Biological Molecules Flashcards
(86 cards)
1
Q
What elements do carbohydrates consist of?
A
Hydrogen
Oxygen
Carbon
2
Q
What elements to lipids consist of?
A
Hydrogen
Carbon
Oxygen
3
Q
What elements do proteins consist of?
A
Nitrogen
Hydrogen
Carbon
Oxygen
Sulphur
4
Q
What elements do Nucleic acids consist of?
A
Phosphorus
Oxygen
Hydrogen
Carbon
Nitrogen
5
Q
What is a molecule?
A
When two or more atoms bond together
6
Q
What is covalent bonding?
A
When two atoms share a pair of electrons.
7
Q
How many bonds can carbon atoms form?
A
4
8
Q
How many bonds can nitrogen atoms form?
A
3
9
Q
How many bonds can oxygen atoms form?
A
2
10
Q
How many bonds can hydrogen form with other atoms?
A
1
11
Q
What are simple covalent structures?
A
Covalent molecules that contain only a few atoms.
12
Q
What are characteristics of covalent structures?
A
Low melting point
Low boiling point
Gases or liquids at room temperature
13
Q
Why are covalent structures liquid or gas at room temperature?
A
The covalent binds within these molecules are strong but the bonds between the molecules are weak and easy to break.
14
Q
How are ions formed ?
A
Ions are formed when an atom gains, or loses electrons.
15
Q
What are monomers?
A
They are the smaller units from which larger molecules are made.
They may combine with other monomers to build up larger molecules called polymers.
16
Q
What are polymers?
A
They are molecules made from a large number of monomers joined together.
Similar monomers joined together by covalent bonds to form a chain or a branched chain.
17
Q
Examples of monomers?
A
Monosaccharides e.g. glucose, fructose, ribose and triode
Amino acids e.g. glycine, valine and alanine.
Nucleotides
18
Q
Examples of polymers?
A
Polysaccharides e.g. starch (amylose), glycogen and cellulose.
Polypeptides e.g. amylase and lysozyme
Polynucleotides e.g. DNA and RNA.
19
Q
How are most biological polymers formed?
A
From their monomers by condensation reactions
20
Q
What’s a condensation reaction>?
A
A chemical reaction where two molecules are joined together with a covalent bond, forming a larger molecule and releasing one molecule of water.
21
Q
How do polymers break?
A
Hydrolysis reaction
22
Q
What is a hydrolysis reaction?
A
A chemical reaction where the covalent bond between two molecules is broken with the addition of a water molecule, separating the two molecules.
23
Q
What is ionic bonding?
A
Normally between non metal and metal
Negative or positive ions formed
Ions held together by the attraction for opposite charges.
24
Q
What elements does water consist of?
A
Hydrogen and oxygen by covalent bonds.
25
Is water polar or non polar?
Polar
26
Why is water classed as a polar molecule?
Since oxygen has a higher electronegativity than hydrogen, the side of the molecule with the oxygen atom has a slightly negative charge and the side with the hydrogen atoms has a slightly positive charge. As there is an uneven distribution of charge throughout the molecule, water is described as a polar molecule and
more specifically as having a dipole nature because of the
charge difference at the two ends.
27
How do hydrogen bonds occur between water molecules?
Opposites attract and the shared negative hydrogen electrons are pulled towards the oxygen atom.
As the slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules.
This attraction is called hydrogen bonding.
28
What is cohesion?
When water molecules get close together, the oppositely charged parts of the molecules attract each other, forming hydrogen bonds.
29
What are some properties of water?
- its a liquid
- it has low viscosity so can flow easily
- water becomes more dense as it gets colder until about 4 degrees.
- its a solvent
- cohesion and surface tension ( the cohesion between water molecules produces surface tension as the hydrogen bods also pull the molecules inwards at the surface)
- high specificity of heat (hydrogen bonds between water molecules absorb a lot of energy which gives water a high specific beat capacity)
- high latent heat of vaporisation (when water evaporates, heat energy, helps the molecules to break away from each other to become gas)
- reactant (like photosynthesis and hydrolysis reactions)
30
What are the two groups or carbohydrates?
Sugars and starches
31
What are monosaccharides?
They are particularly important in living organisms as sources of energy because of the large number of carbon - hydrogen bonds.
32
What are carbohydrates for?
They act as any energy source and support - their function is related o their structure.
33
What are the three main groups of carbohydrates?
Monosaccharides - small simple sugars
Disaccharides - large ‘double’ sugars
Polysaccharides - long chain carbohydrates
34
Describe glucose.
Glucose is a monosaccharide with six carbons so is known as a Hexose monosaccharide.
