2.1.2 biological molecules Flashcards
(114 cards)
1
Q
covalent bonding
A
atoms share a pair of electrons, stronger bonds, between non-metals
2
Q
ionic bonding
A
electrons are transferred from one atom to another, slightly weaker bonds, between metal and non-metal
3
Q
hydrogen bonding
A
slightly negative region of one polar molecule and slightly positive region of another attract each other to form a weak bond but can collectively form important forces that alter physical properties of molecules
4
Q
polymer
A
long chain molecule made up of a large number of repeating units linked together
e.g. protein, DNA, starch
5
Q
monomer
A
small basic molecular unit that make up polymers
e.g. amino acids, nucleotides, monosaccharides
6
Q
monomer: glucose
A
polymer: polysaccharide (amylose, amylopectin, cellulose, glycogen)
7
Q
monomer: amino acid
A
polymer: polypeptide (protein)
8
Q
monomer: nucleotides
A
polymer: nucleic acid (DNA, RNA)
9
Q
all carbohydrates contain…
A
carbon
hydrogen
oxygen
10
Q
all proteins contain…
A
carbon
hydrogen
oxygen
nitrogen
sometimes sulfur
11
Q
all nucleic acids contain…
A
carbon
hydrogen
oxygen
nitrogen
phosphorous
12
Q
all lipids are made of…
A
carbon
hydrogen
oxygen
13
Q
glucose
A
hexose sugar
alpha and beta glucose
14
Q
uses of water
A
- as a reactant in cells e.g. photosynthesis, hydrolysis
- provides structural support in cells
- keeps organisms cool to maintain an optimum body temperature
15
Q
properties of water
A
- metabolic importance
- high heat capacity
- heat of vaporisation
- cohesive properties
- useful as a solvent
16
Q
water molecules are made from…
A
2 oxygen
1 hydrogen
17
Q
what does it mean that water is a polar molecule?
A
oxygen atoms are slightly negatively charged
hydrogen atoms are slightly positively charged
18
Q
explain hydrogen bonding in water
A
the polarity of water molecules means that a hydrogen atom on one water molecules is attracted to the oxygen atom on another water molecule
19
Q
hydrolysis reaction
A
a bond is broken and a water molecule is used up
ATP + H20 –> ADP + P + energy
20
Q
condensation reaction
A
a new bond is formed and a water molecule is released
ADP + P + energy –> ATP + H20
21
Q
what is the latent heat of vaporisation
A
the amount of energy needed to change 1kg of a liquid to a gas
22
Q
explain the high heat of vaporisation that water has
A
as liquid water heats up, the 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 temperature regulation
23
Q
what is specific heat capacity?
A
the amount of heat 1kg of a substance must absorb or lose to change its temperature by 1oC
24
Q
explain the high heat capacity of water
A
water has a high heat capacity so takes a long time to heat and cool
- the SHC of water is much larger than sand - land cools faster than the sea
- water is used by warm blooded animals to more evenly disperse heat in their bodies
25
explain water being a good solvent
- water is a good solvent because ions and polar molecules can easily dissolve in it
- water is a polar molecule - meaning that the positive end of the water molecule attracts negative ions and the negative ends will attract positive ions
26
what does cohesion mean?
the strong attraction between water molecules due to hydrogen bonds
27
explain water having cohesive properties
cohesion produces surface tension where water meets air
- water forms droplets when placed on a dry surface
- plant use this to help transport water from their roots to their leaves
28
explain water as a habitat
- water makes an ideal habitat
- highly stable environment that does not change easily
- provides a stable habitat for many species
29
explain formation
smaller, biological molecules in an organism's cells can form larger, molecules that can be used around the body
these biological molecules are important to allow the organism to survive
30
explain a condensation reaction
forms large, biological molecules
releases water
bonds the smaller components together into larger molecules
31
products of condensation of amino acids
produces proteins
32
products of condensation of two monosaccharides
produces disaccharides
33
products of condensation of fatty acid and monoglyceridess
produces lipids
34
explain breakdown
- when an organism eats, it ingests large, biological molecules
- these biological molecules are important to allow the organism to survive
- molecules could be used in the cells for important reaction but are too large to be transported into the cells
- large molecules must be broken down first
35
explain a hydrolysis reaction
- breaks down large, biological molecules
- requires water
- splits larger molecules into smaller components
- smaller molecules can easily diffuse into cells or be transported using protein channels
36
products of hydrolysis of protein
produces amino acids
37
products of hydrolysis of carbohydrate
produces disaccharides and monosaccharides
38
products of hydrolysis of lipids
produces fatty acids and monoglycerides
39
disaccharide definition
two monosaccharides joined together
40
examples of monosaccharides
simple sugars
- glucose
- galactose
- fructose
41
structure of glucose
hexose sugar with the chemical formula C6H12O6
42
function of glucose
important source of energy in humans
during cellular respiration, the energy released from glucose helps to make ATP
43
what are isomers?
