additional elements do Carbohydrates, Lipids, Proteins and Nucleic Acids contain?
Carbohydrates - Carbon (C), hydrogen (H), and oxygen
(O).
Lipids - Carbon (C), hydrogen (H), and oxygen (O).
Proteins - Carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).
Nucleic acids - Carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P).
What is a Monomer?
A monomer is an individual unit that makes a polymer.
What is a Polymer?
a polymer is many repeating units of monomers.
What is the process by which monomers join to form a polymer?
Polymerisation / condensation.
Carbohydrates - What is the name of its monomer / dimer form?
Monosaccharides / Disaccharides
Carbohydrates - What is the name of its Polymer form?
Polysaccharides
Proteins - What is the name of its monomer form?
Amino acids
Proteins - What is the name of its Polymer form?
Polypeptides
Nucleic Acids - What is the name of its monomer/ dimer form?
Nucleotides / phosphodiester
Nucleic Acids - What is the name of its Polymer form?
Polynucleotides
How are most Polymers Synthesised
By a Condensation reaction
How are most polymers broken down?
By a hydrolysis reaction.
What is a Condensation reaction?
The removal of water to form a chemical bond Between Two molecules
What is a Hydrolysis Reaction?
The addition of water to break a chemical bond between two molecules
What does the ‘Carbo’ in carbohydrates stand for?
Carbo indicates that it contains the element carbon.
What does the ‘Hydrate’ in carbohydrates stand for?
Hydrate indicates that it contains hydrogen and oxygen in a ratio of 2:1 like water (h20)
What is the general formula for carbohydrates?
The general formula for a carbohydrate is Cx(H2O)y.
What are the Roles of Carbohydrates?
- Energy supply for cells (Main role)
- Energy storage - Sugars can be stored as complex carbohydrates (starch or Glycogen)
- Structural components- Cellulose and chitin are used in cell walls
- Cellular recognition - Glycoproteins help cells identify each other and communicate.
- Building blocks for biological molecules - Deoxyribose and ribose can be used to make nucleic acids
What are the three types of carbohydrates?
Monosaccharide (monomer), Disaccharide (dimer) Polysaccharide (polymer)
What are the main features of Monosaccharides?
- has one subunit (monomer)
- examples are Glucose, Fructose and Galactose
- its main function is to be an energy source
- diagram is :
What are the main features of Disaccharides?
- Two subunits (dimer)
- examples are Maltose, Sucrose and lactose
3.. Its main function is to be a transport form of carbs - Its diagram is:
What are the main features of Polysaccharides?
- has many subunits(polymer)
- examples are Starch, Cellulose and Glycogen
- its main function is to be a storage form.
- its diagram is
Information about Monosaccharides
Monosaccharides are the simplest form of carbohydrates, aka ‘simple sugars’. Monosaccharides are soluble, and sweet-tasting and are found in many foods such as fruits, vegetables and grains.
What is the general formula for Monosaccharides?
(CH20)n where ‘n’ can be any number from 3 to 7.
Monosaccharides are classified according to the number of carbon atoms in each molecule. What are the Monosaccharides that have 6 carbon atoms called?
Hexose sugars.
Examples of these are Glucose, Fructose and Galactose.
What are the Monosaccharides that have 5 carbon atoms called?
Pentose sugars
Examples of these are Ribose and deoxyribose.
Glucose is a hexose sugar with the formula C6H12O6 the atoms can be arranged in two different ways. What are the two isomers of Glucose
Alpha-glucose and Beta-glucose.
What is the difference between Alpha glucose and Beta Glucose?
The only difference between the two forms is the hydroxyl group (OH) orientation on carbon 1 (the first carbon atom in the ring).
Where is the Hydroxyl group located in Alpha-glucose?
The hydroxyl group is located below on carbon 1
Where is the Hydroxyl group located in Beta-glucose?
The hydroxyl group is located above on carbon 1
What are the uses of glucose?
Glucose is used as the primary energy source in animals and plants
What are glucose’s features that help it act as an energy source?
- It is soluble- The hydroxyl groups can form hydrogen bonds with water, so it can be transported around organisms.
