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Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are macromolecules?

A

Large molecules such as polysaccharides, proteins (polypeptides) and nucleic acids (polynucleotides)
• Described as polymers

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2
Q

What is a polymer?

A

A giant molecule made from many similar repeating units (monomers) joined tightened in a chains,

Examples:

  1. Polysaccharides
  2. Proteins
  3. Nucleic acids
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3
Q

What are monomers? Give examples

A

A relatively simple molecule which is used as a building block for the synthesis of a polymer.
• many monomers are joined together by covalent bonds to make a polymer, usually by condensation reactions.

Examples:

  1. Monosaccharides > form polysaccharides
  2. Amino acids> form proteins
  3. Nucleotides > form nucleic acids
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4
Q

What are condensation reactions?

A

A chemical reaction involving the joining together of two molecules by the removal of a water molecule.

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5
Q

What are hydrolysis reactions?

A
  • opposite reaction to condensation reactions
  • used to break down polymers into respective monomers

A chemical reaction in which a chemical bond is broken by the addition of a water molecule; commonly used to break down complex molecules Into simpler ones.

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6
Q

Why can polymers be characterized as macromolecules but not all macromolecules are polymers?

A

The subunits of polymers have to be the same repeating units (monomers)

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7
Q

What are carbohydrates?

A 
• contain the the element la C, H and O
• the H and O atoms are always in the ration 2:1
• represented by the formula: Cx(H2O)y
• divided into 3 main groups:
1. Monosaccharides 
2. Disaccharides 
3. Polysaccharides
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8
Q

What are monosaccharides and state their characteristics.

A
  • A molecule consisting of a single sugar unit
  • General formula : ( CH2O)n
  • ALL are REDUCING SUGARS
  • they are sugars > dissolve easily in water to form sweet/tasting solutions.
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9
Q

What are the 3 main types of monosaccharides? Give examples

A
  1. Trioses (3C): glyceraldehyde
  2. Pentoses (5C): ribose and deoxyribose
  3. Hexoses (6C): glucose, fructose , galactose
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10
Q

What is glucose?

A
  • The most well-known carbohydrate monomer/ monosaccharides
  • a hexose (general formula: C6H12O6)

CHECK LINEAR STRUCTURE

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11
Q

What happens when glucose forms a ring structure?

A

C1 Joins ti the oxygen on C5.
The ring therefore contains oxygen, and C6 is not part of the ring.

CHECK STRUCTURE OF ALPHA AND BETA GLUCOSE

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12
Q

State the component isomers of glucose of the polysaccharides glycogen, starch and cellulose.

A

Isomers of a- and B- glucose combine to form different structures:

Glycogen: only a- glucose
Starch: only a- glucose
Cellulose: only B- glucose

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13
Q

Describe the function of monosaccharides in living organisms as sources of energy in respiration

A

E.g glucose is the most important monosaccharide in energy metabolism.

Explanation:

  1. Their is a large number of C-H bonds
  2. These bonds are broken to release large amounts of energy.
  3. This energy is transferred to make ATP from ADP and phosphate during respiration.
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14
Q

Give examples of how monosaccharides are used as building blocks for larger molecules (function of monosaccharides)

A
  1. Glucose is used to make the polysaccharides starch, glycogen and cellulose
  2. Ribose ( a pentose) is one of the molecules used to make RNA and ATP.
  3. Deoxyribose ( a pentose) is one of the molecules used to make DNA
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15
Q

What are disaccharides? Give examples

A

A sugar molecule consisting of two monosaccharides joined together by a glycosidic bond. The two monosaccharides are joined together by a condensation reaction.

Examples:

  1. Maltose (2x glucose)
  2. Sucrose (glucose + fructose): transport sugar in plants.
  3. Lactose ( glucose + galactose): found in milk
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16
Q

What is a glycosidic bond?

A

A C-O-C link between two sugar molecules, formed by a condensation reaction it is a covalent bond

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17
Q

What determines which -OH groups like up alongside each other in the formation of glycosidic bonds?

A

The shape of the enzyme controlling the condensation reaction

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18
Q

Check formation of maltose and fructose.