have the same molecular formula but a different arrangement of atoms in space
e.g. alpha and beta glucose
44
alpha and beta glucose
carbon atoms are numbered from 1-6 and the OH (hydroxyl) groups are in a different orientation around C1
45
what is a pentose sugar?
monosaccharides that have five carbon atoms in their structure e.g. ribose
46
what is ribose
a pentose sugar that is one of the three main components of the nucleotides found in RNA and DNA
47
maltose equation
glucose + glucose --> maltose
48
sucrose equation
glucose + fructose --> sucrose
49
lactose equation
glucose + galactose --> lactose
50
functions of disaccharides
sucrose is table sugar
lactose is found in milk
51
what is lactose intolerance?
common problem where the body is unable to digest lactose
52
what are polysaccharides?
made of two or more monosaccharides joined together by glycosidic bonds
chain may be branched or unbranched
chain may contain different types of monosaccharides
53
examples of polysaccharides
starch
glycogen
cellulose
chitin
54
what are glycosidic bonds?
monosaccharides form glycosidic bonds with neighbouring monosaccharide molecules to form polysaccharides
-OH groups from neighbouring monosaccharides undergo a condensation reaction to form an O-link between two monosaccharides with water being released
55
how to break a glycosidic bond?
reverse reaction of hydrolysis occurs during which water is added
56
what does ATP stand for?
adenosine triphosphate
57
what is starch?
a polysaccharide formed by condensation reactions of alpha-glucose molecules
58
functions of starch
- main energy storage material in plants
- stored in seeds of plants
- broken down into glucose by plants when they need more energy
- can act as a source of food for humans and animals
59
properties of starch
- does not change the water potential in a cell because its insoluble in water
- made up of amylopectin and amylose - both alpha-glucose polysaccharides
60
what is amylopectin?
- highly branched chain of alpha-glucose monomers
- branched structure means that enzymes can easily access the glycosidic bonds and so the glucose molecules can be quickly released when needed
61
what is amylose?
- linear chain of alpha-glucose monomers
- glucose chains have a helical structure meaning that the amylose strands can pack closely together making this form of starch good for storage
62
test for the presence of starch
1. place a small sample into the dimple of a spotting tile or to a boiling tube
2. add a few drops of iodine and observe any colour change
if starch is present, solution will change from orange --> blue-black
63
amylopectin structure and function
long, branched structure that makes it ideal for quick energy release
64
amylose structure and function
long, unbranched, helical structure that makes it ideal for storage
65
what is glycogen?
formed by condensation reactions of alpha-glucose molecules and is the main energy storage material in animals
66
function of glycogen
- highly branched molecule similar to amylopectin
- when animals need to release energy, glycogen's highly branched structure means that glucose can be released fast
67
how is glycogen used in the human body?
- good storage molecule as its compact
- when blood glucose levels decrease, glycogen is broken down to release glucose - glycogenolysis
68
what is cellulose?
major component of cell walls in plants
69
structure of cellulose
- long chain of beta-glucose
- beta-glucose molecules are linked by glycosidic bonds to form linear cellulose chains that are unbranched
- microfibrils are strong fibers that are made of many cellulose chains that are held together by hydrogen bonds
70
function of cellulose
- most abundant natural polymer
- the cell walls of plant cells are mostly made of cellulose
- these cell walls offer structural support because of the strength of the microfibril fibres that they are made of
71
digestion of cellulose
cannot be broken down by human digestive enzymes
herbivores like cows and horses are able to digest plant material rich in cellulose
72
what are triglycerides?
type of lipid that are mainly used as energy storage molecules
73
how are triglycerides formed?
formed by the condensation of one molecule of glycerol and three molecules of fatty acid
ester bonds form between the glycerol and the fatty acid chains
one water molecule is released per ester bond
so three molecules of water are released per triglyceride formed
74
structure of fatty acids
- have long 'tails' made of a chain of hydrocarbons with 4-36 carbon atoms
- the hydrocarbon tail is variable but most fatty acids contain 12-18 carbons
- glycerol links to the central carbon atom on fatty acids
75
types of fatty acids
saturated and unsaturated
76
functions of triglycerides: energy release
- chemical energy is stored in the fatty acid hydrocarbon tails
- so lost of energy is released when triglycerides are broken down
77
functions of triglycerides: energy
- lipids contain lots of energy
78
function of triglycerides: repel water
- lipid micelle structure
- insoluble in water because fatty acid tails are hydrophobic
- means that the cell's water potential is not affected by triglycerides
- this is important so that water does not enter the cell through osmosis
79
function of triglycerides: lipid droplets
- in cells, the insoluble triglycerides crowd together as droplets because the hydrophobic fatty acid tails face inwards
80
what are phospholipids?
