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OCR A-level Biology Module 2: Foundations in Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

Water, Carbohydrates, Lipids and Proteins, its all here and its a lot of content

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1
Q

Explain the following reactions:
1. Condensation
2. Hydrolysis
3. Polermerisation

A
  1. When 2 molecules react together, relasing a molecule of water per reaction
  2. Where water is used to split the larger molecule into 2 smaller molecules
  3. Where small molecules called monomers combine in a reaction to produce a very large chainlike molecule called a polymer .
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2
Q

Explain why water molecules are polar…

A
  • As Oxygen is more electronegative, it will pull more electrons towards itself than hydrogen.
  • This will give it a partial negative, while Hydrogen has partial positive charge

electrons spend more time closer to oxygen…

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3
Q

Define Hydrogen Bonding

A
  • This is the relatively weak interaction between a slightly negative atom and slightly positive hydrogen atom, via polar molecules

HYDROGEN BOND = AN INTERMOLECULAR FORCE

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4
Q

How does Water form Hydrogen Bonds?

A
  • Due to water polarity, the partial negative charge on oxygen will attract to partial positive charge on hydrogen of next molecule.
  • This interaction = hydrogen bond!
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5
Q

Don’t overthink………….

What is a dimer?

A
  • This is simply when 2 monomers react together to form a bonding e.g. disaccharides…..
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6
Q

Why is water liquid at ambient temperature?

A
  • Energy stored in Hydrogen Bonds require a lot of energy to overcome and break, to evaporate gas
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7
Q

Why is liquid water at ambient temperature important for Life?

A
  • Allows for transport mechaisms (e.g. Blood….)
  • Provides important metabolite / reaction medium (e.g. The Cytoplasm)
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8
Q

Why is Ice less dense than Water?

A
  • When frozen, hydrogen bonds freeze in place, forming an open lattice.
  • Larger volume for same mass will mean decrease in density!
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9
Q

Why is decreased ice density important for Life?

A
  • Provides valuable habitats for many antartic organisms
  • Floats on lakes / ponds,** insulating **these places, **retaining thermal energy **and sustaining constant temps.
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10
Q

Why is water a good solvent?

A
  • Due to water being polar, other polar molecules / ionic substances will attract towards the** partial charges of H2O**
  • This will cause dissociation, and will dissolve the substance
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11
Q

Why can’t water dissolve non-polar substances?

A
  • Due to non-polar substances not able to form hydrogen bonds / attract to dipoles of H2O
  • Hence, water can not cause dissociation to dissolve compound
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12
Q

Why is water as a solvent important for Life?

A
  • This will allow for ionic and polar molecule transportations, such as in the transpiration and translocation stream!
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13
Q

Why does water have a high surface tension?

A
  • Due to many hydrogen bonds pulling water molecules inwards and contracting
  • Hence, will resist external applied force to an extent
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14
Q

Why is water high surface tension important?

A
  • This allows for insects pond-skaters to walk on the surfaces
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15
Q

Why are water molecules adhesive / cohesive?

A
  • Due to hydrogen bonds pulling the moleculs togather, less attracted to molecules in air
  • Hence, will give the “rounded droplet” shape!
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16
Q

Difference between Cohesion and Adhesion?

A
  • Co = same molecules
  • Ad = external molecules
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17
Q

Why is water cohesion / adhesion important for Life?

A
  • Water able to be drawn up Plant Xylem and (Phloem)
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18
Q

Why does water have a high SHC?

A
  • Again, due to strong hydrogen bonds that stores a lot of energy, per unit mass.
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19
Q

Why is water’s high SHC important for Life?

A
  • Lakes not able to fully freeze, manatins a stable aquatic environment, temprature - wise
  • Effective thermal energy transfer with blood in mammals!
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20
Q

Why is water’s high SLH of F important?

