Biological Molecules Flashcards
(112 cards)
1
Q
What are all living organisms made up of?
A
All living things are made from four key elements:
Carbon-C
Hydrogen-H
Oxygen-O
Nitrogen-N
Phosphorus-P and Sulfur-S also have important roles in cell biochemistry.
2
Q
What is bonding?
A
When two or more atoms connect.
3
Q
What is a molecule?
A
Two or more atoms covalently bonded together.
4
Q
What is an ion?
A
An atom or molecule in which the total number of electrons is not equal to the total number of protons.
Cations are positivly charged-lost electrons
Anions are negatively charged-gained electrons
5
Q
What is a polymer?
A
Molecules made from many monomers joined together e.g starch,cellulose
6
Q
What is an organic substance?
A
A substance that contains carbon bonded with hydrogen.
7
Q
What is an inorganic substance?
A
A substance that lacks C-H bonds.
8
Q
What is the structure of water in relation to its function?
A
-Hydrogen bonds give water a high specific heat capacity and a high latent heat of evaporation.
-Water’s polarity makes it very cohesiveand a good solvent.
-Water is less dense when it’s solid.
9
Q
What are monomers?
A
Small units which are the components of larger molecules.
10
Q
What is a condensation reaction?
A
A reaction in which two molecules join together by a chemical bond with the release of a watermolecule.
11
Q
What is a hydrolysis reaction?
A
The opposite of condensation reaction and is when water is added to break a chemical bond between molecules.
12
Q
What would a single monomer be called?
A
A monosaccharide
13
Q
What would a pair of monomers be called?
A
A disaccharide
14
Q
What would a large chain of monomers be called?
A
A polymer
15
Q
What are the bonds in carbohydrates called?
A
Glycosidic bonds
16
Q
What is hexose monosaccharide?
A
Glucose
17
Q
What is pentose monosaccharide?
A
Ribose
18
Q
What are the two isomers of glucose?
A
alpha glucose and beta glucose.They have the same chemical formula,but their structures are slightly different.
19
Q
How are disaccharides formed?
A
Two monosaccharides can join together by a glycosidic bond in a condensation reaction to form a dissacharide.In this process a water molecule is produced.
20
Q
What is maltose?
A
A disaccharide formed by condensation of two glucose molecules.
21
Q
What is Sucrose?
A
A disaccharide formed by condensation of glucose & fructose
22
Q
What is lactose?
A
A disaccharide formed by condensation of glucose & galactose
23
Q
What is a polysaccharide?
A
A macromolecule consisting of more than two sugars joined together by glycosidic bonds.They arent sugars.
24
Q
How is glycogen formed?
A
By the condensation of alpha glucose molecules.
25
How is starch formed?
By the condensation of alpha glucose molecules.
26
How is cellulose formed?
By the condensation of beta glucose molecules.
27
What is glycogen?
-The main energy storage molecule in animals.
-A multi-branched alpha glucose polymer.
-Joined together by 1,4 & 1,6 glycosidic bonds
-Has side branches to allow energy to be released quickly.
-Stored in the muscles & liver
-A relatively large and compact molecule.
-Its insoluble to water
28
What is starch?
-A mixture of two polysaccharides called amylose and amylopectin.Which are both long chain alpha glucose polymers.
-Its the main form of carbohydrate used for energy storage in plants.
-Starch grains are stored in the chloroplasts and are insoluble in water.
29
What is cellulose?
-A polysaccharide found in plants.
-Consists of long chain beta glucose polymers joined together by 1,4 glycosidic bonds.
30
What are lipids?
-Macromolecules containing carbon,hydrogen and oxygen atoms-a lower proportion of oxygen than carbohydrates.
-Non-polar and hydrophobic
-2 groups of lipids:Triglycerides and Phospholipids
-Play an important role in energy yield,energy storage,insulation and hormonal communication.
31
How are triglycerides formed?
-A condensation reaction between one glycerol and three fatty acid chains.
-The hydroxyl groups of glycerol combine with the carboxyl groups of the fatty acids to form an ester linkage(esterification).
-Leading to the formation of three molecules of water.
-They're broken down (e.g metabolism) by hydrolyisis reactions.
32
What is an ester linkage(esterification)?
When hydroxyl groups of glycerol combine with the carboxyl groups of the fatty acids in a condensation reaction.:
(-An H from glycerol combines with an OH from the fatty acid to make water)
(-For each ester bond formed a water molecule is released)
33
The structure of water in relation to it's function.
-Hydrogen bonds give water a high specific heat capacity and a high latent heat of evaporation
-Water's polarity makes it very cohesive and a good solvent
-Water is less dense when it's solid
34
What is Specific Heat Capacity?
