(P1) Topic 1- Biological Molecules

Question 1

1)what are biological molecules?
2)Covalent bonding?
3)ionic bonding?

Answer 1

1)Biological molecules are particular groups of chemicals found in living organisms. molecular biology
2) Covalent bonding - atoms share a pair of electrons. outer shell is filled and a more stable compound, (molecule) is formed.
3) ionic bonding electrostatic attraction between two positvely charged ions with opposite charges

Question 2

1)hydrogen bonding?
2)what happens to negative region of a polar molecule?
3)what type of bond is formed between two polar molecules?
4)what do monomers form?
5)what are most monomers made from?
6)Name 3 natural polymers?

Answer 2

1) electrons within a molecule are not evenly distributed but tend to spend more time at one position. This region is more negatively charged than the rest of the molecule. uneven distribution of charge=polarised, (polar molecule.)
2)
->negative region of one polarised molecule and the positively charged region of another attract each other.
3) ->weak electrostatic bond is formed between the two. bond is individually weak, collectively form important forces alter physical properties of molecules.

4) ->monomers (sub-units) link together to form long chains (polymers) by polymerisation.
5)monomers usually based on carbon. E.G: polythene and polyesters (industrially produced.)
6) ->polysaccharides, polypeptides and polynucleotides, naturally by living organisms.

Question 3

1)what is the basic sub unit of polysaccharides?
2) what is the basic sub unit of of polynucleotide?
3) what is the basic sub unit of of polypeptides?

Answer 3

1) ->basic sub-unit of a polysaccharide is a monosaccharide or single sugar (glucose.)
2) Polynucleotides are formed from mononucleotide sub-units.
3) Polypeptides are formed by linking together peptides that have amino acids as their basic sub-unit

Question 4

1)what are condensation reactions and 2 examples?

Answer 4

1)condensation polymerisation in organisms, each time a new sub-unit is attached a molecule of water is formed and formation of a chemical bond. E.G: formation of a polypeptide from amino acids. polysaccharide starch from the monosaccharide glucose

Question 5

1)what are hydrolysis reactions and two examples?
2)what is metabolism?

Answer 5

1) Water molecules are used when breaking the chemical bonds that link the sub-units splitting the molecule (polymer) into its constituent parts.
E.G: polypeptides can be hydrolysed into amino acids, starch can be hydrolysed into glucose.
2) ->metabolism= collectively all chemical processes that take place in living organisms

Question 6

1)what are moles?
2)what are molar solutions?
3)moles equation?

Answer 6

1) One mole contains the same number of particles as there are in 12 g of carbon-12
6.022 × 10^23 carbon atoms. Avogadro number.
2)solution that contains one mole of solute in each litre of solution.
3) mole is the molecular mass/weight expressed as grams (= one gram molecular mass).

Question 7

1)name three monosaccharides?

Answer 7

1) -Monosaccharides, amino acids and nucleotides are examples of monomers.

Question 8

1)what is the mass, location and charge of protons, neutrons and electrons?
2)what is the charge on the atom?
3)what is the atomic number?
4)what is the mass number?

Answer 8

1) • Neutrons - nucleus of an atom and same mass as protons but no electrical charge.
• Protons - nucleus of an atom and same mass as neutrons but do have a positive charge.
• Electrons - orbit in shells, small mass overall mass is negligible. negatively charged and their number determines the chemical properties of an atom.

2)
number of protons and electrons is the same and therefore there is no overall charge.

3)the atomic number - the number of protons in an atom
4)the mass number - the total number of protons and neutrons in an atom.

Question 9

1)what are isotopes?
2)Why do isotopes have the same chemical properties?
3)why do Isotopes have the different physical properties?
4)what are isotopes for?

Answer 9

1) number of protons in an element always remains the same, the number of neutrons can vary.
2) same chemical properties element have the same number of electrons as an atom of that element. electron arrangement=chemical properties.
3) different numbers of neutrons, which affects the mass number. Mass number determines the physical properties such as boiling/melting/density etc.
4) tracing the route of certain elements in biological processes and dating fossils.

Question 10

1)How does ions form and what are the charges?

