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Biology AS chapter 7
Biological molecules
| Question | Answer |
|---|---|
| What is a metabolic reaction? | The chemical reactions that take place in living organisms |
| What is water? | Two hydrogen atoms covalently bonded to one oxygen atom |
| Is the oxygen atom slightly negative or positive? | Slightly NEGATIVE |
| What charge to hydrogen atoms have in water? | Slightly POSITIVE |
| What is ice? | Water molecules in a rigid lattice formation |
| What is temperature? | Temperature relates to the amount of kinetic energy that the water molecules have |
| Why does water have a high specific heat capacity? | A lot of energy is required to break the hydrogen bonds between the water molecules, therefore little energy is left over to raise the temperature |
| Why is the high specific heat capacity of water good in the body? | The body will not change temperature quickly |
| What is the latent heat of evaporation? | The heat needed to evaporate sweat |
| What is dissolving? | Tiny charges on water molecules attract other molecules or ions that have charges on them. The molecules and ions spread around in between the water molecules. |
| What happens when NaCl dissolves in water? | The sodium and chloride ions become separated from each other. This makes it easy for them to react with other ions/ molcules. |
| Where does water flow? | In blood/ xylem vessels/ phloem sieve tubes of a plant |
| What is urea? | The main nitrogenous excretory product of mammals |
| Why is water relatively dense? | Because of the hydrogen bonds between the water molecules |
| What is the density of pure water? | 1.0 grams per cubic centimetre |
| How can aquatic organisms slightly change their average density to enable them to swim? | By filling or emptying parts of their body with air, to help them float or sink |
| What is the viscosity of water? | We say that water is a fairly viscous liquid |
| What is cohesion? | How water molecules tend to stick to each other |
| What are the groups in an amino acid? | Central carbon atom. One carboxyl group, -COOH. On hydrogen atom. One amino group, -NH2. R group. |
| How many different amino acids are there in humans? | 20 |
| When are the amino acids that make up a protein linked together? | During protein synthesis |
| Where does protein synthesis occur? | On the ribosomes in a cell |
| How to amino acids link? | Amino acids are brought close to each other , and react together to form a linkage between them called a peptide bond |
| What bonds to peptide bonds have? | Covalent bonds (so they are strong) |
| What happens when the peptide bond forms? | Two hydrogen atoms from one amino acid and one oxygen atom from another amino acid join together to form a water molecule |
| What is the reaction called when water is formed and released? | Condensation reactions |
| On a ribosome, a long chain of amino acids is formed, linked together by which bond? | A peptide bond |
| What is a long chain of amino acids called? | A polypeptide |
| Proteins molecules chontain one or more chains of what? | Polypeptides |
| How many polypeptides does haemoglobin contain and in what formation? | Haemoglobin contains 4 polypeptides all coiled up with each other |
| How can polypeptides be broken down? | By breaking their peptide bonds |
| Give an example of when polypeptides are broken down | When protein molecules are digested in the stomach with protease enzymes |
| Describe hydrolysis, in reference to breaking down a polypeptide | Combination with a water molecule breaks the peptide bonds between two amino acids and separates them |
| Name 3 different amino acids beginning with V,L and C | Valine, Leucine and Cysteine |
| What is the primary structure? | The sequence of amino acids linked together in a polypeptide or protein |
| Do polypeptide chains usually lie straight? | No! |
| What is an alpha-helix? | A coil in a protein |
| What makes the secondary structure? | Alpha-helixes and Beta-folds |
| How is the shape of alpha-helixes and beta-folds maintained? | By hydrogen bonds that form between different amino acids in the chain |
| What is a hydrogen bond? | It is an attraction between an atom with a very small negative charge and another atom with a very small positive charge |
| Where do the hydrogen bonds form in an alpha helix in a polypeptide? | They form between the oxygen of the -CO group of one amino acid (very small negative charge) and the hydrogen of the -NH2 group (very small positive charge)of the amino acids four places ahead of it in the chain |
| Are hydrogen bonds as strong as the covalent bonds in peptide bonds? | No! |
| Do hydrogen bonds involve sharing electrons? | No! |
| How large are the charges that attract one another in hydrogen bonding? | Relatively small |
| What is the tertiary structure? | The chain can fold itself even more than alpha helixes/ beta-folds. The overall shape is the tertiary structure |
| What types of bonds hold the tertiary structure? | Hydrogen bonds, disulfide bonds, ionic bonds and hydrophobic interactions |
| In the structure of haemoglobin, each polypeptide chain winds itself around what type group of atoms? | A group of atoms with an iron ion at the centre |
