metabolic processes 12

Organisms with Glucose as Their Primary Energy Source

Organisms with Glucose as Their Primary Energy Source

all with the exception of chemoautotrophs

Chemoautotrophs

archaea bacteria, live in extreme conditions (volcanoes, hot springs). they get energy from inorganic compounds like iron and sulphur.

What Organisms do with Glucose

through a series of enzyme controlled reactions, organisms break covalent bonds in glucose and rearrange them into new and more stable configurations. the greater stability of the covalent bonds in the products results in the release of free energy (exergonic process).

Cellular Respiration Overall Reaction

summary of the process. shows us the initial reactants and final products, giving no information about the step by step changes in between.

Overall Goals of Respiration

1. to break the bonds between the 6 carbon atoms of glucose, resulting in 6 carbon dioxide molecules.

2. to move hydrogen atoms from glucose to oxygen, forming 6 water molecules.

3. to trap as much of the free energy released in the process as possible in the form of ATP (adenosine triphosphate). overall: production of energy in the form of ATP molecules

Activation Energy for Glucose

if glucose didn't need energy to react, sugar would react whenever exposed to oxygen or the air and we would be unable to harness the energy. we use enzymes for activation energy.

Energy Produced in Cellular Respiration

energy is produced in the form of light and heat. in cells, around 34% of that energy is trapped so that it can be used by the cell later for specific processes. it traps energy in ATP.

Cellular respiration takes place in _____ stages and _____ places in the cell

four, three

Ways ATP is Made in Respiration

substrate-level phosphorylation and oxidative phosphorylation

Substrate-Level Phosphorylation

ATP is formed directly in an enzyme-catalyzed reaction. for each glucose molecule, four ATP are made this way, two in glycolysis and two in kreb's cycle. ADP + energy + phosphate -> ATP

Oxidative Phosphorylation

a mechanism forming ATP indirectly through a series of enzyme-catalyzed reactions involving oxygen as the final electron acceptor. two chemicals are made in this process: NAD⁺ and FAD. NADH and FADH₂ basically carry energy to the electron transport chain where they can be used to make ATP.

NAD⁺ Made in Oxidative Phosphorylation

nicotinamide adenine dinucleotide NAD⁺ + 2e⁻ + H⁺ -> NADH two are made in glycolysis, two in pyruvate oxidation, and six in the kreb's cycle.

FAD Made in Oxidative Phosphorylation

flavin adenine dinucleotide FAD + 2H -> FADH₂ two are made in the kreb's cycle.

Four Stages to Cellular Respiration

1. glycolysis

2. pyruvate oxidation

3. the kreb's cycle

4. electron transport chain and chemiosmosis

Glycolysis

starting with glucose (a six-carbon sugar), it produces two three-carbon pyruvate molecules. it occurs in the cytoplasm of the cell. glucose -> 2 pyruvate + 2 ATP + 2 NADH

Pyruvate Oxidation

the two pyruvate molecules formed in glycolysis are transported into the matrix of the mitochondria. the remaining product is a two-carbon acetyl group which attaches to coenzyme A to produce acetyl-CoA. 2 pyruvate -> 2 acetyl-CoA + 2 NADH + 2 CO₂

Acetyl-CoA

all molecules (carbohydrates, lipids, and proteins) that are used for energy are converted into this. it can be used to make fat or ATP. if the body needs energy, it goes into the kreb's cycle and makes ATP. if it doesn't, it goes on to produce lipids.

The Kreb's Cycle

it begins when acetyl-CoA reacts with oxaloacetate to produce citrate. the two carbon atoms introduced by acetyl-CoA are removed as two CO₂. the end product is oxaloacetate, which is used to start the reaction again. it occurs in the mitochondrial matrix. 2 acetyl-CoA -> 4CO₂ + 2ATP + 2FADH₂ + 6NADH by the end of the kreb's cycle, the original six-carbon glucose molecule has been turned into six low energy CO₂ molecules.

Electron Transport Chain and Chemiosmosis

the electron transport chain separates the protons from electrons in hydrogen from NADH or FADH₂. it transports the electrons through a series of reactions that release the free energy used to pump the H⁺ into the mitochondrial intermembrane space, creating an electrochemical gradient that is a source of free energy. in chemiosmosis, the H⁺ move through the complexes embedded in the inner membrane, releasing free energy that is used to make ATP.

