Biological Molecules 1 Flashcards
1
Q
What do organic compounds contain?
A
- they all contain carbon atoms
* They also contain atoms of hydrogen, oxygen and less frequently nitrogen, sulfur and phosphorus
2
Q
How many bonds can each carbon make, what shape does this make the carbon atom and what does this lead to the formation of?
A
Each carbon atom can make four bonds which usually form a Tetraherdal shape. This leads to the formation of branched chains, or rings, 9r any number of 3D shapes
3
Q
What is the ability of carbon to combine and make macromoleculee the basis of and what does it provide?
A
it is the basis of all biological molecules and provides the great variety and complexity found in living things
4
Q
What are carbohydrates useful for?
A
- they are important in cells as a usable energy source and for storing energy
- in plants, fungi and bacteria they form an important part of the cell wall
5
Q
What are the best known carbohydrates?
A
Sugars and starch
6
Q
In what forms do we see sucrose and starch?
A
- sucrose is the white crystalline sugar
* glucose is the energy supplier in sports and health drinks
7
Q
Where is starch found?
A
In flour and potatoee
8
Q
What is the basic structure of all carbohydrates?
A
They are all made up of carbon, hydrogen and oxygen
9
Q
What are the three main groups of carbohydrates?
A
Monosaccharides, disaccharides and polysaccharides
10
Q
What are monosaccharides?
A
- Simple sugars in which there is one oxygen atom and two hydrogen arome for each carbon present
- they have the general formula (CH2O)n where n= carbon atoms
11
Q
What are triose sugars, pentose sugars and hexose sugars.
A
- Monosaccharides
- Triose sugars (n =3) have three carbon atome and are important in the mitochondria where glucose is broken down into triose sugars during respiration. Molecular formula C3H6O3
- Pentose sugars (n =5) have 5 carbon atoms. Ribose and deoxyribose are important in the nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) which makes up the genetic material. Molecular formula C5H10O5
- Hexose sugars ( n = 6) have six carbon atoms. They are the best known monosaccharides, often taste swee5 and include glucose, galactose and fructose. C6H12O6
12
Q
What are the isomers of glucose, what do they result from and why do they affect the polymers that are made?
A
- the isomers are a-glucose and b-glucose
- they result from the different arrangements of the atoms on the side chains of the molecule
- the different isomers form different bonds between neighbouring glucose molecules and this affects the polymers made
- a-glucose and b-glucose have their H and OH on the side of the chain molecule the opposite side around
13
Q
Draw an a-glucose and b-glucose molecule
A
Look at snapchat camera roll
14
Q
How are disaccharides formed?
A
- from two monosaccharides joined together.
- they join in a condensation reaction to form a dissacharide and a molecule of water is removed
- the link between the two monosaccharides results in a covalent bond known as a glycosidic
15
Q
How do we show which carbon molecules are involved in a dissacharide bond and give examples
A
- we use numbers
* if carbon 1 on one monosaccharide joims to carbon 4 on another monosaccharide we call it a 1,4-glycosidic bond
16
Q
Draw the formation of a glycosidic bond
A
Look in snapchat camera roll
17
Q
Name the sources that the following disaccharides come from and the monosaccharides that make them: sucrose, lactose and maltose
A
- sucrose is stored in plants such as sugar cane and is made from a-glucose and fructose
- lactose is a milk sugar. The main carbohydrate found in milk. It is formed from a-glucose and b-galactose
- maltose is a malt sugar found in germinating seeds such as barley. It is made from a-gluclose and a-glucose
18
Q
What is a monomer?
A
A small milecule that is a single unit of a larger molecule called a polymer
19
Q
What is a polymer?
A
A long chain molecule made up of many smaller repeating monomer units joined together by chemical bonds
20
Q
What tests for reducing sugars and what are reducing sugars?
A
- Benedicts solution. It goes from blue to orange as the copper II ions are reduced to copper I ions.
- reducing sugars are all monosaccharides and some dissacharides
21
Q
What are polysaccharides?
