deck_5661103 Flashcards
What is a condensation reaction?
When two molecules are joined together with the removal of water
What is a hydrolysis reaction?
When a molecule is split into two smaller molecules with the addition of water
How do almost all condensation reactions happen?
When two -OH groups react together-this reaction involves the breaking and formation of covalent bonds
In condensation reactions, what molecules are joined together?
Monomers
What if formed when lots of monomers join together?
Polymers
What do carbohydrates contain?
Carbon, hydrogen and oxygen. The monomer is a monosaccharide and the polymer is a polusaccharide
What do proteins contain?
Carbon, hydrogen, oxygen, nitrogen and sulfur. The monomer is amino acids and the polymer is polypeptides and proteins
What do nucleic acids contain?
Carbon, hydrogen, oxygen, nitrogen and phosphorus. The monomer is nucleotides and the polymer is DNA and RNA
What does water consist of?
Two hydrogen atoms covalently bonded to one oxygen atom, however the oxygen atom has a greater number of protons in it’s nucleus which exerts a stronger attraction for the shared electrons, so the oxygen atom becomes slightly negative and the hydrogen become slightly positive, the molecule is polar
What is a hydrogen bond?
A weak interaction which happens wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom. It is weaker than a covalent bond however some polymers have thousands of hydrogen bonds that form between chains of monomers, helping stabilise the structure of some biological molecules
How are hydrogen bonds represented in diagrams?
With a dotted line
What are the properties of water?
Latent heat of evaporation, density, transparent, dipolar, surface tension, incompressibility, temperature, specific heat, viscosity, solvent, metabolic, capillarity and state
What is latent heat of evaporation?
Water molecules absorb heat energy from surfaces as they evaporate, cooling them down eg sweating and transpiration
What is density?
Water supports aquatic organisms. Ice floats on water allowing organisms to survive below it in liquid. Polar bears live in an environment of floating ice planks
What is transparent?
Allows the transmission of light eg photosynthesis in aquatic organisms
What is dipolar?
Has positive and negative charges
What is surface tension?
Water has a strong surface film allowing small organisms to be supported on or in it
What is incompressibility?
Provides a hydrostatic skeleton with a surrounding strong wall provides support and protection eg earthworm body cavity, human abdomen and plant cells
What is temperature?
Carries away heat energy when it evaporates from a surface. This cools the surface and helps to lower the temperature
What is specific heat?
High specific heat so gains and loses heat slowly, good for temperature control of aquatic environments
What is viscosity?
Allows free flow for transport of materials inside and outside the organisms
What is solvent?
Universal solvent to dissolve many substances
What is metabolic?
Water takes part as a reactant in some chemical processes-hydrolysis and photosynthesis
What is capillarity?
Water rises in small tubes against gravity because polar molecules are attracted to themselves and to surfaces, useful in plants eg xylem and phloem
What is state?
Solid at 0ºc and vapour above 100ºc provides a wide temperature range as a liquid
What are ‘hydrated carbon’?
For every carbon there are two hydrogen atoms and one oxygen atom. Carbohydrates are hydrated carbon
What are the functions of carbohydrates?
They act as a source of energy (glucose), as a store of energy (starch/glycogen) and as structural units (cellulose in plants and chitin in insects). Some are also part of other molecules such as nucleic acids and glycolipids
What are the three main groups of carbohydrates?
Monosaccharides, disaccharides and polysaccharides (common monosaccharides and disaccharides all have names ending in -ose)
What are monosaccharides?
They are the simplest carbohydrates and are particularly important in living things as a source of energy
How are monosaccharides well suited to their role?
Because they have a large number of carbon-hydrogen bonds
What are the properties of monosaccharides?
They are sugars, which taste sweet, are soluble in water and are insoluble in non-polar solvents
What is the structure of monosaccharides?
They can exist as straight chains or in ring/cyclic forms. They have a backbone of single bonded carbon atoms, with one double-bonded to an oxygen atom to form a carbonyl group
What are the different sugars with different numbers of carbon atoms?
Hexose sugars have six carbon atoms, pentose sugars have five carbon atoms and triose sugars have three carbon atoms
What is an example of a monosaccharide hexose sugar?
Glucose, these types are the monomers of more complex carbohydrates, and they bond together to form disaccharides or polysaccharides
What are triose and tetrose sugars like in solution?
They exist as straight chains
What form are pentoses and hexoses more likely to be found as?
Ring or cyclic form
What are isomers?
Molecules with the same formula, but whose atoms are arranged differently, glucose in both forms can exist as a number of different isomers
How are isomers formed in straight chains?
