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A level bio > Bio molecules > Flashcards

Bio molecules Flashcards

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Biology 101 flashcards
1
Q

Monomers

A
  1. Glucose
  2. Glycerol
  3. Fatty acid
  4. Amino acids
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2
Q

Structure and function of glucose

A

S:
- C6H12O6
- alpha glucose: Hydroxyl group on carbon-1 projecting below the ring
- beta glucose: Hydroxyl group on carbon-1 projecting above the ring

F:
- Monomers of polysacharrides

  • Acts as a substrate for the production of energy in the form of adenosine triphosphate (ATP)
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3
Q

Structure and function of glycerol

A

S:
- An alcohol, which has 3 carbon, each attached to a hydroxyl (-OH) group

F:
- Monomers of lipids

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4
Q

Structure and function of fatty acid

A

S:
- Consists of a hydrophobic hydrocarbon chain and hydrophilic carboxyl group

  • General formula: R-COOH, where R is the hydrocarbon chain
  • Saturated fatty acids: contains carbon-carbon single bonds
  • Unsaturated fatty acids: contains carbon-carbon double bond, resulting in kinks that prevent the tight packing of fatty acid chains

F:
- Monomers of lipids

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5
Q

Structure and function of amino acids

A

S:
Central carbon atom bonded to:
- hydrogen atom
- basic amino (-NH2) group
- acidic carboxyl (-COOH) group
- R group/side chain which is unique to each amino acid

Uncharged R group -> amino acid is non-polar/polar

Charged R group -> amino acid is basic/acidic

F:
- Monomers of proteins

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6
Q

Formation and breakage of glycosidic bonds (between monosaccharides)

A

Formation:
- Formed by condensation reaction between 2 monosaccharides with the removal of 1 molecule of H2O

Breakage:
- Broken by hydrolysis reaction between 2 monosaccharides, with the addition of 1 molecule of H2O, to form a hydroxyl group on each monosaccharide

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7
Q

Formation and breakage of ester bonds (between fatty acid and glycerol)

A

Formation:
- Formed by condensation reaction between hydroxyl group of glycerol and carboxyl group of fatty acid, with the removal of 3 molecules of H2O

Breakage:
- Broken by hydrolysis with the addition of 3 molecules of H2O, to form a hydroxyl group on a glycerol and a carboxyl group on the fatty acid

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8
Q

Formation and breakage of peptide bonds (between amino acids)

A

Formation:
- Formed between the carboxyl group of one amino acid and the amino group of another in a condensation reaction, with the removal of one molecule of water

Breakage:
-Broken between two amino acids during hydrolysis reaction with the addition of one molecule of water, to form the amino group and the carboxyl group on two different amino acids

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9
Q

Polysaccharides

A
  1. Starch
  2. Glycogen
  3. Cellulose
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10
Q

Lipids

A
  1. Triglycerides
  2. Phospholipids
  3. Cholesterol
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11
Q

Properties of starch

A
  1. Large and thus insoluble in water, exerts no osmotic effect on cells when stored in large amounts
  2. Large and thus unable to diffuse out of cells
  3. Fold into compact shaped, hence large amounts can be stored within the cell
  4. Easily hydrolysed into glucose when glucose is needed for metabolic reactions
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12
Q

Properties of glycogen

A
  1. Large and thus insoluble in water, exerts no osmotic effect on cells when stored in large amounts
  2. Large and thus unable to diffuse out of cells
  3. Fold into compact shaped, hence large amounts can be stored within the cell
  4. Easily hydrolysed into glucose when glucose is needed for metabolic reactions
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13
Q

Properties of cellulose

A
  1. Unbranched polymer
  2. Form straight chains, which is ideal for formation of strong fibers
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14
Q

Structure and function of starch

A

S:
- Alpha glucose
- Amylose and amylopectin fit together to form a complex three-dimensional structure in which the amylose helices are entangled in the branches of the amylopectin molecules
- Amylose:
1. Consists of several thousand alpha glucose residues
2. Linked by alpha-1,4-glycosidic bonds
3. Unbranched chain polymer
4. Coils into a helical, compact structure stabilized by hydrogen bonds

