C1.2 Cell Respiration

ATP

Adenosine triphosphate, a nucleotide consisting of 3 phosphate grps, a ribose sugar, and adenine (a nitrogenous base)

What properties make ATP suitable for use a form of energy currency?

-Chemically stable, won’t break down in cell’s neutral pH

-Water soluble, so ATP diffuses freely

-Can’t diffuse out of phospholipid bilayer b/c hydrophilic

-Releases energy when third phosphate is removed

-Easily regenerated by adding a phosphate grp to ADP (Adenosine diphosphate)

Cellular processed requiring ATP

Active transport across membranes (Na+ and K+ pump) synthesis of macromolecules or anabolism, movement of whole cell, & movement of cell components

Movement of whole cell vs. cell components

Whole cell movement via cilia or flagella, cell component movements include chromosomes moving apart during cell replication via spindle finders

Examples of macromolecule synthesis

proteins, DNA, glycogen, and active transport can also include endo and exocytosis

Conversion of ATP to ADP and of ADP to ATP

ATP and ADP are convertible.

ATP is converted to ADP by a hydrolysis reaction, which splits off a phosphate group. Releases energy

ADP is converted to ATP with a condensation reaction, which adds a phosphate grp, or phosphorylation. Requires energy

Energy production from conversion of ATP to ADP

The energy released from this conversion and removal of 3rd phosphate grp is sufficient for many tasks in the cell

Phosphorylation

chemical process of adding a phosphate group to an organic compound conversion of ADP to ATP is a phosphorylation reaction

Cell respiration defined

a system for producing ATP within the cell using energy released from carbon compounds. Happens inside all cell. Glucose and fatty acids are the primary substrates, but other carbon compounds like amino acids can also be used

Ventilation and Gas Exchange defined

ventilation is air moving in and out of lungs, and gas exchange is swapping out 1 gas for another at a surface where cell/organism meets environment

both are different from cell respiration

Anaerobic cell respiration, substrates used, where it occurs, yield of ATP, and waste products

glucose = lactate +energy

doesn’t use O2, glucose and other sugars are substrates, small yield of 2 ATP, waste product of lactate (lactic acid), and only occurs in cytoplasm

Aerobic cell respiration

glucose + O2 = CO2 + H2O + Energy

uses O2, substrates are sugars or lipids, large yield ATP, CO2 and H2O as waste products, and occurs in cytoplasm and mitochondria

Respirometer

device that measures the rate of cell respiration, or O2 uptake/ CO2 release per unit

LEO the lion says GER

Losing electrons, removing hydrogen, and gaining O2 is oxidation

Gaining electrons, gaining hydrogen, and losing O2 is reduction

Dehydrogenation

In respiration, removing pairs of hydrogen atoms from substrates, oxidizing substrates. Hydrogen atoms consisting of 1 H+ and 1 e- are given to a hydrogen carrier, which becomes reduced

Hydrogen Carriers

Accept hydrogen atoms, most common is NAD.

NAD accepts 2 hydrogen atoms, to become NADH.

When oxidized, NAD ⁺ accepts 2 hydrogen atoms to become (NADH⁺) +H⁺

What is a redox reaction?

a reaction where 1 substance is oxidized, and another is reduced.

where does glycolysis occur, and what substrate does it need?

Glycolysis occurs in the cytoplasm of all cells, and is the 1st part of aerobic and anerobic respiration if glucose is the substrate. No O2 used!

Steps of glycolysis

Phosphorylation, lysis, oxidation, and atp formation.