The -H and -OH can be reversed
How is the ring shape formed?
When the oxygen attached to carbon 5 bonds to carbon 1. Because the -OH and -H on carbon 1 can be above or below, there are two isomers (a- and b-glucose), the small difference seems insignificant but becomes very important when glucose polymerises into starch or cellulose
What are the properties of disaccharides?
They are sweet and soluble
What are the most common disaccharides?
Maltose and lactose with are reducing sugars, and sucrose which is a non reducing sugar
How are disaccharides made?
When two monosaccharides join together
What is a-glucose plus a-glucose?
Maltose
What is a-glucose plus fructose?
Sucrose
What is b-glucose plus a-glucose?
Lactose
What is b-glucose plus b-glucose?
Cellobiose
What happens when the monosaccharides join?
A condensation reaction occurs to form a glycosidic bond. Two hydroxyl groups line up next to each other, from which a water molecule is removed, leaving an oxygen atom acting as a link between the two monosaccharide units
How are disaccharides broken into monosaccharides?
By a hydrolysis reaction which requires the addition of water. The water provides a hydroxyl group -OH and a hydrogen -H which help the glycosidic bond to break eg cellobiose is obtained by the hydrolysis of cellulose
Explain a-glucose
All -H’s are above the C, except for at C3. Molecular formula is C6H12O6. It is an energy source/component of starch/glycogen which acts as energy stores. It is a hexose sugar
Explain b-glucose
-OH are above at carob 1 and 3. Molecular formula is C6H12O6. It is an energy source/component of cellulose with provides structural support in plant cell walls. It is a hexose sugar
Explain ribose
Molecular formula is C5H10O5. It is a component of RNA, ATP and NAD. It is a pentose sugar
Explain deoxyribose
Molecular formula is C5H10O4. It is a component of DNA. It is a pentose sugar
What are polysaccharides?
Polymers of monosaccharides made of hundreds/thousands of monosaccharides bonded together
What are homopolysaccharides?
Polysaccharides made solely of one kind of monosaccharide
What are heteropolysaccharides?
Polysaccharides made up of more than one monomer
What is an example of a homopolysaccharide?
Starch
What is an example of a heteropolysaccharide?
Hyaluronic acid
Why is glucose a source of energy?
It is a reactant in respiration. The energy released is used to make ATP, which is the energy currency of the cell
How can you create a store of energy?
By joining lots of glucose molecules together into polysaccharides, this is what living things do
How do plants store energy?
As starch in chloroplasts and in membrane bound starch grains
How do humans store energy?
As glycogen in cells of the muscles and liver
Why are glycogen and starch (amylose and amylopectin) good energy stores?
They are compact so they don’t occupy a large amount of space. They both occur in dense granules within the cell
Why do polysaccharides hold glucose molecules in chains?
So they can be easily ‘snipped off’ from the end of the chain by hydrolysis when required for respiration. Hydrolysis reactions are always catalysed by enzymes
What are amylose chains like?
Unbranched
What are amylopectin and glycogen chains like?
Branched
What are branched chains?
They are more compact but also offer the chance for lots of glucose molecules to be snipped off by hydrolysis at the same time, when lots of energy is required quickly
What is amylase?
The enzyme responsible for hydrolysing 1-4 glycosidic linkages. A 1-4 glycosidic linkage is one between carbon 1 and of one glucose and carbon 4 of the other
Why is it good that polysaccharides are less soluble in water than monosaccharides?
If many glucose molecules did dissolve in the cytoplasm, the water potential would reduce, and excess water would diffuse in, disrupting the normal workings of the cell
Why are polysaccharides less soluble?
Because of their size, and also because regions which could hydrogen bond with water are hidden away inside the molecule
What happens if the amylose molecule forms a double helix?
It presents a hydrophobic external surface in contact with the surrounding surface
What is amylose?
(In plants) The molecule is a long chain of a-glucose molecules. Like maltose, it has glycosidic bonds between carbons 1 and 4
What is the detailed structure of amylose?
Coils into a spiral shape, with hydrogen bonds holding the spiral in place. Hydroxyl groups on carbon 2 are situated on the inside of the coil, making the molecule less soluble and allowing hydrogen bonds to form to maintain the coil’s structure
What is amylopectin?
(In pants) Has glycosidic bonds between carbons 1 and 4 but also has branches formed by glycosidic bonds between carbon 1 and 6
What is the detailed structure of amylopectin?
