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Biology UNIT 2 > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What is key for organism survival (in terms of molecules)?

A
  • organisms must make or take in all molecules required
  • carbohydrates (including fibre)
  • proteins
  • lipids
  • vitamins and minerals
  • nucleic acids
  • water
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2
Q

Role of carbohydrates

A
  • Energy storage and supply
  • Structure
  • (Fibre to give gut a bulk to push against- to ease flow of materials through the gut)
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3
Q

Role of proteins

A
  • structure
  • transport
  • enzymes
  • antibodies
  • hormones
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4
Q

Role of lipids

A
  • membranes
  • energy supply
  • thermal insulation
  • electrical insulation in neurones
  • protective layer
  • some hormones
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5
Q

Role of vitamins and minerals

A

Form parts of larger molecules
Take part in some metabolic reactions
Coenzymes/enzyme activators

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6
Q

Role of nucleic acids

A

Information molecules, carry instructions for life

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7
Q

Role of water

A

Takes part in many reactions
Support in plants
Solvent for metabolic reactions
Transport

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8
Q

What chemical elements are found in most biological molecules?

A

Carbon, hydrogen, oxygen, nitrogen

Sulfur, phosphorus

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9
Q

Why is water sometimes described as a biological molecule?

A

Because of its importance to life

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10
Q

Define metabolism

A

The sum total of all the biochemical reactions taking place in an organism’s cells

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11
Q

Define catabolic and anabolic reactions

A

Catabolic - breaking larger molecules into smaller ones

Anabolic- building smaller molecules into larger ones

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12
Q

Why is carbon so important in biological molecules?

A

Form long chains
Bond with other atoms, different structures and properties
Multiple-bonding feature, valency of 4, carbon is a framework atom

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13
Q

Why aren’t lipids called polymers?

A

The smaller molecules bonded together are very different from each other. A polymer is a group of similar monomers joined together.

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14
Q

What are the basic steps of a condensation reaction?

What are the basic steps of a hydrolysis reaction?

A

Condensation

  • a water molecule is released
  • new covalent bond formed
  • larger molecule formed by the bonding together of smaller molecules

Hydrolysis

  • a water molecule is used
  • a covalent bond is broken
  • smaller molecules formed by the splitting of a larger molecule
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15
Q

How does hydrogen bonding occur between water molecules?

A

Water is a polar molecule, the electrons in the O-H covalent bond aren’t shared evenly.
Hydrogen bonds form between the slightly electropositive hydrogen and the slightly electronegative oxygen atom of another molecule.
Hydrogen bonds are weak interactions that can occur between OH and NH

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16
Q

Relate intermolecular interactions in water to the roles of water in living organisms

A

Hydrogen bonding!

  • cohesion=surface tension, transpiration stream
  • adhesion=xylem capillary action
  • ice less dense, floats, insulates water below=allows aquatic life to survive winter
  • high specific heat capacity= large bodies of water long time to warm, still warm in winter
  • solvent for hydrophilic substances=cell cytoplasm metabolic reactions
  • reactant in hydrolysis (eg photosynthesis)

-good transport medium, and cooling effect of evaporation

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17
Q

Describe the structure of an amino acid

A
  • amine group at one end (excess amine groups toxic, remove by deamination)
  • carboxyl group at the other end
  • carbon in between
  • R group on second carbon (some hydrophobic/philic, glycine has H, 20 different R groups)
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18
Q

Describe the formation and breakage of peptide bonds in the synthesis and hydrolysis of dipeptides and polypeptides

A

Condensation- amino acids joined together.
H from amine group combines with OH from carboxyl group
Water lost.
Covalent peptide bond between amine group of one and carboxyl group of another amino acid.
2 amino acids=dipeptide
Many amino acids=polypeptide

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19
Q

Explain the term, primary structure

A

The specific sequence of amino acids held by peptide bonds (in a polypeptide)

20
Q

Explain the term, secondary structure

A

Coiling (alpha helix) or pleating (beta pleated sheets) due to hydrogen bonds between H and O

21
Q

Explain the term, tertiary structure

A

The final 3D shape of a polypeptide due to disulfide bonds, hydrophobic/hydrophilic interactions (R-group), and ionic interactions (oppositely charged R groups)

22
Q

Explain the term, quaternary structure

A

Multiple polypeptide chains, held by many bonds/interactions

23
Q

Structure of haemoglobin

A 
Globular protein
Peptide bonds between amino acids
4 chains, 2 different subunits
Chains held by hydrogen bonds
Fe2+ prosthetic group
Water soluble
Function is to carry oxygen from alveoli to body tissues and CO2 from body tissues to alveoli
Haemoglobin+4O2-> oxyhemoglobin (HbO8)
24
Q

Describe the structure of a collagen molecules

A

Fibrous protein
Insoluble in water
3 polypeptide chains
Left handed alpha helix
Every 3rd amino acid is glycine
Adjacent molecules joined by covalent cross-links
Function is to provide mechanical strength (artery wall withstand blood pressure, tendons bones to skeletal muscle, cartilage)

