3 Biological molecules Flashcards
(156 cards)
1
Q
What’s the main function of glucose?
A
Energy source in animals and plants
2
Q
Monosaccharides join together by?
A
Glycosidic bonds
3
Q
What is dehydration synthesis?
A
Another word for condensation
4
Q
What happens in a condensation reaction to form 1,4 glycosidic bonds?
A
A hydrogen atom on one molecule bonds to a hydroxyl group (OH) on another molecule which releases a water molecule- creating a 1,4 glycosidic bond (carbon 1 joined to carbon 4)
5
Q
What happens in a hydrolysis reaction in carbohydrates?
A
A molecule of water reacts with the glycosidic bond, breaking the bond
6
Q
Which disaccharide is made from two alpha glucose molecules?
A
Maltose
7
Q
What’s the main function of starch?
A
Main energy store in plants
8
Q
What is starch made of?
A
Mixture of two polysaccharides: amylose and amylopectin
9
Q
What is the structure of amylose?
A
Formed by alpha glucose joined together by 1-4 glycosidic bonds.
Long, unbranched chain.
Angle of bond make it a tight cylindrical coil- further stabilised by hydrogen bonding within molecule.
10
Q
Why is the structure of amylose good?
A
Makes polysaccharide more compact and much less soluble.
11
Q
What is the structure of amylopectin?
A
Branched structure, alpha glucose - has 1-4 and 1-6 glycosidic bonds.
12
Q
What are the key properties of amylopectin?
A
Insoluble, branched and compact
13
Q
Why are the properties of amylopectin good?
A
Ideally suited for storage roles that they carry out
14
Q
What is the main function of glycogen?
A
Main energy store in animals
15
Q
What’s glycogen made of?
A
Polysaccharide of alpha glucose
16
Q
What’s the structure of glycogen?
A
Very branched where glucose can be added or removed- speeds up processes of storing and releasing glucose molecules.
Coiling/branching means they’re compact
17
Q
How do triglycerides release energy?
A
Chemical energy is stored in the fatty acid hydrocarbon tails so lots of energy is released when triglycerides are broken down
18
Q
How are triglycerides formed?
A
By condensation of one molecule of glycerol and three molecules of fatty acid
19
Q
What’s the bond formed between glycerol and fatty acid chains called?
A
Ester bond
20
Q
How many molecules of water are released per triglyceride formed?
A
3 (1 per each ester bond)
21
Q
How much energy do lipids contain compared to carbohydrates?
A
Carbohydrates contain half the amount of energy per gram as lipids do
22
Q
Why are triglycerides insoluble?
A
Because the fatty acid tails are hydrophobic
23
Q
Why is the insolubility of triglycerides important in cells?
A
It means that the cells water potential is not affected by the triglycerides.
This is important because if triglycerides didn’t repel water, the water would enter the cell through the process of osmosis and make the cells swell up.
24
Q
What are lipid droplets?
A
How the insoluble triglycerides crowd together as droplets (micelles) in cells because the hydrophobic fatty acid tails face inwards
25
What’s the difference between the structure of phospholipids and triglycerides?
They are both composed of fatty acid chains attached to glycerol but in phospholipids one of the 3 fatty acid tails is replaced by a hydrophilic phosphate group.
26
A phospholipid molecule has a hydrophobic and hydrophilic part. What is this kind of molecule called?
An amphipathic molecule
27
In membranes, where do the fatty acid tails face and what does this mean?
Inwards
| Means that water-soluble substances can’t easily pass through the membrane
28
Where do the hydrophilic heads face in phospholipids?
The outside
29
What is the list common number of carbon atoms found within fatty acids?
12-18 carbons
30
What kind of energy do lipids store?
Chemical energy
31
What is the structure of saturated fatty acids?
Carbon atoms not joined by any double bonds
| Saturates because number of H atoms attached to carbon skeleton is maximised
32
What are saturated fats at room temperature?
Solids
33
What are saturated fats linked to?
An increased risk of cardiovascular disease in humans
34
What is the origin of saturated fats?
Animal origin usually (from animals)
35
Examples of foods with high proportion of saturated fats?
Cream, cheese, butter, other whole milk dairy products and fatty meats
36
What is the structure of a mono-saturated fat?
One double bond present between carbon atoms
37
What is the structure of a polyunsaturated fat?
More than one double bond between carbon atoms
38
Why are unsaturated fats liquids at room temperature?
Double bonds kink the carbon chains so they can’t pack together tightly
39
What are the chemical elements found in carbohydrates?
Carbon, hydrogen and oxygen
40
What are the chemical elements found in lipids?
Carbon, hydrogen and oxygen
41
What are the chemical elements found in proteins?
