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AS Biology F212 Spec > Biological molecules > Flashcards

Biological molecules Flashcards

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1
Q

Hydrogen bonds in water

A
  • Oxygen attracts the electrons towards itself, becoming slightly negative
  • The hydrogen molecules become slightly positive
  • Hydrogen bonds form between slightly negative oxygens and slightly positive hydrogens
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2
Q

Hydrogen bonds and properties of water

A
  • good solvent, as can interact with other polar/charged molecules due to hydrogen bonds
  • cohesive, as hydrogen bonds stick water molecules together
  • density: ice is less dense as hydrogen bonds form a lattice
  • high specific heat capacity, as lots of energy is needed to raise the temperature of water
  • liquid across a variety of temperatures
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3
Q

Importance of properties of water (6)

A
  • good solvent: metabolic processes rely on chemical reactions occurring in solution
  • liquid: good transport medium for transporting materials around organisms
  • cohesive: creates surface tension as a habitat and prevents columns of water breaking
  • freezing at lower density: water below is insulated (whole lake won’t freeze), provides a habitat
  • thermal stability: large bodies of water have fairly constant temperatures, evaporation can cool surfaces
  • metabolic: takes part in chemical processes
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4
Q

Structure of amino acids

A

H H O amino group (NH2)
N C C acid group (COOH)
H R OH R group

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5
Q

Forming peptide bonds

A 
OH (from acid group) and H (from amino group) form water in a condensation reaction. End up with a peptide bond of:
l
C=O
 l
N-H
 l
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6
Q

Breaking peptide bonds

A

Hydrolysis reaction. OH from water goes to C=O (bonds to carbon), H from water goes to N-H

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7
Q

Primary structure

A

The sequence of amino acids in a polypeptide/protein

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8
Q

Secondary structure

A

Coiling and pleating (alpha helix and beta pleated sheets) of parts of the polypeptide molecules. Held together by hydrogen bonds between carbon-nitrogen backbone (C=O—-H-N) not between R-groups.

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9
Q

Tertiary structure

A

Overall 3D structure of the final polypeptide/protein molecule. Held together by: disulfide bonds, ionic bonds, hydrogen bonds, hydrophobic and hydrophilic interactions. Hydrophobic R-groups will be held together with water excluded; hydrophilic groups will be on the outside

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10
Q

Quaternary structure

A

More than one polypeptide subunit joined together. Protein formed can’t function if not all subunits are present.

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11
Q

Haemoglobin as a protein

A
  • 4 polypeptide subunits
  • 1 prosthetic group on each chain: a haem group with Fe2+ ion
  • Globular protein: vital tertiary structure
  • Soluble in water
  • Wide range of amino acids in primary structure
  • Many alpha helix structures
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12
Q

Collagen molecule as a protein

A
  • Fibrous protein
  • Insoluble in water
  • Not much variety in amino acids: 35% is glycine
  • No prosthetic groups
  • Many left-handed helix structures
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13
Q

Structure of collagen fibres

A
  • Collagen molecules form staggered cross links with adjacent collagen molecules
  • This makes collagen fibril
  • Many fibrils together become collagen fibres.
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14
Q

Function of haemoglobin

A

Carry oxygen from lungs to tissues.

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15
Q

Function of collagen

A

Provide mechanical strength:

  • in walls of arteries (no blood bursting from walls)
  • tendons of collagen connecting skeletal muscle to bone (muscles can pull bones)
  • makes up bones (with other stuff, e.g. calcium phosphate to harden them)
  • Cartilage and connective tissue
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16
Q

Structure of alpha glucose

A

Hexagonal ring, C1, C2, C3, C4, C5, O. C1,2,3,4 have an H and an OH group attached. C5 has C(6)H2OH attached and H. In alpha glucose, the H on C1 is above the plane of the paper (the OH is below the plane of the ring)

17
Q

Alpha and beta glucose

A

In alpha glucose, C1 has H above plane of ring and OH below plane of ring. In beta glucose, C1 has OH above plane of ring and H below plane of ring

18
Q

Forming a glycosidic bond

A

OH of C1 and H from OH of C4 make a water molecule. The O left on C4 forms the glycosidic bond between C1 and C4. This is a condensation reaction

19
Q

Breaking a glycosidic bond

A

OH of a water molecule goes to C1, H of a water molecule binds with the O of the glycosidic bond and forms an OH group on C4. Hydrolysis reaction

20
Q

alpha glucose + alpha glucose ->

A

Maltose, a sweet, soluble disaccharide sugar. Forms a glycosidic bond in a condensation reaction

21
Q

Carbohydrates

A

Group of molecules containing carbon, hydrogen and oxygen in the ration C(n)(H2O)(n)

22
Q

Making amylose

A

Many glycosidic bonds form between many alpha glucoses, forming a long chain of amylose - a polysaccharide.

