3.1 biological molecules

Question 1

what are monomers and polymers?

Answer 1

monomer- small basic molecular unit that forms polymers. e.g. monosaccharides, amino acids and nucleotides.

polymer- large complex molecule composed of long chains of monomers joined by covalent bonds

Question 2

what are the types of reactions?

Answer 2

types of reactions

condensation reaction- makes polymers and forms a chemical bond between monomers, releasing a molecule of water.

hydrolysis reaction- breaks polymers by breaking the chemical bonds using a molecule of water.

Question 3

what are carbohydrates?

Answer 3

all contain carbon, hydrogen and oxygen.
monomer is monosaccharides e.g. glucose, fructose and galactose
glucose is a hexose sugar- a monosaccharide with 6 carbon atoms in each molecule. there are 2 types of glucose- alpha and beta. is also an isomer.

Question 4

what are disaccharides?

Answer 4

disaccharides form when 2 monosaccharides join together by condensation reactions.
glycosidic bonds form between 2 monosaccharides as a molecule of water is released e.g. starch

Question 5

what is starch?

Answer 5

cells get energy from glucose, plants store excess glucose as starch
mixture of 2 polysaccharides of alpha-glucose.

Question 6

what makes up starch?

Answer 6

amylose- long unbranched chain. angles of the glycosidic bonds give it a coiled structure, like a cylinder. compact and good for storage. 1,4-glycosidic bonds.

amylopectin- long branched chain. side branches allow enzymes that break down the molecule to break the glycosidic bonds easily, meaning that glucose can be released quickly. 1,4 and 1,6-glycosidic bonds

Question 7

what is glycogen?

Answer 7

animals store exess glucose as glycogen.
alpha-glucose.
structure is similar to amylopectin but has more branches coming off it and so stored glucose can be released quickly.
compact.
1,4 and 1,6 glycosidic bonds

Question 8

what is cellulose?

Answer 8

long unbranched chain of beta-glucose
when beta-glucose molecules bond, the form straight cellulose chains. chains are linked by hydrogen bonds to form strong fibres called microfibrils and means cellulose gives structural support
1,4 glycosidic bonds

Question 9

what is the characteristics of lipids?

Answer 9

2 main types- triglyceride and phospholipid 
mainly oxygen, carbon and hydrogen
large 
complex (macromolecule)
not polymers
non-polar
wont dissolve in water

Question 10

what are triglycerides?

Answer 10

good energy source
1 molecule of glycerol and 3 fatty acids
ester bonds form via condensation reactions

Question 11

what are phospholipids and what do they make up?

Answer 11

make up the bilayer of membrane
head is hydrophillic and tail is hydrophobic, so form a double layer with head facing out.
has 2 fatty acids, a glycerol and a phosphate group

Question 12

what are proteins?

Answer 12

monomer- amino acid
2 monomer- dipeptide
2 or more monomer- polypeptide
polymer- protein

Question 13

how is an amino acid made up

Answer 13

NH2 is the amine group. COOH is a carboxyl group and R is a side chain.
all 20 amino acids only differ in their R group

Question 14

what is the primary structure of proteins

Answer 14

sequence of amino acids found in polypeptide chains. sequence determines shape and function

Question 15

what is the secondary structure of proteins?

Answer 15

shape polypeptides form as a result of hydrogen bonds

Question 16

what is the tertiary structure of proteins

Answer 16

shape is due to bending and twisting. held together by bonds between R groups. hydrogen bonds between polar R groups, ionic between + and - charged R groups and disulphide links between sulphur atoms on the R groups

Question 17

what is the quaternary structure of proteins?

Answer 17

same as tertiary but between 2 polypeptides

Question 18

what is enzymes?

Answer 18

the tertiary structure of an enzyme may be altered by changes in pH or temperature.
catalyse metabolic reactions i.e. respiration and digestion
involved in the production of collagen

Question 19

how do enzymes work?

Answer 19

speed up chemical reactions by acting as a biological catalyst
have an active site that is complementary to a specific substrate and are highly specific due to tertiary structure.
enzyme-substrate complex is what lowers the activation energy

Question 20

lock and key model

Question 21

induced fit model

Question 22

what are competitive and non-competitive inhibitors?