- Its bonds store lots of energy- this energy is released when bonds are broken
Information about Disaccharides
Disaccharides are formed when two monosaccharides join together. Examples of Disaccharides include maltose (found in grains and cereals), sucrose (used as a transport sugar in plants), and lactose (the main carbohydrate found in milk.
What is maltose made up of?
Maltose is made up of glucose joined to glucose.
What is sucrose made up of?
sucrose is made up of glucose joined to fructose.
What is lactose made up of?
alpha glucose joined to galactose
How are Disaccharides broken down?
Disaccharides are broken down via hydrolysis reactions.
How are Disaccharides formed?
Disaccharides are created via condensation reactions.
What do condensation reactions and hydrolysis reactions involve?
The breakdown of a covalent bond known as a glycosidic bond.
What is involved in the Condensation reaction of a Disaccharide?
when two monosaccharides join, the hydroxyl group (OH) on carbon 1 of the monosaccharide reacts with the hydroxyl group (OH) on carbon 4 of another monosaccharide. A 1-4 glycosidic bond is formed and a water molecule is released.
What is involved in the Hydrolysis reaction of a Disaccharide?
When a water molecule is added the glycosidic bond is broken to release the two monosaccharides.
What are Polysaccharides?
Polysaccharides are complex Carbohydrates made up of many monosaccharides joined via Glycosidic bonds.
Examples of these are starch, glycogen and cellulose
What is starch?
starch is an example of a polysaccharide used by plants to store excess glucose. this means that starch can be broken down into glucose when plants require energy
What is starch made up of?
Starched is made up of many alpha-glucose monomers joined via 1-4 and 1-6 glycosidic bonds. these chains come in two forms: branched and unbranched.
What are the main features of starch that allow it to work well as a store of energy?
- Insoluble - it does not affect the water potential of the cell so water is not drawn in by osmosis.
- large - it cannot diffuse out of cells
- Many side branches- these allow enzymes to hydrolyse the glycosidic bonds easily to rapidly release glucose
- Coiled - This makes it compact so that a lot of glucose can be stored in a small place.
What is glycogen?
Glycogen is an example of a polysaccharide used by animals to store excess glucose. this means that glycogen can be hydrolysed back into glucose when animals require energy. it is made up of many alpha-glucose monomers joined via 1-4 and 1-6 glycosidic bonds to form highly branched chains
What are the main features of glycogen that allow it to work well as a store of energy?
Insoluble - It does not affect the water potential of cells, and so water does not enter cells by osmosis.
Compact - A lot of glucose can be stored in a small space.
More highly branched than starch - Enzymes can easily hydrolyse the glycosidic bonds to rapidly release glucose.
Large - It cannot diffuse out of cells.
Hydrolysis releases alpha-glucose monomers - These are readily used in respiration.
What is cellulose
Cellulose is a polysaccharide formed from beta-glucose .its primary use is to provide structural support for plant cell walls.
What is the problem when trying to get beta-glucose molecules to react to form cellulose?
Cellulose is made up of many beta-glucose monomers joined together via glycosidic bonds. However, when two beta-glucose molecules line up next to each other, the hydroxyl groups on carbon 1 and 4 are too far to react. Therefore every other beta-glucose molecule is flipped 180 degrees (upside down) which brings the hydroxyl groups closer together to be able to react.
What do beta-glucose form when many join together
They form long straight unbranched chains.
What do the alternating inversion of the beta glucose allow for?
they allow for hydrogen bonds to form in between individual chains this provides strength although the hydrogen bonds are kinda weak
What are microfibrils?
Multiple cellulose chains are tightly cross-linked via hydrogen bonds to form bundles called microfibrils.
What are macro fibrils?
Multiple microfibrils which combine to make strong cellulose fibres in the plant cell wall
What are the adaptations of cellulose?
- Long straight, and unbranched chains - These provide rigidity to the cell wall
- Hydrogen bonds - These cross-link the chains to add collective tensile strength
- Microfibrils- These provide additional strength
Comparing starch, Glycogen, and cellulose
What are reducing sugars?
Reducing sugars are sugars that include all monosaccharides and some disaccharides such as maltose and fructose.
What are non-reducing sugars?
non-reducing sugars include some disaccharides such as sucrose and all polysaccharides
How do you test for reducing sugars?