A

Maltose :
•formed from 2 a- glucose
• bond formed between C1 and C4

Sucrose:
• formed from 1 a- glucose and 1 B- fructose
• bond formed between C2 and C2

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19
Q

Check TEST FOR PRESENCE OF SUGARS.

A

.

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20
Q

What is a polysaccharide?

A

A polymers whose subunits are monosaccharides joined together by glycosidic bonds

  • made by joining many monosaccharides monomer molecules by condensation.
  • are macromolecules

Examples; starch, glycogen and cellulose (polymers of glucose)

Note: polysaccharides are NOT SUGARS

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21
Q

Why is glucose an unsuitable storage substance? And how is this counteracted?

A
  1. It is water soluble; dissolves to concentrate cell contents.
    Affects osmotic properties (osmolarity ) of the cell.
  2. It is a very reactive molecule
    Interferes with normal cell chemistry

Counter:
•The storage is converted by condensation reactions into storage polysaccharides.

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22
Q

How are storage polysaccharides more suitable for their function? Give examples.

A

They are convenient, COMPAT, INERT AND INSOLUBLE MOLECULES.

Plants: starch
Animales: glycogen (glucose store in liver and muscle cells)

When needed glucose is made available again by enzyme-controlled hydrolysis reactions.

Note: both Starch and glycogen are folded.
This makes the molecule compact which is ideal for storage

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23
Q

What is starch?

A
  • The storage polysaccharides in plants.
  • A mixture of AMYLOSE (10-30%) and AMYLOPECTIN (70-90%) that build up into relatively large Starch grains
  • found in chloroplast and storage organs(potato tubers)
  • easily seen with light microscope, especially if stained.
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24
Q

What is amylose and Describe its structure

A

A long, UNBRANCHING chain of several thousands 1,4 LINKED a- glucose molecules

  • Made by condensation reactions between a- glucose molecules .
  • the chains are CURVED and COIL UP into HELICAL STRUCTURES like springs, so the final molecule is compact > more resistant to digestion
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25
Q

Describe the structure of amylopectin

A

•Made up of many 1,4 linked a- glucose molecules BUT chains are SHORTER than in amylose.
• ALSO Contains 1,6 linkages that branch out to the sides of the chain
(See diagram)

26
Q

Describe the importance of the branching of amylopectin molecules.

A

Results in many terminal glucose molecules that can be hydrolysed for use during cellular respiration or added to for storage.

Note : the branching occurs after every 20 monomers.

27
Q

Describe the structure of glycogen

A

• has a molecular structure similar to amylopectin.
- made of chains of 1,4 linked a- glucose with 1,6 linkages making beach points.
• NOT COILED

• glycogen molecule clump together to form granules (visible in liver and muscle cells)- form of energy reserve.

28
Q

How do glycogen and amylopectin differ?

A

They differ in the degree of brachinh of their glucose chains; glycogen is MORE BRANCHED than amylopectin.> more terminal glucose molecules.

29
Q

State the effects of the higher degree of branching of glycogen molecules than amylopectin molecules

A
  1. Makes glycogen molecules more compact> helps animals store more
  2. The branching enables more free ends where glucose molecules can either be added or removed allowing condensation and hydrolysis reactions to occur more rapidly > storage and release of glucose can suit the demands of the cell.
30
Q

What are the differences between amylose and amylopectin?

A
  1. Amylose has no 1,6 linkages whereas amylopectin has both 1,4 and 1,6 a- glucose linkages.
  2. The structure or amylose is curved and helical whereas that of amylopectin is NOT CURVED but branched (caused by the 1,6 linkages)
  3. The chains of 1,4 linked a- glucose molecules in amylopectin are shorted
  4. Amylose is more resistant to digestion
31
Q

Check difference between starch and glycogen

A

.

32
Q

Check test for presence of startch

A

.

33
Q

Why is cellulose considered as the most abundant organic molecule?

A

Due to its presence in plant cell walls and it’s slow rate of breakdown in nature.

34
Q

What is cellulose?

