Biological Molecules

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61 Terms

1
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What kinds of bonds occur in carbohydrates

Glycosidic bonds between hydroxyl and hydrogen

<p>Glycosidic bonds between hydroxyl and hydrogen</p>
2
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What is an isomer

A compound with the same chemical formula but a different arrangement of atoms

3
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What are glucose's isomers - add a structural difference

  • Alpha-glucose: OH at C1 is below the plane of the ring

  • Beta-glucose: OH at C1 is above the plane of the ring

<ul><li><p>Alpha-glucose: OH at C1 is below the plane of the ring</p></li><li><p>Beta-glucose: OH at C1 is above the plane of the ring</p></li></ul><p></p>
4
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Whats the difference between a hexose, triose and pentose monosaccharide

  • Hexose - contains 6 carbon atoms

  • Pentose - contains 5 carbon atoms

  • Triose - contains 3 carbon atoms

5
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<p>How is a disaccharide formed?</p>

How is a disaccharide formed?

  • two monosaccharides join together

  • condensation reaction takes place

  • glycosidic bond is formed

  • water is released

6
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How is glucose adapted for its role

  • small and soluble so can dissolve and be transported easily

  • low reactivity

7
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How is a polysaccharide formed?

  • two monosaccharides join where a condensation reaction takes place

  • A glycosidic bond is formed

  • A molecule of water is released each time

  • Many more condensation reactions take place until a long chain is produced

8
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Describe the structure of amylose (starch)

  • long chain of a-glucose

  • has 1,4-alpha glycosidic bonds

  • coiled/helical shape

  • compact, allows large amount packed in small space

  • unbranched

9
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Describe the structure of amylopectin (starch)

  • long chains of a-glucose

  • 1,4-alpha glycosidic bonds

  • branches formed by 1,6-alpha glycosidic bonds

  • coiled shape

  • more compact, allows large amount packed in small space

10
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What is the advantage of having branches?

  • many accessible ends

  • allows rapid release of glucose

11
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Describe the structure of glycogen

  • long chains of a-glucose

  • 1,4-alpha glycosidic bonds

  • HIGHLY branched - VERY compact

  • branches formed by 1,6-alpha glycosidic bonds

  • accessible ends

  • smaller chains than amylopectin → less coiled

12
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Describe the structure of cellulose

  • long, straight chains of beta-glucose molecules

  • b-glucose joined by 1,4 glycosidic links

  • unbranched

  • molecules invert alternatively by 180° (prevent coiling)

13
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What are cellulose microfibrils?

  • parallel cellulose chains that become cross linked by

  • hydrogen bonds in between chains which provides strength (cross links)

14
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Why are polysaccharides good sources of energy? (a-glucose for last)

  • compact - more energy stored in small space

  • can hold glucose in large chains - doesnt diffuse out of cell

  • can be (un)branched

  • insoluble in water - no impact on water potential of a cell

  • easily hydrolysed to a-glucose when energy is needed

15
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What are the properties of water?

  • Polar

  • High SHC

  • High latent heat of evaporation

  • Cohesive

  • Ice has low density

  • Good solvent

16
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Explain waters polarity

  • shared negative H electrons are pulled towards O atom

  • so other ends of H atoms have slight positive charge

  • unshared E-s on O atom give a slight negative charge

17
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How are water molecules held together

  • delta negative O atoms attract the delta positive H atoms of other water molecules

  • this attraction = hydrogen bonding

18
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Why is a high SHC good for water?

• water doesn’t experience rapid temperature changes

• living organisms have a stable temperature - for optimal enzyme reactions

19
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Why is a high LH of evaporation good for water

  • good cooling property for mammals

  • eg when sweat evaporates, it cools surface of skin

20
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Why is cohesion good for water

  • water molecules stick together as they’re polar so there’s a great attraction

  • helps water flow → useful to transport substances

  • provides surface tension

21
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How is the structure of ice different to liquid water?

  • water molecules held further apart as each molecule forms 4 hydrogen bonds

  • this forms a lattice shape

22
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Why is low density good for ice

  • ice forms insulating layer over water

  • ice on top provides habitat

  • animals underneath dont freeze and can still move

23
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What is the benefit of water being a good solvent for living organisms

  • ions can dissolve in water

  • can be transported up the xylem in plants

  • the plant can absorb mineral ions for growth and survival

24
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What is the structure of an amino acid

  • has amine group

  • has carboxyl group

  • has variable ‘R’ group

  • has hydrogen

25
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What bonds occur in proteins

Peptide bonds between amine and carboxyl 

26
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What is meant by primary protein structure

  • sequence of amino acids

  • determined by order of nucleotides in DNA

27
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What is meant by secondary protein structure