| What is the name of the group of atoms with an iron ion at the centre? | The haem group |
| How many haem groups are there in a haemoglobin? | 4 |
| How many oxygen atoms can a haem group carry? | 2 |
| What is a globular protein? | A polypeptide chain curled up into a ball |
| Give an example of a globular protein | An enzyme |
| What is the name of a long, thin protein? | A fibrous protein |
| Give an example of a fibrous protein | Collagen |
| The tertiary shape of the protein determines what? | The function of the molecule |
| The places in which the different kinds of bonds can form are determined by what? | The amino acid sequence in the protein- its primary structure |
| A change in a single amino acid can have an effect on what? | The protein's tertiary structure and its ability to function |
| Where does an ionic bond form in a protein? | Between an R group with a full negative charge and one with a full positive charge |
| Is an ionic bond stronger or weaker than a hydrogen bond? | Much stronger |
| How can an ionic bond be broken down? | By changes in pH |
| What is a hydrogen bond? | A bond between a group with a slight negative charge and one with a slight positive charge |
| Is a hydrogen bond strong? | Not very strong |
| How is a hydrogen bond broken down? | High temperatures/ changes in pH |
| Where do disulfide bonds form? | Between the R groups of the amino acid cysteine |
| What are disulfide bonds? | They are strong covalent bonds |
| How can disulfide bonds be broken down? | By reducing agents |
| What are disulfide bonds important for? | For holding together the different polypeptide chains in the quaternary structure |
| True or false: R groups which contain only carbon and hydrogen atoms are hydrophillic | False- R groups with contain only carbon and hydrogen atoms are hydrophobic |
| Water is nearly always present around a protein and in between its chains, therefore hydrophobic R groups tend to be found where? | Hydrophobic R groups tend to be found together |
| The slight attraction between the hydrophobic bond is a .... bond | A weak bond |
| Four polypeptide chains in haemoglobin make what type of structure? | The quaternary structure |
| What bonds hold the quaternary structure | Same as the tertiary structure- ionic, hydrogen, disulfide and hydrophobic |
| Is haemoglobin soluble or insoluble in water? | Soluble |
| Where is haemoglobin found? | In the cytoplasm of red blood cells |
| The places in which the different kinds of bonds can form are determined by what? | The amino acid sequence in the protein- its primary structure |
| A change in a single amino acid can have an effect on what? | The protein's tertiary structure and its ability to function |
| Where does an ionic bond form in a protein? | Between an R group with a full negative charge and one with a full positive charge |
| Is an ionic bond stronger or weaker than a hydrogen bond? | Much stronger |
| How can an ionic bond be broken down? | By changes in pH |
| What is a hydrogen bond? | A bond between a group with a slight negative charge and one with a slight positive charge |
| Is a hydrogen bond strong? | Not very strong |
| How is a hydrogen bond broken down? | High temperatures/ changes in pH |
| Where do disulfide bonds form? | Between the R groups of the amino acid cysteine |
| What are disulfide bonds? | They are strong covalent bonds |
| How can disulfide bonds be broken down? | By reducing agents |
| What are disulfide bonds important for? | For holding together the different polypeptide chains in the quaternary structure |
| True or false: R groups which contain only carbon and hydrogen atoms are hydrophillic | False- R groups with contain only carbon and hydrogen atoms are hydrophobic |
| Water is nearly always present around a protein and in between its chains, therefore hydrophobic R groups tend to be found where? | Hydrophobic R groups tend to be found together |
| The slight attraction between the hydrophobic bond is a .... bond | A weak bond |
| Four polypeptide chains in haemoglobin make what type of structure? | The quaternary structure |
| What bonds hold the quaternary structure | Same as the tertiary structure- ionic, hydrogen, disulfide and hydrophobic |
| Is haemoglobin soluble or insoluble in water? | Soluble |
| Where is haemoglobin found? | In the cytoplasm of red blood cells |
| The places in which the different kinds of bonds can form are determined by what? | The amino acid sequence in the protein- its primary structure |
| A change in a single amino acid can have an effect on what? | The protein's tertiary structure and its ability to function |
| Where does an ionic bond form in a protein? | Between an R group with a full negative charge and one with a full positive charge |
| Is an ionic bond stronger or weaker than a hydrogen bond? | Much stronger |
| How can an ionic bond be broken down? | By changes in pH |
| What is a hydrogen bond? | A bond between a group with a slight negative charge and one with a slight positive charge |
| Is a hydrogen bond strong? | Not very strong |
| How is a hydrogen bond broken down? | High temperatures/ changes in pH |
