Process Skills in Science

Process Skills in Science

Science- A body of knowledge and a process by which we learn the knowledge (scientific method).
Problem: question you are trying to answer Background Information: Information required to help answer the question Hypothesis: An educated guess (If, then and because statement) Materials: stuff we use Procedure: explains steps in detail (must be simplified enough for anyone to follow but precise enough to ensure that it can be replicated) Observation and Results: what did you see/observe Analysis: relating the results to the problem with background information Conclusion: Answering the problem and supporting/disproving your hypothesis

Variables: things that are changed in an experiment
Manipulated: independent Responding: Dependent Controlled Manipulated: changed by the experimenter The results depend on what you’ve done here Responding: changes because of the manipulated variable Responds to your changes Controlled: Kept constant We use it to compare our results Control of an Experiment: A control group is used as a comparison to the experimental group.

Controlled Experiment: A controlled experiment is one where
A) all of the variables are kept the same except for one B) There is only one manipulated variable and one responding variable Graphing Techniques: Don’t forget a title for the graph Don’t forget to label the axis X-axis: manipulated variable Y-axis: responding variable Lines of best fit  used to describe a relationship that we see in a graph Straight line: ONLY if you see a straight line Curved Line: ONLY if you see a curved line

Cell Energy Why do we care about this? Energy Requirements:
We need energy to keep cells alive Activities require energy Energy Requirements: Energy is released from foods The digestion process breaks down food into molecules Molecules are absorbed by cells

Two uses of food by cells:
1) Anabolism: synthesis of larger molecules required by the cell Example: Enzymes 2) Catabolism: broken down into smaller molecules to release energy for cellular activities Example: contraction of muscle cells Metabolic Activities: Sum of the chemical reactions that occur in cells Two type of chemical reactions: Exergonic Endrogenic

Endrogenic Reactions:
Exergonic Reactions: Example: Cellular Respiration Reactants  Products + Energy Endrogenic Reactions: Requires energy Example: Photosynthesis Reactants + Energy  Products

Energy Conversions All cells must have a constant supply of energy
Energy is trapped and released by two processes: Photosynthesis Cellular Respiration The Basics: Photosynthesis: Light energy is changed into chemical energy and stored in glucose Respiration: Glucose is broken down to release energy to the cell

Photosynthesis Happens only in green plants in the presence of chlorophyll which is found in chloroplasts Chemical Equation: Energy stored in the form of glucose

Cellular Respiration Happens in ALL cells whereby energy is released to perform life processes Chemical Equation: Involves burning of organic fuels by oxygen Energy is released

Photosynthesis and Cellular Respiration
Biology 20- Unit 3

Let’s Review Plants and animals are made up of eukaryotic cells (have a nucleus) In spite of varied size, shape and appearance, cells have several things in common. All cells digest nutrients, excrete wastes, synthesize needed chemicals and reproduce.

Cellular Anatomy All cells are made up of parts known as organelles
Although both plant & animal cells share many common types of organelles there are also organelles which are unique to each type See pgs

The Cell Membrane Separates the internal environment of the cell from its external environment Made of a double layer of phospholipid molecules

Membranes also have other proteins and molecules and molecules that are embedded within them.
Create passageways through the membrane

Membranes are semi-permeable
Two ways molecules and ion move through the membrane are diffusion and osmosis (passive transport)

Diffusion Natural movement of molecules or ions from an area where they are more concentrated to an area of less concentration (moving down its concentration gradient) Does not require energy

Osmosis Diffusion of water across a membrane
Movement of water depends of different things If water concentration of either side is equal than equal amounts of water move in and out (isotonic) If the water concentration is more outside the cell than in the water will move into the cell (hypotonic) If water concentration inside the cell is greater than outside water moves out (hypertonic). -Does not require energy

Facilitated Diffusion
Substances that need help to move in and out of the cell (example: glucose) Particular transport proteins will recognize and help move a specific type of dissolved molecule or ion (carrier protein) Channel proteins also carry molecules across but they must be small enough to fit through the tunnel.

Active Transport Needs energy to move things in and out of the cell
ATP- adenosine triphosphate

Endocytosis and Exocytosis
Used for substances too large to move across a membrane Example: Cholesterol Can use endocytosis- folds in on itself to create a membrane enclosed sac (vesicle) to “eat” the substance

Types of Endocytosis 3 Type of Endocytosis:
Pinocytosis: intake of small amounts of liquids or small particles 2. Phagocytosis: intake of large amounts of liquids or larger particles 3. Receptor- assisted endocytosis: intake of specific molecules that attach to special proteins in the membrane

Exocytosis Removing substances from the cell
Vesicles from inside the cell moves to the membrane and “bursts” releasing its contents

