Presentation on theme: "Cell Structure And Function. Why are cells small? Metabolism determines size. Adequate surface area for exchange of materials. Surface-area-to-volume."— Presentation transcript:
Cell Structure And Function
Why are cells small? Metabolism determines size. Adequate surface area for exchange of materials. Surface-area-to-volume ratio. Volume grows faster then surface area. In larger cells, rates of exchange are inadequate to maintain cell.
Prokaryotic Cells Vs. Eukaryotic Cells Prokaryotic Cells- lack a membrane bound nucleus, and they are small (1- 10um in diameter). Eukaryotic Cells-have membrane bound nucleus, and they are larger (10-100um in diameter).
Prokaryotic Cells There are two groups: Domain Bacteria And Domain Archaea
Plasma Membrane Regulates the movement of molecules.
Prokaryotic Cells Thylakoids Chlorophyll Cell wall-> polysaccharides & proteins. Plasma membrane -> glycerol+hydrocarbons DNA&RNA base similar to eukaryotes They live in extreme habitats.
Prokaryotic ->Eukaryotic Cells Endosymbiotic Theory= Cells living with in cells, in a mutually benificial relationship. (Symbiosis:)). Organelles have own DNA Organelles divide independently of the cell they live in. Double membrane.
Eukaryotic Cells Animal & Plant Cells
The Nucleus It is the command center. It has chromatin in it -forms chromosomes -DNA+RNA+protein Nucleolus: -produces ribosomes Nuclear Envelope: -Double membrane
Ribosomes: Protein Synthesis Occur in Cytoplasm or attached to endoplasmicreticulum.
Rough Endoplasmicreticulum Rough ER Continuous with nuclear envelope Flattened saccules Ribosomes Synthesizes proteins Modifies proteins: -adds sugar chains -helps with folding -forms transport vesicles
Smooth Endoplasmic Reticulum Smooth ER -continuous with rough endoplasmic reticulum -tubular -no ribosomes -main functions: 1.)synthesizes lipids (including sex hormones) 2.) detoxifies drugs -forms transport vesicles
Golgi Apparatus -stack of curved or flattened saccules -inner vs outer face -main functions: Modify ER products Manufacture Macromolecules Sort Products Ship products to vesicles
Endomembrane System Consists of: Nuclear envelope -Endoplasmicreticulum -Golgi Appartus -Lysosomes -Vesicles Importance: - enzymes in certain areas -vesicles move molecules around
Lysosomes Produced by Golgi Apparatus in animal cells Low pH Digestive enzymes-> hydrolyze macromolecules Apoptosis- cell death
Peroxisomes Vesicles that contain enzymes. Enzymes synthesized in cytoplasm( not in ER) Produce H2O2 ( by product), then water. In seedlings, convert fatty acid to sugars In liver, detoxify ETOH (jack daniels)
Energy Transformers of Cells Mitochondria: Cellular respiration-> ATP Chloroplasts: Photosynthesis->Carbohydrates
Vaculoles Store substances Plant cell central vacuole: Cell support Stores nutrients and waste products Acts like lysosomes in animals Pigments are stored Plant cell growth
Cytoskeleton What is it?? Networks of fibers that run through the cytoplasm. What does it do? Mechanical support Maintain cell shape Anchor organelles Enables cells to change shape Entire cell Organelles with in cell wall
Cell Membrane Structure and Function Fluid Mosaic Model Singer and Nicholson Plasma membrane is a mosaic of protein molecules bobbing in a fluid layer of phospholipids.
Regions of Integral Proteins Hydrophobic Regions: Not water friendly Hydrophilic: Water lover
Functions of Cell Membrane Barrier between living contents & surrounding environment. Regulates what goes in and out of cell It is selective It helps maintain homeostatic environment.
Fluid mosaic model Proteins in membrane can be: -peripheral-> inside surface anchored by cytoskeleton(structural role) -integral->imbedded in membrane but can move laterally. Most proteins move laterally in membrane.