Answer 10

1) atom loses or receives an electron it becomes an ion.
• loss electron= positive ion
• receiving electron= negative ion

Question 11

1)what are carbohydrates?

Answer 11

1)carbon molecules (carbo) combined with water (hydrate). small and large.

Question 12

1)What makes carbon such an important molecule? (2)
2)what does carbon attach to?

Answer 12

1)->readily form bonds with other carbon atoms. (allows a sequence of carbon atoms of lengths to be built.)
->form a ‘backbone’ along which other atoms can be attached. Allows large number of different types, sizes of molecule, all based on carbon.

2) relatively few other atoms that attach to carbon. Life is based small number of chemical elements.

Question 13

1)how are polymers made?
2)example of monomers? (3)

Answer 13

1) made up of a chain of individual molecules monomer.
2)Example monomers: monosaccharides, amino acids and nucleotides.

Question 14

1)what are most biological molecules made of?
2)what are carbohydrates monomers called?
3)what does a pair monosaccharides join to form and what do lots of monosaccharides join to form?
4)carbohydrate formula?
5)examples of 3 monosaccharides?
6)what is glucose?

Answer 14

1)carbon, hydrogen, oxygen and nitrogen.
2) monomer unit is sugar (sugar=saccharide.) monosaccharide soluble substances
3)disaccharides and polysaccharides
4) (CH2O)n where n can be any number from three to seven.
5) glucose, galactose and fructose.
6)Glucose is a hexose (6-carbon) sugar and formula C6H12O6

Question 15

1)describe the structure A and B glucose?

Answer 15

1)

Question 16

1)what are reducing sugars?
2)what is the name of a reducing sugar test?

Answer 16

1) monosaccharides and some disaccharides (e.g., maltose) are reducing sugars.
sugar that can donate electrons to (or reduce) another chemical, E.G: Benedict’s reagent.
2)Benedict’s test

Question 17

1)name all three monosaccharides?
2)name all three disaccharides?
3)name all three trisaccharides?

Answer 17

1)Monosaccharides- (one single unit of sugar)
glucose alpha, beta, galactose,fructose
2)Disaccharide- maltose (alpha and beta ), sucrose, lactose
3)Polysaccharides- starch, glucagon, cellulose

Question 18

1)mono?
2)di?
3)tri?
4)tetra?
5)penta?
6)hex?

Answer 18

1) 1
2) 2
3) 3
4) 4
5) 5
6) 6

Question 19

1)maltose is produced from?
2)sucrose is produced from?
3)lactose is produced from?

Answer 19

1)maltose is a disaccharide formed by condensation of two glucose molecules
2)sucrose is a disaccharide formed by condensation of a glucose molecule and a fructose molecule
3)lactose is a disaccharide formed by condensation of a glucose molecule and a galactose molecule.

Question 20

1)what is glycogen and starch formed from?
2)what is cellulose formed from?

Answer 20

1)Glycogen and starch are formed by the condensation of a-glucose.
2)Cellulose is formed by the condensation of B-glucose.

Question 21

1)what is Benedict’s reagent?
2)what are results of the Benedict test?
3)The three steps to Benedict test?

Answer 21

1) Benedict’s reagent is an alkaline solution of copper(I) sulfate.
2) reducing sugar is heated with Benedict’s reagent it forms an insoluble red precipitate of copper(I) oxide.
3)
2) reducing sugar is heated with Benedict’s reagent it forms an insoluble red precipitate of copper(I) oxide.
3)
1-Add 2 cm’ of the food sample to be tested to a test tube. grind it up in water.
2-Add an equal volume of Benedict’s reagent.
3-Heat the mixture in a gently boiling water bath for five minutes.

Question 22

1)what type of test is the Benedict’s test and why?
2)describe the colour results and what they mean?

Answer 22

1) differences in colour mean Benedict’s test is semi-quantitative, estimate the approximate amount of reducing sugar
2)

Question 23

1)what type of reaction forms disaccharides and what bond is formed?
2)describe a hydrolysis reaction?

Answer 23

1)
->monosaccharides join, a molecule of water is removed condensation reaction.
->bond that is formed is called a glycosidic bond.