A

A polysaccharide made from BETA GLUCOSE subunits; used as a strengthening material in plant cell walls

35
Q

Describe the bonding in cellulose (check diagram)

A

• B- glucose subunits are joined together by 1,4 glycosidic bonds.
NOTE: consecutive B- glucose molecules must be rotated 180 degrees relative to each other
• there are hydrogen bonds between molecules

36
Q

Why does the arrangement of the B/ glucose molecules result in a strong molecule?

A
  1. Hydrogen atoms of the -OH Groups are weekly attracted to the oxygen atoms in the same molecule (oxygen of the glucose ring)
  2. Hydrogen atoms of the -OH groups are also attracted to the oxygen atoms of the -OH groups in neighbouring molecules.
37
Q

Describe the formation of microfibrils and fibres.

A
  1. Hydrogen bonding between 60-70 molecules causes them to become tightly cross-linked to form bundles called microfibrils (10 nm in diameter)
  2. Microfibrils are in turn held together by hydrogen bonding in bundles called fibres
38
Q

Further structure of cell walls (in terms of cellulose fibres)

A
  1. A cell wall typically has several layers of fibres running in different directions to increase strength m.
  2. Cellulose makes up 20-40% of the average cell wall.
  3. Other molecules help to cross-link the cellulose fibres and some form a glue-like matrix around the fibres> further Increases strength.
39
Q

Describe the importance of cellulose fibres in the construction of cell walls.

A
  1. They have a very high tensile strength .
    • makes it possible to withstand large osmotic pressures
    • without the cell wall, the cell would burst in dilute solutions
    • these pressures help provide support for the plant by making the tissues TIRGID + responsible for cell expansion during growth.
    • the arrangement of fibres around the cell helps to determine the shape of the cell as it grows
  2. Cellulose fibres are INSOLUBLE AND freely permeable, allowing water and solutes to reach and leave the cell surface membrane

Note: the tensile strength and i solubility of cellulose fibres makes them suitable to construct cell walls.

40
Q

What is a hydrogen bond?

A

A relatively weak bond formed form the attraction between a group with a small positive charge in the hydrogen atom and another group carrying a small negative charge

41
Q

What are polar molecules and state it’s relationship with water

A
  • Polar molecules are molecules that have groups with dipoles (e.g sugars)
  • they are attracted to water molecules because water molecules also have dipoles.
  • they are HYDROPHILIC
42
Q

What are non-polar molecules and state their relationship with water molecules

A
  • molecules that do not have dipoles
  • they are not attracted to water molecules
  • HYDROPHOBIC
43
Q

What are the characteristics of lipids?

A
  • contain the elements C, H and O ( they have a lower proportion of oxygen than carbohydrates)
  • Non-polar and hydrophobic (insoluble in water)
44
Q

What are the different types of lipids?

A
  1. Fats and oils (composed mainly of TRIGLYCERIDES)
  2. Phospholipids
  3. Steroids and waxes (considered as lipids as they are hydrophobic)

Note:
Fats- solid at rtp
Oils- liquids at rtp

45
Q

Describe the structure of fatty acids.

A
  1. They contain the acidic group -COOH, CARBOXYL GROUP.
    • the carboxyl group forms the head of the fatty acid molecule
  2. Common fatty acids have long hydrocarbon chains (4-24 C long) attached to the carboxyl group
  3. The fatty acid tail contains a methyl group at the end

• Chain is often 15-17 C atoms long

46
Q

How can fatty acids vary?

A
  1. They can carry in length of hydrocarbon chain
  2. The fatty acids may be either saturated or unsaturated
    Unsaturated: contains atleast one C=C double bond
47
Q

How are unsaturated lipids formed? Describe its characteristics

A
  • formed from unsaturated fatty acids

* the double bonds make the fatty and lipids melt more easily

48
Q

What are monounsaturated and polyunsaturated fatty acids?

A

Monounsaturated: fatty acid consists of only one C=C bond

Polyunsaturated: more than one C=C double Bonds

49
Q

What are cis- and trans- fatty acids and describe their effects on enzyme activity. (CHECK DIAGRAMS)

A

Cis- : H atoms on the same side of the C=C bond
• can be metabolised by enzymes

Trans-: H atoms on the opposite side of the C=C bond
•cannot form enzyme-substratw complexes
•not metabolised by enzymes
•linked with coronary heart disease.

