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BIOLOGY AS > Mod 2 Chap 3: Biological Molecules > Flashcards

Mod 2 Chap 3: Biological Molecules Flashcards

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1
Q

Define a monomer.

A

A small molecule that binds to other identical molecules to form a polymer.

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2
Q

Define a dimer.

A

Two monomers joined together.

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3
Q

Define a polymer.

A

A large molecule made from many small monomers.

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4
Q

What elements make up the biological molecules carbohydrates?
Also, what are their monomers and polymers?

A

Elements: C, H, and O
Monomer: Monosaccharides (e.g. Glucose)
Polymer: Polysaccharides (e.g. Starch)

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5
Q

What elements make up the biological molecules proteins?

Also, what are their monomers and polymers?

A

Elements: C, H, N, O and S.
Monomer: Amino acids
Polymer: Polypeptides

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6
Q

What elements make up the biological molecules Nucleic Acids?
Also, what are their monomers and polymers?

A

Elements: C, H, O, N and P.
Monomer: nucleotides.
Polymer: DNA.

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7
Q

What is covalent bonding?

A

A bond in which atoms share electrons with other atoms. This allows them to ‘fill’ their outer shell and results in a strong bond with the other atom.

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8
Q

What is a condensation reaction?

A

A condensation reaction occurs when two molecules are joined together with the removal of water.

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9
Q

What is a hydrolysis reaction?

A

A hydrolysis reaction occurs when two molecules are split up by the addition of water.

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10
Q

What elements make up the biological molecules Lipids?

A

Elements: C, H and O.

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11
Q

How does hydrogen bonding occur between water molecules?

A
  • water = 2 H atoms, each covalently bonded w/ O atom.
  • but, as O atom has greater number of protons in its nucleus, it exherts a stronger attraction for shared electrons (O atom has a greater electronegativity), it has greater pull on electrons.
  • so O atom becomes slightly negative + H atoms become slightly positive
  • when this happens, we say molecule is polar (e.g. Structure of water is polar).
  • in structure of water: H = delta positive, O = delta negative.
  • so water forms hydrogen bonds
  • in water molecules, hydrogen bonds are weak + covalent bonds are strong
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12
Q

Describe the properties of water.

A
  • it’s a solvent
  • high specific heat capacity: large heat energy needed to increase kinetic energy
  • has high latent heat of vaporization (heat energy / has an unusually high BP): is a liquid at room temp due to H bonds, takes a lot of energy to increase its temp + turn it gaseous
  • when freezes it turns to ice, + actually then becomes less dense, this due to H bonds as they fix positions of polar molecules slightly further apart than average distance in liquid state, when cooled below 4 degrees
  • has cohesive properties + surface tension: moves as one mass as molecules are attracted to eachother
  • has adhesive properties: water molecules are attracted to other materials, e.g. When you wash hands they become wet
  • it’s a reactant
  • it’s a liquid at room temp
  • it’s dense
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13
Q

Relate the properties of water to its role in living organisms / how this benefits life.

A

SOLVENT:
- molecules + ions can move around + react in it
- so many reactions happen in cytoplasm of cells (as is 70% water)
- molecules + ions can also be transported around living things when dissolved in water
HIGH LATENT HEAT OF VAPORISATION:
- so water can help cool living things + keep their temp stable
- e.g. mammals cooled when sweat evaporates
- e.g. plants cooled when water evaporates from mesophyll cells
COHESION AND SURFACE TENSION:
- columns of water in plant vascular tissue are pulled up xylem tissue together from roots in transpiration stream
- insects like pond-skaters can walk on water
HIGH SPECIFIC HEAT CAPACITY:
- living things need a stable temp for enzyme-controlled reactions to happen properly
- aquatic organisms need a stable environment in which to live
REACTANT:
- important for digestion + synthesis for large biological molecules
LIQUID:
- provides habitats for living things in rivers, lakes + seas
- forms major component of tissues in living organisms
- provides a reaction medium for chemical reactions
DENSITY:
- water more dense than ice, so aquatic organisms have stable environments to live in through winter
- ponds + other water bodies are insulated against extreme cold, as ice layer reduces heat loss.

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14
Q

What are the roles of carbohydrates?