| Where do disulfide bonds form? | Between the R groups of the amino acid cysteine |
| What are disulfide bonds? | They are strong covalent bonds |
| How can disulfide bonds be broken down? | By reducing agents |
| What are disulfide bonds important for? | For holding together the different polypeptide chains in the quaternary structure |
| True or false: R groups which contain only carbon and hydrogen atoms are hydrophillic | False- R groups with contain only carbon and hydrogen atoms are hydrophobic |
| Water is nearly always present around a protein and in between its chains, therefore hydrophobic R groups tend to be found where? | Hydrophobic R groups tend to be found together |
| The slight attraction between the hydrophobic bond is a .... bond | A weak bond |
| Four polypeptide chains in haemoglobin make what type of structure? | The quaternary structure |
| What bonds hold the quaternary structure | Same as the tertiary structure- ionic, hydrogen, disulfide and hydrophobic |
| Is haemoglobin soluble or insoluble in water? | Soluble |
| Where is haemoglobin found? | In the cytoplasm of red blood cells |
| What type of protein is collagen? | A fibrous protein |
| Where is collagen found? | In skin, tendons, cartilage, bones, teeth and the walls of blood vessels |
| Collagen consists of how many polypeptide chains? | 3 polypeptide chains |
| The three helical polepeptides in collagen form what shape? | They wind around each other to form a rope shape |
| Almost every third amino acid in each polypeptide in collagen is what? | Glycine- the smallest amino acid |
| The three strands in collagen is held together by which bond? | Hydrogen bonds |
| Each complete, three-stranded molecule of collagen interacts with other collagen molecules running ........ to it | parallel |
| In between collagen molecules, which bonds form? | Bonds form between the R groups of lysines in molecules lying next to each other |
| What are fibrils? | Many collagen molecules lying side by side |
| The ends of the parallel molecules are what? | Staggered- if they were not, there would be a weak spot running right across the collagen fibril |
| What are fibres? | Fibrils associate to form bundles called fibres |
| Collagen has what type of strength? | A tremendous tensile strength |
| What is tensile strength? | How something can resist strong pulling forces |
| Examples of globular proteins | Haemoglobin, enzymes, antibodies, transfporters in membranes, some hormones such as insulin |
| The primary structure of globular proteins | Very precise, usually made up of a non-repeating sequence of amino acids forming a chain that is always the same length |
| The solubility of globular proteins | Often soluble in water |
| The functions of globular proteins | Usually metabolically active, taking part in chemical reactions in and around cells |
| Examples of fibrous proteins | Collagen, keratin, elastin |
| The primary structure of fibrous proteins | Often made of a repeating sequence of amino acids, and the chain can be of varying length |
| Solubility of fibrous proteins | Insoluble |
| Functions of fibrous proteins | Usually metabolically UNreactive, with a structural role |
| What is an example of a globular proteins that is insoluble in water? | Transporter molecules that are found in cell membranes |
| Do fibrous proteins have a variable structure? | YES! |
| Do globular proteins have a variable structure? | Noooo |
| Fibrous proteins have a ....range of amino acids | A limited range |
| What type of role do fibrous proteins usually have? | A structural role |
| What does keratin form? | Hair, nails and the upper layers of skin |
| The soluble globular protein fibrinogen, found in blood plasma, is converted to what? | Into insoluble fibrous protein fibrin when a blood vessel is damaged |
| When wounded, what do fibrin fibres do? | Fibrin fibres form a network across the wound, in which platelets can be trapped to form a blood clot |
| What does the molecule need to be to be soluble in water? | Not too large and also have groups with an electrical charge on the outside of the molecule |
| In globular proteins, what happens when polypeptide chains fold? | The R groups carrying charges are on the OUTSIDE of the molecule, and the R groups without charges are on the INSIDE |
| Fibrous proteins are too ..... to be ...... in water | Fibrous proteins are too large to be soluble in water |
| What units make up carbohydrates? | Sugar units |
| What is the general formula for a sugar unit? | CnH2nOn |
| Examples of carbohydrates | Sugars, starches, cellulose |
| Examples of polysaccharides | Starches and cellulose- insoluble in water, do not taste sweet |
| Monosaccharide | A carbohydrate whose molecules contain just one sugar unit |
| Examples of monosaccharides | Glucose, fructose and galactose |
| What is the main respiratory substrate in cells, providing energy when it is oxidised? | Glucose |
| How many carbon atoms are there in glucose? | 6, so it is called a HEXOSE |
| What are the two forms of glucose molecules? | Alpha and beta glucose |
| Dissaccharide | Two monosaccharide molecules can link together to form a sugar called a disaccharide |
| Maltose | 2 alpha glucose molecules |