Amylopectin:
1. Consists of several thousand alpha glucose residues
2. Linked by alpha-1,4-glycosidic bonds
3. Branched chain polymer
4. Coils into a helical, compact structure stabilized by hydrogen bonds

F:
1. Main energy storage molecule in plants
2. Accumulates to form starch grains in chloroplasts of plant cells
3. Compact structure allows more glucose molecules to be stored in a small volume within the cell
4. Easily hydrolysed into glucose, when required by cells, for use in respiration to produce ATP

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15
Q

Structure and function of glycogen

A

S:
1. Consists of alpha-glucose residues
2. Linked by alpha-1,4-glycosidic bonds and alpha-1,6-glycosidic bonds where branch point occurs
3. More extensive branching as compared to amylopectin which results in a more compact structure
4. Coils into a helical compact structure stabilized by hydrogen bonds

F:
1. Main energy storage molecule in animals
2. Accumulates to form glycogen granules in liver and muscle cells
3. Compact structure allows more glucose molecules to be stored in a small volume within the cell
4. Easily hydrolysed into glucose, when required by cells, for use in respiration to produce ATP

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16
Q

Structure and function of cellulose

A

S:
1. Consists of beta-glucose residues
2. Linked by beta-1,4-glycosidic bonds
3. Unbranched chain polymer
4. Straight chains of beta-glucose run parallel to each other with numerous hydrogen bonds
5. Adjacent glucose molecules are rotated 180 degrees with respect to each other
6. Macrofibrils of successive layers are interwoven and are embedded in a gel-like matrix, thus having high tensile strength

F:
1. Main component of cellulose cell wall of plants for structural support
2. Large intermolecular spaces between microfibrils cause the cell wall to be permeable because they allow free movement of molecules in and out of the cell

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17
Q

Properties of phospholipids

A
  1. Amphipathic because contain a hydrophilic phosphate head and 2 hydrophobic fatty acid chains

Thus, head of molecule is soluble in water but the tails are insoluble in water

17
Q

Properties of triglycerides

A
  1. Insoluble in water, soluble in organic solvents
  2. Less dense than water and hence floats on the surface of water
  3. Can be classified as oils and fats
  4. The more saturated the triglyceride is, the higher the melting point of the triglycerides
18
Q

Properties of cholesterol

A
  1. Insoluble in water because non-polar
  2. Soluble in organic solvents
19
Q

Structure and function of triglycerides

A

S:
1. Consists of 1 glycerol molecule bonded to 3 fatty acid chains in a condensation reaction
2. Fatty acid is made up of a hydrophobic hydrocarbon chain and a hydrophilic carboxyl group

F:
1. Energy storage because can be used to produce energy in the form of ATP
2. Heat insulation because poor conductor of heat
3. Protection from shock and physical impact
4. Buoyancy

20
Q

Structure and function of phospholipids

A

S:
1. Consists of 1 glycerol, 2 fatty acid chains, 1 phosphate group

F:
1. Forms the basic structure of the cell surface membrane and the internal membranes of cells called the phospholipid bilayer
2. Arrangement of phospholipid in the form of a bilayer allows it to form a barrier in an aqueous environment
3. Can associate with hydrophilic oligosaccharides to form glycolipids which help in cell-cell recognition and cell-cell adhesion

21
Q

Structure and function of cholesterol

A

S:
1. Hydrophilic region interacts with hydrophilic phosphate heads of phospholipid molecules
2. Hydrophobic region interacts with hydrophobic fatty acid tails of the phospholipid bilayer
3. Cholesterol is interspersed among the bilayer to hinder the close packing of phospholipids

F:
1. Regulates membrane fluidity
2. Maintains mechanical stability
3. Prevents leakage of small polar molecules

22
Q

Structure of proteins

A
  1. Primary
  2. Secondary
  3. Tertiary
  4. Quartenary
23
Q

Primary structure

A

Types of bonds involved:
- Peptide bonds formed between carboxyl group of one amino acid and amino group of another amino acid

Primary structure is the specific number and sequence of amino acids joined by peptide bonds in a polypeptide chain