A
  • energy store
  • energy source
  • structural
  • form part of other molecules
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15
Q

Describe the three main groups of carbohydrates.

A

Monosaccharides: (simple sugars)
Disaccharides: (complex sugars)
Polysaccharides: (complex carbohydrates)

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16
Q

How are sugars held together?

A

Glycosidic bonds

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17
Q

Describe monosaccharides (+ structure, role + how they are categorised).

A
  • simple sugars
  • energy source due to large number of C-H bonds
  • soluble
  • exist as single ring shape or straight chain
  • no glycosidic bonds
  • categorized by their number of C atoms, into:
    • hexose: 6 carbons
    • pentose: 5 carbons
    • triose: 3 carbons
  • roles in organisms: energy, transported in blood, monomers for other carbohydrates
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18
Q

Describe glucose as a hexose monosaccharide.

A
  • hexose monosaccharide so has 6 carbons
  • two forms of it: alpha / beta glucose
  • alpha + beta glucose structures drawn differently (draw)
  • alpha + beta glucose are isomers of eachother
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19
Q

Describe ribose as a pentose monosaccharide.

A
  • pentose monosaccharide so has 5 carbons atoms

- is the sugar present in RNA nucleotides

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20
Q

Describe glucose’s molecules’ properties.

A
  • polar
  • soluble in water, due to H bonds between hydroxyl groups + water molecules
  • important they are soluble as means glucose is dissolved in cytosol of cell.
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21
Q

Describe disaccharides (+ structure, role + examples).

A
  • two single sugar molecules joined by a condensation reaction / covalently joined
  • soluble
  • have one single glycosidic bond
    Examples:
  • sucrose (glucose + fructose)
  • lactose (glucose + galactose)
  • maltose (glucose + glucose)
  • roles in living organisms: energy release, storage and transport in plants
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22
Q

Two monosaccharides will form a…

A

Disaccharide

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23
Q

Describe oligosaccharides.

A
  • 3-10 sugar molecules joined into a chain
  • not easily digested
  • found in leaks, onions, garlic etc
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24
Q

Describe polysaccharides ( + structure, role + types).

A
  • polymers or monosaccharides
  • many molecules covalently joined
  • insoluble
  • have many glycosidic bonds
  • long chains that may be branched / coiled
  • two types of them:
    • homopolysaccharides: (monomers are all the same)
    • herteropolysaccharides: (more than one type of monomer)
  • roles in living organisms: energy storage, structural component of cell walls
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25
Q

Describe the structure of the polysaccharide starch through amylose.

A
  • a type of starch
  • formed by alpha glucose molecules joined together by 1-4 glycosidic bonds
  • is a polysaccharide in starch
  • angle of bond means long chain of glucose twists to form a helix
  • helix further stabilized by H bonds within molecule
  • makes polysaccharide more compact + much less soluble than glucose molecules used to make it
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26
Q

Describe the structure of the polysaccharide starch through amylopectin.

A
  • another type of starch
  • formed when glycosidic bonds form in condensation reactions between carbon 1 + 6 on two glucose molecules, unlike amylose
  • so, amylopectin has branched structure
  • made by 1-4 glycosidic bonds between alpha glucose molecules
27
Q

Describe the structure of the polysaccharide glycogen.

A
  • equivalent energy storage molecule in animals + fungi to starch in plants
  • forms more branches than amylopectin so is more compact + less space needed for it to be stored
  • coiling or branching of it also makes it v compact for ideal storage
  • branching also means free ends where glucose molecules can be added or removed, speeding up process of storing / releasing glucose required by cell
  • key properties (as in amylopectin): insoluble, branched + compact, so ideally suited to storage roles they carry out
28
Q

Describe the structure of the polysaccharide cellulose.

A
  • straight chain molecule, formed when polysaccharides formed from glucose are unable to coil / form branches
  • cellulose molecules make H bonds w/ eachother forming micro fibrils
  • micro fibrils join together forming macro fibrils, which continue to produce fibres
  • these fibres = strong, insoluble + used to make cell walls
  • cellulose = v hard to breakdown into its monomers + forms fibre necessary for a healthy digestive system
29
Q

Describe lipids.