- place 2cm^3 of your food sample into a test tube.
- add an equal volume of Benedict’s reagent.
- Heat the mixture in a gently boiling water bath for 5 mins
- if a reducing sugar is present, the mixture will change from a blue solution to a brick-red precipitate
How do you determine the concentration of the reducing sugar?
- Blue - This indicates no reducing sugar is present.
- Green - This indicates a low concentration.
- Orange - This indicates a medium concentration.
- Brick-red - This indicates a high concentration.
What are some Quantitative methods of determining the conc. of reducing sugars? (more accurate)
- use a colourimeter to measure the absorbance of each solution
- filter the solution and weigh the precipitate
How do you test for non-reducing sugars?
- Carry out the test for reducing sugars, and if the result is negative, continue with the next steps.
- Add 2 cm3 of the food sample to 2 cm3 of dilute hydrochloric acid.
- Heat the mixture in a gently boiling water bath for 5 minutes (the acid will hydrolyse disaccharides into monosaccharides).
- Neutralise the mixture by adding sodium hydrogen carbonate solution.
- Retest this mixture using the test for reducing sugars.
- If non-reducing sugars were present, the mixture would change from a blue solution to a brick-red precipitate.
How do you test for starch?
- Place 2 cm3 of your food sample into a test tube.
- Add a couple of drops of iodine solution and shake.
- If starch is present, the solution will turn from orange to blue-black.
What are lipids?
Lipids are biological molecules that contain the elements Carbon (C), Hydrogen (H), and Oxygen (O).
however, lipids contain a much lower proportion of oxygen than carbohydrates.
Are not made up of long chains of monomers, meaning they are not considered to be polymers.
What are the main functions of lipids?
Energy supply - Lipids can be oxidised to provide energy to cells
Structural components - Phospholipids are used in cell membranes
Waterproofing - insoluble lipids are used to form waterproof barriers
Insulation - Lipids can help retain heat or act as electrical insulators
Protection - delicate organs are surrounded by a layer of fat.
What are most Lipids made up of?
Most lipids are made up of Fatty acids combined with an alcohol (usually glycerol)
What do fatty acids consist of?
Fatty acids consist of a carboxyl group (-COOH) attached to a hydrogen chain (R group)
What are the two types of Fatty Acids?
Saturated fatty acids and unsaturated fatty acids
What are saturated Fatty Acids?
- Have hydrocarbon chains that are ‘saturated with hydrogen’ meaning all carbon atoms are bonded to the maximum number of hydrogen atoms
- The hydrocarbon chains have no carbon-carbon double bonds.
- lipids with saturated fats have a higher melting and boiling point and so a solid at room temp. (fats)
What are unsaturated Fatty acids?
- Have hydrocarbon chains that do not contain the maximum number of hydrogen atoms bonded to the carbon atoms.
The hydrocarbon chain has at least one carbon-carbon double bond, which causes the chain to kink. - Lipids that contain unsaturated Fatty Acids have lower melting points and so are usually liquids at room temp. (oils)
What does it mean if an Unsaturated fatty acid is monounsaturated?
It has one double bond between two carbon atoms in the hydrocarbon chain
What does it mean if an Unsaturated fatty acid is polyunsaturated?
It has two or more bonds between two carbon atoms in the hydrocarbon chain
How do you test for lipids?
The emulsion test.
What is the emulsion test?
1- Place your food sample in a test tube.
2- Add 2 cm3 of ethanol.
3 - Shake.
4- Add 2 cm3 of distilled water.
5- If lipids are present, a milky white emulsion will appear.
What is a Triglyceride?
A triglyceride is a type of lipid used as a store of energy in plants, animals, and some bacteria.
What does a Triglyceride consist of?
A glycerone backbone is attached to three fatty acid tails. each fatty acid tail contains a hydrocarbon chain (R) which can vary in length and may be saturated or unsaturated
What is the diagram of a Triglyceride
What are the features of a triglyceride that allow it to store energy efficiently?