Coils into a spiral shape, held together with hydrogen bonds, but with branches emerging from the spiral
What is glycogen?
(In animals) Has glycosidic bonds between carbon 1 and 4, and branches formed by glycosidic bonds between carbon 1 and 6
What is the detailed structure of glycogen?
The 1-4 bonded chains tend to be smaller than in amylopectin, so glycogen has less tendency to coil, however, it does have more branches, which makes it more compact. And it is easier to remove monomer units as there are more ends
What is cellulose?
Found in plants, form cell walls, tough, insoluble, fibrous, homopolysaccharide of b-glucose bonded through condensation reaction forming glycosidic bonds
What form are cellulose chains?
Straight and lie side by side. This different structure is a direct result of bonding
What happens to the hydrogen and hydroxyl group on carbon 1 in b-glucose?
They are inverted, meaning every other b-glucose molecule in the chain is rotated by 180º, and the b-1-4 glycosidic bond help to prevent the chain spiralling
What do the hydrogen bonds do?
They are between the rotated b-molecules in each chain and gives the chain additional strength and stops it spiralling
What does the hydroxyl group on carbon 2 sticking out enable?
Hydrogen bonds to be formed between chains
What happens when 60-70 cellulose chains are bound together in this way?
They form microfibrils, which bundle together into macrofibrils containing up to 400 microfibrils which are embedded in pectins to form plant cell walls. Macrofibrils run in all directions criss-crossing the wall for extra strength
What is the structure of cellulose chains from biggest to smallest?
Cellulose fibres, macrofibrils, microfibrils, chains of cellulose molecules
Why is cellulose an excellent material for plant cell walls?
Micro and macrofibrils have very high tensile strength due to glycosidic bonds and hydrogen bonds between chains. Macrofibrils criss cross in all directions for extra strength. It is difficult to digest cellulose due to glycosidic bonds which are less easy to break and most animals don’t have the enzyme to catalyse the reaction
What are the key features that help the plant cell wall to do it’s job?
Plants don’t have a rigid skeleton so each cell needs strength to support whole plant, space between macrofibrils for water/mineral ions to pass in/out of the cell making the wall fully permeable, wall has high tensile strength preventing cells from bursting, macrofibril structure can be reinforced with other substances for extra support eg Lignin in xylem vessles
How has the structural strength of cellulose been exploited by humans?
Cotton is 90% cellulose. Cellophane and celluloid are derived from cellulose. Cellulose is a main component in paper. Rayon is produced from cellulose
What are bacterial cell walls?
They aren’t made of cellulose. The whole structure surrounding the cell is called a peptidoglycan made from long polysaccharide chains that lie in parallel, cross linked by short peptide chains made of amino acids
What are exoskeletons?
Insect and crustacean exoskeletons are made of chitin. Differs from cellulose as has a acetylamino group instead of a hydroxyl group on carbon 2. It forms crosslinks between long parallel chains of acetylglucosamine, in a similar way to cellulose
What are lipids?
Contain large amounts of carbon and hydrogen, and smaller amounts of oxygen. Insoluble in water as they aren’t polar so don’t attract water molecules. Dissolve in alcohol
What are the three most important lipids in living things?
Triglycerides, phospholipids and steroids. They aren’t polymers but do have different components bounded together, they are examples of macromolecules
What are triglycerides made up of?
Glycerol and fatty acids. Many different types of fatty acid and many can be made in human bodies but some have to be ingested ‘complete’, called essential fatty acids
What is glycerol?
It has three carbon atoms, it is an alcohol which means it has free -OH groups. There are three –OH groups which are important to the structure of triglycerides
What are fatty acids?
They have a carboxyl group on one end, attached to a hydrocarbon tail made of only carbon and hydrogen atoms. This can be 2-20 carbons long. The carboxyl group ionises into H+ and -COO- group. This structure is therefore an acid as it can produce free H+ ions
What are saturated fatty acids?
No c=c bonds in the molecule
What are unsaturated fatty acids?
Contain a double bond between two of the carbon atoms so fewer hydrogen atoms can be bonded to the molecule
What does a single c=c bond do?
Makes a fatty acid monounsaturated
What does more than one c=c bond do?
Makes a fatty acid polyunsaturated
What happens to the hydrocarbon chain if there is more than one c=c bond?
It changes shape, giving it a kink where the double bond is, which push the molecules apart slightly making them more fluid
What sort of fatty acids do animal lipids contain?
Lots off saturated fatty acids which are often solid at 20ºc. Unsaturated fatty acids have a lower melting point
What is an ester bond?