2) ->water is added to a disaccharide under suitable conditions, breaks the glycosidic bond releasing the constituent monosaccharides.

Question 24

1)what must you do before you test for non reducing sugars and an example?

Answer 24

1)
->disaccharides, E.G sucrose non-reducing sugars
->to detect a non-reducing sugar hydrolysed into its monosaccharide components by hydrolysis

Question 25

1)describe the process of testing for non reducing sugars?

Answer 25

1- ground up in water to liquid form
2- Add 2 cm’ of the food sample being tested to 2 cm’ of Benedict’s reagent in a test tube and filter.
3-Place the test tube in a gently boiling water bath for 5 minutes. reagent does not change colour (remains blue), then a reducing sugar is not present.
4-Add another 2 cm° of the food sample to 2 cm° of dilute hydrochloric acid in a test tube and place the test tube in a gently boiling water bath for five minutes.
->dilute hydrochloric acid will hydrolyse any disaccharide present into its constituent monosaccharides.
5-Slowly add some sodium hydrogencarbonate solution to the test tube to neutralise the HCL. (Benedict’s reagent will not work in acidic conditions.) Test pH paper to check that the solution is alkaline.
6-Re-test the resulting solution by heating it with 2 cm’ of Benedict’s reagent in a gently boiling water bath for five minutes.
7-If a non-reducing sugar was present in the original sample, Benedict’s reagent will now turn orange-brown. due to the reducing sugars that were produced from the hydrolysis of the non-reducing sugar.

Question 26

1)Are polysaccharides (very large molecules) soluble or insoluble and why is it useful?
2)what happens when polysaccharides are hydrolysed?

Answer 26

1)insoluble suitable for storage.
2) hydrolysed=polysaccharides break down into disaccharides/ monosaccharides.

Question 27

1)what is cellulose used for?
2)what is starch and where is it found?
3)What is an example of where starch is found?
4)what is the test for starch?
5)how do you perform the starch test and one important condition?

Answer 27

1) structural support to plant cells.
2) Starch is a polysaccharide found parts of plants (granules or grains) (seeds, storage organs)
3) starch grains in chloroplasts. by joining of between 200 and 100 000 a-glucose molecules by glycosidic bonds series of condensation reactions.
4) detected by its ability to change the colour of the iodine in potassium iodide solution from yellow to blue-black
5) ->test at room temperature.
1-Place 2cm sample being tested into a test tube
2-Add two drops of iodine solution and shake or stir.
3-presence of starch is indicated by a blue-black coloration.

Question 28

1)what does starch do in plants?
2)describe the formation of starch?
3)Can the chains of starch be branched or unbranched?
4)what happens to unbranched chains?

Answer 28

1) found in plants in the form of small grains.
(seeds, storage organs)
->energy source
2) chains of a-glucose monosaccharides linked by glycosidic bonds (condensation reactions.)
3)both
4) unbranched chain is wound into a tight coil that makes the molecule very compact.

Question 29

1)Describe how starch is a good energy storage? (4)
2)How can branched chains be a good energy realiser?
3)where is starch never found and what do they have instead?

Answer 29

1)
• insoluble doesn’t affect water potential, so water is not drawn into the cells by osmosis
• large and insoluble, not diffuse out of cells
• compact, stored in a small space
. hydrolysed forms a-glucose, easily transported and used in respiration
2)
branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly.
3) Starch is NEVER found in animal cells.
similar polysaccharide, called glycogen, serves the same role.

Question 30

1)where is glycogen found?
2)what does starch and glycogen have in common?
2)How is glycogen stored?

Answer 30

1) found in animals and bacteria but never in plant cells.
2) Glvcogen similar structure to starch= shorter chains, highly branched.
3) stored as small granules mainly in the muscle and liver

Question 31

1)What is the 3 roles of glycogen?
2)why is glycogen being more branched important to animals?
3)why is glycogen being more branched important to animals?

