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A Level Bio > Chapter 1 Carbs + Biological Molecules (1.1-1.6) > Flashcards

Chapter 1 Carbs + Biological Molecules (1.1-1.6) Flashcards

1
Q

What is hydrolysis used for

A

Breaking up polymers or removing monomers

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2
Q

What is condensation reactions for

A

Making a polymer

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3
Q

Examples of industrial polymers

A
  • Polyester
  • polythene
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4
Q

Natural polymers examples

A

_ polypeptides
- polynucleotide
- polysaccharide

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5
Q

How are hydrogen bonds formed in water

A
  • oxygen is electronegative making it slightly negative causing the hydrogen to be slightly positive
  • this makes it easier for water molecule to bond as H is positive and O is negative so they can bond and the bond between them is a hydrogen bond
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6
Q

What molecules have hydrogen bonding

A
  • hydrogen and fluorine
  • hydrogen and nitrogen
  • hydrogen and oxygen
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7
Q

What monomers are for polypeptide, polysaccharide and polynucleotide

A

Polypeptide- amino acids
Polysaccharide - monosaccharide
Polynucleotide- nucleotides

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8
Q

Properties of monosaccharides

A
  • sweet tasting
  • soluble in water
  • general formula (CH2O)n ——- n is a number from 3-7
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9
Q

Why does the Benedict’s reagent solution turn red as an indicator that there is a reducing sugar

A

Benedict’s reagent is an alkaline solution of copper(11) sulfate (hence why it stays blue if there is no reducing sugar) and when a reducing sugar is heated with the reagent it forms a red precipitate of copper (1) oxide

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10
Q

Large molecules often contain carbon. Explain why is this

A

Carbon easily bonds with other carbon atoms allowing a sequence of carbon atoms of various lengths to be formed, creating a backbone that other atoms can attach to allowing large molecules to form that contain carbon atoms

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11
Q

Examples of reducing sugars

A

All monosaccharides
Some disaccharides

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12
Q

Test for reducing sugars

A

1) add 2cm3 of the food sample into a test tube, if the sample is not a liquid form, first grind it up in water
2) add an equal volume of Benedict’s reagent
3) heat the mixture in gently boiling for 5 minutes

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13
Q

Three types of disaccharides that you need to know

A

Maltose
Lactose
Sucrose

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14
Q

What are the Monosaccharides that make up maltose, the reaction used and the bond formed

A

Monosaccharides: 2 alpha glucose
Reaction: condensation reaction
Bond: glycosidic bond

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15
Q

Monosaccharides that make up lactose

A

Alpha glucose and galactose

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16
Q

Monosaccharides that make up sucrose

A

Alpha glucose and fructose

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17
Q

3 types of polysaccharides that you need to know

A

Starch
Cellulose
Glycogen

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18
Q

What is starch, cellulose and glycogen made from

A

Starch: polymer of alpha glucose
Cellulose: polymer of beta glucose
Glycogen: polymer of alpha glucose

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19
Q

Uses for starch, cellulose, glycogen

A

Starch: storage
Cellulose: structure
Glycogen: storage

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20
Q

What are polysaccharides

A

Polymers formed by combining together many monosaccharide molecules joined together by glycosidic bonds formed in condensation reactions

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21
Q

Test for non reducing sugars

A

1) hydrolyse the disaccharide to form 2 monosaccharides by heating it with dilute hydrochloric acid
2) neutralise by slowly add sodium hydrocarbonate until it stops bubbling HCL as Benedict’s reagent cannot work in acidic conditions
3) test with litmus paper (red → blue) to make sure the solution is alkaline
4) heat with Benedict’s the positive result will form a red precipitate

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22
Q

What is formed when a polysaccharide is hydrolised

A

It forms monosaccharides or disaccharides

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23
Q

Where is glycogen found

A

Brain, liver, muscle

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24
Q

Why is glycogen good for the brain

A

Brain only uses glucose since it is so rich in neurons it is the most energy-demanding organ, using one-half of all the sugar in the body so stores glycogen to convert into glucose