- Long hydrocarbon chains- can be broken down to release energy
- low mass-to-energy ratio - lots of energy in a small volume
- insoluble - they do not affect the water potential of the cell as they are large and non-polar
- High ratio of hydrogen to oxygen atoms - Triglycerides will release water when oxiidised
How are triglycerides synthesised?
they are synthesised via condensation reactions and this involves the formation of covalent bonds known as ester bonds
how are triglycerides broken down?
they are broken down via hydrolysis reactions this involves the breakdown of covalent bonds known as ester bonds
What happens in the condensation reaction of triglycerides?
- The hydroxyl groups (OH) on the glycerol and on the three fatty acids react together to release three water molecules (h2o)
- this results in three ester bonds between the glycerol and the fatty acids.
What happens in the Hydrolysis reactions of triglycerides?
- The addition of three water molecules (h2o) breaks the ester bonds
- this separates the glycerol and fatty acids
What are Phospholipids?
A phospholipid is a type of lipid used as a structural component of the cell membrane they are similar to triglycerides except one of the fatty acid tails is replaced by a phosphate group.
What does it mean when a Phospholipid is said to be ‘polar’?
it means that the ‘head’ attracts water and the ‘tail’ repels water.
A hydrophilic ‘head’ - this contains glycerol and phosphate
A hydrophobic - ‘tail’ - this contains fatty acids
What is the phospholipid bilayer?
When phospholipids are placed in water they arrange themselves into a double layer (bilayer) so that the hydrophilic heads are facing out (toward the water) and the hydrophobic tails are facing in (away from the water). this creates a hydrophobic centre in the bilayer so that water-soluble substances cannot pass through.
What are proteins made up of?
Amino acids. They are monomers.
What structures can amino acids join together to form?
Dimers - Dipeptide (two subunits)
Polymers - Polypeptide (many subunits)
What are the roles of proteins?
Enzymes - these proteins are used to breakdown and synthesise molecules
Antibodies - these proteins are involved in the immune response.
Transport - some proteins move molecules or ions across membranes
Structural - keratin and collagen are used to create strong fibres
Hormones - some of these are proteins that act as chemical messengers in the body.
Muscle contraction - muscles are made up of proteins
How many different amino acid structures are there?
There are around 20 different amino acids that are commonly found in living organisms.
What is the general structure of amino acids?
- A central carbon atom
- An amino group (-NH2)
- A carboxyl group (- COOH)
- A hydrogen atom (-H)
-An R group or a variable side group
The different R groups will determine the amino acid properties.
How is Dipeptide synthesised and broken down?
Dipeptides are synthesised via condensation reactions and broken down via hydrolysis reactions. These reactions involve the formation or the breakdown of a covalent bond known as a peptide bond.
What is involved in the condensation reaction of a Dipeptide?
When two amino acids join, the hydroxyl (OH) in the carboxyl group of one amino acid reacts with the hydrogen (H) in the amino group of another amino acid. this releases a water molecule and forms a peptide bond between the carbon and the nitrogen of both amino acids
What is involved in the Hydrolysis reaction of a Dipeptide?
when a water molecule is added to a dipeptide, the peptide bond is broken to release the two amino acids
How to test for proteins?
- Place your food sample in a test tube. - Add an equal volume of Biuret solution (sodium hydroxide and copper sulfate).
- If proteins are present, the solution will turn from blue to purple. If no protein is present, the solution remains blue.
Why are proteins able to carry out their function?
Proteins are large complex molecules with unique
3D structures. this structure allows them to carry out their function.
What are the four levels of protein structure?
1- Primary
2-Secondary
3- Tertiary
4- Quaternary
each level has specific bonds that hold it together and influence the overall shape
What is the primary structure of proteins?
the primary structure is made up of the unique sequence of amino acids in the polypeptide chain. this structure is held together by peptide bonds (carbon and nitrogen) .
What is the secondary structure of proteins?
The secondary structure involves hydrogen bonds forming between the amino group of one amino acid and the carboxyl group of another amino acid further down the chain. this causes the polypeptide chain to coil into either an alpha-helix or a beta-pleated sheet structure
What is the Tertiary structure of proteins?
The tertiary structure forms when the polypeptide chain folds and twists further to create a complex 3D structure.
Which bonds are held together by the tertiary structure?