A
  • Provides an effective sweating mechanism, without need to loose relitavley large amount of water in mammals.
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21
Q

4 to know

Importance of Calcium Ions (Ca2+)

A
  1. Increases bone and cartiladge rigidity
  2. Component in custaceans exoskelton
  3. Stimulates and regulates cell permeability
  4. Regulates nerve impulses
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22
Q

Importance of Sodium Ion (Na+)

A
  1. Water potential regulation in cells
  2. Mantains vacuole rigidity
  3. Affects small intestine absorbtion (water + carbs)
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23
Q

Importance of Potassium Ions (K+)

A
  1. Helps in regulating water levels in the blood
  2. Assists active transport of materials to cell membrane
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24
Q

Importance of Hydrogencarbonate Ion (HCO3-)

A
  1. Involved with carbon dioxide transportation out of the blood
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25
Q

Importance of Hydroxide Ion (OH-)

A
  1. Involved in regulation of blood pH
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26
Q

Importance of Phosphate Ion (PO43-)

A

1. Component of** hydrophilic “head” phospholipid region***
2. Assists in plant root growth

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27
Q

Importance of Chloride Ions (Cl-)

A

*1. Helps in production of urine in kidney, mantaining water balances.
2. Used to produce HCL for the stomach digestion

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28
Q

Importance of H+ Ions

A

*1. Involved in major chemical reactions (e.g. respiration, photosynthesis)
2. Involved in regulation of blood pH

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29
Q

Importance of Nitrate and Ammonium Ions

A
  1. Key component in nuciec acid, ammino acids and Chlorophyll
  2. Involved in hormone production (e.g. Insulin)
  3. Major role in the Nitrogen Cycle!
30
Q

Define a monosaccharide

A
  • These are the simplest, single units of carbohydrates, being a main source of energy in organisms
31
Q

Define a disaccharide

A
  • This is when 2 monosaccharides react via **condensation reaction **to form a glycosidic bond, releasing water during this process

normally a 1,4 glycosidic bond…..

32
Q

Name the 4 most common disaccharide reactions!

A
  1. a glucose + a glucose&raquo_space; Maltose
  2. a glucoes + fructose&raquo_space; Sucrose
  3. b galactose + a glucose&raquo_space; Lactose
  4. b glucose + b glucose&raquo_space; Cellobiose
33
Q

Define an isomer

A
  • This is when molecules has the same molecular formula, but differing physical, structural arrangements
34
Q

What effect would the addition of water have in a glycosidic bond?

A
  • This will cause a HYDROLYSIS reaction via a hydrolysing enzyme, and will break the di/polymer into its mono/dimers
35
Q

What are reducing sugars?

A
  • These are sugars thats can donate electrons to other molecules / compounds
36
Q

What are non-reducing sugars?

A
  • These are sugars that are unable to release any electrons to other molecules
37
Q

Why is Glucose very soluable in water?

A
  1. This is due to having a large number of hydroxyl groups in the molecule
  2. As water is polar, hydrogen bonds can be formed with such hydroxlyl groups and water
38
Q

What does the structure of Amylose consist of?

A
  1. A polymer of a glucose, vie 1,4 glycosidic bonds
  2. Hydrogen bonding present in between the chains, froming a compacted helix
  3. 1000s of molecules bonded togther in this chain
39
Q

What is the function of Amylose?

A
  1. Main store of energy in plants
  2. When glucose needed, enzymes undergo hydrolysis to acquire glucose for respiration
40
Q

What is the structure of Amylopectin?

A
  1. A polymer of a glucose, but with molecule branching with nearby polymers
  2. Such branches have a 1,6 glycosidic bonding
41
Q

What is the function of Amylopectin?

A
  1. Very, very compact and large molecule
  2. Able to store large amounts of glucose, whilst being insoluble in water
  3. Insolubility = no effect of cell water potential!!!
42
Q

What makes amylopectin different to amylose?

A
  • AMYLOPECTIN: Branched molecule = faster rate of enzyme hydrolysis to release glucose for respiration!
  • AMYLOSE: Completely linear, boring polymer
43
Q

What is the structure of Glycogen?