Fluid Mosaic Model Carbohydrate Chains Glycolipid=phospholipid+carbohydrate (sugar chain) Glycoprotein=protein+carbohydrate (sugar chain). Asymmetry-> Carbohydrate chain on outside surface BLOOD TYPE BASED ON CARBOHYDRATE CHAINS A,B,O
Fluidity of Cell Membrane Body temperature->olive oil More unsaturated fatty acid residues, greater fluidity. Cholesterol (animal cells) stiffens and strengthens membrane Why is it good to be fluid? Proteins only function properly when they can move
Channel Protein Allows particular molecules to cross cell membrane freely. Cystic Fibrosis->faulty chloride channel
Carrier Protein Selectively interacts with a specific molecular ion so that it can cross plasma membrane. Obesity-> problem with sodium- potassium transport
Enzymatic Protein Carry out metabolic reactions Adenylate cyclase->ATP Metabolism Toxin of cholera bacteria disrupts adenylate cyclase-> severe diarrhea
Permeability of Plasma Membrane It is differentialy (selectively) permeable.
How do molecules cross membrane? Passive Transport: DOES NOT REQUIRE ATP!!! Active Transport: REQUIRES LOTS OF ATP!!!!
What is Diffusion? Movement of molecules from a high concentration to a lower concentration until equilibrium is achieved. Movement down a concentration gradient.
What is Osmosis? Diffusion of water across a differentially permeable membrane due to concentration differences. Solution=fluid(the solvent) That contains a dissolved solid(the solute)
Transport Across Membrane:passive transport ->diffusion Co2, O2,glycerol,water, alcohol Diffuse across membrane
Transport across membrane: passive transport-> facilitated Moves molecules from high concentration to low concentration. Sugars and amino acids (non-lipid soluble). Requires carrier protein No energy expenditure needed Are specific Undergo change in shape
Transport across membrane: Active Transport Move molecules across concentration gradient Requires energy (ATP)& carrier proteins Proteins are called Pumps
Active Transport: Exocytosis Secretion- moving out of cell
Active Transport: Endocytosis Endocytosis= taking substance into cell by vesicle formation
Active Transport: Endocytosis Phagocytosis= cellular eating, engulfing of large particles Pinocytosis= cellular drinking engulfing of lliquid and small particles Receptor-Mediated Endocytosis=form of pinocytosis that is specific, this si how cells can bring in a bulk qty of molecules.
Modification of Animal Cell: Surface Extracelluar matrix ECM functions: Support cell and influence behavior Components:protein+polysacharides Structural proteins= Collagen and elastin-> Strength and resiliance Adhesive proteins = Fibronectins and laminins -> Cell migration and communication
Modification of Plant Cell Surface:Cell Wall Functions : Protection Maintain shape Prevent excessive water uptake Hold plant up Cellulose+other polysaccharides+proteins
Metabolism: Energy and Enzymes What is metabolism? All chemical reactions that occur in a cell
What is energy? Capacity to do work and bring about change
Different Kinds of Energy Kinetic=energy of motion Potential= stored energy
Why are we talking about energy? 1.cells must acquire energy from environment 2.cells can not make energy (energy exists and can be transformed) 3in life energy transformations are chemical
Different Kinds of Energy Food has potential energy-> Kinetic energy Food= Chemical energy Energy flows it does not cycle
Laws of Thermodynamics 1st law of thermodynamics: law of conservation of energy. Energy can not be created nor destroyed but it can be changed from one form to another
Laws of Thermodynamics 2nd Law of Thermodynamics: Energy can not be changed from one form to another with out a loss of useable energy
Law of Thermodynamics 2nd law (restated): Every energy transformation makes the universe more disordered. Entropy is a measure of disorder or randomness
Energy Transformation Heat is useable energy Heat is the energy of random molecular motion Release of heat increases entropy in the universe
Cells and Entropy Energy transformation occurs in cells 2nd law: energy transformation in cells increases the total entropy in the universe Cells can be ordered Cellular processes require input of energy from outside cell-> SUN
Linking metabolism and Entropy Chemical reactions occur spontaneously if it increases entropy in the universe Standard for spontaneity -> free energy Free energy= amount of energy available to do work following chemical reactions
Types of Chemical reactions Exergonic: energy out, energy released spontaneously(-) Endergonic: energy in energy absorbed not spontaneous (+)
Exergonic vs Endergonic Many cellular processes are endergonic(ex. Protein synthesis) Endergonic reactions require input of energy. Energy released by exergonic reactions drive endergonic reactions=coupled reactions
ATP:Energy for Cells Energy released during break down of ATP ( exergonic reaction) it helps drive cellular endergonic reactions
How does ATP perform the work? Enzymes transfer phosphate group from one ATP to glutamic acid-> phosphorylation Phosphorylated glutamic acid is reactive (less stable)than original molecule. Ammonia displaces phosphate group -> glutamine
Function of ATP ATP supplies energy for : Chemical Work Synthesis macromolecules transport work Pumpsubstances across plasma membrane Mechanical work Contract muscles, beat cilia, and flagella, etc.