A
- they contain 11 or more monosaccharides
* they are made of many monosaccharide units joined together by condensation reactions that form glycosidic bonds
22
Q
What are molecules with 3-10 sugar units known as?
A
Ogliosaccharides
23
Q
Why does the structure of polysaccharides make them ideal storage molecules?
A
- they can form very compact molecules so large numbersncan be stored in a cell
- the glycosidic bonds are easily broken, allowing rapid release of monosaccharide units for cellular respiration
- they are not very soluble in water so have little effect on water potential within a cell and cause no osmotic water movements
24
Q
How are the gylcosidic bonds betweeen two monosaccharides split and where does this take place?
A
- by a process called hydrolysis
- it is the reverse of the condensation reaction so water is added to the bond.
- polysaccharides are gradually broken down into shorter and shorter chains and eventually single sugars are left.
- hydrolysis takes place during digestion in the gut and also in the muscle and liver cells when the carbohydrate stores are broken down to release sugars for use in cellular respiration
25
Why is starch an important storage molecule in plants and where is it generally found?
* it is insoluble and compact but can be broken down rapidly to release glucose when it is needed
* storage organs such as potatoes are particularly rich in starch
26
What is starch made up of?
• primarily long chains of a-glucose
• it is actually a mixture of two compounds:
- amylose: an unbranched polymer made up of between 200 and 5000 glucose molecules. As the chain lengthens the molecule spirals qhich makes it more compact for storage
- amylopectin: a branched polymer of glucose molecules. The branching chains have many terminal glucose molecules that can ve broken off rapidly when energy is needed
27
What is amylose made up of?
It is made up purely of a-glucose molecules joined by 1,4-glycosidic bonds which is why the molecules are lont unbranched chains
28
What is amylopectin made up of?
Many of the glucose molecules are joined by 1,4-glycosidic bonds but there are a few 1,6-glycosidic bonds. This results in the branching chains that change the properties of a molecule
29
Why are starch rich foods good for you when doing sport?
The amylopectin releases glucose for cellular respiration rapidly when needed. The amylose releasee glucose more slowly over a longer period, keeping you going longer
30
Why is glycogen referred to as animal starch?
Because it's the only carbohydrate energy store found in animals
31
Apart from animals where else is glycogen an important storage carbohydrate?
In fungi
32
What are the similarities and differences between glycogen and starch in terms of structure?
* they are similar chemically
* they are both made up of many a-glucose units
* they are both very compact
* glycogen has more 1-6 glycosidic bonds giving it many side branches
33
Why is glycose an ideal source of glucose for active tissues with a constantly high rate of cellular respiration?
Because it has lots of side branches it can be broken down very rapidly
34
Why is cellulose an important feature in plants?
Because it makes up the cellulose cell wall which gives plants their strength and support
35
How is cellulose similar and different to glycogen and starch
* they all consist of long chains of glucose joined by glycosidic bonds
* However cellulose the monomer units are b-glucose and are held together by 1,4-glycosidic bonds where one of the monomer units has to be turned round (inverted) so the bonding can take place.
* The linking of b-glucose molecules means that the hydroxyl (-OH) groups stick out on both sides of the molecule. This means hydrogen bonds can form between the partially positively positively charged hydrogen atoms of the hydroxyl group and the partially negatively charged oxygen atoms in other areas of the glucose molecules. Thisnis knowm as cross-linking and holds the neighbouring chains firmly together
* cellulose molecules do not coil or spiral, they remain as long straight chains whereas starch molecules form compact globular molecules that are useful for storage
36
Draw the inverted b-glucose in cellulose
Look at snapchat camera roll
37
Why cant the human digest cellulose and what does it act as instead in the human diet? What can digest cellulose?
* they dont posses the enzymes needed to break down the 1,4- glycosidic bonds between the molecules of b-glucose
* it acts as roughage/ fibre in the human diet
* ruminants such as cows and sheep have bacteria, fungi and protozoa living in their gut which produce cellulose digesting enzymes
38
Why cant the human digest cellulose and what does it act as instead in the human diet? What can digest cellulose?
