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Biology > Chapter 3 - Biological Molecules > Flashcards

Chapter 3 - Biological Molecules Flashcards

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1
Q

What are polymers?

A

They are long chain molecules made up by linking of multiple individual molecules (monomers) in a repeating pattern

(e.g. carbohydrates)

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2
Q

Why is water a liquid at room temperature?

A

Because it can form weak hydrogen bonds between the delta neg. O2 and the pos. H+ on another water molecule

Each water molecule can form 4 hydrogen bonds

Requires a lot of energy to break

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3
Q

Discuss the properties and advantages of water

A
  1. Liquid at rtm
  2. Becomes less dense when it freezes
  3. Good solvent
  4. Cohesive
  5. Surface tension
  6. High specific heat capacity
  7. High latent heat of vaporisation
  8. Reactant
  9. Transparent
  10. Not easily compressed
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4
Q

Why is water being a liquid at room temp an advantage?

A
  • provides habitats (lakes)
  • good transport medium (gametes)
  • major component of tissues in organisms
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5
Q

Why does water become less dense when it freezes and is it advantageous?

A

Bc the water molecules are polar, the cooling allows for max n. of Hydrogen bonds to form

Spreading the water molecules out into a lattice structure

+Ice forms an insulating layer so water underneath doesn’t freeze
+Allows aquatic animals to survive

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6
Q

Why is water a Good solvent?

A

Because water is polar

-Other polar molecules (ionic compounds are soluble in water)

+can act as a medium for reactions
+Dissolved polar mole. or ions are transported around organs

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7
Q

Why is water cohesive ?

A

Because of the hydrogen bonding within the molecule, the bonds are attracted to each other

+continuous flow of water to be drawn up the xylem

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8
Q

How does water have surface tension?

A

The water mol. at the surface are H+ bonded to the ones beneath

Gives water the ability to resist force applied

+Allow pond skater to go across

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9
Q

Why does water have a high specific heat capacity?

A

Because there are many hydrogen bonds between the water mol. so a lot of energy is required to force molecules apart

Water doesn’t heat up or cool down easily

+ensures aquatic animals have a thermally stable environment

+internal body envir. remains thermally stable

+Acts as a buffer to temp changes during chemical reactions

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10
Q

Why does water have a high latent heat of vaporisation?

A

Because water mol. are held together by H+ bonds a high amount of energy is required to evaporate

+sweating/panting/ transpiration is used to cool down organism without losing too much water

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11
Q

How is water being transparent an advantage?

A

Allows organisms in water to photosynthesise

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12
Q

Why is water not easily compressed?

A

Because of the hydrogen bonding in water

+allows plant to become turgid and allow organism to have hydrostatic skeletons

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13
Q

Describe adaptations of polysaccharide (3 marks)

A
  • Compact
  • Terminal glucose molecules can be hydrolysed easily to release glucose which can be used to produce ATP for energy
  • Less soluble in water (bc they are a lare mol) so don’t affect the water potential
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14
Q

What are the starch molecules made of?

A

Amylose

Amylopectin

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15
Q

Describe the structure of amylose

A

Made of alpha 1-4 glyosidic bond

Forms unbranched chains with a helical spiral structure

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16
Q

Describe the structure of amylopectin

A

Alpha 1-4 and 1-6 glyosidic bond

Produce a branched structure

Release terminal glucose easily

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17
Q

Describe the difference between the amylopectin and amylose

A

Amylose has short glycosidic bonds so doesn’t coil and is non-fibrous

Amylopectin does coil so is branched and fibrous

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18
Q

How do animals store glucose? and describe the structure

A

As glycogen
-Alpha 1-4 and 1-6 glycosidic bonds

  • Very branched structure, very compact and easier to remove terminal glucose
  • Found in small granules particularly in muscles and liver cells
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19
Q

Describe the structure of cellulose?

A

Beta glucose
beta 1-4 glycosidic bond

  • Every other beta glucose mol. is flipped through 180 deg.
  • Many hydrogen bonds form between hydroxyl on the adjacent chains (gives a lot of strength)
  • In the cell wall of plant
  • Fibrous protein
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20
Q

What is hydrolysis?

A

The break down of molecules with the addition of water

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21
Q

What is condensation?

