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As Level biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

What is a macromolecule

A

A large biological molecule

Examples: polysaccharides, polynucleotides, polypeptides

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2
Q

What is a polymer

A

Molecule made up of many repeating subunits called monomers that are similar or identical to each other

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3
Q

What is a monomer?

A

A simple molecule which is used as a basic building block for the synthesis of polymers
Example: monosaccharides, amino acids, nucleotides

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4
Q

Characteristics of carbohydrates

A

Contain the elements carbon, hydrogen and oxygen
All either aldehydes or ketones
Aldehyde ones are reducing sugars

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5
Q

Characteristics of monosaccharides

A
  • sugars that dissolve in water to give sweet tasting solutions
  • General formula- CnH2nOn
  • crystalline
  • reducing sugars
  • classifies according to number of carbon atoms
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6
Q

Difference between alpha glucose and beta glucose molecules

A

Alpha glucose has its C1 hydroxyl group below the plane of the ring
Beta glucose has its C1 hydroxyl group above the plane of the ring

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7
Q

Alpha glucose structure

A

Diagram

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8
Q

Beta glucose structure

A

Diagram

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9
Q

Functions of monosaccharides

A

Source of energy in respiration
-large number of C-H bonds which can be broken to release a lot of energy
- used to help make ATP from ADP and phosphate
Building block for larger molecules
- glucose used to make starch, cellulose and glycogen
- ribose used to make RNA
- Deoxyribose used to make DNA

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10
Q

Characteristics of disaccharides

A

-made by joining two monosaccharides together by condensation reactions forming an oxygen bridge between the two
- common ones:
Maltose- glucose+glucose
Lactose- galactose+glucose
Sucrose- fructose+glucose
- sugars

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11
Q

Condensation reactions

A

Joining of two molecules together by the elimination of a water molecule

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12
Q

Hydrolysis reactions

A

Splitting of a molecule by the addition of water

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13
Q

Name of oxygen bridge formed between two monosaccharides

A

Glycosidic bond

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14
Q

Diagram of the joining of two alpha glucose molecules reaction

A

Diagram

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15
Q

Which common disaccharides are reducing sugars and which aren’t

A

Maltose and lactose are reducing sugars

Sucrose is not

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16
Q

Characteristics of polysaccharides

A

-monomers are monosaccharides
-not sugars and so don’t taste sweet
-compact meaning able to store a lot in small space
-inert meaning unreactive
-macromolecules
-important ones:
Starch- store energy in plants
Cellulose- main component of plant cell walls
Glycogen- store energy in animals

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17
Q

Starch

A
  • polymer of alpha glucose molecules
  • mixture of two substances called amylose and amylopectin
  • mixtures of these two builds up into relatively large starch grains
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18
Q

Amylose

A

Long coiled helix made up of 1,4 linked alpha glucose molecules

Picture

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19
Q

Amylopectin

A

Molecule made up of 1,4 linked alpha glucose molecules with 1,6 linkages forming branches

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20
Q

Glycogen

A
  • differers to amylopectin by the amount of branching
  • has much more branching
  • made up if chains of 1,4 linked alpha glucose molecules with 1,6 linkages forming branches
  • molecules clump together to form granules which are visible in liver cells and muscle cells where they form a energy reserve
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21
Q

Why glycogen is an ideal energy store

A
  • breaks down rapidly and so is readily available
  • compact
  • inert
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22
Q

Cellulose

A

polymer of beta glucose molecules

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23
Q

How two beta glucose molecules join together

A

In order for the C1 to form a glycoside bond with C4 (where the OH group is below the plane of the ring) one glucose molecule has to be rotated relative to other

Picture

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24
Q

How cellulose fibers form from beta glucose molecules

A

Beta glucose molecules form cellulose molecules

Cellulose molecules tightly cross link with hydrogen bonds to form cellulose microfibrils

Cellulose microfibrils are then held together in bundles by hydrogen bonding to form cellulose fibers

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25
Q

Functions of cellulose in plant cell walls

A
  • Have high tensile strength which allows it to withstand the large pressure that develop within the cell as a result of osmotic pressure
  • prevent cell from bursting in dilute solution
  • freely permeable
  • provides support for plants by making tissues rigid
26
Q

