Biochemistry - Outcome 1 Flashcards
(96 cards)
1
Q
what are nucleic acids?
A
large molecules built up from nucleotides which are joined together to form long unbranded chains
2
Q
what are the 2 types of nucleic acids?
A
- deoxyribonucleic acid (DNA)
- ribonucleic acid (RNA)
3
Q
what 3 components make up nucleotide subunits?
A
- a pentose sugar
- a nitrogenous base
- phosphate/ phosphoric acid
4
Q
what is the formula for the ribose sugar found in RNA?
A
C5H10O5
5
Q
what is the formula for the ribose sugar found in DNA?
A
C5H10O4
6
Q
where on the deoxyribose sugar does it lack an oxygen atom?
A
on carbon 2
7
Q
what are the 2 purine bases found in DNA?
A
adenine and guanine
8
Q
what are the 2 pyrimidine bases found in DNA?
A
cytosine and thymine
9
Q
what are the 2 purine bases found in RNA?
A
adenine and guanine
10
Q
what are the 2 pyrimidine bases found in RNA?
A
cytosine and uracil
11
Q
what are the steps involved in building a nucleotide?
A
- condensation reaction between carbon 1 of the sugar and the base results in the formation of a N-glycosidic bond
- further condensation reaction between this molecule and a phosphate produces a nucleotide
bond formed between carbon 5 of sugar and phosphate is a phosphoester bond
both bonds formed are strong covalent bonds
12
Q
how are DNA nucleotides joined together?
A
- by covalent bonds that have formed between carbon 3 on the sugar and the phosphate group of the next nucleotide
- produces a sugar-phosphate backbone
- forms a phosphodiester bond
13
Q
how many hydrogen bonds are there between adenine and thymine?
A
two hydrogen bonds
14
Q
how many hydrogen bonds are there between cytosine and guanine?
A
three hydrogen bonds
15
Q
how are ribonucleotides joined together?
A
by covalent bonds formed between carbon 3 of the sugar of one nucleotide and the phosphate group of the next nucleotide
16
Q
what are the three types of RNA present in cells and involved in protein synthesis?
A
- mRNA
- rRNA
- tRNA
17
Q
what is the function of mRNA?
A
carries the sequence information from DNA in nucleus to the site of protein synthesis in the cytoplasm
18
Q
what is the function of rRNA?
A
component of ribosomes on which protein synthesis occurs
19
Q
what is the function of tRNA?
A
picks up amino acids and transports them to ribosomes for assembly into polypeptides
20
Q
what are the 2 processes in protein synthesis?
A
transcription and translation
21
Q
describe the process of transcription
A
- occurs in nucleus
- hydrogen bonds in DNA are broken and double helix unwinds
- one strand of DNA acts as a template
- complementary strand of mRNA is produced
- mRNA detaches from DNA strand and leaves through a pore in nuclear envelope
- in cytoplasm mRNA attaches to a ribosome
22
Q
describe the process of translation?
A
- occurs on ribosomes in cytoplasm
- mRNA binds to ribosome and is read 3 bases at a time (codons recognised and paired with complementary anticodons on tRNA molecules)
- two amino acids joined together by peptide bond
- tRNA molecules are then released
- ribosome moves one codon further along the mRNA
23
Q
what bond joins two adjacent amino acids together?
A
peptide bond
24
Q
what are proteins polymers of?
A
amino acids
25
what is the single carbon atom in the middle of an amino acid called?
alpha carbon
26
what are the four groups attached by covalent bonds to a single carbon atom?
- basic amino group
- acidic carboxyl group
- hydrogen atom
- side chain (R group)
27
what is the charge of the R group of on an acidic amino acid?
negatively charged
28
what is the charge of the R group on basic amino acid?
positively charged
29
what can the R group on an uncharged amino acid be classified as?
polar or non-polar
30
what are examples of acidic amino acids?
- aspartic acid (Asp)
- glutamic acid (Glu)
31
what are examples of basic amino acids?
- arginine (Arg)
- lysine (Lys)
- histidine (His)
32
what are examples of uncharged polar amino acids?
- serine (Ser)
- glutamine (Gln)
33
what are examples of uncharged non-polar amino acids?
- leucine (Leu)
- glycine (Fly)
- valine (Val)
34
what are essential amino acids?
amino acids that humans cannot synthesise so they obtain them from their diet
35
what are examples of essential amino acids?
- valine
- leucine
- lysine
36
how many essential amino acids are there?
8
37
what are the four types of structures of proteins?
- primary structure
- secondary structure
- tertiary structure
- quaternary structure
38
what is the primary structure of a protein?
it is specific to each protein and is coded for the by DNA of the cell
39
what can small changes in the amino acid sequence lead to in proteins?
large changes in the properties and functions of the protein
40
what are each ends of an amino acid called?
- N-terminal
- C-terminal
41
what are the two types of secondary structure in proteins?
- α-helix
- β-pleated sheets
42
how are proteins held in an α-helix structure?
- coils in the polypeptide chain are held by hydrogen bonds
- bonds form between H atoms of the amino group of one amino acid and the oxygen atom of the carboxyl group of another amino acid further along the chain
43
how are proteins held in a β-pleated sheet structure?
hydrogen bond formation takes place between carboxyl group and amino groups of the amino acid residues of one chain and the carboxyl group and amino groups of the neighbouring chains
44
what are the types of bonds that are commonly found in tertiary structures of proteins?