Hydrogen bonds - these are individually weak but provide strength in large numbers
Ionic bonds - these form between positive and negative R groups
Disulfide bridges - these form between R groups that contain sulphur (such as cysteine)
Hydrophobic and Hydrophilic interactions - these are weak interactions between polar and non-polar groups
What is the Quarternary structure
Involves two or more peptide chains held together by the same bonds found in the tertiary structure of a protein (hydrogen, ionic, disulfide,hydrophobic+phillic)
Besides polypeptide chains, what else can be found in the quaternary structure of proteins?
Non-protein groups known as prosthetic groups
Do all Proteins have a quarternary structure?
No. It is important to understand that although all proteins have primary, secondary, and tertiary structures, only some proteins have a quaternary structure.
This means that some proteins consist of a single polypeptide chain, but others are made up of multiple chains combined.
What are enzymes?
Enzymes are globular proteins with complex and unique tertiary structures
Why are enzymes known as biological catalysts?
Because they increase the rate of a chemical reaction without being used up in the reaction itself.
What do all chemical reactions require to get started?
All chemical reactions require a certain amount of energy to get started, this is called activation energy. without sufficient activation energy, the reactant molecules will not have enough energy to break their bonds and form the desired products
How do enzymes work?
Enzymes work by lowering the activation energy for a chemical reaction. this means reactions can take place at a lower temperature.
What are intracellular and extracellular enzymes?
Intracellular enzymes - these act within the cells that produce them
Extracellular Enzymes - these act outside the cells that produce them, and are secreted.
How do enzymes bind with substrates?
- Enzymes have unique tertiary structures which determine the shape of their active site. this shape is complimentary to the substrate.
- The substrate binds to the active site to form an enzyme-substrate complex.
- temporary bonds form between the r groups withing the active site and the substrate these bonds lower the activation energy to help break the substrate into products
- the products are released from the active site, leaving the enzyme free to be used again.
What are the two models of enzyme action?
- The lock and key model 2. The induced fit model
What is the induced fit model?
In this model, the substrate does not fit perfectly into the enzyme’s active site. As the substrate enters the enzyme the active site changes shape slightly. this puts a strain on the substrate’s bonds which lowers the activation energy
What is the lock and key model?
In this model, the substrate fits perfectly into the enzyme’s active site in the same way that a key fits into a lock
What is enzyme denaturation?
When drastic temperature increases or changes to the Ph cause the bonds to break, changing the enzyme’s tertiary structure. this causes the active site to change place so the substrate no longer fits this means that enzyme-substrate complexes cannot be formed and the enzyme is denatured.
What four Factors affect the rate of enzyme reactions?
- temperature
- PH
- Substrate concentration
- Enzyme concentration
How does Temperature affect Enzyme activity?
- Increased temperature causes the molecules to have more kinetic energy, causing more collisions and enzyme-substrate complexes.
- all enzymes have an optimum temperature and this temp is where enzyme activity will be the fastest
- too much kinetic energy will cause the active site to change shape and the active site denatures.
What is the model paragraph to describe the graph for how temperature affects enzyme activity?
- As the temperature increases, the rate of reaction increases. this is shown by the increase in the line.
- The maximum rate is reached at the optimum temperature this is shown by the line being at its peak on the graph.
- as the temperature increases past the optimum, the rate of reaction decreases until the reaction stops. this is shown by the decreasing line
How does Ph Affect Enzyme activity?
- In acidic conditions H+ ions break ionic/ hydrogen bonds and denature enzymes.
- The optimum PH is the PH the enzyme works fastest at.
- in alkaline conditions, OH- ions break ionic/hydrogen bonds and denature enzymes
What is the model paragraph to describe how PH affects enzyme activity?
- Below the optimum pH, the rate of reaction is low or zero. indicated by the slowly ascending line
- The maximum rate of reaction is reached at the optimum pH. indicated by the line being at its optimum point
- Above the optimum pH, the rate of reaction is low or zero. indicated by the descending line
How does substrate Concentration affect enzyme activity?
The more substrate molecules there are the more enzyme-substrate complexes can be formed. If there are too many substrate molecules then enzyme activity reaches the saturation point. Where all active sites are occupied by a substrate and enzyme concentration becomes the limiting factor.