Lipids

A
  • organic molecules which are non Polar
  • insoluble in water
  • familiar ones are fats (solids at rtp) and oils (liquids at rtp)
  • release more energy than carbohydrates due the large number of C-H bonds
  • contain the elements carbon,hydrogen and oxygen
27
Q

Fatty acids

A
  • lipids which are acids as well due the presence of a carboxylic group
  • can be either saturated (no double bonds) or unsaturated (has double bonds)
  • unsaturated ones have low melting pints than saturated ones
28
Q

Saturated fatty acids

A
  • maximum hydrogen bonded
  • no double bonds
  • no kinks
  • forms lipids which are solids at rtp
  • not healthy
  • easily converted to cholesterol
  • found in animal fat
29
Q

Unsaturated fatty acids

A
  • not maximum hydrogen bonded
  • has double bonds
  • has kinks at the place of a double bond which causes the chain to straighten
  • forms lipids which are liquids at rtp
  • healthy
  • not easily converted to cholesterol
  • found in plant fat
30
Q

Triglyceride

A
  • Molecule formed from a glycerol molecule, which has three hydroxyl groups, and three fatty acids
  • Each hydroxyl group undergoes condensation with a fatty acid forming an ester bond
  • non polar
  • insoluble in water
31
Q

How a triglyceride molecule forms

A

Picture

32
Q

Functions of triglycerides

A
  • metabolic source of water as the oxidation of lipids produce water which can be used by anime particularly in desserts to survive without drinking water
  • energy source and reserve due to the large amount of CH bonds releasing a lot of energy
  • storage product especially under the semis of the skin where it acts an insulator against heat loss
  • fat stored around delicate organs such as kidneys provide protection
  • low density of these lipids provides buoyancy allowing organism like whales to float
  • synthesis of cell membranes
33
Q

Proteins

A
  • contain the elements C,H,O,N and sometimes even Sulfur and phosphorus
  • amino acid monomers
34
Q

Amino acids

A
  • both acid and a base, so is said to be amphoteric
  • act as buffers in cells helping to maintain pH
  • 20 found in living organisms
  • plants synthesize all 20
  • animals can’t synthesize 8 and must obtain it through their diet: essential amino acids
  • The remaining 12 are called non essential amino acids
35
Q

General formula for an amino acid

A

Picture

36
Q

Peptide bond

A
  • Bond formed when two amino acids joking together by condensation reaction
  • The OH from the carboxyl group of one amines acid and the H from Amine group of the other amino acid combine together to form water

Picture

37
Q

Types of bonds found in proteins

A
  1. Peptide bonds
  2. Disulfide bonds
  3. Hydrogen bonds
  4. Ionic bonds
  5. Hydrophobic interactions
38
Q

Hydrogen bonds

A
  • forms between strong polar groups (-NH, -OH, -CO )
  • individual ones are weak but many together contributes considerably
  • broken by high temperatures and extreme pH
39
Q

Disulfide bonds

A
  • forms between two cysteine (-SH) molecules
  • oxidation takes place between the two sulfur groups forming a strong covalent disulfide bond
  • strongest bond which can be broken only by reducing agents

Pic

40
Q

Ionic bond

A
  • Forms between ionized amine (NH3+) groups and ionized carboxylic (COO-) groups
  • broken done by pH changes
41
Q

Hydrophobic interactions

A
  • occurs between non polar R groups

- interactions are weak but the groups tend to stay together and exclude water

42
Q

Primary structure of a protein

A
  • sequence of amino acids in a protein

- not broken by high temperature or pH changes

43
Q

Secondary structure

A
  • polypeptide chain folds and come hydrogen bonding between carboxylic groups and amine groups
  • structure maintained by hydrogen bonding
  • easily broken by high temperature and extreme pH change
  • two type of structures formed: alpha helix or Beta pleated sheets
44
Q

Alpha helix

A

Polypeptides chain coils into a complex cylindrical shape

45
Q

Beta pleated sheets

A

Polypeptide chains are liked in parallel flat sheets by hydrogen bonding
More looser and straighter than alpha helix
More likely to be found in fibrous proteins

46
Q

Tertiary structure

A

Secondary structure further folds or coils into a more complex unique 3D structure maintained by ionic bonds, disulfide bonds, hydrogen bonds and hydrophobic interactions