ATP Made From NADH in the Electron Transport Chain and Chemiosmosis

each NADH makes three ATP except one that is made in glycolysis. they cannot move through the inner membrane and into the matrix. as a result, these NADH transfer their electrons through the membrane to FAD to make FADH₂. each FADH₂ makes two ATP.

Role of Oxygen in the Electron Transport Chain

it is needed to keep electrons flowing through the electron transport chain because it is the final acceptor for electrons that pass through the chain. if oxygen is not available, the kreb's cycle, electron transport, and chemiosmosis come to a halt.

Two Major Controls of Respiration

1. the third reaction in glycolysis

2. a high concentration of NADH

The Third Reaction in Glycolysis Controlling Respiration

the reaction is catalyzed by the enzyme phosphofructokinase. ATP inhibits phosphofructokinase, while ADP makes it active. therefore, less ATP is produced when ATP levels are high and ADP levels are low, and vice versa.

A High Concentration of NADH Controlling Respiration

a high concentration means that the electron transport chain is full of electrons and ATP levels are high. then NADH inhibits pyruvate decarboxylase and reduces the amount of acetyl-CoA that is fed into the kreb's cycle, restricting the amount of NADH made.

How Organisms Get Energy Without Carbohydrates

carbohydrates are the first nutrients most organisms break down for energy. if carbohydrates aren't available, they may need to use other nutrients for energy, such as proteins or lipids.

Protein Catabolism

normally, proteins are digested into individual amino acids, which are absorbed and used to make the cell's protein. if the protein is needed for energy then the amino groups are removed from the amino acids in a process called deamination. the amino group is converted into ammonia (NH₃), a waste product excreted in urine. other chemical reactions convert the remaining amino acids into various compounds used in glycolysis or the kreb's cycle. where it enters the cycle depends on the amino acid. once it enters, it goes on to produce ATP.

Lipid Catabolism

first, triglycerides are broken down into glycerol and fatty acids. the glycerol is converted into glucose and then goes through glycolysis to produce energy. fatty acids go through β-oxidation in the matrix of the mitochondria. acetyl-carbon groups are removed from both sides of the fatty acid and are combined with coenzyme A to form acetyl-CoA, which enters the kreb's cycle. one 12-carbon fatty acid molecule = 92 ATP. two 6-carbon glucose molecules = 72 ATP.

β-Oxidation

the sequential removal of acetyl groups in the catabolism of fatty acids

Anaerobic Respiration

respiration occurring without oxygen. only glycolysis occurs. in glycolysis, if oxygen isn't present, then NADH can't be oxidized back into NAD⁺ and there is only a limited amount of NAD⁺ in a cell. as a result, cells use fermentation.

Fermentation

a process in which the hydrogen atoms of NADH are transferred to organic compounds other than the electron transport chain.

Two Types of Fermentation

ethanol fermentation and lactic acid fermentation

Ethanol Fermentation

fermentation occurring in yeast in which NADH passes its hydrogen atoms to acetaldehyde, generating CO₂, ethanol, and NAD⁺ (can be recycled and glycolysis continues). only two ATP are made. used in making bread, pastries, wine, beer, etc.

Lactic Acid Fermentation

during strenuous exercise, muscle cells break down glucose faster than oxygen can be supplied. as a result, NADH transfers its hydrogen atoms to pyruvate, regenerating NAD⁺ and lactic acid. lactic acid in muscles causes stiffness, soreness, and fatigue. it's transported through blood from muscles to the liver. when exercise stops, lactic acid is oxidized back to pyruvate which goes through aerobic respiration (why you pant after strenuous exercise).

Organisms that Undergo Photosynthesis

plants, algae, some protists, and some cyanobacteria (blue-green algae)

Chlorophyll

organisms that undergo photosynthesis contain this. a green pigment that absorbs light energy and begins photosynthesis. it absorbs light in the blue, violet, and red regions of the spectrum and reflects those in the green region. as a result, most plants look green.

Membrane of the Thylakoid Sac

electrons in the porphyrin ring absorb light energy and begin the reaction. the hydrocarbon tail anchors the chlorophyll into the membrane of the thylakoid.