Answer 31

1) .insoluble and therefore does not draw water into cells by osmosis (insoluble doesn’t diffuse out)
.compact, so a lot can be stored in small space
2)more highly branched than starch and so has more ends that can be acted on simultaneous by enzvmes. It is theretore more rapidly broken down to form glucose monomers, which are used respiration.
3) important to animals which have a higher metabolic rate= higher respiratory rate

Question 32

1)what is cellulose made from?
2)Are cellulose chains branched or unbranched?
3)what does the large number of hydrogen bonds do for cellulose?

Answer 32

1) made of monomers of B-glucose rather than A-glucose.
2) Rather than forming a coiled chain like starch, cellulose has straight, unbranched chains. ->run parallel to one another, allowing hydrogen bonds to form cross-linkages between adjacent chains.
3) large number hydrogen bonds makes a considerable contribution to strengthening cellulose

Question 33

1)How is cellulose grouped together?
2)What are the three functions of cellulose?
3)How does the cellulose prevent bursting from water entering via osmosis?

Answer 33

1)cellulose molecules are grouped together to form microfibrils arranged in parallel groups (fibres.)
2)
->plant cell walls provides rigidity to the plant cell.
->prevents the cell from bursting as water enters it by osmosis.
->maintaining stems and leaves in a turgid state so that they can provide the maximum surface area for photosynthesis.
3)
.exerting an inward pressure that stops any further influx of water.
=living plant cells are turgid, push against one another rigid

Question 34

1)Why does a reducing sugar turn Benedict’s reagent red when heated with reducing sugar?
2)What does reduction mean?

Answer 34

1)Donate electrons/reduce the Benedict’s reagent forming copper oxide from copper sulfate
2)Reduction is a chemical reaction involving the gain of electrons or hydrogen.

Question 35

1)Is Glycogen branched?
2)Is starch branched?
3)Is cellulose branched?
4)what do the cross links do in cellulose?
5)what carbons create a chain and a beached chain?

Answer 35

1) Glycogen->branched and unbranched
2) Starch-> branched and unbranched
3) Cellulose-> unbranched
4) Cross links->hydrogen bonds lots form microfibres
5)
1-4 carbon linked -> chain
1-6 carbon linked -> branched

Question 36

1)what is an isomer?
2)Name all the isomers of glucose a? (4)
3)what can starch and amylase do which is important for storage?
4)Starch and glycogen examples of branched?

Answer 36

1) Isomer-> same chemical formula different structural formula
2)glucose a, glucose b and fructose, galactose
3) Starch and amylose can coil up and become compact
4)Amylopectin (starch variation), glycogen (glycogen variation) are branched

Question 37

1)what are the two groups of lipids?
2)what are fats made of and what are their states?
3)what are oils made of and what are there states?

Answer 37

1) triglycerides (fats and oils) and phospholipids
2)saturated fatty acids (solid at room temperature 10-20°C)
3) oils are made of unsaturated ones. (oils are liquid at room temperature 10-20°C)

Question 38

1)Describe the characteristics of lipids? (4)

Answer 38

1)
->contain carbon, hydrogen and oxygen.
->proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates.
->insoluble in water.
->soluble in organic solvents e.g alcohols.

Question 39

1)What are the roles of lipids? (7)

Answer 39

1)
->cell membranes (cell-surface membranes and membranes around organelles).
->Phospholipids contribute flexibility of membranes, transfer of lipid-soluble substances across
->source of energy. (When oxidised, lipids provide more energy as the same mass of carbohydrate and release valuable water.)
->Lipids insoluble in water useful as a waterproofing. Both plants, insects have waxy, lipid cuticles conserve water. mammals produce an oily secretion from the sebaceous glands in the skin.
->insulation. slow conductors of heat and when stored beneath the body surface help to retain body heat.
->electrical insulators in the myelin sheath around nerve cells.
->protection. stored around delicate organs

Question 40

1)what are triglycerides?
2)what are the bonds between triglycerides?
3)what reaction can break up a triglycerides?

Answer 40

1) Triglycerides (three (tri) fatty acids combined with glycerol (glyceride).)
2) Each fatty acid forms an ester bond with glycerol in a condensation reaction.
3) Hydrolysis triglyceride produces glycerol and three fatty acids.

