The Cell Cell theory (1838) - Jocha-Biologyjocha-biology.net/handouts/human/04a_Cells and cellular...
Transcript of The Cell Cell theory (1838) - Jocha-Biologyjocha-biology.net/handouts/human/04a_Cells and cellular...
The Cell and Cellular transport
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The CellCell theory (1838):1. All organisms are composed of one or more cells, and the life processes of
metabolism and heredity occur within these cells.2. Cells are the smallest living things, the basic units of organization of all organisms.3. Cells arise only by division of a previously existing cell.
Common to ALL types of cells…
Cell membrane(controls the movement of things in and out of the cell)
Cytoplasm or cytosol(intracellular fluid)
Ribosomes (for protein
synthesis)
Enzymes(for metabolic reactions)
ATPATP
Energy currency(to provide energy for metabolic processes)
DNA for the genetic codeRNA for transcription of the code during protein synthesis
How many types of cells?
Only ribosomes, NO other organelles. Ribosomes are different in structure to those of eukaryotes
Several specialized organelles
Unicellular organisms
bacteria
Unicellular or (most of them) multicellular organisms
Interior of the cellOnly cytoplasm
Interior of the cellComposed of Nucleus + Cytoplasm
Prokaryotic
Eukaryotic
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Why cells are not bigger?Practical reasons! communication
the different regions of a cell need to communicate with one another for the cell as a whole to function effectively
What is the size of a cell?Most of them smaller than 50µm (0.0020 inches)
Ratio: Surface AreaVolume
Increases with 12
Increases with 13
10cm1cm
4,189 cm34.189 cm3Volume (4/3)πr3
1,257 cm212.57 cm2Surface Area (4πr2)
Cell radius (r)
1000 times more volume!
Cell surfaceresponsible for the
interaction with the environment
small cells have bigger surface area per unit of volume than large ones
control is more effective (ex: 3 vs. 0.30)
Cell membranes Extracellular side
CytoplasmCholesterol
Peripheral protein(surface)
integral protein (inside the membrane)Two layers of
phospholipids and proteins
Also cholesterol and proteins
Fluid-mosaic model
Molecules in the membrane are able to flow and move around
Interaction of molecules with its surroundings allows the membrane to maintains its forms
Phospholipids heads (hydrophilic)
FattyAcids tails
(hydrophobic)
phospholipids
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Cellular Organelles in Animal Cells(Eukaryotic cells)
Mitochondria
nucleolus
Nucleus
Golgi apparatus
Endoplasmic reticulum (ER)
Cytoskeleton
Ribosomes
LysosomesCentriolesExclusive
of animalscells
1) “Membrane” organelles
Mithocondrion
Inner membrane
cristae•Aerobic cellular respiration• Glu+O2 CO2+H2O •Energy conversion and release (in the form of ATP)
Nuclear membrane: Protects the DNA inside the cell.
pores allow molecules to pass from one side to the other
nuclear membrane
Nucleolus: site of ribosome manufacture
Endoplasmatic reticulum (ER): folded membranes and tubes huge surface area many chemical reactions in a small place!
Rough ERRibosomes associated to the membrane proteins synthesis
Smooth ERLipids synthesis, destruction of toxic substances
Golgi Apparatus: 5 to 20 membranous and smooth sacs modification of products (ex: activation of enzymes) from the ER, packing and export to the cytoplasm or extracellular space of certain molecules
vesicles
Lysosomes: Vesicles generated in the Golgi apparatus containing hydrolytic enzymes. Are use to degrade molecules
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2) “Protein” organelles
Ribosomes: •Two subunits composed of RNA and proteins •Responsible for proteins synthesis•Associated to the Rough ER or free in cytoplasm
Centrioles: •Arrangement of two sets of microtubules (proteins!) at right angles•Organize microtubules assembly for cell division (chromosomes attach to microtubules)
Cytoskeleton: •Microtubules, microfilaments, and intermediate filaments proteins!•Interconnect and attach to the membrane cell
Cilia and Flagella: • hairlike structures used for locomotion•Made of microtubules (two types of proteins in Eukaryotes and only one type in Prokaryotes) with a specific arrangement•Energy is needed to move microtubules and cause movement
Eukaryotic cilia and flagella
cilia
flagella
Higher concentration
Equal Concentrations (dynamic equilibrium)
Cellular transportMovement of particles across the cell membrane. allow the cell to carry out the metabolic processes needed to live
Passive: NO energy is requiredActive: Energy is used (ATP)
Higher concentration
Equal Concentrations (dynamic equilibrium)
Lowerconcentration
Diffusion:(passive) Movement of molecules down a
concentration gradient from where are in higher concentration to where are in lower concentration.