Sequence:
- Every protein molecule has a unique sequence of amino acids which is determined by the base sequence of DNA
- The unique sequence of amino acids with its side chains of different chemical and physical properties determines the three-dimensional conformation of the protein

Number:
- Every polypeptide possess a carboxyl terminus (C-terminus) and amino terminus (N-terminus)
- The possible amino acid residues in a polypeptide chain can be of any number and arrangement of the 20 common amino acids

24
Q

Secondary structure

A

Types of bonds involved:
- Hydrogen bonds formed between N-H group in a peptide bond of one amino acid and C=O group group in a peptide bond of another amino acid

Secondary structure is the repeated coiling and folding of a polypeptide chain, maintained by hydrogen bonds formed between peptide bonds

Alpha-helix
1. Unbranched polypeptide chain tightly coiled into a spiral
2. Each turn of a helix consists of 3.6 amino acids
3. Held by intra-chain H-bond between N-H group in a peptide bond of one amino acid and C=O group in a peptide bond of another amino acid, four amino acids away
4. Structurally strong and inelastic (cannot be stretched) but flexible (can be bent) eg. hair, nails

Beta-pleated sheets
1. Extended adjacent regions of a single polypeptide chain arranged in a parallel manner
2. “Pleated” appearance arises from the tetrahedral chemical bonding of alpha-carbon atoms
3. Held together by H bonds between N-H group in a peptide bond of one amino acid and C=O group in a peptide bond of an adjacent amino acid of the same chain
4. Very stable and rigid, high tensile strength (cannot be stretched) eg. silk, fibroin protein

25
Q

Tertiary structure

A

Types of bonds involved:
- Hydrogen bonds between an electronegative atom and a hydrogen atom bonded to another electronegative atom (FON)
(between 2 peptide bonds/ between peptide bond and R group/ between 2 R groups)
- Ionic bonds between positively and negatively charged R groups
- Disulfide bonds between sulphydryl (-SH) groups of two neighbouring cysteine R groups
- Hydrophobic interactions between nonpolar R groups
Tertiary structure is the compact unique three-dimensional conformation due to further coiling and folding of the secondary structure

Tertiary structure is the compact unique three-dimensional conformation due to further coiling and folding of the secondary structure

26
Q

Quaternary structure

A

Types of bonds involved:
Involves inter-chain interactions:
- H-bond
- Ionic
- Disulfide
- Hydrophobic interactions
Involves intra-chain interaction seen in pri, sec, ter structures:
- Peptide
- H-bond
- Ionic
- Disulfide
- Hydrophobic interactions

Quaternary structure is when more than one polypeptide chains are held together by hydrogen bonds, ionic bonds, sulfide bonds and hydrophobic interactions between R groups of different polypeptide chains

27
Q

Proteins

A
  1. Haemoglobin
  2. Collagen
  3. G-protein linked receptor
  4. Intrinsic
28
Q

Structure and function of haemoglobin

A

S:
Polypeptide chains:
- 2 identical alpha-chains of 141 amino acids
- 2 identical beta-chains of 146 amino acids
- each p chain coiled into alpha-helices then folded into spherical shape (no beta-pleated sheets)
- 4 polypeptide chains held by hydrophobic interactions, ionic bonds and hydrogen bonds
Haem group:
- Fe2+ binds to O2 reversibly
- Each haem group resides in hydrophobic pocket in the tertiary structure of a polypeptide chain
- 1 haemoglobin, 4 polypeptide chains, 4 haem groups, 4 O2

S to F:
1. Hydrophobic amino acids in the interior of the protein and hydrophilic amino acids found at the exterior surface of the protein…
…allows the haemoglobin to be soluble, to take part in chemical reactions

  1. The haem group is held in the hydrophobic pocket of the polypeptide chain…
    …allows the haemoglobin to bind reversibly to oxygen and transport oxygen to the rest of the body
  2. Quaternary structure, of 4 subunits, held by weak bonds such as hydrophobic interactions, ionic bonds, hydrogen bonds…
    …allows cooperative binding of oxygen to haemoglobin
    …binding of one O2 molecule to one subunit results in a conformation change of the adjacent subunits in the haemoglobin molecule, making it easier for another O2 molecule to bind with the other haem groups in the molecule -> increases rate of uptake of O2 by haemoglobin
  3. Haemoglobin is a globular protein and is folded into a spherical shape…
    …allows the protein to be compact and many haemoglobin molecules to be dissolved in the cytoplasm of a rbc
29
Q