Question 41

1)what creates variations of triglycerides?
2)what are the variations of triglycerides?
3)what makes a fatty acid saturated or unsaturated?
4)what is a single bond classed as?
5)what is it called when when you have more than one double bond?
6)what makes polyunsaturated?

Answer 41

1) glycerol molecule in all triglycerides is the same, differences in the properties of different fats and oils come from variations in fatty acids.
2)70 different fatty acids and all are carboxyl (-COOH) group with a hydrocarbon chain attached.
3) Saturated has no carbon carbon double bonds, unsaturated has at least one double bond
4) single double bond, mono-unsaturated
5) polyunsaturated
6)double bonds cause the molecule to bend they cannot pack together closely making them liquid at room temperature (oils)

Question 42

1)Describe the structure of triglycerides? (4)

Answer 42

->Triglycerides have a high ratio of energy-storing carbon-hydrogen
bonds to carbon atoms therefore excellent source of energy.
->Triglycerides low mass to energy ratio, good storage molecules
because much energy can be stored in a small volume.
.beneficial to animals reduces mass they have carry as they move.
-> large, non-polar molecules, triglycerides insoluble in water.
storage does not affect osmosis in cells or water potential of them.
->high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised= important source of water, especially for organisms living in dry deserts.

Question 43

1)what are phospholipids?
2)What part of phospholipids attract or repel water?
3)Describe how phospholipids interact with water?

Answer 43

1) Phospholipids are similar lipids except one of the fatty acid molecules is replaced by a phosphate molecule
2) fatty acid molecules repel water (hydrophobic), phosphate molecules attract water (are hydrophilic).
3)
->hydrophilic ‘head’, which interacts with water (attracted) but not with fat
->hydrophobic ‘tail’, which orients itself away from water but mixes with fat

Question 44

1)Describe how phospholipids are described as polar?

Answer 44

1)
->Molecules with two ends (poles) behave differently= polar.
.polar phospholipid molecules are placed in water they position themselves so that the hydrophilic heads are as close to the water as possible and the hydrophobic tails are as far away from the water as possible.

Question 45

1)Describe the structure of phospholipids? (3)

Answer 45

1) >polar molecules, hydrophilic phosphate head and a hydrophobic tail of two fatty acids. In an aqueous environment, phospholipid molecules form a bilayer within cell-surface membranes. As a result, hydrophobic barrier is formed between the inside and outside of a cell.
->hydrophilic phosphate ‘heads’ of phospholipid molecules help to hold at the surface of the cell-surface membrane.
->phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane. glycolipids are important in cell recognition.

Question 46

1)Describe how to perform the lipid test?
2)Why does the lipid test appear cloudy?

Answer 46

Test for lipids -emulsion test
1-Take a completely dry and grease-free test tube.
2- 2cm^3 of the sample being tested, add 5 cm^3 of ethanol.
3- Shake the tube thoroughly to dissolve any lipid in the sample.
4- Add 5cm^3 of water and shake gently.
5- milky-white emulsion indicates the presence of a lipid.
6- control: repeat the procedures using water instead of the sample; final solution should remain clear.

2)
->cloudy colour due to any lipid in the sample being finely dispersed in the water to form an emulsion. ->Light passing through this emulsion is refracted as it passes from oil droplets to water droplets, making it appear cloudy.

Question 47

1)Why is Cellulose unbranched?
2) What increases strength and rigidity of cellulose?
3) What do we call a number of cellulose chains collected together (also increasing strength and rigidity)?
4) How is the helical shape of starch related to its function?
5) Why is starch insoluble?
6) How is the branched structure of starch related to its function?
7) Why is starch a large molecule?
8) How is the structure of glycogen being Helix/coiled/branched related to its function?

Answer 47

1) only 1 -4 glycosidic links
2) Many hydrogen bonds (collective strength) join chains together
3) Fibrils
4) The helical shape of starch makes it compact.
5)Starch is insoluble so it is osmotically inactive and does not affect water potential.
6)allows glucose to be easily released for respiration when hydrolysed by enzymes.
7) so cannot leave the cell.
8) so compact.