Lowerconcentration
Osmosis: (passive) Net movement of water through a selectively permeable membrane.
1) Osmosis is a special type of diffusion in which the diffusing substance can be only water2) The regions of different concentrations are separated by a membrane permeable to water but not to the solute
Isotonic Hypotonic HypertonicRed blood cell (RBC) is…
less solutes in the RBC
more solutes in the RBC
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Carrier Proteinscontrolled methods of transporting molecules
conc
entra
tion
-
+
Facilitated diffusion(passive) movement of molecules down a concentration gradient through the membrane by combining with specific carrier proteins.
ATPADP+Pi
Active transport(active)
Movement of molecules up a concentration gradient. An input of energy (ATP) is needed to move the molecule against its concentration gradient.
Endocytosis & Exocytosis: Transport of materials into and out of the cell by
formation of vesicles of cell membrane containing the particles, food, or materials
Pinocytosis: molecules engulfed are dissolved in water liquidsPhagocytosis: solid materials, the sac is named phagosome (ex: viruses, food, bacteria, lipoproteins)
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Special proteins that acts as catalysts in chemical reactionsbetween substances
Speed up reactions but are not used in the reactionWhy do we need to speed up
reactions using enzymes?
Ene
rgy
Ene
rgy
product
reactants
(Products have more energy than reactants)
time
Endergonic reaction
Ea
Estored
product
reactants
Exergonic reaction
(Products have less energy than reactants)
time
Ea
Ereleased
Spontaneously would take millions of years!
Do not occur spontaneously
Energy is stored in covalent bonds of nutrients we incorporate with the food
Enzymes
Extra energy required to destabilize existing chemical bonds and initiate a chemical reaction between two or more molecules
Molecules synthesis/breakdown and energy conversion require energy to initiate the breakdown of nutrients
Energy of Activation (Ea)
reactants
productEne
rgy
rele
ases
Ea No enzyme (uncatalyzed)
1. Enzymes lower the energy of activation (Ea)
Reactions occur very fast
Ea enzyme(catalyzed)
Ene
rgy
used
Summary…
2. Enzymes are substrate specificOnly speed up the reaction
of one type of molecule
3. Enzymes remain unchangedBecause they are not
used in the reaction
4. Enzymes can be reusedbillions of times
One single enzyme can convert millions of substrate molecules per second!
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Ex: amino acid 1
Ex: amino acid 2Ex: hydrolysis
How do enzymes speed reaction rates?Three-dimensional shape of the enzyme allows it to combine with reactants, lower the Ea and accelerate the reaction
Ex: dipeptide(two amino acids)
Enzyme-substrate complex
Ex:dehydration
ACTIVE SITE:Is the part of the ENZYME where the chemical reaction takes place,
where the energy of activation is lowered by the enzyme so the reaction can happen
3) Cofactors ARE inorganic ions (zinc, iron, magnesium). Coenzymes are organic molecules
4) As in the case of some fatty acids and amino acids, some coenzymes cannot be produced by the body and need to be obtained with the diet. Cells need vitamins in order to have coenzymes.
2) Enzymes are substrate specific but coenzymes can work with several different enzymes
ions or molecules that attach to the enzyme and help to speed up the reactionCofactors & coenzymes: enzyme helpers”
1) Cofactors help removing one of the end products or bring in part of the substrate
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What environmental factors affect the enzymes activity?
1) TemperatureOptimum (temperature range at which
the speed of product generation is maximum) is around human body normal temperature
The speed of the reaction, or the number of molecules of substrate that one enzyme can react with in a given time, decreases as temperature moves right or left of the optimum range.
At higher or lower temperatures than the optimum, Enzymes can lose theirconfiguration (be completely unfolded and only retain the primary structure) and be no longer active
DenaturationLost of the structures of a protein, only the primary structure remains
Enzyme DenaturedEnzyme(1ry structure = sequence of amino acids)
Changes in pH determine the number of H+ ions available in the enzyme environment
these H+ may interact with exposed side-chains of the polar enzyme molecule
enzyme activity changes
Is important in defining the final shape of proteinseach enzyme reaches it maximum activity level at a given pH
2) pH
DenaturationLost of the structures of a protein, only the primary structure remains