A
  1. Very similar to amylopectin, but contains MORE BRANCHES and SMALLER 1,4 bonds.
  2. Stored in the Liver and Muscle cells on release of Glucagon
44
Q

What is the function of Glycogen?

also say what energy is actually USED for…

A
  1. MUCH more increased rate of enzyme hydrolysis, due to MORE branching
  2. To be able to supply MASSIVE INCREASES in ENERGY demand in animals in respiration

for Homeostasis, Active Transport, Waste Secretion, Muscle Contraction..

45
Q

What is the structure of Cellulose?

A
  1. Polymer of b glucose!
  2. As OH- group is ABOVE the ring plane, molecules will invert repeatedly, to align this group.
  3. This will cause a COMPLETELY linear shape

to form the bonds in the first place………

46
Q

What is the function of Cellulose?

a sneaky extra…………………

A
  1. Strong Hydrogen bonds = strong tensile strength
  2. Hence, will counter cell expansion via turgidity.

very difficult to digest, due to **strong hydrogen bonds neeeded to brea

47
Q

What makes Cellulose unique compared to the other polymers?

check this bit out rq….

A
  1. Due to no branches, polymer chains can lie VERY colse to each other!
  2. Hydrogen bonds form in between, and will cause GROUPED chains (adding to tensile strength………………)

microfibril > macrofibril > cellulose fibres!!!!!!

48
Q

Why would a plant need to have cell walls of Cellulose?

A
  1. Due to having a lack of a sufficient skeleton, a strong outer layer is very much needed….
49
Q

List some common traits attributed to Carbohydrates

A
  1. All quite inert = metabolically unreactive
  2. Insoluble = will not affect cell water potentials
  3. Large = Can not enter cells in its form
  4. Storage = EXCELLENT energy store molecule, due to all mentioned above!!
50
Q

Distuunguish the difference between polymers and macromolecules!

A
  1. Polymers: A large molecules made of repeating, smaller units called monomers
  2. Macromolecules: Very large organic monomers, doesnt necessariliy have reapeating monomers
51
Q

What is a triglyceride?

A
  1. This is a type of lipid molecule made of 3 fatty acids and 1 glycerol backbone components
52
Q

Describe a triglyceride’s formation and structure

A

1.Will react via CONDENSATION to form ESTER BONDS (-COO)
2.Release of water per ester bond formed
3.4 componetnts (glycerol + F.A) , as understood earlier……….

hence, hydrolysis will BREAK this moleucle down (with enzymes)

53
Q

Outline the difference between saturated and unsaturated
fatty acids……

A
  1. SAT: Completely linear (C-C), no kinks in hydrocarbon chain = packed molecules closer = stronger intermolecula forces
  2. UNSAT: Bent molecule (C=C), spaced out molecules = weaker I.Fs.

Sat = Solids at ambient temp
Unsat = Liquids at ambient temp

54
Q

List ‘n explain 4 Main triglyceride funcitons……

A
  1. BUOYANCY: fatty acids are less densse than water, assisting with floating
  2. Energy Storage: Due to high proportions of C anh H in long chains
  3. Insulation: Stored in mammal adipose tissue, retaning thermal energy
  4. Delicate Organ Protection: provides shock absorbance against impact
55
Q

outline the main role of Phospholipids

A
  • Forms the Phospholipid Bilayer due to its amphiphilic properties

check “Biological Membranes” for more details……………..

56
Q

Outline the main role of Cholesterol

A
  • This will regulate membrane fluidity during hotter and colder tempratures

check “Biological Membranes” for more details……………..

57
Q

What is an amino acid?

A
  1. This is the simplest monomer unit of all protien molecules
58
Q

What is the structure of amino acids?

check itttttttttttttttt…………

A
  1. Contains a central C atom, with and “amine” and “carboxyl” group, along with an “R” group

R Group = Any additional group, differnt for differnt amino acids!!!

btw all amino acids end in : -ine

59
Q

Describe Polypeptide formation!

