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fundamentals of the living cell > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What are carbohydrates?

A

Most common organic compounds on earth
Function : Energy storage, Fuel , Metabolite & Structural element

General Formula = (CH2O)n

Monomer = Monosaccharides - 2 kinds = Ketose & Aldose
Polymer = Disaccharides / Polysaccharides
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2
Q

Examples of Monosaccharides

A

A- glucose (OH bottom) , B-glucose (OH top), Fructose, Galactose

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3
Q

Monosaccharides

A

Number of Carbon atoms decides name ( Triose, Tetrose, Pentose…)

Have chiral centres ( 4 different groups & non-superimposable images)

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4
Q

Example of Monosaccharide: Glucose

A

An Aldose ( Aldehyde based monosaccharide)

6 C atoms = Hexose

D-configuration = Asymmetric C-atom = most distant from aldehyde/ketone group

Can exist in long chain and ring structure

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5
Q

What are Oligosaccharides?

A

Carbohydrates

Type of oligosaccharides present in surface of RBCs = determine blood type

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6
Q

Condensation reactions in Monosaccharides

A

Monosaccharides can be joined together w Hydrogen Bonds

To form Disaccharides & Polysaccharides - releasing a water molecule

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7
Q

Condensation reactions in Disaccharides

A

a-Glucose + Fructose = Sucrose

a-Glucose + Galactose = Lactose

a-Glucose + a-Glucose = Maltose

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8
Q

Condensation reactions in Polysaccharides

A

a-1-4 Glycosidic bond = Starch, Amylase

B-1-4 Glycosidic bond = Cellulose

a-1-4 Glycosidic bind & a-1-6 Glycosidic Bond = Glycogen

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9
Q

D & L structures

A

Count downwards from top & consider penultimate carbon

If OH group = on right = D configuration
If OH group = on left = L configuration

Or

CH2OH group above ring = D configuration
CH2OH group below (in) ring = L configuration

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10
Q

Proteins

A

Made of AAs (form dipeptides/polypeptides)

20 AAs naturally occurring
9 essential - must from diet

Condensation reactions = form peptide bonds - releasing water

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11
Q

Functions of proteins

A

Carrier Functions ( Trafficking Oxygen)

Metabolic Functions ( Enzymes / Energy )

Cellular Machinery ( Spliceosome / ribeosomes)

Structural Scaffold ( Microtubules, conveyor belt, nucleosomes, histone DNA complex)

Sensing Molecules ( Receptors & Ligands)

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12
Q

Amino Acids

A

Have individual functions e.g
Precursors to drugs / hormones such as :

Tyrosine —> Adrenaline = Glycogenolysis

Histidine —> Histamine = Vasodilator

Called “ Residues” singly

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13
Q

Amino Acids Features

A

Tetrahedral arrangement w Chiral Carbon ( apart from glycine w 2H). Glycine = freer to move due to small R chain group

Readily ionises = Can form Zwitterion at neutral pH - where carboxyl group loses H+ & Amine group gains H+
At low pH = acts as base & accepts protons
At high pH = acts as acid & loses protons

Changes depending proportion of acid/ base in R group

D & L isomer can form. L = CORN clockwise. D = CORN backward

L form = common. D residues = bacterial cell walls & therapeutics

R group = usually trans arrangement.
Only 0.1% = CIS so less energetically favourable

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14
Q

Structure of Proteins

A

Primary = Covalent bonds forming polymer - e.g order of AA residues joined by PEPTIDE BONDS

Secondary = Regular folded form - often stabilised by HYDROGEN BONDS - e.g helices & sheets

Tertiary = Overall 3D - stabilised by HYDROGEN bonds, HYDROPHOBIC, HYDROPHILIC, VDW forces & DISULPHIDE BRIDGES

Quaternary = organisation of macromolecules into assemblies - often stabilised by IONIC bonds - e.g several polypeptide chains = can make up a protein

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15
Q

Difference in tertiary & quaternary structures

A

Intra-chain & inter-chain covalent bonds

Quaternary = has cofactors or coenzymes

Tertiary = a combination of secondary structures:

Beta sheet - continuous folded polypeptide chain. Beta strands w H bonds to form cross-links. Anti-parallel or parallel - which= less stable due to longer H bonds linking strands

Beta Strands - Contains 4 AA residues. Allow for 180 turns. Common in Proline, CIS conformation R group & Glycine. Small R group / Flexible.

Alpha Helix - Each turn = contains 3.6 AA residues. Stabilised by H bond between 1 & 5 residues

Side chains protrude outwards for each. Trans arrangement allows for B-sheet

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16
Q

Protein Structure

A

Membrane spanning proteins = have external hydrophobic residues - for lipid interaction & hydrophobic central channels

Water soluble - often have globular shapes
Hydrophilic residues external & Hydrophobic buried within
Can be filaments or coins instead

Proteins = denatured by high heats & changes in pH

17
Q

Nucleotides

A 
Energy Unit ( ATP )
Second Messenger ( cAMP )
RNA Synthesis (DNA / RNA) (AMP)

DNA = more stable than RNA - due to single additional oxygen

Ribonucleotide = OH 
Deoxyribonucleotide = H
18
Q

Amino Acid Classification

A

Glycine = sometimes put in separate group - as it has a single H R group - reducing steric hinderance - so has different properties

Sulphuric AAs - may also be classified separately

Non - polar / Hydrophobic, aromatic, polar

Properties of AA = determined by structure - specifically R group

19
Q

Lipids / Fats - Associate to form Membranes

A

Body Fats
Predominantly - food reserves ( for energy )

Glycerol esters w fatty acids

Lubrication between joints & insulations

Condensation reactions form ester bonds

Triglycerides / Phospholipids - used as bilayers in cell membrane, micelles and liposomes

Saturated fatty acids = X double bonds

Unsaturated-cis fatty acids = H atoms same side ( bent configuration)
Unsaturated-trans fatty acids = H atoms opposite sides

20
Q

Cholesterol

A

Steroid
Can intercalate into the membrane
OH group interacts w polar heads & it’s steroid scaffold w fatty acids
Making them closer together
This decreases fluidity & increases flexibility of the membrane
Reduces permeability for soluble molecules

Hormones building block for aldosterone, cortisol,testosterone & progesterone

21
Q

Structure & Function relationships

A

Proteins -> denature / mutated = affect function

Starch & Glycogen = Major energy sources for humans
Whereas we can’t digest Cellulose

Single oxygen difference makes DNA much more stable than RNA

22
Q

Examples of single molecule disease

A

Diabetes ( insulin - dependent ) - absence of a protein hormone ( insulin ) leads to failure to regulate blood glucose

Sickle Cell disease - one AA change in a globin chain - causes haemoglobin to aggregate ( combine ) into polymers

Cystic Fibrosis - absence of a membrane protein that transports chloride - leads to altered properties of secretions

fundamentals of the living cell (4 decks)

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