- hydrogen bonding
- disulphide bonding
- ionic bonding
45
how can proteins be described as having a quaternary structure?
they may consist of more than one polypeptide chain
46
how is a fibrous protein formed?
- by several spiral-shaped polypeptide molecules linked together by cross bridges
- gives molecule a rope-like structure
47
what are some examples of structural proteins that are made up of fibrous proteins?
- actin
- myosin
- keratin
- collagen
48
are fibrous protein soluble or insoluble in water?
insoluble
49
describe the structure of globular proteins?
folded into spherical shapes
50
what are examples of globular proteins?
- enzymes
- antibodies
- hormones
51
are globular proteins soluble or insoluble in water?
soluble
52
give an example of a fibrous protein and its function
- keratin
- structure - forms structural network in skin, hair and nails
53
give an example of a globular protein and its function
- haemoglobin
- transport- oxygen and carbon dioxide to and from body's cells
54
what are lipids?
fats and oils
55
describe lipid's solubility
- insoluble in water
- soluble in organic solvents eg. chloroform
56
what are the three types of lipids?
- triglycerides (TAGs)
- phospholipids
- glycolipids
57
what are fats and oils and how are they formed?
esters that are formed by a condensation reaction between glycerol and fatty acids
58
what does glycerol contain?
three hydroxyl groups
59
what do fatty acid molecules consist of?
long non-polar hydrocarbon chains with a polar carboxyl group at one end
60
what are saturated fatty acids?
fatty acids that possess only single bonds in their hydrocarbon chain
61
what are unsaturated fatty acids?
fatty acids that have one or more double bond in their hydrocarbon chain
62
how do fatty acids play an important role in cells?
- can be broken down to release energy for cell metabolism or built up into triglycerides forming an energy store
- can be converted into phospholipids which are important constituents of cell membranes
63
what do TAGs from animal sources tend to contain?
saturated fatty acids
64
what do TAGs from plant sources tend to contain?
unsaturated fatty acids
65
what are TAGs main function?
energy store
66
where are fats stored in animals?
adipose tissue (fat cells)
67
what are the functions of TAGs
- protects vital organs
- provides insulation
- in aquatic animals - buoyancy
68
what is stored as triglycerides in adipose tissue and why?
capacity to store TAGs is unlimited
- carbohydrates
- proteins
- triglycerides
69
how are phospholipids different to TAGs?
one of the fatty acid chains has been replaced by a small polar group which is attached to a phosphate molecule
70
what does it mean if a molecule is said to be amphipathic?
they contain both polar and non-polar portions
71
what is a phosphate group further joined by in phospholipids?
alcohol groups
72
what are examples of alcohol groups?
- serine
- ethanolamine
- choline
73
what are examples of glycolipids that are derived from alcohol?
- cerebrosides
- gangliosides
74
what is another group of lipids and what are they synthesised from?
steroids
- synthesised from cholesterol
75
what is cholesterol?
steroid precursor
76
what is the plasma membrane made from?
lipid bilayer
77
what lipids are found in the plasma membrane?
- phospholipids
- glycolipids
- cholesterol
78
what do lipids act as in the plasma membrane?
a barrier to the entry or exit of charged or polar substances such as ions or glucose
79
what molecules can freely diffuse across the membrane?
- small non charged molecules: oxygen, carbon dioxide
- small charged molecules: water
80
what do glycolipids act as in the cell membrane and give an example
cell identity markers
- ABO markers found on red blood cells
81
what is the ratio of carbon, hydrogen, and oxygen in a monosaccharide?
1:2:1
82
what do ALL monosaccharides contain?
- a carbonyl group
- at least two hydroxyl groups
83
what are the simplest monosaccharides called?
trioses
- contain 3 carbon atoms
84
what are examples of hexoses?
- glucose
- galactose
- fructose
85
what is a more stable arrangement for aldoses?
six carbon ring
86
what is a more stable arrangement for ketoses?
five carbon ring
87
what is an α-glucose?
where the hydroxyl group on carbon 1 sits below the ring
88
what is a β-glucose?
where the hydroxyl group on carbon 1 sits above the ring
89
what is the bond called that is formed between two monosaccharides?
α-1,4 glycosidic bond
90
what is starch a mixture of?
amylose and amylopectin
91
what type of glycosidic bond is in amylose and what is its shape?
- α 1,4 glycosidic bond
- unbranched chain wound into helix
92
what type of glycosidic bond is in amylopectin and what is its shape?
- α 1,4 glycosidic bond with some α 1,6 glycosidic bond
- tightly packed branched chain
93
what type of glycosidic bond is in glycogen and what is its shape?
- α 1,4 glycosidic bond with more α 1,6 glycosidic bonds
- very branched compact molecule
94
what type of glycosidic bond is in cellulose and what is its shape?
- β 1,4 glycosidic bond
- unbranched straight chains
95
what does starch act as in plants and why?
- storage molecule
- compact
- insoluble
- no osmotic effects
- easily hydrolysed to soluble sugars by enzyme action when required
96
what does glycogen act as in the liver and muscle of animals and why?
- energy store
- takes up very little space
- reduces glucose concentrations
- no osmotic effects
- readily hydrolysed into glucose