Enzymes and metabolism Enzymes are catalytic proteins that speed up rate of chemical reaction in a cell by lowering activation energy (EA) barrier. Ea is the initial investment of energy for starting a reaction-> energy require to break bonds in reactant molecules
Enzyme and activation Energy Enzymes lower the Ea barrier by bringing the substrates in contact w/ each other. Critical bonds in substances providing favorable microenvironment, direct participation with chemical reaction Substrates= reactants in an enzymatic reaction
Induced Fit Between Enzyme and its Substrate Active Site: undergoes change in shape to fit more snugly around substrate
Factors Affecting enzymatic speed: Substrate Concentration Temperature Ph Rate of reaction Enzyme Concentration
Control of enzymatic Activity Enzyme cofactors Non protein helpers (organic or inorganic)that assist in catalytic activity or enzymes Coenzyme= organic cofactor that assists enzymes, may accept, or contribute atoms to a reaction Vitamins are required for synthesis of coenzymes Phosphorylation=kinases add phosphate groups to enzyme to activate them
Control of Enzyme Activity Enzyme inhibition= active enzyme prevented from combining with substrate. Examples: competitive inhibition Noncompetitive inhibition ( we see this with sulfamide drugs)
Control of Enzyme Activity Specific type of non competitive inhibition: Feedback inhibition=when the end product binds to the first enzyme of a pathway.
Photosynthesis Land plants Multicellular algae Cyanobacteria-(1st living orgs to evolve on earth) Unicellular protists Other photosynthetic prokaryotes
Photosynthesis Is conversion of solar enery->chemical energy Solar energy+co2+H2O->glucose+O2 Solar energy+6CO2+6H2O+C6H12O6+6O2
Photosynthesis Occurs In Chloroplasts Chlorophyll absorbs solar energy and is found in membranes of the thylakoids
Solar Energy Electromagnetic Spectrum Light is a form of electromagnetic energy Electromagnetic energy travels in waves The distance between waves is a wavelength Photon=a discrete amount of light energy
Light absorption by chloroplasts Chlorophyll absorbs mainly blue & red light and transmits or reflects green light
Photon absorption by isolated chlorophyll Electron boosted from ground state ( low energy)-> Excited state ( high energy) Electron returns to ground state emitting energy ( heat and flouresence)
Photon Absorption by chlorophyll in chloroplasts Photo system= chlorophyl+other pigments Photosystem-> light harvesting unit Antenna molecules absorb photon energy and pass to reaction center Chlorophyll a transfer electron to primary electron acceptor Primary electron receptor traps high energy electron in excited state
Overview of Photosynthesis Light reaction: in thylakoid membrane Require light Occur in thylakoid membrane Solar energy absorbed by chlorophyll Solar energy converted to chemical energy ATP & NADPH Water split releasing O2
Overview of Photosynthesis Calvin Cycle reaction: Does not require light directly Occurs in stroma Chemical energy (ATP, NADPH) is used to reduce CO2 to carbohydrate
Light Reactions Step 1 Photon absorbed in photosystem 2 Chlorophyl and electrons become excited Excited electrons trapped by primary electron receptor “hole”left by electrons must be filled
Light Reaction Step2 Water is split by an enzyme Electrons extracted from water fill “hole”in chlorophyll A H+ stay w/in thylakoid space Oxygen released into atmosphere
Light reaction Step 3 Excited electrons pass down through the ETS (electron transport system) ETS composed of cytochromecomplex This is a series of redox reactions Step4 Energy from ETS used to produce ATP
What is the Electron transport systme? A series of membrane bound carriers that transfer electrons from one carrier to another Each transfer results in the release of energy High energy electrons enter Low energy electrons exit Each carrier is reduced and then oxidized in turn
Light reaction Step 5 At end of ETS electrons fill “hole”in chlorophyll A of photosystem1 “hole”result of photon absorption by photosystem 1
Light Reaction Step 6 Excited electrons passed to enzyme NADP+ NADP+ accepts 2 electrons and 2 H+ NADPH os an electron carrier molecule Nadph Carries high energy electrons
How is ATP Made? Thylakoid spae->H+ reservoir H+ from splitting of water molecules Energy from ETS is used to pump across metabolism Diffusion of H+down concentration gradients powers ATP synthase AtP synthase makes ATP through chemiosmosis
Chemiosmosis Use of a H+ to drive ATP synthesis
Calvin Cycle Reaction For 1 sugar molecule to be produced the cycle must take place 3 times It takes 3 molecules of carbon dioxide to produce 1 molecule of sugar
Calvin cycle reaction Phase 1: Carbon Fixation Co2 incorporated into organic material Each co2 is attached to a 5 carbon sugar (RUBP) Rubisco catalyzes this step (most abundant protein in chloroplasts, earth) 6 carbon molecule is unstable-> breaks down into two 3 carbon molecules (PGA)
Calvin Cycle Phase 2 REDUCTION Energy from ATP & electron from NADPH are reused to reduce 6 molecules of PGA to 6 molecules of sugar PGAL 1 PGAL leaves cycle as sugar, sugar has converted 3co2 to 1 sugar 6 ATP consumed, 6 NADPH consumed How many turns of the cycle are needed to produce 1 molecule of glucose?
