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AS LEVEL BIOLOGY > Biological molecules > Flashcards

Biological molecules Flashcards

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1
Q

What are monosaccharides?

A

they’re soluble substances/ simple sugars with a general formula of( cH20) where n can be between 3-7

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2
Q

Examples of monosaccharides?

A
  • glucose
  • is a hexose with 6 carbon atoms (C6H1206)
  • highly soluble
  • galactose
  • hexose
  • not as soluble as glucose
  • important in the process of glycolipids and glycoproteins
  • fructose
  • hexose monosaccharides
  • very soluble
  • pentose
  • has 5 carbons
  • ribose and deoxynbose are in RNA and DNA are pentose
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3
Q

Disaccharides equations

A

glucose +glucose –> maltose
glucose +fructose –> sucrose
glucose + galactose –>lactose

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4
Q

What are Disaccharides?

A

2 monosaccharides joined together by glycosidic bonds

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5
Q

How is the glycosidic bond broken in disaccharides?

A

addition of water= hydrolysis

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6
Q

Hydrolysis in disaccharides

A
  • addition of water
  • breaks the glycosidic bond
  • releasing monosaccharides
  • this is called the hydrolysis
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7
Q

Condensation reaction in disaccharides

A
  • when two monosacchardies join
  • a molecule of water is removed
    this is the condensation reaction!
    a bond is then formed which is the glycosidic bond
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8
Q

Basic facts about polysaccharides

A
  • are polymers
  • large molecules formed by many monosaccharides
  • condensation reaction joins it together
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9
Q

examples of polysaccharides

A
  • starch
  • found in plants
  • cellulose
  • not used for storage but for structural storage to plant cells
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10
Q

Basic facts about starch

A
  • major energy source
  • energy storage
  • made up of chains of alpha glucose monosaccharides –> linked together by glycosidic bonds
  • -> formed by condensation reactions
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11
Q

Starch- alpha glucose molecules arrange in 2 different structural units:

A

Amylose:
- glucose molecules joined by alpha bonds
Amylopectin:
- glucose molecules joined by alpha bonds

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12
Q

starch- structure is suited for because:

A
  • insoluble so water is not drawn into cells by osmosis
  • being large
  • compact, stored in small spaces
  • made up of chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions
  • chains may be branched or unbranched. unbranched is wound into a tight coil making it very compact
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13
Q

basic facts glycogen

A
  • only found in animals and bacteria
  • stored as small granuals in the muscle and liver
  • more soluble than starch
  • use to store carbohydrates as glycogen
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14
Q

glycogen- structure suits if for storage

A
  • doesn’t diffuse out of cells
  • compact
  • insoluble so doesn’t tend to draw water into cells by osmosis
  • highly branched so can be rapidly broken down to form glucose monomers to be used in respiration
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15
Q

basic facts about cellulose

A
  • made of many monomers of b-glucose
  • very strong due to individual hydrogen bonds which prevents cells from bursting
  • cellulose has straight unbranched chains, allowing hydrogen bonds to form linkages
  • molecules are grouped to form microfibrils which provides more strength as they grouped to form fibres
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16
Q

extra facts about cellulose

A
  • major component of plant cells
  • provides ridgity to cell
  • cell wall prevents it from bursting as water enters by osmosis
  • cells are turgid
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17
Q

Cellulose - structure of cellulose issued to its function providing support and ridgity because:

A
  • cellulose molecules are made up of b-glucose
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18
Q

Basic facts about LIPIDS

A
  • Triglycerides are a type of lipid
  • Unsaturated- single bond
  • Saturated- double bond
  • Lipids are fats
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19
Q

Types of lipids

A
  • Triglycerides- fats and oils
  • Phospholipids
  • Steriods
  • Hormones
  • Cholesterol
  • Waxes
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20
Q