type of lipid that forms a bilayer
main component of cell membranes and are responsible for controlling what goes into and out of cells
81
structure of phospholipids
- composed of fatty acid chains attached to glycerol
- two hydrophobic fatty acid tails and a hydrophilic phosphate group
- both hydrophobic and hydrophilic - amphipathic molecule
82
difference between the structure of phospholipids and triglycerides
both: composed of fatty acid chains attached to glycerol
difference: one of the three hydrophobic fatty acid tails is replaced by a hydrophilic phosphate group in phospholipids
83
hydrophobic tail of phospholipid
- two fatty acid chains
- two fatty acid chains are hydrophobic and cannot interact with water
- in membranes, the hydrophobic fatty acid tails face inside the cell - meaning that water-soluble substances can't pass through easily
84
hydrophilic head of phospholipid
- the modified phosphate group in phospholipids is hydrophilic and can interact with water
- in membranes, the hydrophilic phosphate group faces outside
85
what is a saturated fatty acid?
when there are only single bonds between carbon atoms in the hydrocarbon chain
86
structure of saturated fatty acids
- carbon atoms are not joined by double bonds in saturated fatty acids
- the number of hydrogen atoms attached to the carbon skeleton is maximised. this means the fatty acid is saturated
87
function of saturated fatty acids
- saturated fats are solid at room temp and usually of animal origin
- linked to increased risk of cardiovascular disease in humans
- foods with high proportion of saturated fat include cream, cheese butter etc
88
what is an unsaturated fat?
when the hydrocarbon chain contains at least one double bond
89
structure of unsaturated fats
- have one or more double bonds between carbon atoms in the hydrocarbon chain
- foods with unsaturated fatty acids include cooking oil
90
why are unsaturated fats liquid at room temp?
double bonds kink the carbon chain so unsaturated fats cannot pack together tightly
91
structure of proteins
- made up of amino acids
92
what are dipeptides?
formed from the condensation of two amino acids
93
what are polypeptides?
formed by the condensation of many amino acids
94
structure of amino acids
- each amino acid has a central carbon atom (alpha carbon)
- four groups of atoms bonded to the central carbon atom
an amino group
a carboxyl group
a hydrogen atom
a side group
95
what are the four atoms or groups of atoms bonded to the alpha carbon in an amino acid?
NH2 - an amino group
COOH - a carboxyl group
H - a hydrogen atom
R - a side group
96
what is the R group in amino acids?
different in each amino acid
determines how the amino acid interacts and bonds with other amino acids in the polypeptide
97
essential amino acids
there are 20 different types of amino acids
9 of which are essential in humans because the human body cannot produce them and they are obtained from diet
98
what is glycine?
an example of an amino acid
has a hydrogen atom in its R group
the only amino acid that does not have a carbon atom in its R group
99
what are polypeptides?
made from chains of amino acids
amino acids are at the end of each polypeptide chain
these amino acids form the two end terminals:
- N-terminal (amine terminal)
- C-terminal (carboxyl terminal)
100
explain how a peptide bond is formed
when two amino acids react together, a bond forms between the carboxyl group and the amino group
one water molecule is released as a by-product
the bond formed between two amino acids is a type of covalent bond
101
primary structure of proteins
amino acids in a polypeptide chain are arranged in a specific sequence
primary structure is determined by the gene encoding the protein
102
explain the importance of primary structure
- a change in the nucleotide sequence of the gene's coding region may lead to a different amino acid being added to the growing polypeptide chain
- a change in the amino acids in a protein could change the protein's structure and function
103
hydrogen bonding in proteins
amino acids in a polypeptide chain can form hydrogen bonds between other amino acids within the chain
hydrogen bonds cause the protein to fold into specific structures
104
secondary structure of proteins
folding of the polypeptide determines its secondary structure
many bonds throughout the molecule leads to high stability
may be decreased by environmental factors that weaken the hydrogen bonds e.g. temperature
105
types of secondary structures
alpha-helix
beta-pleated sheet
106
tertiary structure of proteins
interactions between R groups creates the complex 3D tertiary structure of proteins
usually coiled or folded
many weak and strong interactions that determine the final 3D shape of a protein - when the 3D shape is lost, it may no longer be functional
107
ionic bonds
charged amino acids have a positively or negatively charged ion in their side chain which can form relatively strong ionic bonds with other charged amino acids
ionic bonds between amino acids are quite rare
108
disulfide bridges
these are covalent bonds set up within proteins containing cysteine amino acids
109
hydrogen bonds in proteins
formed between amino acids
relatively weak but when there are many, the overall stability of the tertiary structure increases
110
quaternary structure of proteins
multiple 3D polypeptides can come together to form a complex, quaternary structure
111
examples of proteins with a quaternary structure:
insulin
collagen
haemoglobin
112
examples of proteins with a quaternary structure: insulin
- weak interactions between the subunits in the insulin polypeptide help to stabilise the quaternary structure
- insulin has a combination of hydrogen bonds and disulfide bridges that cause it to form a clumped, globular shape
113
examples of proteins with a quaternary structure: collagen
fibrous protein found in skin
114
examples of proteins with a quaternary structure: haemoglobin
contains four polypeptides surrounding a central haem group