Glucose molecules are polar and soluble in water.
It is the main energy source in animals and plants. Its structure makes it soluble so it can easily be transported.
35
What are glucose’s two structural variations?
Alpha and beta glucose.
36
Is OH on the bottom or top in an alpha glucose?
Bottom
37
Is OH on the bottom or the top of a beta glucose?
Top
38
What are isomers?
Molecules that have the same molecular formulae, but different arrangements of atoms.
39
What are disaccharides?
Formed by condensation reactions.
Monosaccharides joined together by a glycosidic bond.
They are sweet and soluble
40
Examples of disaccharides
Maltose, sucrose and lactose
41
Which reaction are disaccharides formed by?
Condensation reaction
42
What does ABBA stand for?
Alpha below beta above
43
How is maltose formed?
From two glucose molecules joined by an alpha 1 - 4 glycosidic bond.
44
How is sucrose formed?
Glucose and fructose joined by an alpha 1 - 4 glycosidic bond.
45
How is lactose formed?
Galactose and glucose joined together by a beta 1 - 4 glycosidic bond.
46
What are polysaccharides?
Polymers containing many monosaccharides linked by glycosidic bonds. They are formed by condensation reactions.
They are mainly used as an energy store and as structural components of cells.
47
Examples of polysaccharides?
Starch
Cellulose
Glycogen
48
Describe starch.
It is a polymer of alpha glucose molecules with glycosidic bonds linking the molecules together.
The chains coil up in to an spring shape because the shape of the monomer and the angle of the glycosidic bonds that join C1 of the monomer C4 of the next, forming a 1-4 glycosidic bond.
It is two molecules; amylose and amylopectin.
It is insoluble in water so it does not cause water to enter the cells by osmosis.
49
What is amylose
It is a long, unbranded chain of alpha glucose. The angles of the glycosidic bonds give it a coiled structure, cylinder like. This makes it compact so it is good for storage as you can fit more into a smaller space.
50
What is amylopectin?
It is a long, branched chain of alpha glucose molecules its side branches allow the enzymes that break down the molecules together to get at the glycosidic bonds easily. This means that glucose can be released quickly.
51
What stores starch grains?
Amyloplasts
52
What are plastids?
Specialised membrane bound organelles found in plants e.g. chloroplasts
53
How is starch formed?
When alpha glucose monomers are joined by glycosidic bonds during condensation reactions.
54
Describe glycogen.
- Glycogen is the main energy storage materials in animals.
- Animals store excess glucose as glycogen.
- it has lots of side branches coming off it, lots of branches means that stored glucose can be released quickly.
- it is compact so is ideal for storage.
- glycogen is stored as small granules, particularly in muscles and the liver.
- glycogen is less dense and more soluble than starch which means it is broken down faster. This indicates the higher metabolic requirements of animals compared with plants.
55
Describe the structure of glycogen.
It contains many alpha 1-6 glycosidic bonds that produce and even more branched structure than amylopectin.
56
What breaks down 1-4 glycosidic bonds?
Amylase
57
What breaks down 1-6 glycosidic bonds?
Glucosidase
58
Where in a cell is the majority of water found?
Cytoplasm
59
What will happen to the water potential of the cytoplasm if long chains of glucose are dissolved?
Cell will shrivel, hypertonic solution.
60
If the surrounding areas now have a higher water potential, what will happen?
The cell is immersed in a hypotonic solution and the cell may burst.
61
Why is it important for polysaccharides to be less soluble in water than monosaccharides?
Sugars are soluble in water because they contain polar parts such as -OH groups. Mono saccharides and disaccharides are small enough to disolve readily in water while polysaccharides such as starch, glucogen and cellulose are not due to their size and polymeric character.
62
Describe the structure of cellulose.
- cellulose is made of beta glucose molecules that are joined by glycosidic bonds to form long unbranched chains.
- the arrangement of the -OH and -H groups on the C1 of the beta glucose means that adjacent glucose molecules only join if alternate molecules are inverted.
- when beta glucose molecules bond, they form straight cellulose chains with many -OH groups on the outside.
- it is an unbranched chains of up to 15000 beta glucose molecules joined together by 1 - 4 glycosidic bonds which were formed during condensation reactions.
63
What are the properties of cellulose?
- cellulose is a major component of cell walls in plants.
- the cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils due to the high number of -OH groups on the outside of the cellulose chains.
- the strong fibres mean cellulose provides structural support for cells that is very stable.
64
Describe macrofibrils and microfibrils
- They have a very high tensile strength because of the glycosidic and hydrogen bonds.
- macrofibrils run in all directions, criss crossing the wall and this provides extra strength.
65
What are reducing sugars?