When a condensation reactions bonds together one glycerol molecule and three fatty acids
What are the functions of triglycerides?
Energy source, energy store, insulation, buoyancy and protection
How are triglycerides used as an energy source?
can be broken down in respiration to release energy and generate ATP
How are triglycerides an energy store?
Insoluble in water so they can be stored without affecting the water potential of the cell
How are triglycerides used for insulation?
Adipose tissue is a storage location for lipid in whales, acting as a large insulator. Lipid in nerve cells acts as an electrical insulator. Animals preparing for hibernation store extra fat
How are triglycerides used for buoyancy?
Fat is less dense than water, it is used by aquatic mammals to help them stay afloat
How are triglycerides used for protection?
Humans have fat around delicate organs such as the kidneys, to act as a shock absorber. The peptidoglycan cell wall of some bacteria is covered in a lipid-rich outer coat
What is the structure of phospholipids?
Same structure as triglycerides except one of the fatty acids is replaced by a phosphate group.
What are phospholipids behaviour in water?
The phosphate group has a negative charge making it polar but the fatty acid tails are non polar. Hydrophilic head and hydrophobic tail, making the phospholipid amphipathic
What different properties do amphipathic phospholipids have in water?
They may form a layer on the surface of the water with heads in the water and tails sticking up out of the water. They may also form micelles (tiny balls with the tails tucked inside and heads pointing outwards into the water)
What are amphipathic phospholipids good at forming membranes around cells and organelles?
Inside and outside a cell membrane is an aqueous solution, the phospholipids form a bilayer with tails in and heads out. The individual phospholipids can move but the tails are never exposed, giving the membrane some stability
What does it mean, that the membrane is selectively (partially) permeable?
It is only possible for small and non-polar molecules to move through the tails in the bilayer, such as oxygen and carbon dioxide, letting the membrane control what goes in and out of the cell, and keeps it functioning properly
What is cholesterol?
A steroid alcohol or type of lipid which is not made from glycerol or fatty acids. It consists of four carbon-based rings. it is small and hydrophobic so can sit in the middle of the phospholipid bilayer and regulate the fluidity of the membrane
Where is cholesterol found?
Mainly in the liver in animal cells, plants however also have a cholesterol derivative in their membranes which is different due to a double bond between carbon 22 and 23
What are some hormones made from cholesterol?
The steroid hormones testosterone, oestrogen and vitamin D. They are small and hydrophobic so can pass through the hydrophobic part of the membranes, these hormones are also abundant in plants, and on ingestion and absorption can be converted into animal hormones
What are proteins?
Large polymers comprised of long chains of amino acids
What are proteins functions?
Form structural components of animals in particular eg muscles. Their tendency to adopt specific shapes make proteins important as enzymes, antibodies and some hormones. Membranes have protein constituents that act as carriers and pores for active transport across the membrane and facilitated diffusion
How do animals get amino acids to make proteins?
They can make some but others must be ingested (essential amino acids)
How do plants get amino acids needed to make proteins?
They can make all the amino acids they need but only if they can access fixed nitrogen such as nitrate
What does each amino acid contain?
The elements carbon, hydrogen, oxygen and nitrogen. Some amino acids also contain sulfur
How many amino acids are there?
Over 500, but only 20 of them are proteinogenic (found in proteins)
What does each amino acid chain have?
An amino group (-NH2) at one end, and a carboxyl (-COOH) group at the other end. There is also an R group which is different in each amino acid
What do names of almost all amino acids end in?
-ine, except for those which have an acidic R group
How can R groups vary?
By size, charge, polarity and whether they are hydrophobic or hydrophilic
What is a peptide bond?
A bond formed when two amino acids are joined by a condensation reaction. Enzymes catalyse these reactions. Protease enzymes in intestines break down peptide bonds during digestion. They also break down protein hormones so that their effects are not permanent
What is a primary structure?
The sequence of amino acids found in a molecule
What is a secondary structure?
The coiling or folding of an amino acid chain, which arises often as a result of hydrogen bond formation between different parts of the chain. The main forms of secondary structure are the helix and the pleated sheet
What is a tertiary structure?
The overall three-dimensional shape of a protein molecule. Its shape arises due to interactions including hydrogen bonding, disulphide bridges , ionic bonds and hydrophobic interactions
What is a quaternary structure?
Protein structure where a protein consists of more than one polypeptide chain eg insulin has a quaternary structure
What are fibrous proteins?
Have regular, repetitive sequences of amino acids, and are usually insoluble in water. These features enable them to form fibres which tend to have a structural function
What are examples of fibrous proteins?