  • initial folding of amino acids

  • folds into alpha-helix or / and beta-pleated sheet

28
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What is meant by tertiary structure

  • further folding of proteins to give it a 3D shape

  • gains a function

  • structure determined by the R group

29
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What is meant by quaternary structure

  • clustering of several polypeptide chains to give a final specific shape

30
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Describe structure of a globular protein

  • spherical

  • has specific shapes

  • soluble

  • external hydrophilic R group

  • irregular arrangement

31
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Describe structure of haemoglobin

  • spherical globular protein

  • specific shape

  • made up of 4 polypeptides (2X alpha 2X beta)

  • functional; transports O2

  • cofactor; prosthetic group HAEM Fe2+

  • has external hydrophillic R group

32
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Describe the structure of a fibrous protein

  • form fibres; linear

  • regular and repetitive structure

  • structural

  • insoluble

33
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Describe the structure of collagen

  • forms fibrils→ fibrous protein

  • structural; provides support

  • repeating structure of Gly-Pro-Ala

  • 3 polypeptides → coiled

  • chains are cross linked by hydrogen bonding

  • peptide bonds between AAs

  • insoluble - external hydrophobic R group

34
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What is a beta pleated sheet?

  • secondary protein structure which has hydrogen bonds between R groups

  • sheet folds over itself

35
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What is an alpha helix?

  • secondary protein structure that has a coiled shape

  • hydrogen bonds between R groups

36
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What is a disulfide bond

  • bond between 2 sulfur atoms

  • aa has S atom on its R group

37
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What is an ionic bond

  • forms between an R group with full -charge and one with full +charge

  • bond can be broken by a change in pH

38
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What bonds occur in lipids? HYDROPHOBIC!

ester bonds between hydrogen and hydroxyl

39
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What is the structure of a lipid

  • has glycerol

  • has fatty acids - not identical so there are no monomers

40
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What is the structure of fatty acids? 

  • long hydrocarbon tails 

  • saturated FAC: no double carbon bond, saturated with H atoms, long straight chains

  • unsaturated FAC: double carbon bond, less H atoms, kinked chain

41
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What are unsaturated fatty acids?

  • oils

  • liquid at room temp

42
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What are saturated fatty acids

  • animal fats

  • solid at room temp

43
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What is the structure of a triglyceride and how is it made

  • 1 glycerol + THREE fatty acids 

  • condensation reaction where X3 H2O lost

  • 3 ester bonds formed

44
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What is the function of triglycerides?

  • energy storage

  • insulation

  • provide buoyancy for aquatic animals

45
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What is the structure of a phospholipid? 

  • has glycerol

  • has 2 fatty acid tails which are hydrophobic; nonpolar

  • its third fatty acid replaced by phosphate head; hydrophillic 

  • 2 ester bonds

46
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Whats the difference between phospholipid and triglyceride

  • phospholipid has a phosphate head which replaces the 3rd fatty acid

47
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What is the sructure of cholestrol - STEROL

  • lipid not made from glycerol & fatty acids

  • has 4 carbon rings

  • small hydrophobic molecule

  • sits between hydrophobic tails in bilayer

48
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What are the functions of cholestrol

  • regulates fluidity in the membrane

  • making vitamin D

  • steroid hormone

49
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Describe the similarities of haemoglobin and collagen

  • more than one polypeptide chain

  • have quaternary structure

  • aa chains with peptide bonds

  • disulfide, ionic, hydrogen bonds

50
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Role of H+ ions

  • affects pH - acidic

  • important in photosynthesis and respiration reactions

51
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Role of Ca2+ ions

  • transmission of nerve impulses 

  • bone and enamel structure

52
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Role of Na+ ions

  • generating nerve impulses

  • regulating water potential

53
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Role of K+ ions

  • allow reabsorption of water in kidneys

  • opening of the stomata 

54
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Role of NH4+ ions

  • absorbed by soil in plants as a source of nitrogen

  • deamination of proteins

55
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Role of NO3- ions

  • absorbed by plants as a source of nitrogen

  • used for growth and repair in plants

56
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Role of HCO3- ions

  • transport CO2 in blood

  • acts as a buffer to maintain pH

57
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Role of Cl- ions

  • maintain pH balance

  • acts as cofactor for amylase

58
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Role of PO4 3- 

  • component of cell membrane - phospholipids

  • component of ATP and nucleic acids

59
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Role of OH- ions

  • affects pH of substances - alkali

60
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Which chemical elements make up the biological molecules?

  • carbs & lipids: C, H, O

  • proteins: C, H, O, N, S

  • nucleic acids: C, H, O, P

61
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What is a conjugated protein

  • globular protein with a prosthetic group

  • such as Fe2+

  • attached by covalent bonds