chapter 1 - biological molecules Flashcards
(68 cards)
1
Q
What are monomers and polymers?
A
- monomers = single units which connect to form larger molecules
- polymers = large molecules made from lots of monomers bonded together
2
Q
What are monosaccharides, disaccharides and polysaccharides ?
A
- monosaccharides are simples sugars, the monomers of carbohydrates , with 3 - 7 carbons
- disaccharides are two monosaccharides bonded together
- polysaccharides are many monosaccharides bonded together
3
Q
Give examples of monosaccharides
A
- glucose, fructose, galactose and ribose
4
Q
What is a condensation reaction ?
A
- forming larger biological molecules from smaller biological molecules with water as a product
5
Q
What are hydrolysis reactions ?
A
- breaking down bigger biological molecules to smaller biological molecules using water
6
Q
What is glucose ?
A
- a hexose sugar with molecular formula ,C6H1206 , it is an important form of energy
7
Q
What are isomers ?
A
- molecules with the same molecular formula but different structure
8
Q
What are the two isomers of glucose and what is the difference between them ?
A
- alpha and beta glucose
- alpha glucose = carbon -1 hydroxyl is below the ring
- beta glucose = carbon 1 hydroxyl is above the ring
9
Q
What is glycosidic bond ?
A
- a bond between 2 monosaccharides , between two carbons with an oxygen between them
- they are made during condensation reactions so produce water
10
Q
Give examples of disaccharides
A
- maltose , sucrose and lactose
11
Q
What is maltose made of ?
A
- glucose + glucose
12
Q
What is sucrose made of ?
A
- glucose + fructose
13
Q
What is lactose made of ?
A
- glucose and galactose
14
Q
Give examples of polysaccharides ?
A
- starch, cellulose, glycogen
15
Q
What is starch made up of ?
A
- amylose and amylopectin
- alpha glucose
16
Q
Describe amylose
A
- a long unbranched polymer with 1 - 4 carbon glycosidic bonds
17
Q
Describe amylopectin
A
- a long polymer with branches
- 1-4 bonds between the linear chain
- 1-6 bonds between branches
18
Q
How is starch designed for it function ?
A
- amylose = is very long and unbranched , meaning it can fold into a helical structure and is ideal for storage
- amylopectin = the branched structure increases surface area for rapid hydrolysis back into glucose
- its insoluble so wont change the water potential of the cells
19
Q
Where is starch found?
A
- as a store of energy in plants in seeds
20
Q
What is glycogen made of ?
A
- alpha glucose and it is a highly branched molecule
21
Q
Where is glycogen found ?
A
- as an energy store in animals
22
Q
How is glycogen designed for its function ?
A
- its highly branched meaning it has a rage surface area for it to be broken down into glucose during glycogenolysis
- insoluble so it does not disturb the water potential of cells
23
Q
What is cellulose structured ?
A
- long unbranched chains of beta glucose
- each second beta glucose flips so that a a 1 - 4 glycosidic bond can be formed
24
Q
Where is cellulose found ?
A
- in the cell walls of plant cells
25
How is cellulose designed for its function ?
- cellulose chains are held together by many hydrogen bonds to form microfibrils
- hydrogen bonds are weak but because there are many of them this makes the structure strong
- so cellulose can provide strength for the cell wall
26
What are triglycerides and how are they made ?
- a glycerol with three fatty acids
- made from a condensation reaction with a glycerol and three fatty acids
- so three molecules of water are produced
27
What is the difference between an unsaturated fatty acid and a saturated fatty acid ?
- saturated has only single carbon to carbon bonds
- unsaturated has at least one double carbon to carbon bond
28
How does the structure of triglycerides help with energy storage ?
- the large ratio of energy storing hydrogen to carbon bonds compared to the amount of carbon atoms means a lot of energy is stored in the molecule
29
How does the structure of triglycerides help it be a metabolic water source ?
- as there is a high ratio of hydrogen to oxygen molecules , the triglyceride can produce water if its oxidised ( broken down ) , which is good for animals that live in the desert
30
How are triglycerides designed to make them not disturb the water potential of cells
- the are large and hydrophobic making the insoluble
31
How does the mass of triglycerides help with its function ?
- as the have a relatively low mass ( compared to things like muscle ) lots of the triglyceride can be stored for energy without making the animal heavy and preventing movement
32
How are lipids designed to help with insulation ?
- lipids are found in adipose tissue which insulates the body and is around organs like the kidneys to protect them from injury
33
How are lipids used in waterproofing ?
- in waxy cuticles and when animals secrete oils
34
what is a phospholipid made of ?
- a glycerol, two fatty acids and a phosphate group
35
Describe the head and tails of a phospholipid
- head (phosphate) is polar and there is a negative charge on one of the oxygens , this makes it attracted to water so it hydrophilic
- the tail (fatty acid ) has no charge and so repels water so its hydrophobic
- head will repel other fatty acids
- tails will mix with other lipids
36
How is the structure of a phospholipid designed for its function
- the hydrophobic tail and hydrophilic head mean chains of phospholipids can arrange themselves in a bilayer , with the tails on the inside
- the head can stay in the intracellular fluid
37
How do you test for a non - reducing sugar ?
-add hydrochloric acid , heat in a warm water bath then cool then neutralise ( the acid breaks down the sucrose )
- the complete the normal Benedict’s test
38
Why when completing the Benedict’s test does the colour show up at the top first ?
- due to convection currents , the hotter particles move to the top so the reaction happens at the top first
39
How do we test for lipids ?
- dissolve in ethanol ( shake it )
- then add distilled water
- if positive, a white milky emulsion forms
40
What does a kink do to a fatty acid ?
