De Cel
Aantekeningen boek en hoorcolleges
Inhoud:
2.1 Biomolecules
2.2 Cell cycle
2.3 Transcription
2.4 Translation
2.5 Energy management
2.6 Cell signaling
2.7 Molecular mechanisms of evolution
2.8 Tissue types
2.9 Cancer and immunology
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, 2.1 Biomolecules
Carbon
Organic molecules: molecules containing carbon. Other molecules are inorganic.
Carbon can form large molecules because it can form four covalent bonds with other atoms, including another carbon
atom to form a covalent C-C bond.
Four families of small organic molecules, these can form macromolecules by linking them into chains:
Small organic molecules Large organic molecules
Sugars Polysaccharides, glycogen, starch
Fatty acids Fats and membrane lipids
Amino acids Proteins
Nucleotides Nucleic acids
Different roles: forming macromolecules or energy sources after being broken down.
Sugar
The formula of sugar molecules: (CH2O)n. Sugars are called carbohydrates.
Sugar molecules exists in two forms: L-form and D-form (gespiegeld).
Isomers are molecules with the same chemical formula but different structures. These mirror image pairs are called optical
isomers.
The covalent bonds between monosaccharides are called glycosidic bonds. De bindingen worden gevormd tussen de OH-
groepen van de suikermoleculen.
Monosaccharides disaccharide oligosaccharides polysaccharides
Condensation reaction: het binden van 2 monosacharides tot een disacharide. H2O komt vrij. Energetically unfavorable.
Hydrolysis: het ontbinden van een disacharide in 2 monosacharides. H2O wordt opgenomen. Energetically favorable.
Glycogen in animals and starch in plants are polysaccharides composed only of glucose. Hydrolyse hiervan maakt veel
energie vrij.
Suiker polysachariden zorgen niet alleen voor energie, maar functioneren ook als mechanical support, zoals cellulose in
planten cel wanden.
In the cell membrane:
Suiker oligosacharide + protein = glycoproteins
Suiker oligosacharide + lipid = glycolipids
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Suikers met een aldehyde groep H-C=O heten aldoses.
Suikers met een ketone groep C=O heten ketoses.
Ring formation: In een waterige oplossing, reageren de ketonen of aldehyde groepen met de hydroxyl OH groep van
hetzelfe molecuul, waardoor deze zich omsluit tot een ringvorm.
Isomeren: glucose, falaxtose and mannose only differ in arrangement of groups, recognized by enzymes and proteins.
en -links: de aldehyde of keton groep kunnen verwisselen van kant aan het C-atoom. Dit kan tot het suikermolecuul aan
een andere bindt, dan zit de groep vast.
Sugar derivatives: vervanging van de hydroxyl OH groep door een andere groep.
Fatty acids
Fatty acids contain a hydrophobic, hydrocarbon tail (not chemically reactive) and a hydrophilic, carboxylic head
(chemically reactive), so it’s amphipathic.
Saturated: There are no double bonds between its carbon atoms.
Unsaturated: There are more double bonds, creating kinks in tails.
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,Des te meer ruimte tussen en korter de fatty acids, des te meer vloeibaar de vloeistof in het membraan is.
Fatty acids zijn een energiebron, stored in the cytoplasm in de vorm van een triacylglycerol: 3 fatty acid chains samen.
Lipids: molecules that are insoluble in water but soluble in fat and organic solvents, for example a fatty acid.
Cell membrane <- lipid bilayer <- phospholipids <- fatty acid + glycerol + phosphate + polar group
Amino acids
Amino acids contain a -carbon atom + amino group NH2 (aan N-terminus kant, begin bij lezen eiwitketen)
+ carboxyl group COOH (aan C-terminus kant, eind bij lezen eiwitketen) + side chain
Peptide bond: Bond between two amino acids. Multiple amino acids, forming a polypeptide is a protein.
Amino acid sequence: de volgorde van aminozuren in een polypeptide ofwel protein molecuul.
Er zijn 20 verschillende soorten amino acids, elke met een andere side chain.
Er komen alleen L-forms amino acids in proteins voor.
15 Amino acids zijn uncharged, 5 zijn charged vanwege de vorming van ionen in oplossingen. Sommige amino acids zijn
polar en hydropholic, anderen nonpolar en hydrophobic.
Hydrofoob – binnenkant
Hydrofield – buitenkant
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Amino acids are grouped according to whether their side chains are: basic, acidic, uncharged polar or nonpolar.
Basic and positively Acid and negatively Uncharged polar Nonpolar
Charged polar Charged polar
Lysine Aspartic acid Asparagine Alanine
Arginine Glutamic acid Glutamine Valine
Histidine Serine Leucine
Threonine Isoleucine
Tyrosine Proline
Phenylalanine
Methionine
Tryptophan
Glycine
Cysteine
Proteins
The shape of a protein determines its function. A protein contains a polypeptide backbone, a repeating sequence of the core
atoms -N-C-C- Hieraan zitten de site chains vast. Polypeptide chains are flexible because the covalent bonds between carbon
atoms allow free rotation (only with C-C, not C-N bonds).
Proteins fold because of four noncovalent bonds: hydrogen bonds, electrostatic attractions, van der Waals attractions
and hydrophobic force. In water gaan de hydrophobic side chains bij elkaar zitten, en staan de hydrophilic side chains aan
de buitenkant in contact met water en andere protein molecule.
Nucleotides
A nucleotide contains a nitrogen-containing ring (base), five-carbon sugar and a phosphate group.
If the sugar is a ribose, is the nucleotide is part of ribonucleotides (RNA).
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, If the sugar is a deoxyribose, the nucleotide is part deoxyribonucleotides (DNA).
A base can bind a H+ proton under acidic conditions, increasing the concentration of OH- ions in aqueous solutions.
Pyrimidines: C, T and U bases six membered ring
Purines: A and G bases five membered ring
Nucleoside: a base + sugar (without phosphate group)
The phosphate group at the 5’ end of a nucleotide binds to the free hydroxyl OH group at the 3’ end of another nucleotide.
ADP + inorganic phosphate + energy = ATP + H20
RNA
Transcription: copying the nucleotide sequence into RNA.
Differences RNA and DNA:
- RNA contains the base U instead of T, like in DNA.
- RNA is single stranded, and DNA is double stranded.
- Because RNA is single stranded, it can fold into three-dimensional shapes, DNA cannot.
- RNA contains the sugar ribose, and DNA contains deoxyribose.
Ethylene responsive genes worden getranscribeerd als ethyleen de ethyleen-receptor bindt en zo een geassocieerd
kinase inactiveert.
Macromolecules
Proteins can:
- act as enzymes, catalyzing the chemical reactions that take place in the cell.
- be used to build structural components.
- act as molecular motors to produce force and movement.
Proteins verschillen in amino acids en in sequence.
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