EVPP 110 Lecture
Dr. Largen - Fall 2003

• Levels of organization of life
• non-living components of life
• atom
• molecule
• within cells
• macromolecule (biological)
• organelle
• cell
• within multicellular organisms
• tissue
• organ
• organ systems
• among organisms
• species
• population
• community
• ecosystem
• biosphere
• ecosphere

• represent a hierarchy
• each level incorporates lower levels of organization

Introduction to the cell

• Before microscopes (first used in 17th century), no one knew living organisms were composed of cells

All cells share fundamental features

• Major features common to all cells
• plasma membrane
• encloses cell
• separates contents from surroundings
• phospholipid bilayer
• 5-10 nanometers thick
• contains embedded proteins
• DNA – the hereditary molecule
• prokaryotes
• nucleoid
• area near center of cell, contains circular molecule of DNA
• not differentiated from rest of cell’s contents by membrane
• eukaryotes
• nucleus
• double-membrane bound organelle contains DNA
• cytoplasm
• semi-fluid matrix
• contains chemicals of cell
• sugars
• amino acids
• proteins
• contains organelles in eukaryotes
• carry out metabolism
• interconversion of different forms of energy and of chemical materials
• two major metabolic processes
• photosynthesis
• cellular respiration

• primary tenants of Cell Theory
• all organisms composed of 1 or 1+cells
• cell is smallest (basic) unit of life
• smallest living thing
• cells arise only by division of a previously existing cell
• all life on earth represents continuous line of descent from early cells

Introduction to the cell

• Two kinds of structurally different cells have evolved over time
• prokaryotic cells
• Archaebacteria
• Eubacteria
• eukaryotic cells
• Protista
• Fungi
• Plantae
• Animalia

• Prokaryotic cell characteristics
• small (1/10th size of eukaryote)
• lacks a nucleus
• DNA in nucleoid region (not membrane bound)
• plasma membrane
• bacterial cell wall
• some have pili (sticky)
• some propelled by flagellum

• Eukaryotic cells
• from Greek eu for "true" and karyon for kernal or "nucleus"
• fundamentally similar to each other
• profoundly different from prokaryoes
• characteristics of eukaryotic cells
• in general
• comparing animal and plant cell
• presence vs. absence of cell walls
• animal cells lack cell walls
• some protists lack cell walls
• plants, fungi and some protists have cell walls
• complex interior organization
• extensive compartmentalization
• many membrane-bound organelles
• true, membrane-bound nucleus
• complex DNA molecule
• contain vesicles and vacuoles which function in storage and transport

• membranes partition cytoplasm into compartments called membranous organelles
• location of many chemical activities known as cellular metabolism
• Eukaryotic cells, animal vs. plant
• animal cells
• cell wall absent
• chloroplasts absent
• central vacuole absent
• mitochondria present
• centrioles present
• lysosome present
• flagella may be present

• plant cells
• cell wall present
• chloroplasts present
• mitochondria present
• central vacuole present
• flagella absent (except in some sperm)
• lysosome absent
• centrioles absent

• membranous organelles
• nucleus
• endoplasmic reticulum
• Golgi apparatus
• mitochondria
• lysosome
• peroxisome
• chloroplast
• central vacuole

• non-membranous structures
• centriole
• flagellum
• ribosome
• microtubule
• microfilament
• cell wall

Energy converting organelles

• Chloroplasts
• photosynthesizing organelles of plants and protists
• internal membranes create 3 compartments
• space between inner & outer membranes
• intermembrane space
• space enclosed by inner membrane
• contains
• fluid called stroma
• network of tubules and hollow disks
• space inside tubules and disks
• disks occur in stacks, called grana
• grana are chloroplasts’ solar power packs

• Mitochondria
• energy converting organelles of heterotrophs
• carryout cellular respiration
• chemical energy of foods
• converted to chemical energy of a molecule such as ATP (adenosine triphosphate)
• ATP is main energy source for cellular work
• enclosed by 2 membranes, has 2 compartments
• space between inner & outer membrane
• intermembrane space
• fluid filled compartment
• space enclosed by inner membrane
• contains fluid called mitochondrial matrix
• space enclosed by inner membrane
• contains mitochondrial matrix
• many of chemical reactions of cellular respiration occur here
• inner membrane has many folds
• called cristae
• increases surface area
• contains enzymes that make ATP

Fueling the activities of life

• two main mechanisms by which organisms obtain food
• autotrophs (self-sustaining)
• heterotrophs (not self-sustaining)