Characteristics of lipids

A
  • Contains C, H, O (less oxygen)
  • insoluble in water
  • water hating (hydrophobic)
  • don’t form polymers
  • soluble in organic solvents
  • building blocks are glycerol & fatty acids
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21
Q

function

A
  • Source of energy: when oxidised, lipids provide more than twice the energy
  • Waterproofing: lipids are insoluble in water
  • Insulation: Fats are slow conductors of heat and when stored beneath the body surface to retain body heat
  • Protection: Fat is often stored around delicate organs like kidneys
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22
Q

Lipids without fatty acids

A
  • steroids

- hormones

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23
Q

Lipids with fatty acids

A
  • triglycerides
  • phospholipids
  • waxes
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24
Q

Cis and Trans Fats

A
  • unsaturated fats can be cis and trans
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25
Q

In the Cis arrangement

A

the hydgrogen’s are on the same side of the double bond

26
Q

In the Trans arrangement

A

the hydrogen’s are the opposite side of the double bond

27
Q

Cis and Trans refers to the arrangement

A

of 2 hydrogen atoms to the carbon atoms involved in a double bond

28
Q

Formation of Triglyceride

A

1) reactions between fatty acids and glycerol are condensation reaction
2) the glyceride molecule is always the same but fatty acids vary
3) condensation reactions occur between the carboxyl group (COOH) the fatty acid and the hydroxyl group (OH) of the glycerol
4) an ester bond is formed
5) the hydrocarbon tail can be saturated or unsaturated. it can also vary in length
6) Triglycerides and hydrophone– there are no spare oxygen molecules for water to form hydrogen bonds with this makes them insoluble in water.

29
Q

Function of triglycerides

A
  • Triglycerides are insoluble in water, storage doesn’t affect osmosis in cells or the water potential of them
  • high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised and therefore provide a source of water
30
Q

Formation of phospholipids

A

1) reactions between fatty acids and phosphate group are condensation reactions
2) an ester bond is formed
3) phosphate head is hydrophillic
4) fatty acids tails are hydrophobic
5) molecules are polar due to the nature of having 2 opposing poles

31
Q

Protein basic facts

A
  • large complex polymers

- made up of long chains of amino acids

32
Q

proteins range of roles

A
  • structural – main component pf body tissue like muscle, skin and hair
  • catalytic 00 all enzymes are proteins
  • signalling – many hormones and receptors are proteins
  • immunological – all antibodies are proteins
33
Q

Structure of Amino acids

A
  • Amino group
  • Carboxyl group
  • Hydrogen atom
  • R group: variety of different chemical groups. 20 naturally occurring amino acids differ only in their R group
34
Q

Peptide bonds

A
  • 2 amino acids can join together to form a dipeptide, linked by peptide bond
  • peptide bond forms between carboxyl group on 1 amino acids and the amino group on the other
  • this produces water = condensation reactions
  • dipeptide can be split into 2 amino acids= hydrolysis reactions
35
Q

Polypeptides

A
  • more amino acids added to dipeptide = polypeptide
  • a protein consists of one or more poly peptide chains folded into highly specific 3D shape
  • 4 levels of structure:
  • primary
  • secondary
  • teritary
  • quarternary
36
Q

Dipeptide and Polypeptide formation

A
  • amino acids are linked together by condensation reactions to form dipeptides and polypeptides. A molecule of water released during the reaction. The bond formed between the amino acids are called peptide bonds
37
Q

Test for reducing sugars:

A

Maltose is a reducing sugar. A reducing sugar is a sugar that can donate electrons. The Benedicts test is a test for reducing sugar. Benedicts reagent is an alkaline solution of copper sulfate. The test:

  • Add 2cm3 of sample to the tube. if the sample isn’t in liquid form, grind it in water
  • Add an equal volume of Benedicts reagent
  • Heat the mixture in a water bath, reducing sugar is present if the solution turns into a brick red precipitate
38
Q

Test for non reducing sugars

A

Sucrose is a non reducing sugar. The test:

  • If the sample isn’t in liquid form, it needs to be ground up in water
  • Add 2cm3 of the sample to benedicts reagent in a test tube and filter
  • Place the test tube in a boiling water bath for 5 mins , if solution remains blue then a reducing sugar is not present
  • Add another 2cm3 of sample of dilute hydrochloric acid and then heat, the dilute hydrochloric acid will hydrolyse any disaccharide present into its monosaccharide
  • Then add sodium hydrogencarbonate to neutralise hydrochloric acid. Test with pH paper to check that the solution is alkaline
  • Re- test the resulting solution by heating it with 2cm3 of Benedict’s reagent in a water bath for 5 mins
  • If a non- reducing sugar is present, the benedicts reagent will now turn orange-brown. This is due to the reducing sugars produced from the hydrolysis of the non reducing sugar
39
Q

Test for Starch

A

Starch is detected by its ability to change the colour of iodine in potassium ioding from yellow to black. The test:

  • place 2cm3 of the sample into a test tube
  • add two drops of iodine solution and shake or stir
  • the presence of starch is indicated by a blue or black colouration
40
Q

A phospholipid is made up of two parts:

A
  • A hydrophillic ‘head’ which interacts with water (attracted to it) but not with fat
  • A hydrophobic ‘tail’ orients itself away from water but mixes itself with fat

Molecules that have two ends so are polar

41
Q

Structure of phospholipids

A
  • phospholipids are polar molecules, meaning in an aqauatic environment, phospholipid molecules form a bilayer within cell surface membrane. As a result, a hydrophobic barrie is formed between the inside and outside of cell
  • Hydrophillic phosphate ‘heads’ help hold the surface of the cell surface membrane
  • The phospholipid structure allows them to form glycolipids by combining with carbohydrates. These glycolipids are important in cell recognition
42
Q

Test for Lipids

A

Emulsion test:

  • To 2cm3 of sample being tested, add 5cm3 of ethanol
  • Shake the tube
  • Add 5cm3 of water and shake
  • A cloudy-white colour indicates the presence of a lipid
  • repeat procedures using water instead of the sample, the final solution should remain clear
43
Q

Primary structure of proteins - polypeptides

A

many amino acid monomers can be joined by polymerisation. The resulting chain of many hundred of amino acids is called a polypeptide. The sequence of amino acids in a polypeptide chain forms the primary structure of any protein

44
Q

Secondary structure of proteins

A

The linked amino acids that make up a polypeptide possess both -NH and -C =O groups on either side of every peptide bond
The hydrogen of -NH group has an overall positive charge while the O of the -C=O group has an overall negative charge.
These two groups therefore readily form weak bonds called hydrogen bonds
- This causes the long polypeptide chain can be twisted into a 3-D shape, such as the coil known as an a- helix

45
Q

Tertiary Structure of proteins

A

The a-helices of the secondary protein structure can be twisted and folded even more to give the complex and 3-D structure
The bonds:
- Disulfide bridges: which are fairly strong and therefore not easily broken
- Ionic bonds: which are formed between any carboxyl and amino groups. They’re weaker than disulfide bonds and are easily broken by changes in pH
- Hydrogen bonds: numerous but are easily broken because they’re weak

46
Q

Quarternary Structure of proteins

A
  • large proteins often form complex molecules containing polypeptide chains
  • iron containing haem groups in haemoglobin may be associated with molecules
  • it is the sequence of amino acids that determined the 3-D shape
47
Q

Test for proteins

A

Biuret test which detects peptide bonds:

  • add sodium hydroxide to the sample of the solution
  • add a few drops of very dilute copper sulfate solution and mix gently
  • a purple coloration indicates the presence of peptide bonds and hence a protein. if no protein is present, the solution remains blue
48
Q

What are enzymes?