A
  1. Amino acids will react via CONDENSATION, to form PEPTIDE BONDS from carboxyl (-OH) group and amine (-H) group releasing water
  2. Amino Acids > Dipeptide molecules > Polypeptide
60
Q

Define the 4 different structure levels of protiens

A
  1. Primary = the sequencing of amino acids in a molecule
  2. Secondary = coiling of amino acid chain
  3. Tertiary = Overall 3D shape of protein molecule
  4. Quaternary = Where multiple poypeptides are involved in this structure
61
Q

What acronym can we use to remeber the protein structure main bondings?

A

People Promise Some Horses To Facilitate Domed Igloos

62
Q

What are Fibourous Protiens?

A
  1. These are relitavly long and linear protiens
  2. Insoluble in water, bieng unreactive (mostly)
  3. Holds the STRUCTURAL ROLE IN ORGANISMS
63
Q

State some examples of Fibrous Protiens!

A
  1. Collagen - used in artery walls, bone structure and connective tissue
  2. Keratin = Anywhere touch (claws,nails…)
  3. Elastin = Skins and blood vessel walls
    4.
64
Q

What are Globular Protiens?

A
  1. Relitavly spherical shaped protiens, being soluble in water, holding *metabolic roles in organisms
65
Q

State some examples of Globular Protiens

A
  1. Haemolgobin - used in binding of oxygen in reb blood cells
  2. Insulin - blood sugar hormonoe produced in pancreas
  3. Pepsin - Stomach enzyme, digesting protein molecules
66
Q

`

Steps in invesigating a reducing sugar?

A

Preparation: Dissolve a small amount of the sample (like glucose) in water.

Adding Benedict’s solution: Mix the sample solution with an equal volume of Benedict’s solution in a test tube.

Heating: Heat the mixture in a boiling water bath for a few minutes.

Observation: A color change will occur if reducing sugars are present:

Blue (no reducing sugar)

Green/yellow (low concentration)

Orange/red (moderate concentration)

Brick-red precipitate (high concentration)

67
Q

Steps in invesigating a non -reducing sugar?

A

Initial Benedict’s Test:

Add Benedict’s reagent to the sample solution.

Heat in a boiling water bath.

*Observation: No color change indicates the absence of reducing sugars.
*
Hydrolysis:

Add dilute hydrochloric acid (HCl) to the sample solution.

Heat the mixture in a boiling water bath for a few minutes.

*Purpose: Acid hydrolysis breaks down non-reducing sugars into their monosaccharide components.
*
Neutralisation:

Add sodium hydroxide (NaOH) to the hydrolyzed solution.

Purpose: Neutralise the acid to prepare for the Benedict’s test.

Second Benedict’s Test:

Add Benedict’s reagent to the neutralized solution.

Heat in a boiling water bath.

Observation: A color change (green, yellow, orange, or brick-red precipitate) indicates the presence of reducing sugars, confirming that non-reducing sugars were originally present.

68
Q

Steps to investigate Lipids?

A

Sample Preparation:

Place the sample (solid or liquid) into a clean test tube.

Add a few milliliters of ethanol to the sample.

Purpose: Ethanol dissolves lipids present in the sample.

Shaking:
Shake the test tube vigorously for about one minute.

Ensure the sample is thoroughly mixed with ethanol.

Adding Water:

Add an equal volume of distilled water to the test tube.

Purpose: Water causes lipids to precipitate out of the ethanol solution.

Observation:

Observe any changes in the solution.

Positive Result: A milky or cloudy emulsion forms, indicating the presence of lipids.

Negative Result: The solution remains clear, indicating the absence of lipids.

Key Points:

***Emulsion Formation: Lipids are insoluble in water but soluble in ethanol. When water is added, lipids precipitate out, forming a milky emulsion.

*

69
Q

What is a Qualitative approach for testing Sugars?

A
  1. Investgating the LIGHT ABSORBANCE of colour changing Benedict’s Solution via a COLORIMETER
70
Q

Testing for Carbohydrates?

A
  1. The good ‘ol iodine (blue/black and orange) test!!!

OCR A-level Biology Module 2: Foundations in Biology (6 decks)

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