Structure and function of collagen

A

S:
Structural unit of collagen:
Tropocollagen - comprises 3 polypeptide chains wound around each other to form a triple helix

Each p chain:
- 1050 amino acid residues
- repeated triplet seq of Gly-Proline-Hydroxyproline
- proline and hydroxyproline is bulky and relatively inflexible
- coiled into a helix

S to F:
1. Every 3rd amino acid residue is a glycine -> allows each helical chain to make a turn every 3 residues and intertwine around 2 other chains to form the tropocollagen (only glycine is small enough to fit into the centre)…
…allows the structure to be compact

  1. 3 helical chains are held together by hydrogen bonds forming tropocollagen…
    …allows the structure to be relatively rigid
  2. Hydrophobic amino acids found at exterior surface of collagen…
    …allows collagen to be insoluble and metabolically inactive, thus resistant to chemical changes
  3. Many triple helices lie parallel in a staggered pattern to form fibrils with covalent bonds between neighbouring triple helix chains. Fibrils unite to form fibers…
    …allows collagen to have high tensile strength, thus resistant to stretching
30
Q

Structure and function of G-protein linked receptor

A

S:
- Each GPLR is closely associated with a G protein, a protein that binds to GTP/GDP
- G protein consists of 3 subunits - Galpha, Gbeta, Gy
- Galpha subunit binds to GDP/GTP
- GTP is an energy molecule similar to ATP

S to F:
1. A single polypeptide chain with 7 hydrophobic transmembrane alpha-helices…
…allows the protein to be embedded within the cell membrane by forming hydrophobic interactions with the fatty acid chains of the phospholipid bilayer

  1. Extracellular amino terminus and specific loops between the helices…
    …allows the protein to have an extracellular ligand-binding site
  2. Intracellular carboxyl terminus and specific loops between the helices…
    …allows the protein to have an intracellular G protein-binding site
31
Q

Structure and function of intrinsic protein

A

S:
- Unilateral (embedded in monolayer)
- Transmembrane (embedded in bilayer)

S to F:
1. Embedded in hydrophobic core of phospholipid bilayer…
…Hydrophobic region forms hydrophobic interactions with the hydrophobic fatty acid tails of the phospholipid bilayer
Hydrophilic region forms hydrogen bonds with aqueous medium and hydrophilic phosphate head of the phospholipid molecules

32
Q

Defn. Denaturation

A

The loss of the specific 3-dimensional conformation of a protein molecule. This involves the breakage of bonds maintaining the protein structure, resulting in the protein losing its biological function.

33
Q

Factors causing denaturation and bonds involved

A
  1. Temp. - hydrophobic interactions & hydrogen bonds & ionic bonds
  2. pH - hydrogen bonds & ionic bonds
  3. Heavy metal ions - ionic bonds
  4. Reducing/ oxidising agents - Disulfide bonds
  5. Organic solvents and detergents - hydrophobic interactions and hydrogen bonds
34
Q

Temp. causing denaturation

A
  1. High temperature increases kinetic energy and causes atoms in protein to vibrate
  2. therefore, disrupting the weak hydrophobic interactions, hydrogen bonds and ionic bonds
35
Q
A
36
Q

pH causing denaturation

A
  1. Drastic change in pH affects charged and polar R-groups and disrupts ionic bonds and hydrogen bonds of proteins
37
Q

Heavy metal ions causing denaturation

A
  1. Heavy metal ions are positively charged and form strong bonds with negatively charged carboxyl R-groups of proteins, disrupting ionic bonds
37
Q

Reducing/oxidising agents causing denaturation

A
  1. Disrupts disulfide bonds formed between cysteine, thus causing proteins to lose their 3-dimensional conformation
38
Q

Organic solvents and detergents causing denaturation

A
  1. Disrupts hydrogen bonding and hydrophobic interactions of proteins

A level bio (9 decks)

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