Cell Wall-Plant Cells A surrounding layer outside the cell membrane
Composed of small fibres (microfibrils) of cellulose

Animal cells

Animal Cell Parts Mitochondria: provide the energy a cell needs to move, divide, reproduce Power Centre of the cell Cristae are folded to increase surface area

Parts of an Animal cell Cytoplasm: fluid that fills the cell
Distributes materials such as oxygen and food to different parts of the cell Also helps support all the other parts of the cell

Parts of an Animal Cell Nucleus: large dark nucleus is often the most easily seen structure in the cell Controls the cell activities Contains the chromosomes Enclosed in a nuclear membrane which controls what enters and leaves the cell

Parts of an Animal Cell Nucleolus: prominent structure in the nucleus
Produces ribosomes

Parts of an Animal Cell Vacuoles: Storage places for surplus food, wastes and other substances that the cell cannot use right away.

Parts of an Animal Cell Lysosomes: digestion

Parts of An Animal Cell Golgi Apparatus: important in packaging proteins for transport elsewhere in the cell

Parts of An Animal Cell Rough Endoplasmic Reticulum: Appears pebbled due to the presence of ribosomes. Synthesizes proteins

Parts of An Animal Cell Smooth Endoplasmic Reticulum: Appears smooth
Functions: lipid and steroid synthesizes

Parts of an Animal Cell Ribosome: Site of protein synthesis

Animal cells

What You Need to have in an Animal Cell
Nucleus Cell Membrane Cytoplasm Vacuoles Ribosomes Golgi Apparatus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Lysosomes Mitochondria Nucleolus

Plant cells

Parts of a Plant Cell Lucky for you plants have many of the same structures 1)Nucleus 2) Nucleolus 3) Cytoplasm 4) Golgi Apparatus 5) Lysosome 6) Mitochondria 7) Vacuole 8) Cell Wall 9) Smooth ER 10) Rough ER 11) Chloroplast

Parts of a Plant Cell Cell Wall: are much thicker and more rigid than cell membranes and are made mostly of a tough material called cellulose. Provide support for the cell

Parts of a Plant Cell Chloroplasts: Structures where photosynthesis takes place

Photosynthesis & Cellular Respiration
Introduction

ATP and Cellular Activity
How does ATP supply energy for cellular activity?

ATP Supplies the energy for cellular activities
Used rapidly so cells must be constantly creating it Used for: Active transport Movement of chromosomes Movement of muscles Cilia or flagella etc.

Photosynthesis Needed in order for life to survive on Earth
Photosynthesizing organisms contain chloroplasts that trap the Sun’s energy Converted into chemical energy and stored as sugars and carbohydrates Other products produced by the Sun’s energy are oxygen. ATP and heat

Cellular Respiration Used by plants, animals and other multicellular organisms The break down of energy-rich compounds to release stored energy Broken down inside the mitochondria This makes ATP

Photosynthesis – Chemical reaction
Energy from the sun is captured by green plants by the process called photosynthesis (P/S) 6 CO2 + 6 H2O + E (light)  C6H12O6 + 6 O2

Photosynthesis - Pigments
For light energy to be used by living systems it must first be absorbed. A pigment is any substance that absorbs light. (Some pigments absorb all light and thus appear black. Others absorb light in the violet-blue and the orange-red spectrum and reflect green light.)

Various pigments absorb energy of different wavelengths. (absorption spectrum)

All photosynthetic organisms contain chlorophyll Different types of plants use various pigments in P/S.

Chlorophyll a (blue-green) and chlorophyll b (yellow- green) are the most common pigments but most plants also contain a pigment group called carotenes (Example: beta-carotene) They absorb photons with energies in the blue-violet and red regions and reflect everything else Chlorophyll a- blue-green ( is the only pigment that can transfer the energy from sunlight to photosynthesis) Chlorophyll b- yellow-green (acts as an accessory pigment (“helper”) to catch the photons “a” misses and transfer the energy absorbed to “a” They absorb photons with energies in the blue-violet and red regions and reflect everything else -There are other compounds, carotenoids are also “helper” pigments

Chlorophyll a and b Chlorophyll a is the only pigment that can transfer the energy from sunlight to photosynthesis Chlorophyll b acts as an accessory pigment “helper” to catch the photons a misses and transfer the energy absorbed to a There are other compound, carotenoids , are also “helper” pigments.