Carbon, hydrogen, oxygen, nitrogen, sulfur
42
What are the chemical elements found in nucleic acids?
Carbon, hydrogen, oxygen, nitrogen and phosphorus
43
What are the uses of water?
As a reactant in cells (e.g. photosynthesis, hydrolysis)
Provides structural support in cells
Keeps organisms cool to maintain optimum body temperature
44
What are the properties of water?
```
Good metabolite
High heat of vaporisation
High heat capacity
Good solvent
Cohesive properties
```
45
What is a water molecule made from?
One oxygen atom
| Two hydrogen atoms
46
Why is water a polar molecule?
Oxygen atoms are slightly negatively charged and the hydrogen atoms are slightly positively charged
47
What is hydrogen bonding between water molecules?
The polarity of water molecules means that a hydrogen atom (+) on one water molecule is attracted to the oxygen atom (-) on another water molecule
48
Why is O slightly neg and H slightly pos in a water molecule?
H shares a pair of electrons with O. O has a greater affinity for elections than H so ‘pulls’ electrons closer making it slightly negative
49
Why is water a good metabolite?
Water is used or formed in many metabolic reactions such as condensation and hydrolysis
50
What is the latent heat of vaporisation?
The amount of energy needed to change one gram of liquid substance to a gas
51
Why does water have a high heat of vaporisation and why is this good?
As liquid water heats up, hydrogen bonding makes it difficult to separate the water molecules from each other. This means that a lot of energy is needed for water to evaporate.
When water evaporates, energy is used up- this cools the environment where the evaporation is taking place. This is why sweating helps with body temp regulation.
52
What is specific heat capacity?
The amount of heat one kg of a substance must absorb or lose to change its temp by 1 degree Celsius
53
Why is it beneficial that water has a high heat capacity?
It takes a long time to heat and cool. This makes it a stable habitat and means that internal temp changes in body are minimised- easier to achieve a stable body temp.
Water is used by warm blooded animals to evenly disperse heat in their bodies
54
Why is water a good solvent?
Ions and polar molecules can easily dissolve in it.
| Water is a polar molecule- means that + end of water molecule attracts - ions and - end will attract + ions.
55
What is cohesion?
The strong attraction between water molecules due to hydrogen bonds.
56
Why are the cohesive properties of water good?
Cohesion produces surface tension where water meets air.
| Used for transpiration in plants and allows creatures to skate and settle on surface of water.
57
Why is water an ideal habitat?
It is a highly stable environment that does not change easily.
58
What % of the human body is made up of water?
60-70%
59
What bond is formed between amino acids?
Peptide bonds
60
What are proteins?
A diverse group of large and complex polymer molecules, made up of long chains of amino acids
61
What bond is formed between amino acids?
Peptide bonds
62
What forms when many amino acids are joined together?
Polypeptide
63
What enzyme catalyses the reaction between amino acids?
Peptidyl transferase
64
Give three examples of monosaccharides in order of sweetness (high to low)
Fructose
Glucose
Galactose
65
What is a sugar with 5 carbon atoms called?
Pentose sugar
66
Give two important pentose sugars
Ribose (in RNA nucleotides)
| Deoxyribose (in DNA nucleotides)
67
What is formed when 2 monosaccharides join together?
A disaccharide
68
What do two glucose monosaccharides form?
Maltose
69
What do glucose and fructose form?
Sucrose (table sugar)
70
What do glucose and galactose form?
Lactose (in milk)
71
What is a polysaccharide?
2+ monosaccharides joined by glycosidic bonds
72
Give 4 examples of polysaccharides
Starch
Glycogen
Cellulose
Chitin
73
How are glycosidic bonds formed?
When OH groups from neighbouring monosaccharides undergo a condensation reaction to form a O-link between two monosaccharides
74
What is released during a condensation reaction?
Water
75
How do you break a glycosidic bond?
By hydrolysis
76
What type of monosaccharide is glucose?
Hexose
77
Why is energy released from glucose useful in cellular respiration?
Helps make ATP
78
Properties of glucose?
Polar and soluble in water
79
What is starch?
The main energy store in plants
80
Where is starch stored in plants?
In the seeds
81
Why is starch’s insolubility good?
Does not change water potential in cell
82
What are the two polysaccharides starch is made from?
Amylose and amylopectin
83
What is glycogenolysis?
When blood glucose levels decrease, glycogen is broken down to release glucose
84
What is glycogen stored as?
Small granules, especially in muscles and liver
85
What is the most abundant natural polymer?
Cellulose
86
What is the function of cellulose?
Main part of plant cell walls. Microfibrils provide structural support
87
What is the structure of cellulose?