Fueling the activities of life

• two main mechanisms by which organisms obtain food
• autotrophs (self-sustaining)
• plants and other photosynthetic organisms
• can produce from inorganic compounds the organic molecules they need for life
• heterotrophs (not self-sustaining)
• animals
• must obtain organic molecules they need by consuming organic molecules already produced by other organisms

How organisms harvest energy from food molecules

• Two major processes enable organisms to fuel the processes of life
• hetertrophs
• ingest their food
• cellular respiration harvests energy from ingested food molecules
• autotrophs
• manufacture their own food via photosynthesis
• cellular respiration harvests energy manufactured food molecules

Cellular Respiration

Introduction to Cellular Respiration

• Respiration
• refers to exchange of gases
• organism obtains O₂ from its environment & releases CO₂
• Cellular respiration
• aerobic harvesting of energy from food molecules by cells

• Breathing and cellular respiration are related
• organism takes in O₂ from environment
• distributes O₂ to its cells
• mitochondria use O₂ in cellular respiration

Fig. 4.8 - Cellular repsiration

Introduction to Cellular Respiration

• Harvesting energy from food molecules
• glucose - used as a representative food molecule

• summary equation for cellular respiration
• C₆H₁₂O₆ + 6O₂ ® 6CO₂ + 6H₂O + ATPs
• bond energy from reactants is stored in chemical bonds of ATP

• Efficiency of cellular respiration
• glucose contains chemical energy
• each ATP molecule made by cellular respiration contains ~ 1% of chemical energy in glucose molecule
• cellular respiration is not able to harvest all energy of glucose in a usable form
• typical cell banks ~ 40% of glucose’s energy in ATP molecules
• other ~ 60% is converted to heat
• comparison
• glucose burned in lab

• glucose "burned" in cell

• gasoline engine

• more efficient than any other process a cell can perform without oxygen
• yeast cell in an anaerobic environment harvests only about 2% of energy in glucose

Basic Mechanisms of Energy Release & Storage

• Underlying mechanisms of energy release and harvest in cell
• energy available to cell is contained in chemical bonds of a molecule (glucose)
• cellular respiration dismantles glucose in a series of steps
• taps the energy carried by electrons
• that are rearranged when old bonds break and new bonds form

• cellular respiration shuttles electrons through a series of energy releasing reactions
• electrons start in a molecule where they have more energy & end up in molecule where they have less energy
• energy is released in small amounts
• cell stores some of that energy in ATP
• cells transfer energy from glucose to ATP by coupling exergonic & endergonic reactions

• cellular respiration shuttles electrons through a series of energy releasing reactions
• movement of hydrogen atoms illustrates electron transfers
• glucose loses hydrogen atoms as it is converted to carbon dioxide
• molecular oxygen gains hydrogen atoms as it converted to water
• oxygen serves as the ultimate electron acceptor

Mechanisms of Energy Release & Storage

• Movement of electrons from one molecule to another is oxidation-reduction reaction (redox)
• oxidation
• loss of electrons from one substance (molecule is oxidized)
• reduction
• addition of electrons to another substance (molecule is reduced)
• reactions always go together because electron transfer requires donor and acceptor

• oxidation-reduction reaction (redox)
• glucose gives up energy as it is oxidized
• electrons are moved about by moving hydrogen atoms (along with their electrons)

• electron cascade occurs
• electrons "fall" down an energy "hill" of carriers
• each carrier is different molecule
• electrons move "downhill"
• increasing electron affinity
• redox reactions release energy in small amounts at each step, useful to the cell
• last molecule at bottom of hill is O₂
• greatest electron affinity of all carriers

• Electron transport chains
• series of electron carriers
• ordered groups of molecules embedded in membranes of mitochondria
• located in plasma membrane in prokaryotes
• as electrons pass along chain, they lose energy
• which cell can use to make ATP

Stages of Cellular Respiration

• Cellular respiration
• continuous process
• three main stages
• 1st & 2nd stages
• glycolysis
• Krebs cycle
• 3rd stage
• electron transport chain & chemiosmosis

• Glycolysis
• first stage
• occurs outside mitochondria in cytoplasm of
• means "splitting of sugar"
• universal energy-harvesting process of life
• occurs in all cells
• because of its universality, is thought to be ancient metabolic system
• starts with glucose

• Krebs cycle
• 2nd stage
• takes place in mitochondria
• completes breakdown of glucose
• producing carbon dioxide
• contributes electrons to 3rd stage
• produces 2 molecules of ATP
• produces other energy-rich molecules