The capacity needed to raise the temperature of 1 kilogram of a substance by 1 degree.
35
What is latent heat of evaporation?
The temperature needed to cause 1kg of a substance to evaporise.
36
What is cohesion?
The attraction between molecules of the same type
37
What gives water a high specific heat capacity?
The hydrogen bonds as they can absorb a lot of energy
38
Why does water have a high latent heat of evaporation?
It takes a lot of energy to break the hydrogen bonds between water molecules so,it uses a lot of energy when it evaporates.
39
Why is water cohesive?
Water molecules are attracted to eachother due to their hydrogen bonds, helping it to flow making it good for transporting substances.It also helps water be transported up plant stems in the transpiration stream.
40
Why is water polar?
-It has a slightly positive end and a slightly negative end.
-Therefore,the positive end attracts to the negative ion and the negative end attracts to the positive ion.
-This ensures the ion is fully surrounded by water molecules dissolving it.
41
Why is water being polar beneficial?
Water's polarity makes it a useful solvent in living organisms e.g in humans,important ions can dissolve in the water in blood and be transported around the body.
42
Why is water less dense when it's solid?
-At low temperatures water freezes
-Water molecules are held further apart from eachother as they each form four hydrogen bonds to other water molecules,creating a lattice structure.
-This then causes ice to be less dense than liquid water - which is why ice floats.
43
Why is ice being less dense useful for living organisms?
In cold temperatures,ice forms an insulating layer on top of water - the water below doesn't freeze.This means organisms like fish don't freeze and can still move around freely.
44
Why is water a good solvent?
-Molecules are polar enabling water molecules to bind to solute molecules.
-Hydrogen ions used to regulate pH
-Sodium ions regulate water potential
45
Why is water acting as a solvent important for the survival of organisms?
-It works as a medium for (metabolic reactions)
-Able to dilute toxic substances
-Allow ionic compounds to separate
46
What is capillary action?
-The process by which water can rise up a narrow tube against the force of gravity.
-It happens as a result of cohesion and adhesion in water.
47
What is adhesion?
Adhesion is the ability of water molecules to bond with other molecules. This allows water to stick to windows and other substances
48
What properties of water make it an ideal habitat for amphibians?
-Its a good solvent with high specific heat capacity and temperature stability
-It also has high density as ice is less dense than water therefore amphibians like frogs float/are buoyant.
49
How are polymers broken down to become monomers?
They break down by hydrolysis reactions,which break the chemical bond between monomers using a water molecule.
50
What are the functions of lipids?
-Storage of energy for long term use (e.g triglycerides)
-Hormonal roles (e.g steroids such as oestrogen and testosterone)
-Insulation - both thermal (triglycerides) and electrical (sphingolipids)
-Protection of internal organs (e.g triglycerides and waxes)
-Structural components of cells (e.g phospholipids and cholesterol)
Mneumonic-SHIPS
51
What are the main types of lipids?
-Triglycerides
-Phospholipids
52
What are the two types of triglycerides?
Saturated and Unsaturated
53
What are Saturated triglycerides?
-Fatty acids that possess no double bonds.
-This generates fats that are usually solid at room temperature
-Saturated fatty acids are linear in structure and originate from animal sources.
54
What are Unsaturated triglycerides?
-Fatty with double bonds - either monounsaturated (1 double bond) or polyunsaturated (>double bond)
-They're bent in structure and originate from plant sources (i.e oils)
-Usually liquid at room temperature and are called oils
55
What are phospholipids?
-Structurally similar to triglycerides but one fatty acid chain is replaced with a phosphate group
-Has a hydrophilic 'polar head' meaning it attracts water
-Has hydrophobic fatty acid 'tails' meaning they repel water
56
What is a phospholipid bilayer?
Phospholipids are amphipathic (have both hydrophobic and hydrophilic parts)
This as a result causes the phospholipid molecules to form bilayers in water.
57
What is the function of phospholipids?
-Play a crucial role in forming the plasma membrane of cells.
-In an aqueous environment being polar means a bilayer can be formed.
-They form a bilayer with the Fatty acid tails facing into eachother,and the polar heads face outwards dissolving in the aqueous intra and extracellular fluids.
-Hydrophilic heads can hold the structure of the cell surface membrane.
Structure allows them to form with glycolipids with carbohydrates which are important on the cell surface membrane for cell recognition.
58
What are phospholipids ideal for?
Forming plasma membranes as they enable integration of other molecules into the 'mosaic' and help to regulate the movement in and out of the cell.
59
Which lipid is found in cell membranes?
Phospholipids
60
What are sterols
They're another type of lipid found in cells
61
What is Cholesterol?