A
  • have large amounts of carbon + hydrogen, but low amounts of oxygen
  • insoluble in water as non-polar, but water is polar
    (Only polar molecules are soluble in polar solvents)
  • soluble in alcohol

3 most important lipids:

  • triglycerides
  • phospholipids
  • cholesterol
30
Q

Describe the lipid triglycerides (as an example of a macromolecule).

A
  • made of fatty acids + glycerol

- 3 fatty acids per 1 glycerol

31
Q

Draw the structure of glycerol.

A

3 C’s in middle
3 H’s coming off top of them
3 OH’s coming off bottom of them
2 H’s, one each side

(Draw)

32
Q

Describe / draw the general structure of fatty acids.

A
  • hydrocarbon chains attached to a carboxyl group (-COOH)

Carboxyl group on end: C w/ double bond to O above, and a bond to HO beneath

Hydrocarbon chains: a number of C’s in middle (any number from 2 - 22+), w/ H’s above + beneath them + one at end

33
Q 
How many carbons are in a:
short hydrocarbon chain?
Medium hydrocarbon chain?
Long hydrocarbon chain?
Very long hydrocarbon chain?
A

Short: <6
Medium: 6-12
Long: 13-21
Very long: 22+

34
Q

Describe saturated fatty acids (in triglycerides).

A
  • no C=C double bonds

- example of saturated fatty acids: palmitic acid (in animal fat)

35
Q

Describe monounsaturated fatty acids (in triglycerides).

A
  • one C=C double bond

- example of monounsaturated fatty acid: oleic acid (in olive oil)

36
Q

Describe polyunsaturated fatty acids (in triglycerides).

A
  • two or more C=C double bonds

- example of polyunsaturated fatty acid: linoleic acid (in nuts)

37
Q

Describe animal lipids.

A
  • saturated
  • solid at room temp
  • fats
38
Q

Describe plant lipids.

A
  • unsaturated
  • liquid at room temp
  • oils
  • fatty acids in them contain a kink which makes them more fluid
39
Q

Describe ester bonds.

A
  • formed by condensation reactions

Draw

40
Q

Describe the lipid phospholipids.

A
  • same structure as triglycerides, except one fatty acid has been replaced by a phosphate group
  • phosphate head is attached to a water soluble group e.g. Choline
  • when surrounded by water, phosphate group becomes negatively charged (so polar), so now top part of molecule (phosphate + choline group) are attracted to water - HYDROPHILIC
  • fatty acid tails still repelled by water - HYDROPHOBIC
  • so overall, whole phospholipid is AMPHIPATHIC - part of them is hydrophilic + part is hydrophobic.
41
Q

Explain how phospholipids being amphipathic determines their behaviour when exposed to water.

A
  • they form micelles: heads face out towards water (hydrophilic), tails face in away from water (hydrophobic)

OR

  • they form bi-layers: 2 rows of phospholipids, facing opposite / away from eachother, heads face outwards (hydrophilic), tails face in towards eachother (hydrophobic)
42
Q

Describe the roles of the lipid triglycerides (as an example of a macromolecule) in living organisms.

A
  • long hydrocarbon tails contain lots of chemical energy, so good for energy storage
  • storage of carbon in bacteria
  • thermal insulation
  • buoyancy for aquatic animals
  • cushioning to protect vital organs e.g. Heart
43
Q

Describe the role of the lipid phospholipids (as an example of a macromolecule) in living organisms.

A
  • found in cell membrane in all eukaryotes + prokaryotes to control what enters + leaves cell
    - this poss due to hydrophilic heads + hydrophobic tails, as form a double layer (bi-layer) w/ a hydrophobic centre, so soluble substances can’t easily pass through
44
Q

Describe the role of the lipid cholesterol in living organisms.

A
  • help strengthen cell membrane by interacting w/ phospholipid bilayer in eukaryotic cells
45
Q

Describe the type of lipid, sterols.

A
  • type of lipid found in cells
  • complex alcohol molecule
  • based on a four carbon ring structure w/ a Hydroxyl (OH) group at one end
  • have dual hydrophobic + hydrophilic characteristics like phospholipids (only hydroxyl group is hydrophilic)
  • types of sterols: cholesterol
46
Q

Describe cholesterol as a type of sterol, and lipid.