They are simple sugars and include all monosaccharides and most disaccharides.
They do not have an aldehyde functional group. Which means they cannot reduce copper (1)(blue) to the copper (II)(red)
66
Examples of monosaccharides.
Glucose, fructose and galactose.
67
What is a reducing agent?
It donates electrons during redox reaction and is itself oxidised.
68
What is the test for reducing sugars?
Benedict’s test
69
What is the test for non reducing sugars?
Benedict’s test
70
What are lipids?
- They are a group of substances that are soluble in alcohol rather than water.
- They are not polar so do not attract water molecules.
- Lipids are macromolecules.
71
What is a triglyceride?
It consists of a glycerol and 3 fatty acid tails. It is not a polymer but instead is a very large, organic molecule known as a macromolecule.
72
What are the three types of lipids?
- triglycerides
- phospholipids
- cholesterol
73
Why are lipids not polymers?
They are not made of repeating units
74
What is a fatty acid?
A molecule with a hydrocarbon chain and a carboxylic acid.
75
What’s a glycerol?
A three carbon alcohol molecule that forms the basic structure to which fatty acids are joined in a triglyceride.
76
What happens during the synthesis of triglycerides?
1)Both of these molecules contain hydroxyl
(OH) groups.
2) The hydroxyl groups interact leading to the formation of
three water molecules and bonds between the fatty acids
and glycerol molecule.
3) These bonds are called ester bonds and this reaction is called
esterification.
4) Esterification is another example of a condensation reaction.
77
Describe what happens during the breakdown of triglycerides.
Three water molecules need to be supplied to reverse the reaction that formed the triglyceride. This is another example of hydrolysis reaction.
78
What do kinks in hydrocarbon tails do?
They push the molecules slightly apart and make the fatty acids more fluid meaning polyunsaturated lipids have lower melting points.
79
Describe phospholipids.
- they are present in all biological membranes.
- phospholipids have the same structure as triglycerides except one of the fatty acid tails are replaced by a phosphate.
80
What is the structure of a phospholipid?
They have non polar long chain hydrocarbons they are hydrophobic so repel water
They have a charged end of the molecule that is hydrophilic so attracts water.
Has a phosphate group
81
What are the functions of lipids?
1) membrane formation and the creation of hydrophobic barriers.
2) hormone production.
3) electrical insulation necessary for impulse transmission
4) waterproofing, e.g. bird feathers and on plant leaves.
82
What are the functions of triglycerides?
1) energy source: can be broken down in respiration to release energy and generate ATP.
2) energy source: are insoluble in water and so can be stored without affecting the water potential of the cell.
3)insulation: adipose tissue is a storage location for lipids. Lipid in nerve cells acts as an electrical insulator.
4) buoyancy: because fat is less dense than water, it is used by aquatic mammals to help them stay float.
5) protection: humans have fat around delicate organs.
83
What are the functions of phospholipids?
1) Phospholipids are found in the cell membranes of all eukaryotes and
prokaryotes. They make up the phospholipid bilayer.
2) Cell membranes control what enters and leaves a cell. Phospholipid heads
are hydrophilic and their tails are hydrophobic, so they form a double layer with
their heads facing outwards towards the
water on either side of the membrane.
3) The middle of the phospholipid
bilayer is hydrophobic. This means that
water-soluble substances can’t easily
pass through it and so the membrane
acts as a barrier.
84
What are sterols?
1) Sterols are also known as steroid alcohols and are another type of lipid
found in cells.
2) They are not fats or oils and have very little structurally in common with
them.
3) Sterols are complex alcohol molecules based on a four carbon ring structure
with a hydroxyl (OH) group at one end.
4) They have dual hydrophilic/hydrophobic characteristics like phospholipids.
5) Cholesterol is an example of a sterol.
85
What is cholesterol?
1) Cholesterol is a small and hydrophobic molecule, which means it can sit in
the middle of the hydrophobic part of the bilayer.
2) Cholesterol has a hydrocarbon ring structure attached to a hydrocarbon tail.
3) The ring structure has a polar hydroxyl (OH) group attached to it. This part is
hydrophilic. The rest of the structure is hydrophobic.
86
What is the role of cholesterol?
1) The body manufactures cholesterol primarily in the liver and intestines.
2) Important role in the formation of cell membranes, becoming positioned
between the phospholipids. This adds to the stability of cell membranes and
regulates their fluidity by keeping the membranes fluid at low temperatures
and stopping them becoming too fluid at high temperatures.
3) The steroid hormones testosterone,
oestrogen and vitamin D are all made
from cholesterol. Because they are
small and hydrophobic they can pass
through the hydrophobic part of the
cell membrane.