-A sterol manufactured primarily in the liver and intestines
-Has a 4 carbon ring structure with a hydroxyl(OH) group at one end.
-It is insoluble in water
62
Why is cholesterol important?
-It's important for the formation and fluidity of cell surface membranes and in the production of hormones e.g. testosterone
-Needed to make Vitamin D
63
How is insoluble cholesterol transported in the bloodstream?
It is combined with proteins to form soluble lipoproteins.
64
What are lipoproteins?
Cholesterol that has combined with proteins.
65
What are the two major lipoproteins
Low density lipoproteins(LDLs)
High density lipoproteins(HDLs)
66
What are low density lipoproteins(LDLs)?
-Made when Triglycerides(from fats in our diet) that combine with cholesterol and proteins
-Carry cholesterol from the liver to the rest of the body(body cells).
-Bind to receptors on cell surface membranes before being taken up by the cells where the cholesterol is involved in the synthesis and maintenance of cell membranes.
67
What happens to excess LDL?
It overloads on the membrane receptors resulting in high blood cholesterol levels,which may be deposited in the artery walls forming atheromas
68
What are high density lipoproteins(HDLs)?
-Made when Triglycerides(from fats in our diet) that combine with cholesterol and proteins
-Have a higher percentage of protein and less cholesterol in comparison to LDLs,hence their higher density
-They scavenge ex cess cholesterol in the body tssues and carry it back to the liver where it is broken down.
-This lowers blood cholesterol levels,and helps to remove the fatty plaques of atherosclerosis.
69
Why is it desirable to maintain a higher HDL:LDL ratio in the blood?
LDLs are associated with formation of atherosclerotic plaques whereas HDLs reduce blood cholesterol deposition.
70
What are some dietary factors that increase cholesterol levels?
Saturated fats - increase LDL levels within the body.
Trans fats - increase LDL levels and decrease HDL levels within the body,causing a significant rise in blood cholesterol levels.
71
What are some dietary factors that decrease cholesterol levels?
Saturated fats - increase HDL (but increase in LDL is greater)
Monounsaturated fats - Help the removal of LDLs from the blood
Polyunsaturated fats - Increase activity of the LDL receptor sites so the LDLs are actively removed from the blood
72
What are proteins?
Polymers containing monomers of amino acids.They're made up of one or more polypeptides
73
What is a dipeptide?
Two amino acids joined together by a peptide bond.
They are covalently bonded in a condensation reaction to form a dipeptide and the release of a water molecule.
74
What is a polypeptide?
-More than two amino acids joined together by peptide bonds.
-Can be broken down via hydrolysis reactions,which requires water to reverse the process.
75
What are amino acid?
They are recurring monomers found in proteins
Share a common basic structure,with a central carbon bound to:
-An amine (amino) group (-NH2)
-A carboxylic acid group (-COOH)
-A variable side chain (R)(there are 20 different R groups,therefore there are 20 different types of amino acid).
76
What is a peptide bond?
A covalent bond between amino acids.
Form between the amine and carboxylic groups of adjacent amino acids.
This is a C-N
The amino group loses a hydrogen (H) and the carboxylic acid loses a hydroxyl (OH) forming water.
77
What is the primary structure of a protein?
The specific sequence (order) and number of amino acids in a protein.
78
How is the primary structure of a protein determined?
It is determined by the gene.
79
What is the secondary structure of a protein?
The shape of the amino acids chains - either:
-alpha helix(Strong helical shape)
-beta pleated sheet (Weak - strength achieved through layering and bonds between layers)
80
What happens as a result of a-helices and B-pleated sheets?
Both a-helices and B-pleated sheets result from hydrogen bonds forming between non-adjacent amine and carboxyl groups
81
What is the tertiary structure of a protein?
The 3D shape of the protein formed from further twisting and folding
Held together by:
-Disulfide bridges
-Ionic bonds
-Hydrogen bonds]
-Hydrophilic/hydrophobic interactions
(NOT ALL PROTEINS HAVE ONE!)
82
How does the tertiary structure determine the function?
-A polypeptide chain will fold differently due to the interactions (and hence the bonds that form) between R groups.
-Each of the twenty amino acids that make up proteins has a unique R group and therefore many different interactions can occur creating a vast range of protein configurations and therefore functions.
83
What are hydrophobic/hydrophilic interactions?
When hydrophobic R groups are close together in the protein,they tend to clump together.This means that hydrophilic R groups are more likely to be pushed to the outside,which affects how the protein folds up in its final structure.
84
What are disulfide bridges?
Interactions between the sulfur in the R group of amino acid cysteine these.