What is the model paragraph for how pH affects enzyme activity?
As the substrate concentration increases, the rate of reaction increases.
As the substrate concentration increases further, the rate of reaction plateaus (levels off).
How does enzyme concentration affect enzyme activity?
The more enzyme molecules there are the more enzyme-substrate complexes can be formed. Where all enzyme molecules are occupied by a substrate then enzyme concentration becomes the limiting factor.
What is the model paragraph for how Enzyme concentration affects enzyme activity?
As the enzyme concentration increases, the rate of reaction increases.
As the enzyme concentration increases further, the rate of reaction plateaus (levels off).
What is an inhibitor?
Inhibitors are molecules that bind to enzymes to reduce their activity
What are reversible and irreversible inhibitors?
Reversible inhibitors - These form weak bonds (e.g. hydrogen or ionic) with the enzyme. that can easily be broken
Irreversible inhibitors - These form strong bonds (e.g. covalent) with the enzyme.that cant be broken so easily.
What are competitive inhibitors?
Competitive inhibitors bind to the active site of an enzyme to prevent enzyme-substrate complexes. They have a similar shape to the substrate and so prevent the substrate from binding and thus reduce the formation of enzyme-substrate complexes. this results in a decrease in the rate of the enzyme-catalysed reaction.
Are competitive inhibitors reversible?
most competitive inhibitors are reversible as they only temporarily bind to the enzyme
How can you overcome competitive inhibitors?
If you increase the substrate concentration. the higher the conc.the more likely it is that substrates will bind to active sites rather than inhibitor molecules. this can overcome the effects of the competitive inhibitor
What are non-competitive inhibitors?
non-competitive inhibitors bind to enzymes away from the active site (allosteric site). this binding changes the tertiary structure of the enzyme, causing the active site to change shape. this means that fewer enzyme-substrate complexes are formed.
How can you overcome Non- competitive inhibitors?
You can’t. increasing substrate concentration does not affect the rate of reaction. this is because non-competitive inhibitors do not compete with the substrate for the active site so increasing substrate conc. has no effect.
What are nucleotides?
Nucleotides are the building blocks of nucleic acids such as DNA and RNA. Nucleotides are monomers and can join together to form dimers. (dinucleotides) and polymers (Polynucleotides or nucleic acids.)
What three components are nucleotides made up of?
- A Pentose sugar. This contains 5 carbon atoms.
- A Nitrogenous base. This contains Carbon and nitrogen
- A phosphate group. This contains phosphate
What are Polynucleotides?
Polynucleotides are Nucleotides joined together via Condensation reactions to form a polynucleotide.
How Are Polynucleotides formed?
They are formed when the phosphate group of one nucleotide forms a covalent bond with the pentose sugar of another. this forms a phosphodiester bond.
What is the Sugar-Phosphate backbone?
When many nucleotides form polynucleotides and create a chain of sugars and phosphates known as the sugar-phosphate backbone.
How can Phosphodiester bonds be broken?
They can be broken via hydrolysis reactions, which release the nucleotide monomers.
What is DNA?
Deoxyribonucleic acid (DNA) is a type of nucleic acid that contains the instructions to make proteins
What three components is DNA made up of?
- Deoxyribose - A nucleic acid
- A, T, G, or C base - Adenine, Thymine, Guanine, or Cytosine
- A phosphate group
What is a phosphate group?
Phosphate, chemical formula PO43-, is a compound of one phosphorus and four oxygen atoms. It is called a phosphate group when it is attached to a molecule containing carbon.
Who figured out the structure of DNA?
In 1953 James Watson and Francis Crick were credited with working out the structure of DNA.
What is the structure of DNA?
DNA is made up of two polynucleotide strands wound around each other to form a double helix
What features allow DNA to pass genetic information from one generation to another?
- A sugar-phosphate backbone
- Double-stranded
- Large molecule
- Double helix
- Complimentary base paring
- Weak hydrogen bonds.
How does the sugar-phosphate feature help DNA to pass genetic information?
The sugar-phosphate backbone protects coding bases on the inside of the helix from reacting with its envrironment.
How does the double-stranded feature help DNA to pass genetic information?