In green leaves carotenes are masked by chlorophyll, thus when chlorophyll production slows in the fall the leaves change color to show the carotenes. -In winter there is not enough light or water for photosynthesis to occur -plants begin to break down chlorophyll they have and stop to appear (yellow, orange, red) - These colors were always there they were just covered up by the green chlorophyll

Photosynthesis - Chloroplast
Chlorophyll pigments reflect green and absorb blue and red wavelengths. Carotenoids absorb violet and blue wavelengths reflecting yellow. Pigments absorb light of the correct wavelength to excite electrons to a higher energy level In winter there is not enough light or water for photosynthesis to occur Plants begin to break down the chlorophyll they have and stop making more -the green color disappears and other colors start to appear (yellow, orange and red) -these colors were always there they were just covered up by the green chlorophyll

Photosynthesis - Plastids
Plastids are structures that contain pigment and give plants their colour. The most common plastid is the chloroplast in which the chemical reactions of P/S occur.

C6H12O6 + 6 O2 + 6 H2O  6 CO2 + 12 H2O + E (ATP)
Cellular Respiration Produces ATP energy by the combustion reaction of glucose called cellular respiration. C6H12O6 + 6 O2 + 6 H2O  6 CO H2O + E (ATP) Site of cellular respiration Found in all organisms

Mitochondrial structure
Respiration occurs at the mitochondrian Mitochondrian is composed of 4 regions: 1. outer membrane - smooth and freely permeable; contains enzymes to catabolize fats The mitochondria has two membranes The fluid-filled space within the inner membrane is known as the matrix Contains many of the chemicals and proteins required to break down carbohydrates The inner membrane has numerous folds called cristae Provide a large surface area for the production of ATP

2. inner membrane – folded membrane in the mitochondria (cristae); made mostly of protein including the enzyme that makes ATP; impermeable to most small molecules and ions

3. Intermembrane space - contains enzymes which use ATP

4. matrix - control region; mixture of proteins including enzymes which oxidize major compounds

Metabolic Pathways In a metabolic pathway the product of one reaction is the starting reactant for another

The Role of Enzymes Metabolism refers to all the chemical reactions that occur within a cell to support and sustain life functions Can be broken into two distinct types of reactions: Anabolic reactions & pathways create larger molecules from small subunits and require energy Catabolic reactions & pathways break down large molecules into smaller pieces and release energy

Energy required to start a reaction is known as activation energy
Catalysts and enzymes reduce the activation energy Allows the reactions to proceed more rapidly Enzymes are specialized proteins that lower the energy needed to activate biological reactions

Activation Energy Catalyzed vs. Uncatalyzed Reactions

Oxidation & Reduction Oxidation is a reaction where an atom or molecule loses electrons LEO – Loses Electrons = Oxidation Reduction is a reaction where an atom or molecule gains electrons GER – Gains Electrons = Reduction Free electrons from oxidation cannot exist on their own Electrons that are lost through oxidation of one substance cause the reduction of another compound Molecules in their reduced form contain large amounts of energy -When an atom or molecule loses an electron it is said to be oxidized When an atom or molecule gains an electron, it is said to be reduced -Electron lost by one atom or molecule are gained by another - Atoms or molecules in their reduced form have more energy

Example: X + Y --> X+ + Y-
reducing oxidizing oxidized reduced agent agent agent agent

Adenosine Triphosphate
The cell obtains its energy requirements through cellular respiration which is an exothermic reaction manufacturing ATP

ATP produces energy by breaking a bond to a phosphate group
This produces ADP (adenosine diphosphate) and a free phosphate group ATP  ADP + Pi This process works in reverse to create more ATP

Adenosine triphosphate (ATP) consists of: nitrogenous base adenine (1/5 types of nitrogenous bases) an attached ribose sugar. attached to the sugar are phosphate groups.

The terminal phosphate is bonded by a covalent bond of unusually high energy.

During cellular respiration a free phosphate group is attached to a molecule of ADP to make ATP in a process called phosphorylation

ATP is used to provide the activation energy needed to power cell reactions (Energy is liberated by detaching the terminal phosphate group) From Now On You Must ALWAYS ASK YOURSELF WHERE IS THE ATP

Review Cellular respiration is the process by which cells break down high-energy compounds and generate ATP.

Review Adenosine triphosphate, or ATP, is the direct source of energy for nearly all types of energy-requiring activities of living organisms.

Mitochondria Review Mitochondria have outer and inner membranes that surround a fluid-filled region called the matrix. The inner membrane has many deep infoldings called cristae. -Mitochondria enable cells to extract energy from food - Site of cellular respiration

Review The chemical reactions of photosynthesis and cellular respiration take place in a series of step-by-step reactions called metabolic pathways. Enzymes are biological catalysts that reduce the amount of startup energy needed for the reactions in the metabolic pathways. In the absence of enzymes, the reactions could not occur at temperatures at which living organisms thrive.

Review When a compound is oxidized in a chemical reaction, it loses electrons. When a compound is reduced in a chemical reaction, it gains electrons. Compounds contain more chemical energy in their reduced form than they do in their oxidized form.