Answer 22

competitive inhibitors- similar shape to the substrate and so compete with the substrate to bind to the active site but no reaction occurs.

non-competitive inhibitors- doesn’t bind to active sites and bind away from the active site but still changes the shape

Question 23

what is the effect of temperature on enzymes?

Answer 23

As temp increases, the enzyme-controlled reaction will speed up.More heat means more kinetic energy, which increases collisions.The energy of collisions also increases, so each collision is more likely to result in a reaction.

Question 24

what happens to enzymes if the temperature gets too high?

Answer 24

If temperature getstoohigh, enzymes vibrate more and as the temperature goes above a certain temperature, the vibrations breaks some of the bonds that hold the enzymes in place
The active site changes shape and the enzyme is denatured and no longer functions as a catalyst.

Question 25

what is the effect of substrate concentration on enzymes

Answer 25

The higher the substrate concentration, the faster the reaction   However, this is only to the saturation point.   The saturation point- where all of the enzymes active site are occupied. 

Question 26

what is the effect of enzyme concentration on the reaction

Answer 26

The more enzymes there are the more likely collisions are  A point will come where there are more than enough enzymes to deal with available substrate, so adding more enzymes has no further effects  

Question 27

what is the iodine test?

Answer 27

test for starch  Add iodine dissolved in potassium iodine solution to the test sample   If starch is present;  Brown/orange--> dark blue/ black 

Question 28

what is the biuret test?

Answer 28

test for proteins Add an equal volume of sodium hydroxide to sample Add a few drops of dilute copper (II) sulphate Solution goes from blue to purple

Question 29

what is the emulsion test?

Answer 29

test for lipids Shake the sample with ethanol Add water and shake again Any lipids will show as a milky emulsion

Question 30

what is the test for reducing-sugars?

Answer 30

Can give electrons to reduce other molecules   All monosaccharides and some disaccharides               Benedicts test for reducing sugars              Heat sample with benedicts reagent   Sample goes blue -> green -> yellow -> orange -> brick  red precipitate Reducing sugar is present   Sample stays blue  

Question 31

what is the test if non-reducing sugars are present?

Answer 31

Heat sample with benedicts reagent   no colour change Non-reducing sugar is present   Heat with dilute hydrochloric acid and neutralize with sodium hydrogencarbonate.   Heat  new sample with benedicts reagent.   Sample stays blue   Non-reducing sugar is present  

Question 32

what is DNA

Answer 32

A DNA nucleotide is made from a phosphate group, the pentose sugar deoxyribose and a nitrogen-containing organic base   The four bases are adenine. Thymine, cytosine and guanine   double stranded long

Question 33

what is complementary base pairing?

Answer 33

Two DNA polynucleotide strands join together by hydrogen bonds between the bases.   A bonds with T with a double bond   G bonds with T with a triple bond   There are equal amounts of A and T  and G and T   The two polynucleotide strands are antiparallel- they run in opposite directions  

Question 34

what is RNA?

Answer 34

Made of nucleotides that contain a sugar phosphate group and are of 4 bases  The sugar is ribose sugar   Uracil replaces thymine and so pairs with adenine   The nucleotides form a single polynucleotide strand  RNA strands are shorter than DNA polynucleotides  

Question 35

what is the process of DNA replication?

Answer 35

 Step 1- the enzyme DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands . This makes the helix unwinds to form two single strands   Step 2- each original strand acts as a template for a new strand. Complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand   Step 3- condensation reactions join the nucleotides of the new strand together- catalyzed by the enzyme DNA polymerase. Hydrogen bonds form between bases on the original and new strands.   Step 4- each end of the DNA strand is slightly different in structure, one end is 3' and the other is 5'. During replication, the active site of polymerase is only complementary to 3', so the enzyme can only add nucleotides to the new strand at the 3' end. This means that the new strand is made in a  5' to an 3' direction and that DNA polymerase moves down the template in a 3' to an 5' direction. 

Question 36

what is the evidence for semi-conservative replication?