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25
Characteristics of polysaccharides
- Large molecules so are insoluble - good for storage as they don’t alter osmotic pressure since they can't dissolve is water
26
Test for starch
1) add 2cm3 of the sample into a test tube 2) add 2 drops of iodine solution and Shake 3) positive - blue-black negative- red-brown
27
Monomers of starch
Alpha glucose
28
Monomers of glycogen
Alpha glucose
29
Monomers of cellulose
Beta glucose
30
Function of starch
Insoluble store of glucose
31
Structure of starch
- Coiled into a helix making it compact for storage - large and insoluble so doesn't diffuse out the cell or affect water potential and osmosis - amylose is an unbranched polymer of starch whilst amylopectin is a highly branched polymer of starch therefore amylopectin has more ends for faster hydrolysis - polymer of glucose so can be hydrolysed
32
Polymers of starch
- Amylose - amylopectin
33
Bond between monomers of starch
1-4 glycosidic bond (amylose) and 1-6 glycosidic band (amylopectin)
34
Monomers of glycogen
Alpha glucose
35
Bonds between monomers of glycogen
1-6 glycosidic bonds and 1-4 glycosidic bonds
36
Function of glycogen
Insoluble store of glucose
37
Structure of glycogen related to function
1) Highly branched - as it has more 1-6 glycosidic bonds so more ends for faster hydrolysis 2) Coiled into a helix so is compact 3) Polymer of glucose so easily hydrolysed 4) Insoluble so does not diffuse out of the cell and does not affect water potential
38
Bonds between monomers of cellulose
1-4 glycosidic bonds
39
Function of cellulose
Provides structural strength to cell wall
40
Structure of cellulose
- Straight unbranched chains parallel to each other held by many hydrogen bonds to form fibrils - the number of fibril creates a strong structure usual for its structural role
41
Test for lipids
1) take a dry and grease free test tube 2) add 2cm3 of the food sample to the test tube then add 5 cm3 of ethanol 3) Shake the tube thoroughly to dissolve any lipids in the sample 4) add 5cm3 of water and Shake gently Positive cloudy white emulsion negative clear
42
Control for test for lipids
Repeat the experiment using water instead of the sample and the final solution should be clear
43
Why is a cloudy white emulsion formed in lipid test
The lipids does not dissolve in the water so will float on top of the sample forming an emulsion and the Light passing through the lipid will be refracted as it passes from the oil to the water droplets making it appear cloudy
44
What causes lipids to be different
The fatty acids
45
What always stays the same in lipids
Glycerol
46
How are triglycerides formed
Through condensation between one molecule of glycerol and 3 molecules of fatty acids
47
What is the bond between fatty acids and glycerol called
Ester bond
48
Ester bond
C-o -c=o
49
Saturated
Carbon to carbon single bond
50
Unsaturated
Carbon to carbon double bond
51
How fatty acids differ
Length of carbon bonds Degree of saturation (number and presence of c=c )
52
Properties of triglycerides
- Energy source - metabolic water source - hydrophobic - good energy store
53
Why are triglycerides a good energy source
Due to a high ratio of energy storing Carbon to hydrogen bonds compared to the number of carbon atoms
54
Why are triglycerides a metabolic water source
Due to the high ratio of hydrogen to oxygen atoms they act as a metabolic water source as they can release water when oxidised
55
Why are triglycerides hydrophobic
they have a non-polar structure, which makes them insoluble in water
56
Why are triglycerides a good energy store
- they have a low mass to energy ratio so a lot can be stored without increasing the mass and therefore preventing the movement of an animal - they are large and insoluble so they don't affect water potential and osmosis so you can store lots of them for energy
57
What are phospholipids made up of
2 fatty acid chains and a phosphate group both attached to a glycerol
58
Why can the phosphate group of a phospholipid dissolve in water
As it contains a negative charge causing it to have a hydrophilic head and due to its negative charge it causes the molecule to be polar and since its polar it can dissolve in water
59
Why can't the lipids in phospholipids dissolve in water
As they Are non polar so will be hydrophobic
60
How are phospholipids positioned in water
The heads are exposed to water and the tails (lipids) are not forming a phospholipid bilayer membrane structure
61
Phospholipids properties
- Phospholipidbilayer creates a hydrophobic barrier between inside and outside the cell - phosphate heads maintains the structure of the membrane - phosphate heads can attach to carbs to form glycoproteins - useful in cell signalling
62
Roles of lipids
- Energy store - waterproof - Insulation and electricity - Protection
63
Why are lipids a good energy store
They are compact and lightweight so can store excess energy and stores twice as much energy as carbs
64
Examples of lipids being a good insulator of heat and electricity
- Heat layer of fat under skin - - electrical insulator in myelin sheath around nerves