Long straight chain of beta glucose
88
Why is the straight chain structure of cellulose good?
Makes it very strong meaning it prevents cells bursting when they take in excess water
89
What are microfibrils?
String fibres made of cellulose chains held together by hydrogen bonds
90
What do microfibrils join together to make?
Macrofibrils
91
What do macrofibrils join together to form?
Fibres
92
Properties of fibres?
Strong and insoluble
93
What gives structural stability in cellulose?
Hydrogen bonds formed between hydroxyl groups on adjacent parallel chains
94
Which polysaccharide cannot be broken down by human digestive enzymes?
Cellulose
95
What does cellulose form in our diet?
Very hard to break down into monomers so forms ‘fibres’ or ‘roughage’ necessary for a healthy digestive system
96
What’s special about the bonding of beta glucose monomers?
Alternate glucose monomers turn upside down to ensure hydroxyl groups are on the same side (top or bottom)
97
What happens when stored glucose is needed for respiration?
Biochemical energy in stored nutrients is converted into a useable energy source for cell
98
What reaction does starch/glycogen undergo to release glucose?
Hydrolysis
99
What is required for a hydrolysis reaction?
Water molecules
100
What elements do nucleic acids contain?
Carbon, hydrogen, oxygen, nitrogen and phosphorus
101
What does a nucleotide contain?
A pentose monosaccharide (sugar)
A phosphate group- an inorganic molecule that is acidic and negatively charged
A nitrogenous base- complex molecule containing one or two carbon rings in its structure as well as nitrogen
Many nucleotides= nucleic acid
102
What polymer is formed when nucleotides are linked together by condensation reactions?
Polynucleotide
103
How do nucleotides link together?
Phosphate group at fifth carbon of pentose sugar of one nucleotide forms a covalent bond with the hydroxyl group at the third carbon of the pentose sugar of the adjacent nucleotide. These bonds are called phosphodiester bonds.
104
What do linked nucleotides form?
A long, strong sugar-phosphate backbone with a base attached to each sugar.
105
How are individual nucleotides released from a nucleic acid?
Phosphodiester bonds are broken by hydrolysis.
106
What does DNA stand for?
Deoxyribonucleic acid.
107
What is the sugar in DNA?
Deoxyribose. (Fewer oxygen atoms than ribose)
108
What are the two groups of bases?
Pyrimidines and purines.
109
What are the two pYrimidines? And what is their structure?
ThYmine and cYtosine- contain single carbon ring structures.
110
What are the two purines?
Adenine and guanine- contain double carbon ring structures.
111
What is the DNA double helix?
Two strands of polynucleotides coiled into a helix.
Two strands held together by hydrogen bonds.
Each strand has phosphate groups at one end and OH group at other end.
Parallel strands arranged so that they run in opposite directions- they are antiparallel.
112
What are the bonds between bases in a DNA molecule?
Hydrogen bonds.
113
What does adenine pair with?
Thymine.
114
How many bonds can adenine and thymine both form?
2
115
How many bonds can both cytosine and guanine both form?
3
116
What base does cytosine pair with?
Guanine.
117
What does RNA stand for?
Ribonucleic acid.
118
What does RNA do?
Plays an essential role in the transfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body.
119
How are RNA nucleotides different to DNA nucleotides?
RNA have ribose as the pentose sugar rather than deoxyribose and thymine base is replaced with uracil.
120
What is uracil?
A pyrimidine that forms two hydrogen bonds with adenine.
121
What happens to the RNA molecules after protein synthesis?
They are degraded in the cytoplasm. The phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused.
122
Why do cells divide?
To produce more cells needed for growth or repair of tissues.
123
What do two daughter cells produced as a result of cell divisions contain?
DNA with a base sequence identical to the original parent cell.
124
What is semi-conservative replication?
1. DNA helicase breaks hydrogen bonds between two polynucleotide DNA strands causing them to separate.
2. Free-floating DNA nucleotides join to the exposed complementary bases on each original template strand.
3. Activated nucleotides line up and are joined together by DNA polymerase. Hydrogen bonds form between the strands and strands twist to form a double helix.
4. Sugar phosphate backbone is formed by covalent bonds between the phosphate of one nucleotide and the deoxyribose sugar of the next.
5. Two new DNA molecules formed. Each new DNA molecule contains one strand from original molecule and one newly formed molecule (semi-conservative replication).
125
What causes a mutation?
Sequences of bases are not always matched exactly, and an incorrect sequence may occur in the newly copied strand. These errors occur randomly and spontaneously and lead to a change in the sequence of bases, known as a mutation.
126
What is the genetic code?
The sequence of bases along its DNA. Contains thousands of sections called genes of cistrons. Each gene codes for a specific polypeptide.