This allows strands to act as templates in DNA replication
How does the large molecule feature help DNA to pass genetic information?
it stores lots of information.
How does the double helix feature help DNA to pass genetic information?
this feature makes the molecule compact
How does the complimentary base pairing feature help DNA to pass genetic information?
this allows accurate DNA replication
How does the weak hydrogen bonds feature help DNA to pass genetic information?
This allows strands to separate in DNA replication
What are purines and pyrimidines
These are the four nitrogenous bases found in DNA: adenine (A), Guanine (G), Thymine (T), and cytosine (C). these bases can be grouped into two categories: purines and Pyrimidines.
What is a Purine?
These are larger bases that contain Two carbon ring structures (A and G)
What is a Pyrimidines
these are smaller bases that contain one carbon ring structure (T and C)
What is complementary base pairing?
Where the two DNA strands are held together via hydrogen bonding between bases
What happens in complimentary base pairing?
- adenine pairs with thymine via 2 hydrogen bonds
- cytosine pairs with guanine via 3 hydrogen bonds
A smaller pyrimidine base always binds to a larger purine base. This arrangement maintains a constant distance between the two sugar-phosphate backbones.
What is RNA?
Ribonucleic acid is a type of nucleic acid that uses information from DNA to synthesise proteins
What three components is RNA made up of?
- Ribose - A pentose sugar
- A, U, G, or C base - Adenine, uracil, Guanine or cytosine
- A phosphate group
What is the structure of RNA?
- RNA contains sugar Ribose instead of Deoxyribose they also contain the base uracil instead of thymine (uracil pairs with adenine)
- RNA is single-stranded and made up of just one polynucleotide strand. these strands are much shorted than the DNA strands
What is DNA replication
The process of copying DNA is known as semi-conservative replication. this produces DNA molecules consisting of
one original DNA strand and one newly synthesised DNA strand.
What is the process by which DNA replicates?
- The enzyme DNA helicase breaks hydrogen bonds between complementary bases. this unwinds the double helix and separates the strands
- each strand acts as a template as free nucleotides attract to their complementary bases. adenine pairs with thymine, while cysteine pairs with guanine
- The enzyme DNA polymerase joins the free nucleotides together via condensation reactions in the 5’ to 3’ direction. . this forms phosphodiester bonds to create the sugar-phosphate backbone of the new DNA strand
- Two identical copies of DNA are made. each copy is made up of one original DNA strand and one new DNA strand (semi-conservative replication)
What is ATP?
ATP is an important molecule involved in energy transfer within cells and is often referred to as the energy currency of the cell. it is a nucleotide derivative
What is the structure of ATP?
- adenine - Nitrogenous base
- ribose - 5-carbon sugar
- Phosphates - 3 phosphate groups.
What are the uses of ATP in the body?
- Movement (muscle contraction or sperm)
- Active transport of molecules against the concentration gradient
- Synthesis of large molecules such as DNA and proteins
- Secretion of substances from cells, such as releasing hormones from glands
- activation of molecules such as when ATP is hydrolysed, the phosphate can be added to other molecules (such as enzymes) to make them more reactive
The breakdown and synthesis of ATP is an example of what?
A reversible reaction
What happens in the hydrolysis of ATP?
When water is added to ATP, it breaks down into adenosine diphosphate ADP and inorganic phosphate (Pi). This reaction is catalysed by the enzyme ATP hydrolase and releases energy for use in cells.
What happens in the condensation of ATP?
When a phosphate group and ADP join, a water molecule is released. this reaction is catalysed by the enzyme ATP synthase. this process requires energy and traps chemical energy in the bond.
What features allow ATP to work well as an immediate energy source?
- The hydrolysis of ATP releases a small amount of energy, meaning little energy is lost as heat.
- ATP is broken down in one step, meaning energy is released quickly.
- ATP is rapidly re-synthesised so that ATP is always readily available.
- The inorganic phosphate from ATP hydrolysis can phosphorylate other compounds, which makes them more reactive.
- The bonds between the phosphate groups are unstable, have a low activation energy and are easily broken.
- ATP is soluble, so it can easily be transported around cells.
What is the structure of water?
