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01 A sejtek felépítése és anyagcseréje

2014.04.09

 

Cells: chemicals, structure, metabolism
 
Elements
Carbon:
          Can join to each other: chains, rings
          4 strong covalent bonds (saturated, unsaturated)
Oxygen: in organic molecules
Hydrogen: in organic molecules
Nitrogen: proteins, nucleic acids, ATP
Sulphur: proteins
Sodium: for nerve working
Potassium: for nerve working
Magnesium: chlorophyll
Chlorine: for nerve working
Iron: haemoglobin
Silicon: in seaweeds
 
Compounds
          Water
          Carbohydrates
          Lipids
          Proteins
          Nucleic acids
Water
Water content in cells: 60-80%
Important properties:
          Solvent
          Takes part in reactions
          Carries by diffusion
          Takes part in thermoregulation
Diffusion
Passive transport
Osmosis
          passage of water molecules from a dilute solution into a more concentrated solution through a partially permeable membrane
          „Diffusion of water”:
          moves from „high water concentration”
to the „low water concentration”
Colloids
          Size of particles: 1-500 nm
          Opalescent (Faraday-Tyndall effect)
          Surface area/volume ratio: maximal (materials can be adsorbed on it)
Coagulation
          Colloidic particles stick closely together: became insoluble
          Reversible: can be reversed (e.g. by salt)
          Irreversible: cannot be reversed (e.g. heating, heavy metal solutions, strong acids and alkalines)
 
Carbohydrates
Monosaccharides: one sugar unit, sweet, soluble in water
          Aldose (aldóz): aldehidcsoport, ketose (ketóz): ketocsoport
          Triose (trióz): 3 szénatom
          Pentose (pentóz): 5 szénatom
          Hexose (Hexóz): 6 szénatom
Trioses
          Glycerinaldehyd (glicerinaldehid)
Pentoses
          Ribose (ribóz)
          2-deoxyribose (2-dezoxiribóz)
Hexoses
          Glucose (szőlőcukor)
          Fructose (gyümölcscukor): ketóz!
          Galactose (galaktóz)
Disaccharides
2 monosaccharides linked, sweet, soluble in water
          Saccharose (répacukor): α-glucose + β-fructose
          Lactose (tejcukor): β-galactose + β-glucose
          Maltose: α-glucose + α-glucose
          Cellobiose: β-glucose + β-glucose
Polysaccharides
          Glucose-based macromolecules
          Are not sweet, are insoluble in water
Cellulose (β-glucoses): plant cell wall
Starch (α-glucoses): plant carbohydrate reserve
          Amylose: soluble (blue reaction with iodine)
          Amylopectin: insoluble, wall of the starch grains
Glycogen: animal carbohydrate reserve
 
Lipids
Nonpolar molecules
Insoluble in water, soluble in oil, gasoline
Main groups:
          Triglycerides
          Phospholipids
          Carotenoids
          Steroids
Triglycerides
Glycerol + fatty acids
Saturated fatty acids: stearic and palmitic acid (C17H35-COOH), (C15H31-COOH)
Unsaturated fatty acid: oleic acid (C17H33-COOH
Fats: contain mainly saturated acids (solid at room temperature, animal fats)
Oils: contain mainly unsaturated acids (liquid at room temperature, plant oils)
Role:
          Energy store
          Insulator
          Mechanical protector
          Vitamin store (ADEK)
Phospholipids
          Bonded to glycerol: 2 nonpolar fatty acids and 1 polar group
          A nonpolar (hydrophobic) and a polar (hydrophilic) part: form bilayers (membranes) in water
Carotenoids : long molecules with double bonds: can be induced by the light
          Carotene (carrot)
          Lycopene (tomato)
          Xanthophyll (leaves)
          Vitamin A (eyesight, skin)
Steroids
          Cholesterol: in membranes
          Vitamin D: (ergosterol + UV light) we need it for healthy bones
          Bile acids: emulgeate fats
          Hormones: cortison, estrogen, testosteron, progesteron
Proteins
          Are made of amino acids (p.26)
          Amino acids are bonded with peptide bonds
           