• Electron transport chain
• 3rd stage
• takes place in mitochondria
• chain uses downhill flow of electrons from electron carriers to oxygen

Photosynthesis uses light energy to make food molecules

• Photosynthesis
• most of living world depends on this process
• on global scale - billions of tons of organic matter are produced each year
• no other chemical process of Earth matches this output
• consists of two stages that occur in chloroplast

Fig. 4.7 - photosynthesis

Autotrophs are the producers of the biosphere

• Plants are autotrophs
• "self-feeders"
• make own food
• sustain themselves
• chloroplasts capture energy in sunlight
• convert sun’s energy to chemical energy using water and carbon dioxide
• stored in form of glucose and other organic molecules

• Producers
• produce food consumed by heterotrophs
• all organisms that use light energy to make food molecules from inorganic molecules
• photosynthetic autotrophs
• producers include
• plants
• certain archaea
• certain bacteria
• certain protists
• Predominant producers
• terrestrial
• plants such as trees
• aquatic
• photosynthetic protists (algae)
• photosynthetic bacteria

Photosynthesis occurs in chloroplasts

• All green parts of a plant have chloroplasts and can carry out photosynthesis
• leaves have most chloroplasts
• are major sites of photosynthesis
• green color in plants - from chlorophyll pigments in chloroplasts
• chloroplhyll absorbs light energy from sun

• Green tissue in interior of leaf is called mesophyll
• each mesophyll cell has numerous chloroplasts
• membranes in chloroplast - many reactions of photosynthesis occur
• inner membrane encloses a compartment filled with a thick fluid called stroma
• within the stroma, disklike membranous sacs called thylakoids are suspended
• thylakoids are concentrated in sacks called grana

Plants produce O₂ gas by splitting water

• Photosynthesis equation
• CO₂ + H₂O ® light® C₆ H₁₂ O₆ + H₂O + O₂

Photosynthesis is a redox process, as is cellular respiration

• Photosynthesis is a redox process
• water is oxidized to O₂
• when water molecules are split apart
• they lose electrons & hydrogen ions
• CO₂ is reduced to sugar
• when electrons & hydrogen ions are added to it
• water is oxidized & carbon dioxide is reduced
• electrons gain energy by being boosted up an energy hill
• converts light energy to chemical energy
• Cellular respiration is a redox process
• sugar is oxidized and oxygen is reduced
• electrons lose energy as they travel down an energy hill
• converts chemical energy from one form to another

Photosynthesis occurs in two stages

• Photosynthesis
• two stages
• light dependent reactions
• first stage
• converts light energy to chemical energy and oxygen gas
• light independent reactions (Calvin cycle)
• second stage
• assembles sugar molecules using CO₂ and energy-containing products of the light reactions

• Light dependent reactions
• occur in thylakoid membranes
• absorb solar energy & convert it to chemical energy by
• making ATP from ADP + P
• transferring electrons from H₂O to NADP⁺ to form NADPH
• electron carrier
• no sugar is produced during these reactions
• requires light

• Light independent reactions (Calvin cycle)
• occurs in stroma of chloroplasts
• carries out process of carbon fixation
• incorporation of C from CO₂ into organic compounds
• enzymes of cycle then make sugars by further reducing fixed carbon
• by adding high-energy electrons and hydrogen ions to it
• does not require light directly
• but occurs during day in most plants

• light dependent reactions
• occur in thylakoid membrane
• photosystems I & II capture solar energy and energize electrons
• water is split and O₂ is released
• photosystems transfer electrons to ETCs
• where energy is harvested and used to make NADPH and ATP

• Light independent reactions (Calvin cycle)
• occurs in stroma
• incorporates carbon from CO₂ into sugar G3P
• G3P is used to make sugars which are
• used as fuel for cellular respiration
• used as starting material for other organic molecules such as cellulose
• stored as starch in chloroplasts, roots, tubers, fruits

• photosynthesis
• location: chloroplasts
• equation
• CO₂ + H₂O ® light® C₆ H₁₂ O₆ + H₂O + O₂
• manufactures food molecules
• used by: autotrophs
• cellular respiration
• location: mitochondria (stage 2-3)
• equation
• C₆H₁₂O₆ + 6O₂ ® 6CO₂ + 6H₂O + ATPs
• harvests energy in food molecules
• used by: autotrophs and heterotrophs

The end