Keratin, elastin and collagen
What is keratin?
Rich in cysteine with lots of disulphide bridges between it’s polypeptide chains. Also hydrogen bonding makes the molecule very strong. Found wherever body parts need strength and hardness eg nails, hairs, claws, hooves, horns, scales, fur and feathers. It provides mechanical protection and an impermeable barrier to infection as it’s waterproof
What is elastin?
Cross-linking/coiling make structure strong. Found in living things where they need to stretch or adapt their shape as part of life processes eg skin stretched around bones and muscles, elastin in lungs lets them inflate and deflate, and helps blood vessels to stretch and recoil
What is collagen?
Provides mechanical strength. In the artery walls it prevents arteries bursting when withstanding high pressure from blood being pumped by the heart, and tendons are made of collagen and connect muscles to bones allowing them to pull on bonesq
What are globular proteins?
Tend to recoil into an almost spherical shape. Any hydrophobic R groups are turned inwards towards centre of molecule while hydrophilic groups are on the outside. Makes proteins water soluble as water molecules can easily cluster round and bind to them. Have specific shapes which help their roles as enzymes, hormones and haemoglobin
What are examples of globular proteins?
Insulin, haemoglobin and pepsin
What is insulin?
Made of two polypeptide chains, A chain beings with alpha helix and B chain ends with a beta pleat. Both fold into tertiary structure and join by disulphate links. Amino acids with hydrophilic R group are on outside making it water soluble. Insulin binds to glycoprotein receptors on outside of muscle and fat cells to increase uptake of glucose from blood and increase rate of consumption of glucose
What is haemoglobin?
Consists of four polypeptide subunits, two are a-chains and two are b-chains. It is a water-soluble globular protein
What is pepsin?
An enzyme that digests protein in the stomach. The enzyme is made of a single polypeptide chain of 327 amino acids, but folds into a symmetrical tertiary structure
What are examples of cations?
Calcium, Sodium, Potassium, Hydrogen and Ammonium
What is calcium?
Ca2+ Increases rigidity of bone, teeth and cartilage. Component of exoskeleton. Blood clotting and muscle contraction. Activator for enzymes. Regulates permeability of cell membranes. Cell wall development in plants
What is sodium?
Na+ Regulation of osmotic pressure, water levels and pH. Absorption of carbohydrates in intestine and water in kidney. Nervous transmission and muscle contraction. Constituent of vacuole
What is potassium?
K+ Control water levels and pH. Assists active transport across cell membrane. Synthesis of glycogen/protein and breakdown of glucose. Generates healthy leaves and flowers. Nervous transmission and muscle contraction. Component of vacuole
What is hydrogen?
H+ Photosynthesis/respiration. Transport of oxygen and carbon dioxide in blood. Regulation of blood pH
What is ammonium?
NH4+ Component of amino acids/proteins/vitamins/chlorophyll, some hormones, essential component of nucleic acids, maintenance of pH inhuman body, component of nitrogen cycle
What are examples of anions
Nitrate, hydrogencarbonate, chloride, phosphate and hydroxide
What is nitrate?
NO3- Component of amino acids/proteins/vitamins/chlorophyll. Component of nucleic acids. Some hormones. Component of nitrogen cycle
What is hydrogencarbonate?
HCO3- Regulation of blood pH. Transport of carbon dioxide into and out of blood
What is chloride?
Cl- Production of urine in kidney/maintaining water balance. Transport of carbon dioxide into and out of blood. Regulation of haemoglobin. Regulation of blood pH. Production of hydrochloric acid in stomach
What is phosphate?
PO43- Increases rigidity in bone, teeth and cartilage. Component of exoskeleton. Component of phospholipids, ATP, nucleic acids, enzymes. Regulation of blood pH. Root growth in plants
What is hydroxide?
OH- Regulation of blood pH
What is the test for starch?
Add iodine solution to a sample. If starch is present the colour changes from yellow/brown to blue/black
What is the test for reducing sugars?
Add glucose, water and Benedict’s solution in boiling water. Orange-red participate indicates a reducing sugar is present
What is the test for non-reducing sugars?
If reducing test is negative, boil with HCL, cool and neutralise with sodium carbonate solution then repeat Benedict’s test. On second test it should turn blue to orange/red
What is the test for proteins?
Add biuret reagent. If present then it will turn blue to lilac
What is the test for lipids?
Add ethanol, then pour into another test tube of water. White emulsion forms near top of water if there are lipids