25
Features of globular proteins
Type of tertiary structure Rolled up, ball shaped Hydrophobic R groups turned inwards towards centre Hydrophilic R groups on outside, so water-soluble since water molecules can easily cluster around them. Metabolic roles Enzymes, plasma proteins, mammal antibodies
26
Features of fibrous proteins
``` Form fibres Regular, repetitive primary structure Insoluble in water Structural roles Bone, cartilage, keratin in fingernails and hair ```
27
Describe the molecular structure of alpha-glucose | And some properties
Monosaccharide carbohydrate Chain or ring structure OH at C1 below the plane of the ring Hexose, one water molecule for every carbon atom present C2H12O6 Soluble in water Sweet-tasting Form crystals
28
Monosaccharides are grouped according to the number of carbon atoms in the molecule, give the names of three different types
3 carbon, triose sugars 5 carbon pentose sugars 6 carbon hexose sugars
29
State the structural difference between alpha- and beta- glucose
Alpha- OH on carbon 1 is below the plane of the ring | Beta- OH on carbon 1 is above the plane of the ring
30
Describe the formation and breakage of a named disaccharide a named polysaccharide
Disaccharide- maltose Condensation OH on carbon 1 reacts with H on carbon 4 of another alpha glucose Water is lost Glycosidic (covalent)bond formed (1,4-glycosidic bond) Hydrolysis, water molecule breaks covalent 1,4-glycosidic bond Polysaccharide- amylose (thousands of alpha glucose) Condensation, many alpha glucose molecules bonding, one water molecule released for every glycosidic bond Hydrolysis, glycosidic bonds broken, water used up
31
What happens to nutrients in the body
- become a part of your body, digested and rebuilt - provide energy for metabolism - removed from body if it can't be digested
32
Starch: structure, functions and relate to living organisms
A mixture of long, straight chained amylose and branched amylopectin (1,6- and 1,4-glycosidic bonds, all alpha glucose) Insoluble in water Can be broken down to glucose and respire to release energy Energy storage polysaccharide in plants, in chloroplasts, membrane-bound starch grains and plant-storage organs
33
Cellulose: structure, functions and relate to living organisms
- Beta-glucose subunits - Straight chained - Hydrogen bond cross links between many molecules (forms micro/macro fibrils, cross over for extra strength) - Arrangement of macrofibrils determines how cells can grow or change shape - Embedded in pectins (glue) to form cell wall - Can be embedded with other substances for waterproofing or extra support - structural polysaccharide in plant cell walls - Natural arrangement allows apoplast pathway - Water moving into plant cell doesn't cause it to burst, the cell wall prevents it - In turgid cells, it helps to support the whoe plant
34
Glycogen: structure, functions and relate to living organisms
Made of alpha-glucose subunits 1-4 linked chains are shorter and more branched than starch, so more compact Insoluble in water Can be broken down to glucose and respired to release energy Energy storage in animals Forms glycogen granules in liver, muscle and other cells
35
Glucose: functions and relate to living organisms
Soluble in water Energy SOURCE (not store) Takes part in metabolic reactions Can enter the respiratory pathway that releases energy which can be used to generate ATP
36
Structure and function of a triglyceride
One glycerol molecule, covalent ester bond, three fatty acid molecules. Hydrophobic (water insoluble) charges evenly distributed, can't form hydrogen bonds with water, won't affect cell water potential Compact energy store (fats in adipose tissue) Thermal insulation Protective properties Respiration of lipid gives out more water than carbohydrates Respiration of lipid gives out twice as much energy as carbohydrates Water used as metabolic water in organisms
37
Structure and functions of phospholipids
One glycerol molecule, two fatty acid chains, one phosphate group. All covalent bonds formed by condensation reactions. Phosphate head hydrophilic, fatty acid tails hydrophobic Insoluble in water, most of molecule is hydrophobic Water soluble head allows formation of membranes Organisms in cold climates more unsaturated fatty acids, so membranes remain fluid Phosphate groups may have carbohydrates attached for cell signalling
38
Cholesterol functions in living organisms
- 4 carbon based ring structures - Made mostly by liver cells - Small, narrow, can sit between phospholipid tails to regulate membrane fluidity - Strength to membrane - Steroid hormones, directly pass through phospholipid bilayer to reach target receptor - Can pass through nuclear envelope if target receptor is inside the nucleus (steroid hormones) - Can be deposited in blood vessel linings and cause atherosclerosis, leads to circulatory problems - Familial hypercholesterolaemia, genetic disorder, cells keep secreting cholesterol above requirements (lack a particular cell surface receptor)
39
Test for presence of protein
Biuret test Add biuret reagent (NaOH and CuSO4) Reacts with peptide bonds Pale blue-> lilac
40
Test for reducing sugars
Add Benedict's solution (alkaline CuSO4) Heat to 80'C Blue-> red(orangey) precipitate
41
Test for non-reducing sugar
``` Boil in HCl Cool and neutralise with Na2CO3 Add Benedict's solution Heat to 80'C Blue-> orange(red) precipitate ```
42
Test for starch
Add solution of iodine | Brown->blue(black)
43
Test for lipids
Mix with ethanol (dissolves lipid) Pour mixture into water, mix it Cloudy white emulsion forms Lipid comes out of solution near top of water
44
How to use colorimetry to determine the concentration of glucose in a solution
Benedict’s test reveals the presence of reducing sugars It results in an orange-brown precipitate The more reducing sugar there is present, the more precipitate will be formed and the more Benedict’s solution will be ‘used up’. If the precipitate is filtered out, the concentration of the remaining solution can be measured This will tell you how much Benedict’s solution has been used up, and this can be used to estimate the concentration of reducing sugar in the original sample Zero the device using a cuvette containing a ‘blank’- usually water Prepare a calibration curve by Taking a range of known concentrations of reducing sugars Carry out Benedict’s test on each one then filter the precipitate out of each solution. Use a colorimeter to give readings of the amount of light passing through the solutions Plot the readings on a graph to show % transmission against concentration Measure the % transmission of the unknown in the colorimeter Use this to read the equivalent reducing sugar concentration from the % transmission
45
Which sugars are reducing or non reducing sugars?
Reducing sugars- Loses electrons to other substances (reduces other things, it itself gets oxidised) All monosaccharides Some disaccharides (Maltose, lactose, fructose) Non-reducing sugars- Some disaccharides All larger sugars

Biology UNIT 2 (9 decks)

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