Structure
Primary structure: sequence of amino acids: alanine – arginine – histidine
Secondary structure: shape of the amino acid chain:
           α-helix: twisted chain
           β-pleated sheet: parallel chains
Tertiary structure: higher shape of the chain
Stabilized by covalent, Hydrogen- and Van der Waals-bonds
          Globular: spherical
          Fibrous: line
Quaternary structure: 1 protein – more than 1 polypeptide chains: related position of chains to each other
Features
Denaturation: protein is irreversibly destroyed
Coagulation: Colloidic particles stick closely together: became insoluble (reversible – irreversible)
Dangerous: conformation of the chain changes
Heating, changing of pH, mechanical effects, heavy metal ions
Functions of proteins
          Structure: keratin, collagen
          Transport: haemoglobin
          Moving: muscle proteins
          Enzymes
          Protection: globulines
           
Nucleotides
Components:
Sugar (ribose, 2-deoxyribose)
Phosphate group
Nitrogen-containing base
          Purines: adenine, guanine
          Pirimidines: cytosine, thymine, uracile
Adenosine triphosphate
          ATP = ADP + Pi + energy (30 kJ/mol)
          It can store and release energy
Nicotinamide adenine dinucleotide
          NAD: carries H at the break-down (energy-releasing) processes
          NADP (nicotinamide adenine dinucleotide phosphate): carries H at the build-up processes
          NAD(P) + 2H = NAD(P)H + H+
          2e- and 1p+ are carried on the molecule, 1 p+ near this
Coenzyme A
          Acethyl group (CH3CO-) is carried by it
Deoxyribonucleic acid (DNA)
          Pentose: deoxyribose
          Base: adenine, guanine, cytosine, thymine
          Paired parallel α-helix
          Chain-stabilizer bonds: A-(2 H-bonds)-T, G-(3 H-bonds)-C
          Can be copied perfectly: carries the genetic information
Ribonucleic acid (RNA)
          Pentose:ribose
          Base: adenine, guanine, cytosine, uracile
          Single α-helix
          Chain-stabilizer bonds: A-(2 H-bonds)-U, G-(3 H-bonds)-C
Types of RNA:
          Messenger RNA: a copy of the nuclear DNA, carries information to the ribosomes
          Transfer RNA: carries amino-acids to the ribosomes
          Ribosomal RNA: builds up the ribosomes (protein synthesis occurs here)
 
THE CELL
It is the smallest independent unit of life
All organisms are made up of cell(s)
Prokaryotes („before the nucleus”):
·         DNA is ring-shaped, is not separated by nuclear membrane
·         Cytoplasm is not divided by endoplasmatic membrane
·         Diameter: 0,1-10 μm
Eukaryotic cell („true nucleus”): nucleus is surrounded by nuclear membrane
·         Diameter: 10-100 μm
·         Organelles (visible by light microscope): Nucleus, cell membrane, cell wall, chloroplast, mitochondria, chloroplast, starch grains, Golgi apparatus, sometimes chromosomes
·         Organelles (visible by electron microscope): Endoplasmic reticulum, lysosomes, ribosomes, cytoskeleton
CELL ORGANELLES:
Cytoplasm: jelly
·         Water (80%)
·         Cytoskeleton: protein filaments (move molecules and organelles, gives support to the cell)
·         RNA
·         ions
Nucleus
·         Is surrounded by nuclear envelope (membrane)
·         Nucleolus: synthetizes RNA, builds up ribosomes
·         Nuclear sap (water, ions, molecules)
·         Chromatin: nucleosomes (DNA and histon proteins) (euchromatin: light – heterochromatin: dark /packed DNA/)
MEMBRANES:
Cell membrane
Borders and connects
Structure:
·         Double layer of phospholipid molecules
·         Proteins: peripheral, integral (pores, transport proteins)
·         Carbohydrate chains (bonded to proteins): receptor molecules (marks)
Endoplasmic reticulum
·         Complex tunnel system
·         Joins to the nuclear envelope
·         Rough ER: ribosomes (synthesis of protein molecules)
·         Smooth ER: no ribosomes (synthesis of steroids and other substances, detoxication)
Golgi apparatus:
·         Flattened cavities and vesicles
·         Modifies, packages and in vesicles carries substances synthetised by ER
Lysosomes:
·         Small vesicles with digestive enzymes
Nuclear envelop
·         Two parallel membranes with pores
·         Surrounds the nucleus, it is connected with ER
OTHER CELL ORGANELLES:
Mitochondria
·         Size: as a bacterium
·         Ring-shaped DNA
·         Outer membrane: smooth
·         Inner membrane: folded, large surface
·         Function: synthesis of ATP (inner membrane) – „power station of the cell”
Chloroplast
·         Size: as a bacterium
·         Ring-shaped DNA
·         Outer membrane: smooth
·         Inner membrane: granum (small column built up of small membrane discs)
·         Function: molecular processes of photosynthesis
 