Photosynthesis Various energy containing molecules are formed during photosynthesis: Glucose: energy stored in most cells ATP (adenosine triphostphate) : used by all living cells for immediate energy NADPH: starts as NADP+ (nicotinamide dinucleotide phosphate)

Photosynthesis Transforms the energy of the sun into chemical energy in glucose, ATP and NADPH Involves over 100 individual chemical reactions that work together These reactions can be summarized in two groups: Light-Dependent Reactions – generates high energy compounds ATP and NADPH Light-Independent Reactions – energy of ATP and reducing power NADPH are used to reduce carbon dioxide to make glucose which can then be converted to starch for storage Light dependent – converts light E to ATP and NADPH Light independent – use E from light dependent to convert CO2 -> glucose

Light Dependent Light Independent
Light Dependent: requires sunlight in order to work Requires chlorophyll; occurs in the thylakoid - involves photosystems (I and II) Responsible for capturing light energy

Light-Dependent Reactions
Requires sunlight in order to work During these reactions, the pigments contained inside the thylakoid absorb light energy Although plants have a number of pigments, the most important for photosynthesis is chlorophyll these energy capturing reactions occur in the thylakoid membranes of the chloroplast light energy trapped in the chloroplast by chlorophyll and carotene molecules is used to form ATP from ADP and make NADPH from NADP

Photosystems Within the thylakoid membrane, chlorophyll and other pigments are organized into photosystems. Chloroplasts of plants have two photosystems: Photosystem I (PSI) Photosystem II (PSII) Each system is made of pigment molecules that include chlorophyll and carotenoid molecules All the pigment molecules in each photosystem can absorb various wavelengths of light energy -Solar energy is captured when an electron in a chlorophyll molecule absorbs a photon (photosystem II) -electrons go from low energy to high energy -The excited electron is removed from photosystem II and passed through an electron transport chain

The various pigment molecules produce free electrons when light hits them
These free electrons are passed along to the reaction center, a specialized chlorophyll a molecule When the electron in the reaction center is “excited” by the addition of energy, it passes to the electron-acceptor molecule This reduces the electron acceptor and puts it at a high energy level

A summary of the Steps: The light reactions use the solar power of photons absorbed by both photosystem I and photosystem II to provide chemical energy in the form of ATP and reducing power in the form of the electrons carried by NADPH. Takes place in the thylakoid membranes of the chloroplast

Light Dependent Reaction – The Details: Photosystem II (PSII)
Light enters PSII and is trapped by Pigment-680 (P680) An electron from P680 is boosted to a higher energy level where it is passed to an electron acceptor molecule This electron passes down an electron transport chain (cytochromes) to PSI forming ATP from ADP in a process called photophosphorylation -Once the excited electron has left photosystem II there are four steps that occur: Step 1: the electron that left photosystem II needs to be replaced before more light can be absorbed -This is done through photolysis (splitting of water) Step 2: The electron in the electron-transport chain is passed from molecule to molecule - As it is passed along it releases energy - This energy pull hydrogen ions from the stroma into the thylakoid lumen Step 3: light hits photosystem I - An electron in this photosystem is “excited” and passed onto the smaller electron transport chain Step 4: The electron that went from photosystem I to the next electron transport chain is used to reduce NADP+ to make NADPH

Light Dependent Reaction – The Details: Photosystem II (PSII)
The lost electrons from P680 are replaced by electrons produced by the lysis of water photolysis, which liberates O2 as a waste product

Light Dependent Reaction – The Details: Photosystem I (PSI)
The electron arriving from PSII is boosted to another electron acceptor molecule As it is passed along it releases energy This energy pulls hydrogen ions from the stroma into the thylakoid lumen

Light hits photosystem 1
An electron in this photosystem is “excited” and passed onto the smaller electron transport chain The excited electron from photosystem 1 passes down a chain of coenzymes (cytochromes) to make NADPH molecules from NADP

Light Dependent Reaction
DRAW FLOWCHART OF P/S ON BOARD P/S DIVIDED INTO TWO – L. DEP AND L IN SHOW L DEP DIVIED INTO PS2 AND PS1

ATP Production - Chemiosmosis
The energy from the electrons in photosystem II is used to produce ATP indirectly The H+ ions in the thylakoid lumen are unable to escape except through special proteins called ATP synthase complexes As the H+ ion moves though this complex they release energy The complex uses some of this energy to combine ADP and Pi making ATP This ATP then moves onto the light-independent reaction to make glucose -The H+ ions in the thylakoid lumen are unable to escape except through special proteins called ATP synthase complexes -As the H+ ions move through this complex they release energy The complex uses some of this energy to combine ADP with Pi making ATP This ATP then moves onto the light-independent reaction to make glucose