- a kink = a cis double bond prevents the lipids from packing tightly , making them liquid at room temperature
41
What is the difference between cis fat and trans fat ?
- cis fat = the hydrogens on carbon to carbon double bond are on same plane
- trans fat = the hydrogens on the carbon to carbon double bonds are on different planes
42
What are proteins and what are they made of ?
- polymers made of amino acids
43
What is the general structure of amino acids ?
- and amino group, a central carbon with a hydrogen attached to it, an R group and a carboxyl group
44
How do amino acids join to form dipeptides and polypeptides ?
- the OH from the carboxyl group of one amino acid and the H from the amino group of another amino acid join to form water .
- a peptide bond forms between the carbon and nitrogen.
- this is a condensation reaction
45
What are the 4 levels of structure in proteins ?
- primary, secondary, tertiary and quaternary
46
What is the primary structure of proteins ?
- the order of amino acids in the polypeptide chain
47
What is the secondary structure of proteins ?
- hydrogen bonds form between the H in the amine group from one amino acid and the and th C=O from the carboxyl group of another amino acid.
- the hydrogen bonds help hold the chains in either an alpha helix or a beta pleated sheet
- how they bend depends on the sequence of the amino acids
48
What is the tertiary structure of proteins ?
- the secondary structure folds even more to form a unique 3D shape
- these are held together by ionic, disulphide and hydrogen bonds which form between R groups of different amino acids
- hydrophilic and hydrophobic interactions happens between polar and non polar groups, they are weak
49
What is the quaternary structure of proteins ?
- when a protein is made up of more than one polypeptide chain which are held by hydrogen, ionic and disulphide bonds and hydrophobic and hydrophilic interactions
- e.g haemoglobin
50
How do proteins become denatured ?
- when the bonds that hold the secondary or tertiary structure break, the unique 3D shape of the protein is lost
- this is caused by too high temperatures = to much kinetic energy
- or to low/high pH ( too many H+ or OH- ions
51
- how can the 3D structure of proteins change ?
- if one of the amino acids in the sequence changes , the hydrogen, ionic and disulphide bonds form in different places which means the 3D shape will change
52
What is the test for proteins ?
- add biuret regents = an alkali + plus copper sulphate solution
- there must be at least 2 peptide bonds for the test to work
- a positive result will go from blue to lilac
53
What are proteins used for ?
- enzymes
- antibodies
- transport across membranes
- structural components ( creating strong fibres )
- hormones
- muscle contraction
54
What are enzymes ?
- they are biological catalysts
- they are globular proteins with a unique tertiary structure
55
How do enzymes act as catalysts ?
They lower the activation energy needed
56
What are intracellular and extracellular enzymes ( + give examples )
- intracellular enzymes = act within the cells that produce them , e.g used in DNA replication and ATP synthesis
- extracellular enzymes = act outside the cells that produce them and are secreted, e,g used in digestion, pepsin and amylase
57
How does the lock and key theory of enzymes work ?
- the active site of the enzymes fits perfectly with the substrate
- the two form an enzyme - substrate complex
- charged R groups within the active site distort the substrate ( by forming temporary bonds )
- this lowers the activation energy needed to break the substrate
58
How does the induced fit model of enzymes work ?
- the active site is a slightly different shape to the substrate
- when the substrate enters, the active site changes shape slightly and moulds around the substrate
- this puts a strain around the bonds in the substrate which lowers the activation energy needed to break them
- when the products of the substrate leaves, the active site returns to its original shape
59
What are the factors that affect the rates of enzyme controlled reactions ?
- temperature
- pH
- substrate concentration
- enzyme concentration
- inhibitors
60
How does temperature affect the rate of enzyme controlled reactions ?
- at temp increases: particles have more kinetic energy = more collisions = more enzyme - substrate complexes formed
- optimum temp: enzyme workings it’s fastest
- too high temp: to much kinetic energy which causes bonds in tertiary structure to break = active site changes shape
61
How does pH affect the rate of enzyme controlled reactions ?
- at low pH: H+ ions break ionic / hydrogen bonds in tertiary structure = enzyme denatures
- at optimum pH: pH best for enzyme and is working at its fastest
- too high pH: OH- ions break ionic / hydrogen bonds = enzyme denatures
62
How does the substrate concentration affect the rate of enzyme controlled reactions ?
- as substrate concetration increases , rate of reaction increases are more enzyme substrates can be formed
- as some point the rate of reaction will stop increasing as all the enzymes are being used so adding more substrate doesn’t do anything
63
How does enzyme concentration affect the rate of reaction ?
- as the enzyme concentration increases, the rate of reaction increases as more enzyme - substrate complexes can be formed
- at some point the rate of reaction will stop chasing as all the substrates are being acted upon so adding more enzymes doesn’t do anything ( there are now empty active sites )
64
What are the two types of inhibitors ?
- competitive and non- competitive
65
How do competitive inhibitors work ?
- they have a similar shape to the substrate
- so bind to the active site which stops the substrate from biding to it
- which means less enzyme - substrate complexes are formed so rate of reaction decreases
66
How do non - competitive inhibitors work ?
- they bind away from the active site ( the allosteric site )
- this cause the tertiary structure of the enzyme to change shape so the active site changes shape
- so no enzyme - substrate complexes can be formed which decreases the rate of reaction
67
How does increasing the concentration of the substrate affect the competitive inhibitors ?
- if there is a lot of substrate, it can knock of the competitive inhibitor so the rate of reaction can increase again
68
How does increasing the concentration of substrate affect non - competing inhibitors ?
- it does not affect them
- as the active site has changed shape
- so adding more substrate will not do anything to increase the rate of reaction