50
Q

What are saturated fatty acids? ( CHECK DIAGRAM)

A

Contain NO C=C bonds

• no links

51
Q

What are the differences between saturated and unsaturated fatty acids?

A
  1. Saturated fatty acids have C=C bonds and thus kinks are found in the fatty acid tails (how to distinguish > saturated fatty acids have no kinks)
  2. Animal lipids are often saturated and occur as fats
  3. Plant lipids are often unsaturated and occur as oils (e.g olive and sunflower oil)
52
Q

What are alcohols and give an example

A

Homologous series of organic molecules containing a hydroxyl group, -OH, attached to a carbon atom.

Example: glycerol: an alcohol with 3 hydroxyl groups

53
Q

How as esters formed?

A
  • By a reaction between an alcohol and an acid.

* link called an ester linkage

54
Q

What is the ester linkage and how is it formed?

A

A chemical bond represented as -COO- formed when an acids reacts with an alcohol

  • the carboxyl group on the acid reacts with the hydroxyl group on the alcohol to form the water bond
  • a condensation reaction (water is removed)
  • the resulting ester can be converted back into its constituent acid and alcohol by hydrolysis
55
Q

What is a glyceride?

A

An ester formed by a fatty acid combining with the alcohol glycerol.

56
Q

What are triglycerides and state it’s characteristics. (Check diagram)

A

A type of lipid formed when three fatty acid molecules combine with glycerol, an alcohol with 3 hydroxyl groups.

• most common lipids; they are fats and oils.
• formed by estérification:
-each of the 3 hydroxyl groups of a glycerol molecule undergoes a condensation reaction with a fatty acid
-final molecule contains 3 fatty acid tails and 3 ester bonds
-the tails can vary in length, depending on the fatty acids used.

Note:
Ensure familiarity with the structure of triglycerides and recognize the nature of the fatty acid (either saturated or unsaturated)

57
Q

Explain the insolubility of triglycerides

A

Insoluble in water but soluble in some organic solvents such as ethanol

Explanation:

  1. The hydrocarbon tails are non-polar : they have no uneven distribution of electric charge
  2. Consequently they are hydrophobic and do not mix freely with water molecules.
58
Q

Why do triglycerides store and release large amounts of energy? (Role)

A

Release:

  1. The long hydrocarbon chains contain many C-H bonds with little oxygen ( triglycerides are highly reduced)
  2. So when triglycerides are oxidized during cellular respiration this causes the bonds to break real easing energy used to produce ATP.

Storage:

  1. Because triglycerides are even richer in C-H bonds than carbohydrates, they therefore store more energy per gram (higher calorific value)
  2. As triglycerides are hydrophobic they do not cause osmotic water uptake in cells> more can be stored.
59
Q

How to plants and animals store triglycerides respectively?

A

Plants:
• store triglycerides in the form of oils in seeds and fruits.
• if extracted from seeds and fruits these are generally liquid at room temperature due to the presence of double bonds which add kinks to the fatty acid chains> alters their properties.

Mammals:
• Store triglycerides in adipose tissue (e.g below the skin and around the kidneys) as oil droplets.
• this helps them survive when food is scarce (r.g hibernating bears)

60
Q

Describe the role of triglycerides as metabolic sources of water.

A

• when oxidized during respiration, triglycerides are converted into carbon dioxide and water.
> metabolic water
-Desert animals (e.g dry habitats) retain this water when liquid water is scarce.
- birds and reptiles embryos in their shells also use this water.

61
Q

Describe the role of triglycerides in insulation

A

• form part of the composition of the myelin sheath that surrounds nerve fibres.
-provides insulation which I crease then speed of transmission of nerve impulses.

• compose part of the adipose layer below the skin
- acts as an insulator gainer heat loss (e.g blubber in whales)

62
Q

Describe the role of triglycerides in buoyancy and protection.

A

Buoyancy:
The low density of fat tissue increase the ability of sea animals to float more easily (e.g blubber in whales)

Protection;
Adipose tissue in mammals helps protect organs (e.g heart and kidneys) from risk of damage.

Biology (3 decks)

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