A

The formation of molecules taking away water

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22
Q

Give examples of mono
Di
Poly
saccharides

A

Mono: Glucose, ribose, fructose

di: Sucrose, lactose

Poly: Cellulose and starch

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23
Q

What are the uses of carbohydrates?

A
  • Energy source (glucose)
  • Energy store (starch and glycogen)
  • Structural units (e.g. cellulose)
  • Form part of other molecules (e.g. nucleic acids)
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24
Q

Describe the uses and properties of monosaccharides

A

Energy source bc they have a large n. of C-H bonds which are easily hydrolysed

Small so can pass across membrane through channels

Soluble in polar molecules

Straight or ring

E.g:

  • Ribose
  • Glucose
  • Fructose
  • Galactose
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25
Q

What is the importance of glucose in living organisms?

A
  • Soluble so can easily be transported
  • Small so can be transported across c. membrane
  • Can be quickly hydrolysed to release energy

–Can be joined to other glucose molec. to produce di/poly saccharides

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26
Q

How are disaccharides formed?

A

From a condensation reaction forming a glycosidic bond and water

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27
Q

What is a glycosidic bond?

A

A covalent bond formed between molecules

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28
Q

What is maltose formed from?

A

2 alpha glucose

1-4 glycosidic bond

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29
Q

What is sucrose formed from?

A

Alpha glucose and fructose

alpha 1-4 glycosidic

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30
Q

What is lactose formed from?

A

Glactose and beta glucose

1-4 glycosidic bond

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31
Q

Why do we store glucose as glycogen?

A

Because glycogen is more compact, therefore easier to remove the terminal glucose molecule from the end

used to produce ATP for energy

We have a higher metabolic demand, therefore energy is made available more quickly

Less soluble bc it’s a big molecule so doesn’t affect water potential (osmosis)

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32
Q

What is the test for starch?

A

Iodine solution

Yellow/brown to blue black

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33
Q

Describe the test for reducing sugars

A
  • Heat with Benedict’s reagent

Blue - Green - Yellow - Orange - Brick red

Reducing sugars can give electrons to other molecules

Benedicts reagent is Cu2+ and the reducing sugar donates an e- to the reagent

Becomes Cu+ loses its blue colour

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34
Q

What is a reducing sugar?

A

Reducing sugars can donate electrons or reduce another molecule and reducing sugars are all monosaccharides and some disaccharides

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35
Q

What is the test for non-reducing sugar?

A

Test for reducing sugar by heating with benedict’s reagent (negative)

Take a separate sample and boil w hydrochloric acid and cool

Add hydrogen carbonate which neutralises the mixture

Test again for reducing heating with benedict’s solution

36
Q

What are the quantitative test for reducing sugars?

A
  1. Add benedict’s solution in EXCESS
    - Intensity of the colour is proportional to the concentration of sugar
  2. Test solution with test strip and compare against calibration curve
  3. Colorimetry
37
Q

Describe the reducing test using a colorimetry

A
  1. Carry out a serial dilution to create solutions of known glucose conc
  2. Heat with excess benedict’s reagent and observe colour change
  3. Centrifuge the mixture of sugar and benedict’s reagent (to separate precipitate and the excess benedicts solution, the supernatant)
  4. Place supernatant in cuvette
  5. Blue solution reflects blue light but absorbs red, so use red filter and measure the percentage absorption of red light
38
Q

How does one use a calibration curve?

A
  1. Take a series of known concentrations of reducing sugar and carry out benedict’s test
  2. Use a colourimeter to measure the transmission of light through each supernatant
  3. Plot graph to show transmission of light vs conc
  4. Test unknown sugar with benedict’s test and measure the transmission through the supernatant
  5. Use the calibration curve to determine the conc of unknown sugar
39
Q

Low percentage transmission of light mean……..

A

little amount of reducing sugar= low percentage transmission (bc a lot of absorbtion)

40
Q

Lipids are/aren’t polar molecules

A

Are not

41
Q

Lipids are known as macromolecules

What are macromolecules?

A

Large complex molecules with a large molecular weight

Not built from monomers

42
Q

Name 3 types of lipids

A

Triglycerides, phospholipids, sterols

43
Q

Describe the structure of a triglyceride

A

One glycerol (an alcohol) molecule with 3 fatty acids (carboxylic acid)

44
Q

Describe the reaction of glycerol and fatty acids

A

Ester bonds formed
hence esterification condensation reaction
Water is removed

45
Q

What is the difference between saturated and unsaturated?