Chemiosmosis Linking the movement of hydrogen ions to the production of ATP Occurs in a series of steps: To return to the stroma, the H+ ions must move through a structure known as ATP synthase which provides the only pathway for H+ ions to move down their concentration gradient ATP synthase uses the movement of the H+ ions to run a mechanism that bonds together ADP and free phosphates to form ATP

Your Task Case Study page 184 questions 1 and 2  optional
Section Questions page 185 questions 1-4  somewhat optional Practice Questions page 187 #1-3 getting less optional Practice Questions page 188 #4-6  not really a choice Practice Questions page 190 # 7-10  I wouldn’t ignore these Practice Question page 191 #  Do or suffer the consequences Expect a Quiz next class

Light Independent Reactions
Does not require light Also known as the Calvin-Benson Cycle Occur in the stroma of the chloroplast Glucose is synthesized which requires: a. energy in the form of ATP and NADPH (there has to be enough) b. H since each glucose molecule has 12 H atoms Once enough ATP and NADPH has been produced by the chloroplasts, glucose can be synthesized This involves a series of reactions known as the Calvin-Benson Cycle

The Calvin-Benson Cycle
The Calvin cycle regenerates its starting material after molecules enter and leave the cycle CO2 enters the cycle and leaves as sugar The cycle spends the energy of ATP and the reducing power of electrons carried by NADPH to make the sugar The actual sugar product of the Calvin cycle is not glucose, but a three-carbon sugar, glyceraldehyde-3-phosphate (PGAL)

Each turn of the Calvin cycle fixes one carbon.
For the net synthesis of one PGAL molecule, the cycle must take place three times, fixing three molecules of CO2. To make one glucose molecules would require six cycles and the fixation of six CO2 molecules. The Calvin cycle has three phases. Calvin - Benson Cycle

Calvin Benson Cycle–The General Details
The Calvin-Benson cycle can be thought of as having three stages: Carbon fixation Chemical reshuffling Reforming RuBP

Light Independent Occurs in 3 stages: Step 1: Carbon Fixation
RuBP (ribulose biphosphate) joins with CO2 (catalyzed by Rubisco) to form an unstable 6 carbon molecule which splits to become PGA (phosphoglyceric acid)

Light Independent Step 2: Reduction
The 3 carbon compounds are activated by ATP (given energy) and then reduced by NAPDH (given more energy) The molecule now become 12 molecules known as PGAL 2 PGAL molecules move on to make glucose, 10 go to step 3

Light Independent Step 3: Replacing RuBP
Remaining PGAL will be used to make more RuBP ATP will help break and reform the chemical bonds to make the 5-carbon RuBP Hydrogen (from water) in the form of NADPH is transferred (using ATP energy) to PGA to form PGAL (phosphoglyceraldehyde) two PGALs can join to form glucose or be used to regenerate RuBP

Calvin-Benson Cycle - Simplified

Calvin Benson Cycle – more details

Let’s Put It All Together…

Photosynthesis Stores Energy in Organic Compounds Review
Photosynthesis consists of two separate sets of chemical reactions: light-dependent and light-independent reactions. light-dependent reactions NADPH light-independent reactions ATP chemiosmosis

Chlorophylls a and b and the carotenoids are photosynthetic pigments that absorb light.

Light energy trapped by a pigment molecule excites electrons. When an electron in photosystem II is excited, it is transferred to and then passed along an electron transport system.

Energy released during electron transport is used to force hydrogen ions across the thylakoid membrane and create a concentration gradient. Energy from the concentration gradient is used to generate ATP from ADP and phosphate by means of chemiosmosis. As hydrogen ions move down their concentration gradient, they drive the reaction that generates ATP.

An electron from water replaces the electron that was lost from photosystem II. The oxygen from the water molecule is converted to molecular oxygen. When an electron from photosystem I is excited, it is eventually used to reduce NADP+ to NADPH.

The series of reactions that synthesize carbohydrates is the Calvin-Benson cycle, which occurs in the stroma. In this cycle, carbon dioxide combines with RuBP to form a six-carbon compound that immediately splits into two three-carbon compounds.

ATP and NADPH from the light-dependent reactions provide energy and reducing power to form PGAL from the newly formed three-carbon compounds. Six cycles produce 12 PGAL molecules, 10 of which regenerate RuBP and 2 of which are used to make glucose.