* they dont posses the enzymes needed to break down the 1,4- glycosidic bonds between the molecules of b-glucose
* it acts as roughage/ fibre in the human diet
* ruminants such as cows and sheep have bacteria, fungi and protozoa living in their gut which produce cellulose digesting enzymes
39
What are lipids used for?
* they form an intergral part of the cell membrane
* used as an energy store
* plants and animals convert spare food into oils or fats to use when needed
* seeds of plants contain lipids to provide energy for the seedling when it starts to grow
40
What is the difference between fats and oils and what are they both examples of?
* fats are solids at room temperatures
* oils are liquids at room temperature
* they are an important group of lipids
41
What are fats and oils made up of and how are these joined?
* fatty acids and glycerol
| * combined by ester bonds
42
What is the chemical formula of glycerol?
C3H803
43
What is the structure of fatty acids?
•all have a long hydrocarbon chain - a pleated backbone of carbon atoms with hydrogen atoms attached and a carboxyl group (-COOH) at one end
44
In what two ways can fatty acids vary?
* the length of the carbon chain can differ
| * the fatty acid may be saturated of unsaturated
45
What are the differences between saturated and unsaturated fatty acids?
• in saturated fatty acids each carbon atom is joined to the one next to it by a single covalent bond.
• in unsaturated fatty acids the carbon chains have one or more double covalent bonds in them:
- a monounsaturated fatty acid has one double bond
- a polyunsaturated fatty acid has more than one double bond
46
How is a fat or oil formed?
* A fat or oil results when glycerol combines with one, two, or three fatty acids to form a monoglyceride, diglyceride or a triglyceride
* a bond is formed in a condensation reaction between the carboxyl group (-COOH) of a fatty acid and one of the hydroxyl groups (-OH) of the glycerol.
* a molecule of water is removed and the resulting bond is known as an ester bond.
* this type of condensation reaction is called esterification.
* the nature of the lipid formes depends on which fatty acids are present. Lipids containing saturated fatty acids are more likely ro be solid at room temperature than unsaturated fatty acids
47
Draw the formation of a triglyceride
Look in snapchat camera roll
48
What happens when lipids are oxidised in respiration?
The bonds are broken and carbon dioxide and water are the ultimate products
49
What can the reaction of rhe oxidation of lipids be ised for?
To drive the production of a lot of ATP. Lipids, especially triglycerides store about three times as much energy as the same mass of carbohydrates
50
What is a key feature of lipids role in waterproofing organisms?
* Their hydrophobic nature
* oils are important in waterproofing the fur and feathers of mammals and birds
* insects and plants use waxes for waterproofing their outer surfaces
51
How do lipids act as insulators?
* a fatty sheath of lipids insulates your nerves so the electrical impulses travel quicker
* they insulate animals against heat loss (e.g. in whales they form a thick layer of blubber)
52
What does the low density of lipids help with?
The body fat of water mammals helps them to float easily
53
Why don't lipids interfere with the many water-based activities that go on in the cytoplasm of the cell?
Because they are insoluble in water
54
How are phospholipids formed?
Inorganic phosphate ions (-PO43-) are present in the cytoplasm of every cell. Sometimes one of the hydroxyl groups of glycerol undergoes an esterfication reaction with a phosphate group instead of with a fatty acid, and a simple phospholipid is formed
55
What different properties do the lipid and the phosphate parts of the phospholipid molecule have?
* the phosphate head carries a small negative charge and is soluble in water whereas the fatty acid chains of a phospholipid are neutral and insoluble in water.
* when phopholipids come inro contact with water the two parts of the molecule behave differently
* the polar phosphate part is hydrophillic and disolves readily in water. The lipid tails are hydrophobic so they do not dissolve in water.