Answer 36

Used 2 isotopes of nitrogen (DNA contains nitrogen. Heavy nitrogen is 15N and light nitrogen 14N   2 bacteria samples grow for many generations- one on a nutrient broth with light nitrogen and one with heavy nitrogen. As bacteria reproduces, they take up nitrogen to make up nucleotides for DNA   a DNA sample is taken from both and spun in a centrifuge. DNA from the heavier sample settles lower down the tube because its heavier    bacteria grown in heavier nitrogen was taken out and put in a broth containing only light nitrogen. The bacteria is left out for 1 round of replication and another sample was taken out and spun    if replication was conservative, the original heavy DNA which would still be together would settle at the bottom and the new light DNA would settle at the top.   if replication was semi-conservative, the new bacterial DNA molecules would contain 1 strand of old DNA with heavy nitrogen and 1 strand of new DNA with light nitrogen. So DNA would settle out between where light nitrogen settled and heavy nitrogen settled.   DNA did settle in the middle, showing DNA molecules contain a mix of heavy and light nitrogen. Bacterial DNA has replicated semi-conservatively in light DNA  

Question 37

why do we need energy?

Answer 37

In plants and animals: | active transport, DNA replication, cell division, protein synthesis  

Question 38

what is ATP and why do we need it?

Answer 38

Plant and animal cells release energy from glucose. A cell can't get energy directly from glucose, so in respiration, energy released from glucose makes ATP.   Adenine triphosphate is made from the nucleotide base adenine with ribose sugar and 3 phosphate groups 

Question 39

what happens when ATP is made?

Answer 39

Once made, ATP diffuses to the part of the cell that needs energy.   When energy is needed by a cell, ATP is broken down into ADP (adenine diphosphate) and pi (inorganic phosphate) this is a hydrolysis reaction. A phosphate bond is broken and energy is released. The reaction is catalysed by the enzyme ATP hydrolase

Question 40

how can ATP be coupled?

Answer 40

ATP can be 'coupled' to other energy-requiring reactions in the cell which means the energy released can be used directly to make coupled reaction, rather than being lost as heat   

Question 41

what is the use of inorganic phosphate?

Answer 41

Released inorganic phosphate can be added to another compound (known as phosphorylation) which often makes the compound more reactive.  

Question 42

how is ATP resynthesised

Answer 42

ATP can be resynthesized in a condensation reaction between ADP and Pi. This happens during both respiration and photosynthesis and is catalysed by enzyme ATP synthase

Question 43

what are inorganic ions?

Answer 43

Means there is no carbon. There are inorganic ions in solution in the cytoplasm of cells and in the body fluids of organisms Haemoglobin is a large protein that carries oxygen around the body in red blood cells. Iron ions are what actually carry the oxygen. This is because oxygen binds to the Fe2+ ion ti become Fe3+ pH is calculated based on the concentration of hydrogen ions in the environment, the more H+ ions present, the lower the pH. A molecule of glucose/ amino acids can be transported alongside Na+. When a phosphate ion (PO43-) is attached to another molecule, it is known as a phosphate group.

Question 44

how is water an important metabolite?

Answer 44

May metabolic reactions involve a condensation and a hydrolysis reactions.   A hydrolysis reaction requires a water molecule to break a bond.   Condensation reactions release a water molecule as a new bond is formed.  

Question 45

how is water a buffer to temperature changes?

Answer 45

Hydrogen bonds give water a high specific heat capacity ( energy needed to raise temperature of 1g of substances by 1 degree)   When water is heated, a lot of heat energy is used to break hydrogen bonds. Means theres less heat energy available to actually increase temperature of water. So water has a high specific heat capacity- takes a lot of energy to heat up 

Question 46

how is water cohesive?

Answer 46

Cohesion- attraction between molecules of the same type   Water is very cohesive because its polar   Strong cohesion helps water flow and have a high surface tension when it comes into contact with water. 

Question 47

how does water have a high latent heat of vaporisation?

Answer 47

Water evaporates when hydrogen bonds holding water molecules together are broken  Requires a lot of energy to break the hydrogen bonds so a lot of energy is used up when water evaporates   Lots of heat is used to change it from a liquid to a gas.   Useful because living organisms can use water loss through evaporation to cool down without loosing too much water   

Question 48

how is water a good solvent?

Answer 48

A lot of important substances in biological reactions are ionic   Because water is polar, slightly positive charges attracts the negative ions and vice versa The ions will get surrounded by water molecules (dissolves). Polarity makes a good solvent