Each step is glycolysis is catalyzed by a different enzyme

Phosphorylation

glucose is phosphorylated twice to form hexose biphosphate. This raises energy level of molecule, making it less stable and more reaction. 2 ATP molecules are used to phosphorylate 1 glucose

Lysis

Hexose biphosphate is split to form 2 triose phosphate molecules. Lysis is splitting molecules into smaller ones

Oxidation

Each triose phosphate molecule is oxidated. 2 hydrogen atoms are removed from each triose phosphate, and given to NAD carriers, forming NADH. Total of 2 NADH formed

ATP formation

oxidation reaction are usually exothermic, and energy released from oxidizing each triose phosphate molecule is enough to convert 2 ADP to ATP. Since there are 2 triose phosphate molecules, 4 ATP formed total

Final Product of glycolysis

after each triose phosphate molecule is oxidized, and the energy is used form 2 ATP, 2 pyruvate molecules formed

Glycolysis summary

1 glucose made into 2 pyruvates, 2 NAD reduced to 2 NADH, 2 ATP used during phosphorylation, 4 ATP made, net yield of 2 ATP

1 glucose makes 2 ATP, with no oxygen, so production is rapid!

What is needed for glycolysis to continue?

glycolysis (and anerobic cell respiration) needs a supply of ADP and NAD. ADP is regenerated in ATP is used

How is NAD regenerated in human cells?

NAD is regenerated by transferring hydrogen atoms from NADH to pyruvate, which oxidizes NADH back to NAD, and reduces pyruvate to lactate

Lactate as a waste product

lactate lowers pH of cytoplasm and blood, so anerobic respiration only used for a short time so blood pH doesn’t get too low

How do yeast respire and how to do they regenerate NAD?

yeast respire using glycolysis too, same metabolic pathway, but yeast regenerate NAD by converting pyruvate to ethanol

How is pyruvate converted to ethanol?

pyruvate is converted by decarboxylating, or removing CO2, which converts it to ethanal. Ethanal then is reduced to ethanol by transferring 2 hydrogen atoms from NADH, forming NAD

Waste products of anaerobic respiration in humans vs yeast

humans produce lactate, yeast produces CO2 and ethanol. Brewing and fuel use fermentation of yeast and ethanol production, baking uses CO2 produced by yeast

What is the link reaction?

the conversion of pyruvate to acetyl groups to be used in the krebs cycle, so the pyruvate can be oxidized further and release more energy- only occurs when oxygen is available

How is pyruvate converted to an acetyl group?

decarboxylated, where CO2 is removed, and then oxidated, where a pair of hydrogen atoms is removed and given to NAD, forming reduced NAD.

What is acetyl CoA?

acetyl grp formed from carboxylation and oxidation is attached to Coenzyme A, or CoA, to from acetyl-CoA and be fed into Krebs cycle

How are fatty acids used as a substrate in aerobic respiration?

Fatty acids can be a substrate for aerobic respiration when 2 carbon fragments are removed from hydrocarbon chain of fatty acids, and these fragments are made into a acetyl group, attached to CoA, and fed into krebs cycle

Where does link reaction take place?

link reaction takes place in the matrix of mitochondria- mitochondria membranes have transporter proteins for absorbing pyruvate and fatty acids from surrounding cytoplasm

Where does the krebs cycle occur?

the krebs cycle occurs in the matrix of the mitochondria

How is acetyl-CoA fed into the krebs cycle?

acetyl groups are fed into the Krebs cycle by transferring the acetyl group from CoA, and to oxaloacetate (4C). This produces citrate (6C). Citrate is then converted back to oxaloacetate via a series of intermediates

What reactions occur during the krebs cycle?

8-enzyme catalyzed reactions in cycle, including the initial reaction of converting oxaloacetate to citrate. Includes 2 decarboxylation reaction, 4 oxidation reactions, and 1 substrate-level phosphorylation reaction forming ATP. Oxaloacetate is regenerated

what is a substrate level-phosphorylation?

when ATP is formed by transferring a phosphate group from a high energy compound to ADP

decarboxylation in krebs cycle

CO2 is removed in 2 decarboxylation reactions, and CO2 is excreted as a waste product

Oxidation reactions in krebs cycle

hydrogen is removed in 4 reactions, and hydrogen atoms each have e^-, so its an oxidation and dehydrogenation reaction. 3 of oxidation reactions, hydrogen is accepted by NAD, but in 1 oxidation reaction, FAD accepts hydrogen. Carriers become reduced. Oxidation reactions release energy, which are given to carriers

ATP production in krebs cycle?

ATP is produced in one of the reactions, and is a substrate-level phosphorylation

Where is the ETC?