A

Enzymes are globular proteins that act as catalysts therefore they speed up occuring reactions

49
Q

Enzymes acting as catalysts lowering activation energy

A

sucrose+water –> glucose + fructose
this reaction should take place under certain conditions:
- sucrose and water molecules must collide with sufficient energy to form glucose and fructose
- glucose and fructose must be less than that of the substances
- Many reactions require an initial amount of energy to start. The minimum amount of energy needed to activate the reaction –> activation energy

50
Q

Enzyme structure

A
  • Enzymes being globular proteins have a specific 3-D shape that is a result of their sequence of amino acids
  • A specific area of the enzyme is functional, this is known as the active site
  • The molecule on which the enzyme acts is called the substrate. This fits into the active site and forms an enzyme substrate complex
51
Q

Induced fit model

A

The enzyme is flexible and can mould itself around the substrate. As it alters its shape, the enzyme puts a strain on the substance molecule. The strain distorts a particular bond in the substrate and lowers the activation energy needed to break the bond

52
Q

Enzymes need to

A
  • come into physical contact with its substrate

- have an active which fits the substrate

53
Q

Effect of temperature on enzyme action

A
  • A rise in temperature increases the kinetic energy so molecules move around more rapidly and collide with each other
  • More effective collisions result in more enzyme substrate complexes and the rate of reaction increases
54
Q

Effect of temperature on a graph

A
  • the rising curve begins to cause the hydrogen and other bonds in the enzyme to break
  • active site changes shape
  • at first, substrate fits less easily into the changed active site, slowing the rate of reaction.
  • At some point, usually around 60 degrees, the enzyme is so disrupted that it stops working all together so its denatured which is a permanent change meaning it can’t function again
55
Q

Body temperature as 37 degrees

A
  • higher body temperatures would increase the metabolic rate, these advantages offset by the additional energy (food) that would be needed to maintain the higher temperature
  • Other proteins apart from enzymes, may be denatured at higher temperatures
  • At higher temperatures, any further rise in temperature, for example, during illness, might denature
56
Q

Effect of pH on enzyme action

A

An increase or decrease in pH reduces the rate of enzyme action. If the pH is extreme. The pH can affect how an enzyme works in a variety of ways:

  • A change in pH alters the charges on the amino acids that make up the active sites. As a result ESC can’t be formed
  • depending on how extreme the pH is, it may break the bonds holding together the tertiary structure
57
Q

Effect of enzyme concentration on the rates of reaction

A
  • once an active site on an enzyme has acted on it’s substrate, it repeats the procedure on another molecule. This means that the enzymes being catalysts are not used up in the reaction and therefore work efficiently at low concentration
58
Q

Different Enzyme Concentration

A
  • Low enzyme concentration: there are too few enzyme molecules to find an active site at one time. The rate of reaction is therefore only half the maximum possible for the number of substrate molecules available
  • Intermediate enzyme concentration: with twice as many enzyme molecules available, all the substrate molecules can occupy a site at the same time. The rate of reaction has doubled to its maximum because all active site are filled
  • High enzyme concentration: the addition of further enzyme molecules has no effect as there are already enough active sites to accomodate the available substrate molecules. There is no increase in rate of reaction
59
Q

Effects of substrate concentration on rate of enzyme action

A
  • if the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion
  • At the low substrate concentrations, the enzyme molecule to collide with and therefore the active sites of the enzymes aren’t working to full capacity
  • As more substrate is added the active sites gradually become filled till the point where they’re working as fast as they can
  • After that the addition of more substrate will have no effect on the rate of reaction
60
Q

types of enzyme inhibitor

A

competitive: which bind to the active site of the enzyme

non competitive: which bind to the enzyme at a position other than the active site

61
Q

Competitive inhibitors

A
  • they have a molecular shape that’s similar to the substrate
  • this allows them to occupy the active site of an enzyme
  • if the substrate concentration is increased the effect of the inhibitor is reduced
  • the inhibitor is not permanently bound to the active site so when it leaves, another molecule can take its place by a substrate or inhibitor molecule
  • malonate can inhibit the enzyme because it has a very similar molecular shape to succinate
62
Q

Non competitive inhibitors

A
  • they attach themselves to the enzyme binding site which is not the active site
  • upon attaching to the enzyme, the inhibitor alters the shape of the enzyme and thus its active site in such a way that substrate molecules can no longer occupy it so the enzyme can’t function
  • As the substrate and the inhibitor are not competing for the same site, an increase in substrate concentration doesn’t decrease the effect of the inhibitor

AS LEVEL BIOLOGY (9 decks)

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