* if the molecules are tightly packed in water they either form a monolayer, with the hydrophillic heads in the water and the hydrophobic lipid tails in the air or clusters called micelles. In a micelle all the hydrophillic heads point outwards and all the hydrophobic tails are inside
56
What is the structure of the unit membrane which is the basis of all membranes?
•with water on either side the phospholipid molecules form a bilayer with the hydrophillic heads pointing into the water, protecting the hydrophobic tails in the middle
57
What are the functions of proteins?
* they form hair, skin and nails
* they form the enzymes needed for metabolism and digestion
* they form many of the hormones that controp various body systems
* they enable muscle fibres to contract
* they form antibodies
* they help clot your blood
* they transporr oxygen in the form of haemoglobin
58
What elements do proteins contain?
They all have carbon, hydrogen, oxygen and nitrogen ane many contain sulfur
59
What monomers join together in condensation reactions to form proteins and how many are there?
* amino acids
* there are about 20 naturally occuring amino acids that can combine in different ways to form a vast range of different proteins
60
What is the basic structure of amino acids?
* They all have an amino group (-NH2) and a carboxyl group (-COOH) attached to a carbon atom. They also all have an R group.
* The R group is what varies between amino acids.
* the R group is where sulfur and selenium are found in the structure of a few amino acids.
* the structure of the R group affects the way the amino acid bonds with others in the protein, depending largely on whether the R group is polar or not
61
How do amino acids join together?
* they join together by a reaction between the amino group of one amino acid and the carboxyll group of another
* they join in a condensation reaction a d and a molecule of water is lost.
* A peptide bond is formed when two amino acids join and a dipeptide is the result
* the R group is not involved in this reaction
* more and more amino acids join to form polypeptide chains which contain from a hundred to many thousands of amino acids
62
Draw two amino acids joining together to form a dipeptide
Look in snapchat camera roll
63
What other bonds apart from peptide bonds form between the amino acids in a chain to form the 3D structure of a protein?
Hydrogen bonds, disulfide bonds and ionic bonds
64
What are hydrogen bonds?
* in amino acids tiny negative charges are present on the oxygen of rhe carboxyl groups and tiny positive charges are present on the hydrogen of the amino groups
* when these charged groups are close to eachother the opposites attract, forming a hydrogen bond
* hydrogen bonds are weak, but they can potentially form between any two amino acids positioned correctly, so there are lots of them holding the protein together very firmly
* hydrogen bonds break easily and reform if pH or temperature conditions change. They are very important in the folding and coiling of the polypeptide chains
65
What are disulfide bonds?
* they form when two cysteine molecules are close together in the structure of a polypeptide
* an oxidation reaction takes place between the two sulfur containing groups, resulting in a strong covalent bond known as a disulfide bond.
* these bonds are much stronger than hydrogen bonds but occur much less often
* they are important for holding the folded polypeptide chains in place
66
What are ionic bonds?
* they can form between some of the strongly positive and negative amino acid side chains found buried deep in the protein molecule
* these links are known as salt bridges.
* they are strong bonds but they are not as common as the other structural bonds
67
What does blow drying or straightening your hair do?
Breaks the hydrogen bonds and reforms them with the hair curling a different way temporarily until the hydrogen bonds reform in their original places
68
What does perming do?
Reaks the disilfude bonds between the polypeptide chains and reforms them in a different place. This effect is permenant
69
In what ways can the structure of proteins be described?
They have a primary, secondary, tertiary and quaternary structures
70
What is the primary structure of a protein?
The sequence of amino acids that make up the polypeptide chain, held together by peptide bonds
71
What is the secondary structure of a protein?
* The arrangement of the polypeptide chain into a regular repeating structure held together by hydrogen bonds
* one example is the right handed a-helix, a spiral coil with the peptide bonds forming the backbone and the R groups sticking out in all directions.
* another is the b-pleated sheet in which the polypeptide chain folds into regular pleats held together by hydrogen bonds between the amino and carboxyl ends of different amino acids. Most fibrous proteins have this sort of structure
* sometimes there is no regular secondary structure and the polypeptide forms a random coil.