47
Q

Quaternary structure

A

3D structure of 2 or more polypeptide chains which is maintained by ionic bonds, disulfide bonds, hydrogen bonds and hydrophobic interactions

48
Q

Haemoglobin

A

Oxygen carrying pigment found in red blood cells

49
Q

Structure of haemoglobin

A
  • contains 4 polypeptide chains where each one is a protein itself called globin
  • has two types of globin proteins: alpha globin and beta globin
  • each chain folds into a compact shape and all four linked together to form a spherical haemoglobin molecule
  • hydrophobic interactions within molecule help to maintain its structure
  • hydrophilic R group enable to maintain its solubility
  • each chain has a haem group (prosthetic group) which contains a Fe2+ ions
  • each Fe ion combines with one oxygen molecule
  • haem groups combined with oxygen (oxyhaemoglobin) is red in color, otherwise it’s purplish in coloring
50
Q

Structure of collagen

A
  • three polypeptide chains each in helix shape
  • these three helical chains wound around each other to form a triple helix maintained by H bond and some covalent bonds
  • each third amino acid is glycine (smallest amino acid) which allows the triple helix to form tightly
51
Q

How collagen molecules form collagen fibers

A

Three helical polypeptide chain would around each other forming triple helix collagen molecules

Collagen molecules lie side by side and form cross links of hydrogen bond between R groups of adjacent amino acids to form collagen microfibrils

Collagen microfibrils are then held together in bundles by hydrogen bonding to form collagen fibers

Has very high tensile strength

Collagen fibers oriented according to pressure they have to withstand

52
Q

Physical properties of water affected by hydrogen bonding

A
  1. Solvent properties
  2. High specific latent heat of vaporization
  3. High heat capacity
  4. Ice less dense than water at 4 degrees Celsius
  5. High surface tension and cohesion
53
Q

Effect of hydrogen bonding on solvent properties of water

A

Water being polar makes it an excellent solvent

Collects around ions and polar molecules and separates them to form hydrogen bonding with them

Solvent properties allows it to be used as a transport medium and medium for metabolic reactions to take place

54
Q

Effect of hydrogen bonding on heat capacity of water

A

Hydrogen bonding makes it hard for water molecules to move around freely so high amount of energy needed to raise temperature

Makes water resistant to changes in temperatures

Helps to maintain constant temperature within bodies

55
Q

Effect of hydrogen bonding on latent heat of vaporization of water

A

Hydrogen bonding needs high energy to break which makes it hard to vaporize water

Hence water evaporation used a cooling mechanism because large amount of heat ca be lost with relatively little water loss reducing risk of dehydration

As it also needs to lose a lot of energy in order to freeze, makes it unlikely to freeze in bodied increasing survival rate in cold areas

56
Q

How hydrogen bonding makes ice less dense than water

A

He

57
Q

Effect of hydrogen bonding on surface tension and cohesion of water

A

Water molecules form a hydrogen bonded network on the surface of water which increases surface tension

Attraction of water molecules to each allows water to move in unbroken columns through vascular tissue in plants

High surface tension also allows light weigh organism like pond skaters to skate or settle on the water surface

58
Q

Describe the Benedict’s test on reducing sugars

A
  1. Add excess of Benedict’s reagent (endure all sugar reacts) ,which is blue in colour, to the sample being rated in a test tube
  2. Heat test tube in water bath already brought to boil (100 degrees Celsius)

Reducing sugars reduce Cu2+ ions to brick red copper oxide ppt

  1. Color of ppt changes is reducing sugars present
    Blue
59
Q

Benedict’s test on non reducing sugars

A
  1. To sample being tested in a test tube, add some dilute HCl
  2. Heat in a water bath and then add sodium hydrogencarbonate to neutralize
  3. Repeat the Benedict’s test on this sample

If a ppt forms, this means that a non reducing sugar is present

If no ppt forms then it means that it doesn’t contain neither a reducing sugar or non reducing sugars

60
Q

Test for starch

A

To sample being tested, add few drops of iodine solution which is orange in colour

If starch present, starch-iodine complex quickly forms to quickly to give a blue back colour

61
Q

Test for presence of lipids

A

To sample being tested in a test tube, add some absolute ethanol and shake to dissolve any lipids present

Then add some water to this solution

A milky emulsion will form if any lipids are present

The more lipid there is, the more noticeable the milky colour will be

As Level biology (1 decks)

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