 
METABOLISM
Metabolism = getting up, transforming and getting rid of materials
ENZYMES
Biochemical reactions in cells: must be rapid at low temperature
Enzymes: biological catalysts
Two types:
·         Breakers: break down molecules
·         Builders: build up molecules
 
How an enzyme works:
·         Enzymes: proteins (long amino-acid chains)
·         Active site: special shape
·         Substrate: substance which fits into active site
 
Properties of enzymes:
·         They are proteins
·         Each enzyme controls one reaction (they are SPECIFIC)
·         They can be used again
·         They are affected by temperature
·         They are affected by pH
Enzymes in digestion:
·         Large molecules can not get through the gut wall
·         CARBOHYDRASE: breaks down carbohydrate (e.g. starch)
·         PROTEASE: breaks down protein
·         CATALASE: breaks down hydrogen-peroxide (poisonous product of reactions) to oxygen and water (It is the fastest enzyme!)
·         AMYLASE:          a special carbohydrase in saliva. Breaks down starch to sugar
·         LIPASE: breaks down fats
Hotting up
·         At high temperature the shape of protein changes:
·         Substrate can not fit into the active site
·         Enzyme is DENATURED
Enzymes and pH
·         Many enzymes work best in neutral conditions
·         These enzymes are denatured in very acid or alkaline conditions
·         PEPSIN works best in very acid conditions in stomach
Active transport
·         Uptake of particles against a concentration gradient.
·         It needs energy.
·         A carrier protein takes up particles to the other side
 
·         Endocytosis: cell membrane surrounds a piece of material bringing into the cell within a vesicle
 
·         Exocytosis: vesicle membrane fuses with the cell membrane (kicks out the waste material)
 
 
METABOLISM (anyagcsere)
·         Katabolism: breaking down large molecules to smaller ones, releasing energy
·         Anabolism: building up large molecules from smaller ones, using energy
Building up
Autotroph: uses inorganic substances
·         Photosynthesis: uses energy of light
·         Chemosynthesis: releases energy from inorganic compound oxidation
Heterotroph: uses organic compounds
Photosynthesis
i. Light-dependent reaction: Releasing energy of light
Pigments: chlorophyll (a, b), carotene, xanthophyll
ii. Light-independent reaction (Calvin cycle): absorbing CO2, synthesis of glycose
 
 
Biological oxidation (aerob, with O2)
Glycolysis: glycose - - pyruvate (piroszőlősav) + ATP (cytoplasm)
Pyruvate oxidation: pyruvate - - acetyl CoA
(Szentgyörgyi) – Krebs cycle (citromsavciklus): carbon oxidation to CO2, ATP, NADH+H+ synthesis (mitochondria matrix)
Electron transport chain (terminális oxidáció): electron transpor to ATP synthesis
(using electrons from NADH) (mitochondria inner membrane)
1 mol glucose -------------- 38 mol ATP!!!
Fermentation (anaerob, without O2)
1 mol glycose ------ 2 mol ATP!!!
Alcoholic fermentation: pyruvate ---- ethanol + CO2
Lactic acid fermentation : pyruvate ----- lactic acid