The electron transport chain is a series of carriers in the inner mitochondrial membrane, which in folded to form cristae- the electron carriers are a series of protein complexes

What happens along the ETC?

reduced NAD passes 2 electrons in the form of hydrogen atoms to the first carrier. The electrons come from NADH formed from glycolysis, the link reaction, and Krebs cycle. Transferring electrons regenerates NAD to be used in respiration

What happens as electrons are passed along the chain of carriers?

as electrons are passed along the chain of carriers, they release energy. The electron carriers use this energy to pump protons from the matrix of the mitochondria to the intermembrane space- they use energy of electron flow to act as proton pumps

What happens after protons are pumped to intermembrane space?

a proton gradient happens across inner mitochondrial membrane, with intermembrane space having a high concentration, and matrix low proton concentration. This concentration gradient gives membrane a potential voltage

What is chemiosmosis?

the coupling of energy releasing process of electron transport to energy-releasing process of ATP production! Proton concentration gradient stores potential energy, which is used by the enzyme, ATP synthase to make ATP via phosphorylation of ADP.

How does ATP synthase allow protons to move down concentration gradient?

ATP synthase has a rotor that can spin on an axis, and a non-rotating part- rotor is embedded in inner mitochondrial membrane. Allows protons (H+) to diffuse down concentration gradient and into matrix, by allowing protons to bind to rotor, and when rotor is rotated, protons are released into matrix

How does the rotor of ATP synthase rotate?

Protons diffuse from high to low concentration, they release sufficient energy, causing rotation, so protons that bind to synthase are released via rotation. Rotation transforms potential energy of gradient into kinetic energy

How does ATP synthase form ATP?

rotor has a central stalk that projects out into matrix, with 3 globs of ATP synthase around it. Each glob has an active site where ADP is phosphorylated into ATP. After ADP and phosphate grp bind to active site, the rotation of synthase causes conformational changes, forcing ADP and phosphate together to form ATP

How does ATP formation and the proton gradient relate to each other?

ATP synthase allows protons to bind to it, and diffuse from intermembrane space to matrix, down the concentration gradient via rotation. Moving down the concentration gradient releases energy, which powers the rotation. This rotation from protons is also used to cause conformational changes to active sites of synthase, forcing ADP and phosphate together to form ATP

How much ATP does chemiosmosis make?

Most of the ATP from aerobic respiration is formed here. Around 28. In total, around 30-32 ATP made total aerobically. 2 from glycolysis, and 2 during Krebs cycle from each acetyl grp

How much ATP does each rotation make?

3 molecules of ATP are produced from 9 protons of ATP synthase. So 3 protons needed to make 1 ATP via chemiosmosis

Why is O2 the terminal electron acceptor?

electrons pass down electron transport chain from carrier to carrier, losing energy, and then electrons are passed to O2. This happens on inner mitochondrial membrane using O2 dissolved in matrix. O2 also reacts with hydrogen protons in matrix to from water (H2O)

How does oxygen help with the concentration gradient?

O2 reactions with hydrogen protons in matrix, lowering proton concentration in matrix, helping with chemiosmosis

Why is O2 vital?

Acts as terminal electron acceptor in electron transport chain, so reduced NAD is oxidized back into NAD. Without O2, no supply of NAD, and link reaction and krebs cycle no longer occur. Only glycolysis can continue, because it can regenerate NAD by forming lactate, and glycolysis occurs in cytoplasm, not mitochondria.

Lipids vs carbo C:H:O ratio

lipids have 1:2:0.065 ratio, carb has 1:2:1. Lipids have less oxidized, more energy yield

Lipids vs. carbs energy released

lipids release more energy per gram because less oxygen, and more oxidizable carbon and hydrogen.

Lipids vs carbs metabolic pathways if O2 is available

beta oxidation makes lipids into acetyl groups to go into krebs cycle and chemiosmosis. Carbs use glycolysis + link reaction to make acetyl grps for krebs cycle and chemiosmosis

Lipids vs. carbs types of respiration

lipids only aerobic, carbs can do aerobic and anaerobic. Anaerobic and glycolysis only occur with carbs