A molecule of water (H2O) is made up of one oxygen atom (O) joined to two hydrogen atoms (H). These atoms are held together by two covalent bonds. Oxygen shares one electron with each hydrogen atom while each hydrogen atom shares its one electron with oxygen
What does it mean when we say water is a dipolar molecule?
when the shared electrons are pulled towards the oxygen atom, giving the oxygen atom a slightly negative charge. this leaves the hydrogen atoms with a slightly positive charge. this means that water has both positive and negative poles, making it a dipolar molecule.
How do water molecules form hydrogen bonds?
When the partially negative end of an oxygen molecule and a partially positive end of a hydrogen molecule interact. the force of attraction between these two poles is known as a hydrogen bond.
What are the roles of water?
- Solvent
- Temperature control
- Cooling mechanism
- Habitat
- Metabolite
- Transport
How does water act as a solvent?
Water splits up ionic compounds in cells. it does this as the slightly negative oxygens are attracted to the slightly positive ions whilst the slightly positive hydrogen are attracted to the negative ions. each ion is then surrounded by water molecules and the compound dissolves.
Why is water known as the universal solvent?
This is because it dissolves more substances than any other liquid.
Why is it it useful for water to be the universal solvent?
1.Most biological reactions take place in solution - e.g. in the cytoplasm of eukaryotes and prokaryotes
2.Dissolved substances can be transported around the body - e.g. ions can be transported in the blood plasma
How does water act as a temperature buffer?
Because water has such a high specific heat capacity and the hydrogen bonds can absorb a lot of energy before breaking. it is resistant to rapid changes in temperature. this allows the body to remain a fairly stable temperature.
How does water act as a cooling mechanism?
As water has a high latent heat of vaporisation a lot of energy is required to break the hydrogen bonds to change it from a liquid to gas. this means that organisms can cool themselves off through the evaporation of water off the skin without loosing too much water in the system.
How does water act as a habitat?
Since water has a high SHC and LHV it does not change temperature or evaporate very easily making a stable environment for many organisms to work in. when ice freezes the water molecules are held further apart making it less dense causing it to float. this means that organisms can still live under the ice. such as in the artic.
How does water act as a Metabolite?
Water in involved in many chemical reactions inside organisms.
These reactions include Hydrolysis reactions - These use water to break down complex molecules.
Condensation reactions - These release water to join molecules together.
Photosynthesis - This uses water as a raw material.
How does water act as a transport medium?
Strong cohesion (tendency of water molecules to stick together), and adhesion (tendency of water molecules to stick to other things), helps water to flow through organisms, carrying substances along with it. such as in plats through the xylem in a continuous column.
How do water molecules react when they meet air?
they create a high surface tension. This forms a skin-like structure at the surface of the water which is strong enough to support small organisms such as pond-skaters.
What is an ion?
An atom with an electric charge
What is an inorganic ion?
An ion that does not contain carbon (with some exceptions)
What is a cation?
An ion with a positive charge
What is an anion
An ion with a negative charge
Role of Calcium Cation? (Ca2+)
- nerve impulse transmission
- muscle contraction
- cofactor for enzymes
Role of sodium cation? (Na+)
- generating nerve impulses
- muscle contraction
- co- transport of glucose and amino acids
Role of Potassium cation? (K+)
- generating nerve impulses
- muscle contraction
- Regulating fluid balance
Role of hydrogen cation? (H+)
- Determines pH of solutions
- used in photosynthesis reactions
Role of Ammonium Cation (NH4+)
- source of nitrogen in plants
Role of iron Cation? (Fe2+)
- bind to oxygen within haemoglobin
Role of Chloride Anion (Cl-)
- Maintains blood pH in gas exchange
- Cofactor for amylase enzyme
Role of phosphate anion? (PO4-3)
- component of nucleotides and phospholipids
- bonds store energy in ATP
Role of hydroxide anion? (OH-)
- Determines the pH of solutions
Role of nitrate anion? (NO3-)1
- source of nitrogen
Role of Hydrogencarbonate anion? (HCO3-)
- Maintains blood pH
What is maltose made up of?
glucose bonded to glucose
What is sucrose made up of?
glucose bonded to fructose.
What is lactose made up of?
glucose bonded to galactose