| What is the reaction when two alpha glucose molecules react? | A condensation reaction |
| Where is a glycosidic bond? | The linkage between two monosaccharides |
| What type of bond is in a glycosidic bond? | Covalent bonds, which are very strong |
| Disaccharides are soluble in ... | water |
| Where is the glycosidic bond in maltose? | Between carbon 1 and 4 |
| A glycosidic bond between alpha molecules is called a... | alpha n-n glycosidic bond |
| What is the enzyme called that breaks down maltose? | Maltase |
| What is the reaction called when enzymes break down maltase? | A hydrolysis reaction |
| What is the carbohydrate amylose? | Thousands of alpha glucose molecules linked together by 1-4 glycosidic bonds |
| Where is amylose found? | Starch |
| Is starch soluble or insoluble? | Insoluble and metabolically inactive, therefore it does not interfere with chemical reactions inside the cell, nor does it affect the water potential |
| Amylose molecules coil to form what shape? | A long spiral |
| How is the coil in amylose held in place? | By hydrogen bonds |
| What is cellulose? | A polysaccharide made of thousands of glucose molecules |
| How does cellulose differ from starch? | Cellulose is made of beta-glucose molecules; starch is made of alpha-glucose molecules |
| What bonds does cellulose have? | Beta 1-4 glycosidic bonds |
| Do cellulose molecules lie straight or coil? | They lie straight |
| Where do cellulose molecules form hydrogen bonds? | With the neighbour cellulose molecule |
| Bundles of cellulose molecules are called what? | Fibrils |
| Larger bundles of fibrils form what? | Fibres |
| What polysaccharides to plants contain? | Amylose (starch) and cellulose |
| What polysaccharide do animals have? | Glycogen |
| The structure of glycogen is similar to what? | Amylose |
| What type of glucose molecules is glycogen made up of? | Alpha glucose molecules linked by 1-4 glycosidic bonds |
| How does glycogen differ from amylose? | It has branches, where 1-6 glycosidic bonds are formed |
| How to branches affect the structure of glycogen? | It makes it more difficult for glycogen molecules to form helices, so they are not as tightly coiled as starch molecules |
| Where are glycogen stores found? | In the liver and in the muscles |
| How can glycogen turn to glucose? | By the enzyme glycogen phosphorylase, which is activated by insulin when blood glucose levels are low |
| What are lipids made of? | Carbon, hydrogen and oxygen |
| What do lipids have more of than carbohydrates? | Lipids have a higher proportion of hydrogen than carbohydrates |
| Are lipids soluble or insoluble in water? | Insoluble in water |
| What are triglycerides made of? | Three fatty acids attached to a glycerol molecule |
| What is the functional group in a fatty acid? | -COOH |
| The carboxyl groups of fatty acids are able to react with what group of glycerol? | The -OH (hydroxyl) group |
| What is the bond called between the fatty acid and the glycerol molecule? | An ester bond |
| What makes ester bonds strong? | They have covalent bonds |
| What is the reaction called when a fatty acid bonds with a glycerol molecule? | A condensation reaction |
| What is the reaction called when you break an ester bond? | A hydrolysis reaction |
| Are triglycerides soluble in water? | No! |
| Why are triglycerides insoluble in water? | None of their atoms carry an electrical charge, and so they are not attracted to water molecules |
| A diet rich in saturated fats may increase what in the blood? | Cholesterol |
| What is a saturated fat? | A saturated fat is one in which the fatty acids all contain as much hydrogen as possible. Each carbon atom in the fatty acid 'tail' is linked to its neighbouring carbon atoms by single bonds |
| What is an unsaturated fat? | An unsaturated fat has one or more fatty acids in which at least one carbon atom is using two of its bonds to link to the neighbouring carbon atom. The double bond forms a 'kink' in the chain |
| Are triglycerides rich or low in energy? | They are rich in energy, and so they are often used as energy stores in living organisms |
| Describe adipose tissue | The cells are filled with globules of triglycerides, and they make very good thermal insulators |
| Which animals have thick layers of adipose tissue under the skin? | Animals that live in cold environments such as whales and polar bears |
| What vitamins are stored in triglycerides? | Fat-soluble vitamins, especially vitamin D and A |
| What is a phospholipid | A phospholipid is like a triglyceride in which one of the fatty acids is replaced by a phosphate group |
| The fatty acid tails of phospholipid are... | HYDROPHOBIC |
| The phosphate heads in a phospholipid are... | HYDROPHILIC- they are attracted to water molecules, because the phosphate group has a negative electrical charge |
| What happens to the phospholipid molecules in water? | The phosphate is drawn towards the water molecules and dissolves in them. The fatty acids are repelled by water molecules and avoid them. |
| What group is cholesterol part of ? | Lipids |
| What are steroids? | Cholesterol and other substances with similar structures |
Created by:
LaurenJeffers
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