127
How was replication proven to be semi-conservative?
All bases in DNA contain Nitrogen and Nitrogen has two forms: light (14N) and heavy (15N).
Bacteria will incorporate nitrogen from their growing medium into any new DNA they make.
1. Grow bacteria in 15 N, 15N strand (2 strands of 15N) is heavy so makes a band low down the test tube.
2. Transfer cells to 14N and grow for one generation. Hybrid of 15N/14N (one of each) formed so one band in middle of test tube.
3. Grow for second generation in 14N. Light DNA (14N) (2 strands of 14N) and hybrid DNA (15N/14N) (one of each) mean two bands in test tube- one high up and one in middle.
This proves that the DNA split and kept one original strand while free nucleotides joined to make the second strand.
128
What does helicase do?
Separates the two DNA strands before replication. (like scissors)
129
What does a single-strand bunting protein do?
Keeps the separated DNA strands apart during replication.
130
What does DNA polymerase do?
Catalyses the formation of a new polynucleotide chain. (like glue)
131
What does DNA ligase do?
Joins together short sections of the lagging strand.
132
What is a gene?
A section of DNA that contains the complete sequence of bases (codons) to code for an entire protein.
133
What is a triplet code?
A sequence of three bases, called a codon. Each codon codes for one amino acid.
The code in the base sequences is a triplet code.
134
How many regularly occurring amino acids are there in biological proteins?
20
135
What is meant by the degenerate code?
Many amino acids can be coded for by more than one codon.
E.g, GAT GAA GAC and GAG all code for leucine.
136
What is a start codon?
Signals the start of a sequence that codes for a protein.
137
What do the three stop codons do?
Signal the end of the sequence.
138
What does having a single codon to signal the start of a sequence ensure?
The codons are read ‘in frame’. The DNA base sequence is ‘read’ from base 1, rather than base 2 or 3. So the genetic code is non-overlapping.
139
What is RNA?
A single-stranded chain of nucleotides.
140
What do cellular organisms use mRNA for?
Conveying genetic information that directs synthesis of specific proteins.
141
What sugar is present in mRNA and tRNA?
Ribose
142
What bases are present in mRNA and tRNA?
A G U C
143
How many DNA nucleotide bases code for a single amino acid?
3
144
Which nucleotide bases are common to DNA and RNA?
Adenine, guanine and cytosine.
145
Why is complementary base pairing important in DNA replication?
DNA can be replicated without error. Same sequence of nucleotides is produced.
Refuses occurrence of mutation.
Allows formation of hydrogen bonds.
146
Why is glucose well suited to its function in living organisms?
Soluble so easily transported.
Small so can diffuse across membranes.
Easily broken down to release energy.
Molecules can join to produce polysaccharides e.g. glycogen.
147
What types of activity to cells require energy for?
Synthesis
Transport
Movement
148
How is energy release from ATP?
Energy stored in phosphate bond- ATP broken down into ADP and inorganic phosphate. Energy released from the phosphate bond and used by cell.
149
What is ATP made up of?
Ribose sugar.
Adenine.
3 phosphate groups.
150
What does ADP made up of?
Adenine.
Ribose.
2 phosphate groups.
151
What’s messenger RNA?
Made in the nucleus.
| Carries genetic code from DNA in nucleus to cytoplasm, where it’s used to make a protein during translation.
152
What is transfer RNA?
Found in cytoplasm.
Has an amino acid binding site at one end and a sequence of three bases at the other end (anticodon).
Carries amino acids that are used to make proteins to the ribosomes during translation.
153
What happens in translation?
1. mRNA binds to small subunit of ribosome at its start codon.
2. tRNA with complementary anticodon binds to mRNA start codon. Carries corresponding amino acid.
3. tRNA with complementary anticodon to next codon and carrying the corresponding amino acid binds to the next codon on the mRNA.
3. Peptide bond forms between two amino acids, catalysed by peptide transferase.
4. Ribosome moves along mRNA, releasing first tRNA.
5. Process continues, producing polypeptide chain until stop codon in mRNA and polypeptide is released. Results in primary structure of protein.
154
What is glycine?
The smallest amino acid- the R group is a hydrogen atom.
155
What are the properties of ATP?
Small- moves easily into/out of cells.
Water soluble- energy-requiring processes happen in aqueous environments.
Contains bonds between phosphates with intermediate energy: large enough to be useful for cellular reactions but not so large that every is not wasted as heat.
Releases energy in small quantities- quantities are suitable to mist cellular needs, so energy not wasted as heat.
Easily regenerated- can be recharged with energy.
156
What does ATP stand for?
Adenosine triphosphate.