A

Saturated = no double C-C bonds

Unsaturated = with double C-C bond

46
Q

What common characteristic do unsaturated fatty acids have/

A

They are liquid at room temp rather than solid (called oils)

double C-C- bond causes the molecule to kink or bend

Can’t pack as closely together

47
Q

Describe the structure of the phospholipid molecule and reaction

A

1 glycerol molecule and 2 fatty acid chains and a phosphate group

Condensation reaction between OH group on phosphoric acid and one on glycerol

48
Q

Which side of the phospholipid is non- polar?

A

Tail - non polar, hydrophobic

Head- polar hydrophilic

49
Q

How do phospholipids behave in water?

A

They form a layer on the surface with hydrophilic phosphate heads in water and hydrophobic tails sticking out

Called surfactants

Also forms micelles (ball shape)

50
Q

Phospholipids are both polar and non-polar therefore they are…

A

Amphipathic

51
Q

What are sterols?

A

Type of lipid, complex alcohol molecules

4 c ring structure with OH at one end

OH group is polar and therefore hydrophilic and the rest is hydrophobic

52
Q

Describe the role of cholesterol

A

Positioned between the phospholipids

Adds to the stability of the cell membranes and regulates the fluidity by keeping membranes fluid at low temp

53
Q

Where is cholesterol made an give examples

A

Liver and intestines

Hormones: testosterone, oestrogen and Vit D

54
Q

Describe the function of lipids ( 6 marks)

A
  • Creates membranes and hydrophobic barriers
  • Produce hormones
  • Electrical insulation for impulse transmission
  • Waterproofing (e.g feathers)
  • Energy store, insoluble in water so can be stored without affecting the water potential
  • Energy source, broken down in respiration, ester bonds are hydrolysed and are broken down into C02 and H20
55
Q

Why do organisms store lipids as a long term energy store?

A
  • Thermal insulation to reduce heat loss (penguin)
  • Cushioning to protect organs (heart and kidney) bc its less dense than water
  • Buoyancy (whales)
56
Q

Describe how a student could test if her sample contained lipids

A

Emulsion test

-nonpolar molecules don’t dissolve in water but will dissolve in organic solvents such as ethanol

Add ethanol to the sample and shake

add the mixture to a test tube of water

If lipids are present, a milky emulsion will form (the solution appears ‘cloudy’)

57
Q

What are peptides and proteins made from?

A

Amino acid molecules

One or more polypeptide

58
Q

Describe the structure of amino acids

A 
(NH2)                H
                           |
Amino group -  C - (carboxyl)
                           |
                          R
59
Q

What bonds form between the amino acids?

A

Peptide bond (condensation reaction)

dipeptide formed

Covalent bond

60
Q

What is the enzyme that catalyses the synthesis of a polypeptide?

A

Peptidyl transferase (in ribosome)

61
Q

What is the use of chromatography?

A

To separate a mixture into its constituents

62
Q

State the two phases involved in chromatography

A
  1. Stationary phase
    - Silica gel is applied to the chromatography paper
  2. Mobile phase
    - Picks up amino acids and separates them
63
Q

Describe a test for a student to identify a mixture of amino acids (7 marks)

A
  1. Draw a pencil line on the chromatography paper around 2 cm from bottom
  2. Add 4 dots with pencil equally spaced
  3. Add a drop of sample using a pipette on the first dot
  4. Add drops of known amino acids on the other 3 dots
  5. Suspend the chromatography paper in a jar containing water using a paper clip, ensure solvent is no more than 1 cm deep
  6. Leave chromatography paper until water reaches 2cm from top
    (7. spray paper with ninhydrin, aa react with it and produce a colour)
64
Q

What is the primary structure?

A

The sequence of aa in a polypeptide molecule.

The sequence will influence how the pp folds, its final shape and determining its function

Only peptide bonds

65
Q

What is the secondary structure?

A

The coiling or folding of an aa chain, structure of aa interact

Hydrogen bonds form pulling into a coil shape = alpha helix

pp chains can lie parallel and form hydrogen bonds = beta pleated sheet

66
Q

What is the tertiary structure?