Photosynthesis happens partly in the ____________ and within the ______________

stroma, thylakoid

Photosynthesis Overall Reaction

6CO₂ + 6H₂O + light energy -> C₆H₁₂O₆ + 6O₂

Overall Goal of Photosynthesis

to produce glucose

Reverse Process of Cellular Respiration

photosynthesis

Three Stages to Photosynthesis

1. capturing light energy

2. make ATP and NADPH (nicotinamide adenine dinucleotide phosphate)

3. the calvin cycle (making sugar out of CO₂, uses the ATP and NADPH from stage 2)

Two Processes of Photosynthesis

the light reactions (stage 1 and 2) and carbon fixation (stage 3)

Light Reactions Overview

occurs in the thylakoids. overall goal is to transfer light energy to ATP and NADPH which will be used in carbon fixation. begins with a red photon striking photosystem II. the excited electron travels down an ETC, resulting in H⁺ being pumped into the thylakoid sac. next, a blue photon excites an electron in photosystem I. it passes down another ETC, resulting in the production of NADPH. finally, H⁺ is pumped through the ATP synthase, causing ATP to be made.

Red Photon Average Wavelength

680

Blue Photon Average Wavelength

700

Light Reactions at Photosystem II Details

a red photon of light strikes photosystem II and excites an electron. the electron is transferred to an electron carrier called plastoquinone (PQ) and then to an ETC similar to that in cellular respiration. this happens twice, causing two electrons to go through the chain. a water molecule splits into oxygen, hydrogen ions, and electrons. the two electrons are used to replace the missing ones in photosystem II. oxygen leaves as a byproduct and the electrons of PQ cause hydrogen to get pumped in by the cytochrome complex.

Light Reactions at Photosystem I Details

after the hydrogen is pumped through the cytochrome complex, the electrons get passed on to photosystem I, replacing the ones that were knocked out by blue photons of light. the electrons from photosystem I travel down an ETC to NADP reductase enzyme. NADP reductase uses the two electrons and two hydrogens to make NADPH. the H⁺ move through ATP synthase causing ATP to be created.

Calvin Cycle (Carbon Fixation or Dark Reaction)

doesn't use any photons. occurs in the stroma of chloroplasts. the reaction converts carbon dioxide into carbohydrate molecules. there are three phases: carbon fixation, reduction reactions, and RuBP regeneration.

Carbon Fixation

CO₂ is added to ribolose biphosphate (RuBP). this quickly splits into two 3-carbon molecules. in order to allow the calvin cycle to continue, it occurs in multiples of three, so three CO₂ are added to three molecules of RuBP. by occurring in multiples of three, RuBP molecules are left at the end of the reaction so that it can continue.

Reduction Reactions

ATP and NADPH are used to make G3P (glyceraldehyde 3-phosphate). six G3P molecules are made and only one leaves. G3P can easily be turned into a sugar molecule.

RuBP Regeneration

in a series of enzyme catalyzed reactions, the remaining five molecules of G3P are rearranged to make three molecules of RuBP.

Glucose Produced From Photosynthesis

it may be made from G3P by a series of enzyme-catalyzed reactions. when more is produced than immediately required, enzymes turn it into starch so that it can be stored.

Mitochondria Diagram (Site of Cellular Respiration)

intermembrane space between inner and outer membrane.

Chloroplast Diagram (Site of Photosynthesis)

Structural Comparisons of Mitochondria and Chloroplasts

both have a double membrane. both have the electron transport chain and chemiosmosis. mitochondria has a folded innersac (cristae), enzyme rich. the innermembrane is the site of respiration pathways (kreb's). chloroplasts have a highly organized membrane-bound sacs arranged as thylakoids in granums, enzyme rich. innermembrane and intermembrane are the site of calvin cycle.

Overview of Metabolic Process in Mitochondria and Chloroplasts

mitochondria: H⁺ from the matrix into the intermembrane. ATP synthesis occurring in the matrix. chloroplasts: H⁺ are pumped from the stroma into the thylakoid lumin. ATP synthesis occurring in the stroma.

Comparison of Reactants and Products in Mitochondria and Chloroplasts

mitochondria starts with glucose and oxygen and ends with carbon dioxide, water, and ATP energy. chloroplasts are opposite, except it uses light energy instead of ATP.

Comparison of Pathways in Mitochondria and Chloroplasts

mitochondria: glucose is broken down into two 3-carbon sugars. further broken down into CO₂ with ATP being produced and H₂O (using up O₂) released. NAD⁺ -> NADH in kreb's cycle. chloroplasts: sunlight is used to produce ATP and NADPH (used to build CO₂ up into 3-carbon intermediate - converted into carbohydrate). NADP⁺ -> NADPH in calvin cycle.