A
  • manufactured in liver + intestines
  • important role in formation of cell membranes
  • becomes positioned between phospholipids w/ hydroxyl group at periphery end of membrane
  • this adds stability to cell membranes + keeps fluidity regulated
  • used to manufacture vitamin D, steroid hormones + bile
47
Q

Describe proteins.

A
  • elements present in them: C, H, O, N + sometimes S

- over 500 amino acids exist, but only 20 used to make proteins

48
Q

Describe the general amino acid structure.

Draw

A
  • amino group on left: (N bonded to one H above it, + one below)
  • carboxyl group on right: (C double bonded to O above + bonded to OH below)
  • C in middle bonded to R above (that varies in each amino acid), + bonded to H below
49
Q

What is R in the amino acid glycine?

A

H

50
Q

What is R in the amino acid alanine?

A

CH3

51
Q

What is R in the amino acid cysteine?

A

CH3S

52
Q

Describe how dipeptides are formed.

A
  • amino acids join + are held together by peptide bonds (example of a condensation reaction)
  • water produced
  • result is a dipeptide
  • peptide bonds can be broken by hydrolysis reactions
53
Q

How can bonds in proteins such as amino acids be denatured?

A

High temperature:
- give molecules more kinetic energy so vibrate more, causing weak H bonds to break, breaks down tertiary structure of protein, changing 3D shape of protein so can’t perform its function

Changes in pH:
- if rises or falls too much, amount of H+ & OH- ions unbalanceds, causing ionic bonds + H bonds to break, + breaks proteins tertiary (3D) structure, changing it so cannot perform its function.

54
Q

What bonds are present in the primary structure of proteins?

A

Peptide bonds only.

55
Q

What bonds are present in the secondary structure of a protein?

A

Hydrogen bonds: pull amino acid chain into a coil shape (an alpha helix)

56
Q

What bonds are present in the tertiary structure of a protein?

A
  • disulfide bonds
  • ionic bonds
  • hydrogen bonds
  • hydrophobic + hydrophilic interactions
57
Q

What bonds are present in the quaternary structure of a protein?

A
  • linking together of polypeptide chains

- interactions between diff subunits (individual proteins).

58
Q

What types of proteins are there? Give examples of each type.

A

Globular:

  • haemoglobin (a globular conjugated)
  • insulin
  • pepsin

Fibrous:

  • collagen
  • keratin
  • elastin
59
Q

Describe the globular protein haemoglobin.

A
  • quaternary protein made of four polypeptides, two alpha + two beta subunits
  • each subunit contains a prosthetic haem group
  • iron II in haem helps it transport O2 around body
  • also a conjugated protein (subdivision of globular)
60
Q

Describe the globular protein insulin.

A
  • hormone involved in regulation of blood glucose concentration
  • hormone, so has precise shape to fit on receptors on cell surface membranes
  • soluble as has to be transported in bloodstream.
61
Q

Describe the globular protein pepsin.

A
  • enzyme that breaks down proteins into smaller peptides
  • produced in stomach + one of main digestive enzymes
  • expressed as zymogen called pepsinogen
  • can break peptide bonds next to aromatic amino acids
  • has hydrogen bonds
  • has 3 di-sulfide bridges
62
Q

Describe the fibrous protein collagen.

A
  • connective tissue found in skin, tendons, ligaments etc
  • number of diff forms of collagen, all made of 3 polypeptides wound together in rope like structure (triple helix)
  • flexible
  • has H bonds between polypeptide chains, forming long quaternary proteins w/ staggered ends
  • allows proteins to form long fibrils called tropcollagen, which cross link to produce strong fibres
63
Q

Describe the fibrous protein keratin.

A
  • present in hair, skin, nails.
  • has large proportion of amino acid cysteine, which contains sulfur
  • results in many strong, inflexible + insoluble materials
  • degree of disulfide bonds determines flexibility
  • large quantities of sulfur present, explaining unpleasant smell of burnt hair, for e.g.
64
Q

Describe the fibrous protein elastin.

A
  • found in elastic fibres present in wall of blood vessels
  • gives these structures flexibility
  • a quaternary protein made from stretchy molecules: tropoelastin, link to make elastin a large stable structure
  • tropoelastin helps stretch + recoiling
  • elastin structure stabilized by cross link in covalent bonds

BIOLOGY AS (12 decks)

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