72
What is the teriary structure of a protein?
* it is a level of 3D organisation imposed on top of the secondary structure in many proteins.
* the amino acid chain, including any a-helices and b-pleated sheets is folded further into complicated shapes.
* hydrogen bonds, disulfide bonds and ionic bonds hold these 3D shapes in place
* globular proteins are an example of tertiary structures
73
What is the quaternary structure of a protein?
* it is only seen in proteins consisting of several polypeptide chains.
* the quaternary structure describes the way these seperate polypeptide chains fit together in 3 dimensions
* examples include some important membranes and haemoglobin
74
What is the structure and function of fibrous proteins?
* they have little or no tertiary structure
* they are long, parallel polypeptide chains with occasional cross linkages that form into fibres
* they are insoluble in water and are very tough which makes them ideally suited to their structural functions within organisms
* they appear in the structure of connective tissue in tendons and the matrix of bones, in the structure of muscles, as the silk of spiders webs and silkworm cocoons and as the keratin that makes up hair, nails, horns and feathers
75
What is collagen?
A fibrous protein that gives strength to tendons, ligaments, bones and skin. It is the most common structural protein found in animals.
76
What is the unusual structure of collagen that make it's strength comparable to that of steel?
* it is made up of 3 polypeptide chains which are each up to 1000 amino acids long.
* the primary structure of these chains is repeating sequences of glycine with two other amino acids, often proline and hydroxyproline.
* the three a-chains are arranged in a unique triple helix held together by large numbers of hydrogen bonds.
* these collagen molecules which can be up to several mm long are often found together in fibrils that in turn are held together to form collagen fibres
77
What is the genetic disease called where the collagen triple helix may not form properly and what does this mean in terms of symptoms?
* osteogenesis imperfecta
* this means the bone lacks tensile strength because collagen fibres are usually found combined with bone tissues. This means the bone is brittle and breaks very easily
78
What is the structure of globular proteins?
* They have complex tertiary and sometimes quaternary structures.
* they fold into spherical (globular) shapes
* they are very large
79
How do globular proteins behave in water?
they are so big that they form a colloid and so play an important role in holding molecules in position in the cytoplasm
80
In what ways are globular proteins important?
* they are important in your immune system as they make up antibodies
* they form enzymes and some hormones
* they are involved in maintaining the structure of the cytoplasm
81
Haemoglobin is a globular protein. Describe the rest of it's structure
* it is a very large molecule made up of 574 amino acids arranged in four polypeptide chains which are held together by disulfide bonds.
* each chain is arranged around an iron containing haem group
* it is a conjugated protein as well as a globular one
* it is the iron that enables the haemoglobin to bind and release oxygen molecules
* it is the arrangement of the polypeptide chains that determines how easily the oxygen binds and is released
82
What are conjugated proteins?
Protein molecules joined with or conjugated to another molecule called a prosthetic group
83
Chlorophyll is a conjugated protein. What prosthetic group does it contain?
A prosthetic group that contains magnesium
84
What are glycoproteins, what is their function and where are they found?
* they are proteins with a carbohydrate prosthetic group
* the carbohydrate part of the molecule helps them hold onto a lot of water and also makes it harder for protein digesting enzymes (proteases) to break them down.
* lots of lubricants used by the human body such as mucus and the synovial fluid in joints are glycoproteins whose water holding properties make them slipery and viscous which reduces friction.
85
What are lipoproteins, what is their structure and what do they do?
• they are proteins conjugated with lipids and are verg important in the transport of cholesterol in the blood
• the lipid part of the molecule enables it to combine with the lipid cholesterol.
• there are two main forms of lipoproteins in the blood:
- low density lipoproteins (LDLs). About 22nm in diameter
- high density lipoproteins (HDLs). About 8-11 nm in diameter
• the HDLs contain more protein than LDLs which is partly why they are denser: proteins are more compact than lipids
86
What does a prosthetic group in a protein do?
It usually affects the performance and function of the molecule