23
Q

Starch

A

Made of amylose and branched amylopectin (when C1 - C6 bond forms). Energy-storage molecule for plants. Stored in chloroplasts and in membrane bound starch grains. Can be broken down into glucose molecules for respiration. Insoluble, so doesn’t effect water potential.

24
Q

Amylose

A

Long chain of many alpha glucoses glycosidically bonded together. Long chain coils up into a compact molecule; iodine can become trapped in the coils of the spring, causing iodine in potassium iodide change colour (starch test)

25
Q

Glycogen

A

The energy-storage molecule in animals. Made of alpha glucose subunits that can be broken down to release glucose for respiration. Glycogen has more branches than starch, making it more compact. Insoluble, so doesn’t effect water potential. As animals are more active, more branches means glucose can be released quicker.

26
Q

Cellulose

A

Polymer with beta glucose monomers. Makes long, straight chains, with alternating orientations of beta glucose monomers. OH groups form hydrogen bonds forming cross links. 60-70 chains forms a microfibril. They form macrofibrils. They are very strong, and embedded in pectins (a sort of glue) to form plant cell walls. Structure allows easy passage of water, provides strength to cells (no burst, support plant), change shape e.g. in guard cells.

27
Q

Structure of a triglyceride

A

A glycerol molecule bonded to 3 fatty acid molecules:
H
l
H-C-O-C=O (and a fatty acid chain attached to the C)
l
H-C-O-C=O (and a fatty acid chain attached to the C)
l
H-C-O-C=O (and a fatty acid chain attached to the C)
l
H
The O-C=O bond is an ester bond. Made by COOH group of a fatty acid reacting with OH on glycerol. H of glycerol is lost, OH of fatty acid is lost

28
Q

Structure of glycerol

A 
H
    l
H-C-OH
    l
H-C-OH
    l
H-C-OH
    l
   H
29
Q

Structure of a phospholipid

A 
H
    l
H-C-O-phosphate group
    l
H-C-O-C=O (and a fatty acid chain attached to the C)
    l
H-C-O-C=O (and a fatty acid chain attached to the C)
    l
    H
30
Q

Structure and function of triglycerides

A
  • Glycerol and 3 fatty acids
  • Compact energy store, insoluble so no effect water potential
  • stored as fat, also an insulator and protector
31
Q

Structure and function of phospholipids

A
  • Glycerol and 2 fatty acids and a phosphate group
  • A hydrophilic and hydrophobic molecule for a cell surface membrane
  • Phosphate group may have carbohydrates attached involved in cell signalling
32
Q

Structure and function of cholesterol

A
  • 4 carbon-based ring structures joined together
  • Thin, small, hydrophobic molecule that fits into the lipid bilayer giving strength and stability
  • Forms steroid hormones
33
Q

Testing for proteins

A

Adding biuret reagent to a sample. Biuret reagent contains sodium hydroxide and copper sulfate. Colour change is observed from pale blue to lilac

34
Q

Testing for reducing sugars

A

Heat with benedict’s solution (alkaline copper sulfate). Colour change from blue to orange-red precipitate

35
Q

Reducing sugars

A

All monosaccharides and many dissaccharides. Can give an electron to other molecules

36
Q

Testing for non-reducing sugars

A

E.g. sucrose. First, test for reducing sugars. Only if negative: boil with hydrochloric acid (splitting non-reducing sugars into reducing sugars, e.g. sucrose -> glucose and fructose), cool solution and neutralise it with sodium hydrogencarbonate solution/sodium carbonate solution. Carry out reducing sugar test again, if positive, non-reducing sugars are present

37
Q

Testing for starch

A

Add iodine in potassium iodide solution. Colour change from yellow-brown to blue-black

38
Q

Testing for lipids

A

Mix sample with ethanol, dissolving lipids present. Pour liquid into water in a test tube. Emulsion will form if a lipid is present (comes out of solution)

39
Q

Measuring concentration of glucose in a solution

A

Carry out a benedict’s test to get an orange-red precipitate. Filter out precipitate, can see how much benedict’s solution is left. Use a colorimeter to measure how much light can pass through - lots will if there is lots of glucose as a lot of benedict’s solution has been used. Make a calibration curve with known concentrations of glucose, then read off what concentration you have. BE CAREFUL OF PERCENTAGE TRANSMISSION/PERCENTAGE ABSORPTION!!!

AS Biology F212 Spec (9 decks)

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