Cellular Respiration http://www.youtube.com/watch?v=X-ZZETT6F-s

Cellular Respiration The cell obtains most of its energy requirements through the cellular respiration of glucose (glycogen, glycerol & amino acids may also be used) Releases the energy that is stored in carbohydrates Glucose is oxidized to form carbon dioxide, water and energy

Releasing Stored Energy
There are 3 ways of releasing the energy stored in food: Aerobic cellular respiration is carried out by organisms that live in aerobic environments Examples: fungi, bacteria, plants, animals Anaerobic cellular respiration is carried out by organisms that live in anaerobic environments Examples: nitrogen fixing bacteria, deep ocean producers Fermentation - modified form of anaerobic cellular respiration Examples: Yeast, bacteria that cause milk to sour

Aerobic Cellular Respiration
The controlled process of respiration can be divided into three groups: 1. Glycolysis - anaerobic process which converts glucose to pyruvic acid (aka pyruvate) 2. Kreb's (Citric Acid) cycle - aerobic process in which the breakdown of pyruvic acid yields energy in the form of ATP and NADH/FADH 3. Respiratory (Electron Transport) Chain - an electron transfer system that produces ATP

Glycolysis Anaerobic reaction that occurs in the cytoplasm
Glycolysis Anaerobic reaction that occurs in the cytoplasm Occurs in all living cells Does not provide enough energy to sustain life Animation Location: occurs outside the mitochondria in the cytoplasm of the cell in glycolysis the cell supplies the activation energy which is needed to initiate the reaction net result is 2 ATP

Stage of Glycolysis Summary
1. Glucose (6 C sugar) enters respiration pathway 2. Two ATP from cytoplasm provide the activation energy to begin the reaction ( - 2 ATP ) which converts glucose to glucose phosphate (6 carbon molecule)

Stage of Glycolysis Summary
3. Glucose phosphate is split into 2 PGAL (phosphoglyceraldehyde) (3 carbon molecule) 4. Each PGAL continues through glycolysis to yield: 1 NADH, 2 ATP & 1 H2O forming the 3 carbon molecule - pyruvate

↓ (ATP -> ADP) [phosphorylation]
Stage 1 of Glycolysis Glucose ↓ (ATP -> ADP) [phosphorylation] Glucose phosphate ↓ [rearranged] Fructose phosphate Fructose diphosphate ↓ [split] PGAL  PGAL

Stage 2 Glycolysis PGAL PGAL DPGA DPGA PGA PGA Pyruvate Pyruvate
↓ NAD -> NADH ↓ NAD -> NADH DPGA DPGA ↓ ADP -> ATP ↓ ADP -> ATP PGA PGA Pyruvate Pyruvate

Energy Gained from Glycolysis
Glycolysis nets: 2 ATP (PGAL -> pyruvic acid) X 2 = 4 ATP ATP (activation energy) = - 2 ATP 2 ATP Also 2 NADH

The Fate of Pyruvate Pyruvate can proceed to two processes dependent on the availability of oxygen: Aerobic Cellular Respiration Pyruvate is transported from the cytoplasm into the mitochondria Anaerobic Cellular Respiration - Fermentation Pyruvate remains in the cytoplasm The fate of pyruvate, the final product of glycolysis, depends on the availability of oxygen and on the type of organism. When oxygen is available, pyruvate enters the matrix of the mitochondrion. A series of reactions yield carbon dioxide and acetyl-CoA. NAD+ is reduced to NADH.

Preparation for the Kreb’s Cycle Transition Reaction (aka oxidative decarboxylation)
Occurs in the mitochondria Pyruvate combines with coenzyme A (CoA) Loses a carbon atom in the form of CO2 Remaining 2 carbon molecule attaches to CoA to form acetyl CoA Coenzyme A “tows” the acetyl group (2 carbon compound) into the Krebs cycle During the Krebs cycle, two carbon atoms are fully oxidized to carbon dioxide, NAD+ and FAD are reduced to NADH and FADH2, and a small amount of ATP is produced.

Krebs Cycle The NADH and FADH2 from the Krebs cycle donate their electrons to the electron carriers in the electron transport chain. As electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions across the mitochondrial inner membrane into the intermembrane space, creating a concentration gradient. The energy stored in the gradient is used to generate ATP by chemiosmosis.

Krebs Cycle Citric Acid Cycle
Occurs in the mitochondria Cycle must be completed 2x per glucose molecule Net gains per glucose molecule: 2 ATP 6 NADH 2 FADH2 Animation Reduced compounds – carry electrons need for electron transport system Occurs in the mitochondrial matrix for each glucose ---> 2 pyruvate molecules therefore giving 2 turns of Krebs cycle yields of Krebs cycle ATP - 1 molecule/cycle -> 2 ATP/glucose molecule NADH - 3 molecules/cycle -> 6 NADH/glucose molecule FADH - 1 molecule/cycle -> 2 FADH/glucose molecule

Kreb’s Cycle Steps The 2 C acetyl group from the transition reaction combines with a 4 C oxaloacetic acid to produce a 6 C called citric acid Citric acid steps through a number of reactions, losing a CO2 and forming NADH to become a 5C - ketoglutaric acid