A

The overall 3D shape of the protein

The coiling/folding into 2nd brings aa closer so they are close enough to interact and fold further

67
Q

Name the interactions that can form in the tertiary structure

A

Hydrophobic and hydrophilic interactions - weak interaction btwn polar and non-polar R groups

Hydrogen bonds - weakest bonds

Ionic bonds - form between oppositely charged R groups

Disulphide bridges - strong covalent bonds, form bwtn R groups with sulfur

68
Q

What is the quaternary structure?

A

The association of 2+ individual proteins called subunits

Interaction is same as tertiary but between protein molecules

Either identical or different

69
Q

Describe globular proteins

A

Molecules that are usually spherical

Compact, water soluble

70
Q

How do globular proteins form?

A

When proteins fold into tertiary structure so that the hydrophobic R groups are kept away from aqueous environ.

Hydrophilic R-groups are on outside of mole. therefore water can easily cluster around and bind

71
Q

Give 3 examples of globular proteins

A

Haemoglobin
Pepsin
Insulin

72
Q

Suggest how the prosthetic group in haemoglobin allow it to carry out its function

A
  • Quaternary structure ( 2 alpha and 2 beta subunits)
  • Each subunit has 1 haem group
  • Oxygen molecule binds to each of haem group and transports it to the body
  • Releases oxygen when tissue is reached
73
Q

What does catalase do?

A

It contains 4 haem groups

Catalase interacts w hydrogen peroxide and speeds up its breakdown

Hydrogen peroxide is a common by product of metabolism but is toxic

Catalase helps break down

74
Q

Describe the structure and function of insulin

A

2 pp chains - alpha helix and beta pleated sheet

Both chains fold into tertiary structure and joined by disulfide bridges

Has aa w hydrophilic R-groups on outside of mol. so is soluble in water

Binds to glycoprotein receptors on muscle to increase uptake of glucose

75
Q

Describe the general structure of fibrous proteins

A

Relatively long, thin structure, insoluble in water, metabolically inactive

Structural role

76
Q

State 3 examples of fibrous proteins

A

Collagen
Keratin
Elastin

77
Q

Describe the structure and function of collagen

A

3 pp chains, wound together to form rope-like structure

Many H+ bonds form btwn ppc forming long quaternary proteins w staggered ends = much longer and stronger

Has high proportions of aa that repel each other which adds to stability

  • Provide mechanical strength
    e. g. Tendons, cartilage, connective tissues
78
Q

Describe the main characteristics and functions of keratin

A

Function : to provide mechanical protection and impermeable barrier to infection, bc its water proof prevents water bourne infections

Found in: hair, skin, nails

Rich in cysteine = > strong disulfide bonds forming strong inflexible material

also H+

79
Q

Suggest differences between fibrous and globular proteins

A
  • Globular proteins are soluble in water whereas fibrous proteins are insoluble
  • Globular are spherical whereas fibrous are long
  • Fibrous are helical whereas globular are ball structured
  • Fibrous is involved in forming structures whereas globular proteins involved in metabolic reactions

Examples of fibrous:
-Collagen, fibrin, keratin, elastin

Globular:
Haemoglobin, insulin

80
Q

Which protein is rich in lystine?

A

Elastin

81
Q

Which protein is rich in glycine and proline?

A

Collagen

82
Q

Describe how you could find the type of amino acid

A
  1. Digest proteins into aa using protease
  2. Draw a line in pencil on cp and dot sample onto cp
  3. Dot and dry and repeat
  4. Place chromatography paper into solvent
  5. More soluble aa will b carrier further
  6. Stain with ninhydrin to visualise dots
  7. Calculate the Rf value and compare to known Rf values to determine aa
83
Q

How can you increase the accuracy?

A

Getting the correct value

  • Higher resolution of equipment
  • Smaller intervals (using temp)
  • Repeat and take a mean, to reduce the limitations of outliers
84
Q

How can you increase resolution?

A

Use an instrument with more decimal places

85
Q

What is precision? and how increase

A
  • The closeness of agreement between individual measurements
  • Anything to reduce the factor that affects how far the results are from the true value
  • To reduce human error (e.g. use biosensor with benedicts)
86
Q

Why would you repeat experiment?

A

To access precision and repeatability

87
Q

Independent variable and dependant

A

Independent variable- changed

Dependent -one that’s measured

Biology (15 decks)

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