Calvin Cycle Phase 3 Regeneration of RUBP 5 molecules of pgal are rearranged to form 3 molecules of RUBP with the help of ATP for energy 3 ATP are consumed
Cellular Respiration “redox reaction” Cellular respiration: takes place in cytoplasm and mitochindrion. Chemical energy->chemical energy C6H12O6+6O2 (oxi) (reduc.) ->6CO2+6H2O+atp+heat
Molecules of Importance NAD+ Redox coenzyme Accepts 2 electrons andH+->NADH NADH carries high energy electrons to ETS(electron transport system)
Molecules of Importance FAD Redox coenzyme Accepts 2 electrons and 2H+->FADH2 FADH2 carries high energy electrons to ETS(electron transport system)
Molecules of importance ATP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Overview of cellular respiration Four main reactions: Glycolysis-occurs in cytoplasm is split of sugars in 1/2, pyruvate. Energy Investment Transition reaction- link from cytoplasm to mitochondrion Cytric Cycle Cellular Respiration
Glycolysis Occurs in Cytoplasm Glucose broke down into 2 pyruvate molecules Energy Investment phase: active glucose w/ 2 ATP Energy Pay Off phase: oxidation the removal of H, production of NADH, ATP This makes 4 molecules of ATP
Glycolysis Aerobic environment(likes O2)-> pyruvate enters mitochondrion still has lots of energy in them Anaerobic environment (no O2)-> Fermentation
Glycolysis Inputs: glucose 2NAD+ 2 ATP 2ADP+2P Outputs: 2 Pyruvate 2NADH 2ATP net
How is ATP made in Glycolysis? Enzymatic transfer of a phosphate group from a high energy substrate to ADP
Transition reaction Connects glycolysis to citric acid cycle Pyruvate ( charged molecule)enters mitochondria via active transport Reaction occurs in the matrix: Pyruvate->acetyl Co A Occurs 2x per glucose molecule
Summary of Citric Acid Cycle Input Output 2acetyl groups 4CO2 6NAD+ 6 NADH 2FAD 2FADH2 2 ADP+2P 2ATP made by substr. Phos Circles 2 x to make 1 glucose molecule
Electron transport System Located in crisate of Mitochondrion High energy electrons enter Low energy electrons leave O2 is final electron acceptor As electrons pass down ETS energy is captured and ATP is produced NADH->3ATP FADH2->2ATP
How is ATP made in ETS? Oxidative phosphorlation Produces ATP from energy released by ETS H+ pumped into intermembrane space H+ flow down concentration gradient into matrix ATP made by ATP synthase-> chemiosmosis
Energy yield from Glucose breakdown 39% of available energy transferred from glucose to ATP Rest is lost to heat Yield ATP
Fermentation Alcohol Fermentation Pyruvate converted into ethanol Yeast-> beer, wine, and bread
Fermentation Lactic Acid Fermentation: Pyruvate converted to Lactate Bacteria and yeast-> cheese, yougurt Muscle Cells!!!!!!
Fermentation Input output Glucose 2 lactate or 2 ATP 2alcohol&2CO2 2ADP+2P 2ATP net
Breakdown of other foods Carbohydrates & fats & proteins Can all be used as fuel for cellular respiration Monomers of these molecules enter glycolysis or CAC at various points