Kreb’s Cycle Ketoglutaric acid proceeds through a number of reactions losing CO2 and producing NADH and ATP to become a 4C - succinyl acid Succinyl acid becomes fumeric acid (4 C) producing FADH Fumeric acid is transformed to oxaloacetic acid forming NADH

Kreb’s Cycle The oxaloacetic acid molecule the cycle ends with is not the same molecule with which the cycle began [proven using radioactive markers in glucose entering - markers end up in oxaloacetic acid]

Video – The Kreb’s Cycle

Electron Transport Provides large quantities of ATP during aerobic cellular respiration Electrons are passed down a chain of protein complexes imbedded in the inner membrane Energy is pump hydrogen ions, H+, from the matrix into the intermembrane space Against concentration gradient Requires oxygen to function Oxygen is the final electron acceptor of the electron transport system producing water 2H+ + ½ O2  H2O Animation Electron transport system occurs on the inner membrane in the cristae Kreb’s cycle and glycolysis convert some of glucose’s energy to produce ATP from ADP most energy from the first two stages of respiration is held as high energy electrons in the electron carriers NAD and FAD

Electron Transport System
Oxidative phosphorylation has these high energy electrons being passed step by step to a lower energy acceptor -> oxygen In oxidative phosphorylation a series of electron carriers, each holding the electron at a slightly lower energy level, pass the electrons along the pathway to make ATP At the top of the energy hill, the electrons are held by NADH and FADH

Cytochromes The principle components of the electron transport chain are cytochromes Composed of a protein enclosing an atom of iron each with a different capacity for holding electrons at different energy levels The enclosed iron atom alternately accepts and releases an electron passing it along to the next cytochrome at a slightly lower level of energy

Electron Transport System
At the end of each chain the electrons are accepted by oxygen which then combines with protons (H+) from the solution to produce water For each NADH entering the electron transport chain a yield of 3 ATP is realized For each FADH entering the electron transport chain a yield of 2 ATP is realized

Role of Oxygen Video – Oxidative Phosphorylation

C/R - Energy Harvest Glycolysis
ATP produced 4 ATP ( - 2 ATP activation E) Net gain = 2 ATP 1 glucose molecule Net Gain = 2 NADH Transition Rxn. 1 NADH/pyruvate Net Gain = 2 NADH Krebs cycle 3 NADH/cyle Net Gain = 6 NADH 1 FADH/cycle Net Gain = 2 FADH 1 ATP/cycle Net Gain = 2 ATP Total before ETC ATP; 8 NADH & 2 FADH

C/R - Energy Harvest ETC 2 x 2 = 4 ATP 3 x 8 = 24 ATP 2x2 = 4 ATP
2 ATP for each NADH from glycolysis 2 x 2 = 4 ATP 3 ATP for each NADH after glycolysis 3 x 8 = 24 ATP 2 ATP for FADH 2x2 = 4 ATP ATP from glycolysis and Krebs 4 ATP Total E Harvest – 36 ATP

Net gain of 36 ATP molecules per 1 glucose during cellular respiration Majority of ATP is produced using Electron Transport System and Chemiosmosis

Cellular Respiration Song
Link ATP Sythase Video

Anaerobic Cellular Respiration
No oxygen available Only produces the amount of ATP generated by glycolysis Converts excess pyruvate that cannot be processed in the Krebs cycle to lactate or ethanol Fermentation – pathway taken by pyruvate to produce ATP in anaerobic conditions Two types: Lactate Fermentation Ethanol Fermentation The type of organism and oxygen availability determines the pathway of pyruvic acid process which occurs in the absence of oxygen [anoxia v hypoxia] and converts glucose to lactic acid (in animals) or alcohol and carbon dioxide (fermentation in yeast) Using only glycolysis the net result is 2 ATP

Lactate Fermentation Occurs in the cytoplasm
Occurs when energy demands exceed oxygen supply Cells convert pyruvate molecules into lactate or lactic acid Use NADH as energy source Lactate is stored When oxygen levels increase lactate is converted back to pyruvate Pyruvate proceeds to Krebs cycle animals and some micro-organisms form lactic acid if there is an oxygen deficiency uses H+ from NADH to convert pyruvic acid -> lactic acid

Ethanol Fermentation Anaerobic process
Occurs in the cytoplasm of cells Process in which yeasts and some bacteria convert pyruvate to ethanol and CO2 Used to produce alcoholic beverages and aid in the rising of bread in most plants and many micro-organisms oxygen deficiency leads to alcoholic fermentation carbon dioxide is removed from pyruvic acid & H+ from NAD+

Anaerobic Respiration
Both types of fermentation use energy but free NAD+ to accept H+ supplying a small amount of energy and preventing the cell from becoming acidic Various other chemical pathways exist which allow some organisms to thrive in anoxic and hypoxic conditions

Summary

Cellular Respiration Releases Energy from Organic Compounds - Review
Three metabolic pathways make up aerobic cellular respiration. B. C.