Question 48

1) What is glycogen made of?
2) Why is glycogen branched?
3) Why is it important that it is a polymer of glucose?
4) Why is glycogen large and insoluble?
5) Why is glycogen insoluble?

Answer 48

1) Polymer of alpha glucose.
2) To provide more ends for faster hydrolysis by enzymes
3) Provides respiratory substrate for energy release.
4) so not lost from cell
5) so does not affect water potential

Question 49

1)Definition of condensation reactions?
2)Definition of hydrolysis reactions?
3) Give two difterences between the structure of cellulose and glycogen?

Answer 49

1) A condensation reaction joins monomers together and forms a chemical bond and releases water.
2)A hydrolysis reaction breaks a chemical bond between monomers and uses
water.
3)
-Cellulose is made up of B-glucose (monomers) and glycogen is made up of a-glucose (monomers);
-Cellulose molecule has straight chain and glycogen is branched;
-Cellulose molecule has straight chain and glycogen is coiled;
-glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds;

Question 50

1) Explain why starch is a good storage molecule?
2) Describe the test for starch?
3) Describe the structure of glycogen?

Answer 50

1)
-Insoluble (in water), so doesn’t affect water potential;
-Branched / coiled / (a-)helix, so makes molecule compact;
-Polymer of (a-)glucose so provides glucose for respiration;
-Branched / more ends for fast breakdown / enzyme action;
-Large (molecule), so can’t cross the cell membrane
2)
Iodine
Turns black
3)
-Polysaccharide of a-glucose/ polymer of a-glucose;
-(Joined by) glycosidic bonds/Branched structure;

Question 51

1)How is the structure of glycogen linked to its function?
2)Give two differences between the structure of glycogen and starch.

Answer 51

1)
-Helix/coiled/branched so compact
-Polymer of glucose so easily hydrolysed;
-Branched so more ends for faster hydrolysis;
-Glucose (polymer) so provides respiratory substrate for energy (release);
-Insoluble so not (easily) lost (from cell) doesn’t affect water potential
2)
Starch is made from amylose (linear) and amylopectin (branched).
Glycogen is only made from glycogen molecules.
2. Glycogen is more branched than starch.

Question 52

1)compare cellulose and starch?

Answer 52

1)
Starch is helical, both contain CHO, both have glycosidic, bonds, both are condensation reactions, both insoluble, both polysaccharides of glucose
Starch has 1,4 and 1,6 glycosidic bonds, cellulose only has 1,4, starch is coiled

Question 53

How to draw phospholipids?

Answer 53

Question 54

What bond is formed between glycerol and a fatty acid?

Answer 54

Ester bond

Question 55

What is sucrose?

Answer 55

Disaccharides that is a reducing sugar

Question 56

Definition of monomers?

Answer 56

Reacting small unit, many join to make a polymer, joined by condensation reaction to make polymers by chemical bonds

Question 57

What are fungi cell walls made off?

Answer 57

Chitin

Question 58

1)Are lipids polymers?
2) Example of a hydrogen bond?
3) Examples of ionic bonds?
4) Example of covalent bonds?
5) What happens when a molecule is polarised?
6) Describe hydrogen bonds?

Answer 58

1)Not polymers not made of monomers
2) Multiple Water molecules
3) Na+-molecule
NaCl- compound
4)water
5) Polar molecules can attract each other through electrostatic charges between the slightly negative and positive regions.
6) Electronegative elements in a molecule pull electrons towards them. This means that electrons spend more time in one position giving this position slightly negative charge and rest of the molecule slightly positive charge. It is polarised.

Question 59

1) Give an example of a 6, 5, 3 carbon sugar?
2) What is the carbohydrate formula?
3) Polymerisation?
4)Polymer?
5) What is an isomer?
6) What is a glycosidic bond?

Answer 59

1) 6- glucose , 5-sucrose, 3-ribose
2) (CH2O)n
3) Process of bonding monomers together to form polymers
4)A molecule made from a large Chain of monomers
5) Same chemical formula but different arrangement of atoms
6) Formed by condensation reaction to join monomers to make larger carbohydrates