Strong and not easily broken
85
What are ionic bonds?
Form between carboxyl and amino groups that are not involved in the peptide bond.
They are easily broken by pH and are weaker than disulfide bridges
86
What is the quaternary structure of a protein?
Interaction between two or more polypeptides.
Only exist therefore in proteins consisting of one or more polypeptides
87
Example of quaternary structure.
A good example is haemoglobin.
It becomes an active molecule upon the establishment of its quaternary structure.
Has 4 sub chains - its role is to carry iron and oxygen around the body
Has a globular quaternary structure
88
Another example of quaternary structure.
Collagen - has a fibrous quaternary structure.
89
What is a conjugated protein
It is a globular protein that contain a non-protein component called a prosthetic group.
An example is haemoglobin.
90
What do you call proteins without a prosthetic group?
A simple protein
91
What is the structure of haemoglobin?
A globular conjugated protein - has a prosthetic group attached
Made up of 4 polypeptide chains/sub units (2 a subunits and 2 B subunits)
Each of the four polypeptide chains have a prosthetic group called Haem
A Haem group contains iron,which oxygen binds to.
Hydrophobic R groups inside,Hydrophilic R groups outside
92
What is a fibrous protein?
Generally composed of long and narrow stands and have a structural role.
93
Name 3 fibrous proteins.
Collagen
Keratin
Elastin
94
What is collagen?
Its a fibrous protein
Its a connective tissue found in skin,tendons,ligaments and the nervous system.
One molecule of collagen is made up of 3 polypeptide chains twisted around each other in a long,strong rope-like structure.
Its flexible
95
What is Keratin
Group of proteins found in skin,hair,nails.
Contains a large proportion of the sulphur containing amino acid Cysteine.
This results in the formation of many strong disulphide bridges,forming strong,inflexible and insoluble materials
Degree of disulphide bonds determine the flexibility of the protein.
96
What is elastin
A fibrous protein
Found in elastic fibres
Present in the walls of blood vessels & in the alveoli of the lungs
Elastin gives these structures the flexibility to expand when needed
Quaternary protein
Made from many stretchy molecles called tropelastin
97
What are the 5 nucleotides?
Guanine
Thymine (DNA only)
Uracil (RNA only)
Adenine
Cytosine
98
What is the common structure of nucleotides?
A ribose sugar joined to a phosphate group and a nitrogenous base
99
What is DNA?
Deoxyribonucleic acid
100
What is RNA?
Ribonucleic acid
101
Which nucleotides are purines?
Adenine and Guanine
102
Which nucleotides are pyrimidines?
Cytosine,Thymine and Uracil
103
What is the difference between purines and pyrimidines?
Purines have a double ring structure whereas pyrimidines have a single ring structure
104
What are nucleotides?
They are monomers that need to bond to other nucleotides to form polynucleotide molecules (e.g. mRNA).
Nucleotides bond between the phosphate group of one nucleotide and the sugar of another nucleotide.This is via a condensation reaction and the formation of a phosphodiester bond (consisting of the phosphate group and 2 ester bonds)
The chain of sugars and phosphates is known as the sugar-phosphate backbone
Polynucleotides can be broken down into nucleotides again via a hydrolysis reaction breaking the phosphodiester bonds.
105
What is ATP?
Adenosine triphosphate
106
How does DNA replicate?(continuous replication)
DNA polymerase always moves along the template strand in the same direction.It can only bind to the 3' (OH) end, so travels in the direction of 3' to 5'.
As DNA only unwinds and unzips in on direction,DNA polymerase has to replicate each of the template strands in opposite directions.
The strand that is unzipped from the 3' end can be continuously replicated is called the leading strand and goes through continuous replication.
107
How does DNA replicate?(discontinuous replication)
The other strand is unzipped from the 5' end,so DNA polymerase has to wait until a section of the strand has been unzipped and then work back along.
This results in DNA being produced in sections,called Okazaki fragments.These fragments then have to be joined.This strand is called the lagging strand and is said to undergo discontinuous replication.
108
What is a codon?
A triplet code in which three bases code for an amino acid.
109
Why is there different triplet codes?
There are 20 different amino acids and 64 different combinations of triplet code therefore some triplets code for the same amino acid
110
Why is the genetic code universal?
In almost all living organisms the same triplet of DNA bases codes for the same amino acid.
111
Why is the genetic code described as degenerate?
Its because for all amino acids (except methionine and tryptophan),there is more than one base triplet.
112
How is the genetic code non-overlapping?
it is read starting from a fixed point in groups of three bases.If a base is added or deleted then it causes a frame shift,as every base triplet after that,and hence every amino acid coded for,is changed.