The first set of reactions in aerobic cellular respiration is called glycolysis. It is an anaerobic process. During glycolysis, a small amount of ATP is generated, and NAD+ is reduced to NADH.

Stage 1 of Glycolysis glucose phosphate fructose phosphate
↓ (ATP -> ADP) [phosphorylation] glucose phosphate ↓ [rearranged] fructose phosphate fructose diphosphate ↓ [split] PGAL  PGAL a. b. c. d.

Stage 2 Glycolysis a. b. c. PGA PGA PGA PGA Pyruvate Pyruvate
PGAL PGAL ↓ NAD -> NADH ↓ NAD -> NADH PGA PGA ↓ ADP -> ATP ↓ ADP -> ATP PGA PGA ↓ ADP -> ATP ↓ ADP -> ATP Pyruvate Pyruvate a. b. c.

The fate of pyruvate, the final product of glycolysis, depends on the availability of oxygen (anerobic and aerobic) and on the type of organism. When oxygen is available, pyruvate enters the matrix of the mitochondrion. A series of reactions yield carbon dioxide and acetyl-CoA. NAD+ is reduced to NADH. Transition Reaction

Acetyl-CoA enters the Krebs cycle by combining with a four- carbon compound. During the Krebs cycle, two carbon atoms are fully oxidized to carbon dioxide, NAD+ and FAD are reduced to NADH and FADH2, and a small amount of ATP is produced. citrate

The NADH and FADH2 from the Krebs cycle donate their electrons to the electron carriers in the electron transport chain. As electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions across the mitochondrial inner membrane into the intermembrane space, creating a concentration gradient. The energy stored in the gradient is used to generate ATP by chemiosmosis.

Organisms that carry out anaerobic cellular respiration use inorganic chemicals other than oxygen as the final electron- acceptor. This produces ATP for the cell, but not as much as in aerobic respiration. breakdown of glucose in the presence of oxygen 36 ATP breakdown of glucose by lactate or ethanol fermentation 2 ATP

In muscle that is functioning anaerobically, pyruvate is converted to lactate and the reduced NADH is reoxidized so that glycolysis can continue. This process is called lactate fermentation.

In yeast growing anaerobically, pyruvate is converted to carbon dioxide and ethanol. This process is known as ethanol fermentation.

Fermentation is used on an industrial scale to produce ethanol. Ethanol is used as an additive to gasoline to reduce some environmental contaminants. Selected Fermentation Products and their Uses

Chapter Concept Organizer

Chapter Summary P/S and C/R proceed through many different rxns to produce energy-rich compounds and break them down to release their stored energy (ATP) When the bond to the last phosphate group is broken, leaving ADP and a free phosphate group, the energy released is available to do cellular work. In P/S the CO2 and H2O are involved in two separate sets of reactions: H2O is split into hydrogen ions, electrons, and oxygen in the light-dependent reactions CO2 is incorporated into carbohydrates in the light-independent reactions.

Chapter Summary (cont’d)
light-dependent rxns (thylakoid membranes) capture light energy and use it to excite electrons to produce ATP and NADPH. light-independent reactions (stroma) use the chemical potential energy of ATP and the reducing power of NADPH to reduce carbon dioxide and form glucose via the Calvin-Benson cycle. Glucose is processed to release energy through glycolysis, the Krebs cycle, and electron transport Glycolysis is an anaerobic process that occurs in the cytoplasm and breaks down glucose into pyruvate Pyruvate enters the mitochondria, where it is broken down into carbon dioxide and acetyl CoA.

Chapter Summary (cont’d)
Acetyl CoA enters the Krebs cycle (matrix) and energy released from breakdown of compounds in the Krebs cycle is used to reduce NAD -> NADH and FAD -> FADH NADH & FADH donate electrons to the ETC on the inner mitochondrial membranes Energy, released as electrons, is passed along the chain & used to create a hydrogen ion gradient that powers chemiosmosis, which generates ATP. Glycolysis is the only source of energy for some organisms. Pyruvate is broken down into carbon dioxide and alcohol (ethanol fermentation) or lactate (lactate fermentation). This process occurs anaerobically.

Chapter Review What molecule provides energy for most cellular processes? Would photosynthesis and respiration be able to proceed without enzymes? Why or why not? Where are chlorophyll molecules found? What happens when a compound is oxidized? Reduced? Which form contains more energy? What occurs during chemiosmosis? Where does it occur? What metabolic pathways are involved in cellular respiration? Where do they occur?

Process Skills in Science

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