65
How are animals and plants waterproof
Plants: cuticles on leaves Animals: oils from sebeaecaus glands
66
What are proteins
Polymers made up of the monomer amino acid
67
What are amino acids
Monomers that are joined by condensation reactions to form a polypeptide chain
68
4 levels of the structure of protein
Primary Secondary Tertiary Quaternary
69
What is the primary structure
The order of amino acids in the polypeptide chain, all held together by peptide bonds
70
What is a polypeptide chain
Chain of amino acids all joined together by condensation reactions supported by peptide bonds
71
What is the secondary structure
The coiling or folding of the polypeptide chains (from the primary structure) into alpha helices or beta pleated sheets due to the formation of hydrogen bonds between the amine group and carboxyl group of amino acids in the chain
72
Why does the secondary structure form the shapes of alpha helices and beta pleated sheets
Due to the hydrogen bonding between the c=o groups of the carboxylic acid of one amino acid and the n - h in the amine group of another amino acid ( o is electronegative and h is slightly positive forming hydrogen bonding)
73
What causes the tertiary structure to form
By the interaction (hydrogen bond/disulphide/ionic) between R groups causing the polypeptide chains to fold forming a more complex and specific 3d structure
74
Types of bonds used in a tertiary structure and where they are located and their strength
- Disulphide bridges- between R groups that contain sulfur such as cysteine molecules - fairly strong and not easily broken - Ionic bonds - between c=o and NH groups found on the R group - weaker than disulphide bridges and broken by pH changes - Hydrogen bonds - individually weak but provide strength in numbers - Hydrophobic and hydrophilic interactions - These are weak interactions between polar and non-polar R groups
75
What is the quaternary structure
many polypeptide chains and/or prosthetic groups bonded together by the same bonds found in the tertiary structure
76
What happens if a protein is denatured
The bonds which hold the secondary structure and tertiary structure in shape break and the unique 3d shape is lost
77
Conditions to denature a protein
- high temperature - high or low pH
78
Why is the primary structure important
As if one amino acid in the sequence is different it will cause the ionic/hydrogen/disulphide bonds to form in a different location causing a change in the 3d shape so will no longer function or have a different function
79
Why are saturated lipids better than unsaturated lipids
Since they can store more energy as they have a higher ratio of hydrogen to carbon bonds
80
What are conjugated proteins
Proteins in the quaternary structure contains prosthetic groups (non proteins) to help the protein carry out its role
81
Test for proteins
1) place the sample of the solution to be tested in a test tube and add equal volumes of the biuret reagent (sodium hydroxide solution) at room temperature 2) add a few drops of dilute copper (11) sulphate solution and mix gently (Blue->purple)
82
When bread becomes stale, the structure of some of the starch is changed. This changed starch is called retrograded starch. Scientists have suggested retrograded starch is a competitive inhibitor of amylase in the small intestine. Assuming the scientists are correct, suggest how eating stale bread could help to reduce weight gain
Less hydrolysis of starch; Accept no hydrolysis (To) maltose; (So) less absorption (of glucose)
83
define monomer
(a monomer is a smaller / repeating) unit / molecule from which larger molecules / polymers are made
84
define polymer
molecules made from a large number of monomers joined together
85
define monosaccharide
Monosaccharides are the monomers from which larger carbohydrates are made
86
how are triglycerides formed
Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid to form an ester bond
87
Roles of proteins
Enzymes - These proteins are used to breakdown and synthesise molecules. Antibodies - These proteins are involved in the immune response. Transport - Some proteins can move molecules or ions across membranes. Structural components - Proteins like keratin and collagen are used to create strong fibres. Hormones - Some of these are proteins that act as chemical messengers in the body. Muscle contraction - Muscles are made up of proteins.
88
Draw alpha and beta glucose and draw amino acid and draw fatty acid
89
How do Dipeptidase form
- Via a condensation reaction (key point) between two amino acids When two amino acids join, the hydroxyl (OH) in the carboxyl group of one amino acid reacts with the hydrogen (H) in the amino group of another amino acid. This releases a water molecule (H2O) and forms a peptide bond between the carbon of one amino acid and the nitrogen of another.
90
How do dipeptides form amino acids
Via a hydrolysis reaction a water molecule (H2O) is added to a dipeptide, the peptide bond is broken to release the two amino acids.

A Level Bio (25 decks)

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