cell respiration & metabolism

metabolism

- All of the reactions in the body that involve energy transformation

- complete set of chemical reactions that occur in living cells

- basis of life, allowing cells to grow and reproduce, maintain their structures, and respond to their environments

metabolic pathways

one chemical is transformed into another by a sequence of enzymes

enzymes

allow the regulation of metabolic pathways in response to changes in the cell's environment or signals from other cells

What is catabolism?

The process that releases energy by breaking down larger organic molecules into smaller molecules.

What are the primary sources of energy for the synthesis of ATP?

Reactions that break down glucose, fatty acids, and amino acids.

What happens to some of the chemical-bond energy in glucose during catabolism?

Some of it is transferred to the chemical bond energy in ATP, but some is lost as heat.

anabolism

- require the input of energy and include the synthesis of large energy-storage molecules, including glycogen, fat, and protein

What does aerobic cell respiration require?

Oxygen

What is the preferred method of pyruvate breakdown from glycolysis?

Aerobic respiration

Where does pyruvate enter to be fully oxidized?

Mitochondrion

What is the main product of aerobic cell respiration?

ATP (Adenosine Triphosphate)

What type of phosphorylation occurs during aerobic respiration?

Substrate-level phosphorylation, NADH

What type of reactions are involved in energy transfer during aerobic respiration?

Oxidation-reduction reactions

What happens to a molecule during oxidation?

It loses electrons

What is the final electron acceptor in aerobic respiration?

Oxygen

What is produced when glucose is completely broken down in an animal cell?

Carbon dioxide and water

definition for aerobic cell respiration

- cell receives the oxygen and releases carbon dioxide

- converts molecules such as glucose or fatty acid to carbon dioxide and water (transferring some of the energy to ATP)

What is glycolysis?

The breakdown of glucose.

What is glucose?

-A six-carbon sugar

- C6H12O6

What is produced from the conversion of glucose in glycolysis?

Two molecules of pyruvic acid (or pyruvate).

what is in each pyruvic acid molecule

Three carbons, three oxygen, four hydrogen

How many hydrogen atoms are removed during glycolysis?

Four hydrogen atoms.

- Two in cytoplasm is dissolved but the other 2 are reduced by NAD (coenzyme) to create 2 NADH and 2 ATP

What is the role of hydrogen atoms in glycolysis?

They are used to reduce a molecule of NAD.

How many electrons does each pair of hydrogen atoms donate to NAD?

Two electrons.

what is the formula for glycolysis

Glucose + 2NAD+2 ADP+ 2Pi= 2pyruvic acid +2 NADH+ 2ATP

what is the formula for pyruvic acid

C3H4O3

what happens if the cell receives sufficient oxygen supply

then pyruvic acid is able to enter mitochondria via Krebs cycle for production of ATP

what is NAD

Nicotinamide adenine dinucleotide (NAD)

- important coenzyme found in cells

- carrier of electrons in the transfer of reduction potential

- NADH is the reduced form of NAD+

-NAD+ is the oxidized form of NADH

formula for lactic acid

C3H6O3

What happens to pyruvic acid during anaerobic respiration?

It stays in the cytoplasm and is converted into lactic acid.

What occurs to NADH during anaerobic respiration when oxygen is not available?

NADH is oxidized in the cytoplasm by donating its electrons to pyruvic acid.

What is produced when two hydrogen atoms are added to pyruvic acid?

Lactic acid.

What is the metabolic pathway that converts glucose to lactic acid called?

Anaerobic respiration.

lactic acid fermentation

In skeletal muscles, the waste product is lactic acid

alcoholic or ethanol fermentation

In yeast, the waste products are ethanol and carbon dioxide

what is lactic acid important when it comes to myocardial infarction

can be measured in cardiac infarction which does not receive sufficient oxygen due to atherosclerosis which leads to cell death at the heart

What is fermentation?

Fermentation is a process of energy production in a cell under anaerobic conditions (with no oxygen required).

What is a more strict definition of fermentation?

Fermentation is respiration under anaerobic conditions with no external electron acceptor.

What do yeast cells prefer for energy production?

Yeast cells greatly prefer fermentation as long as sugars are readily available for consumption.

What is the common substrate for fermentation?

Sugars are the common substrate for fermentation.

What are typical products of fermentation?

Typical products of fermentation include ethanol, lactic acid, and hydrogen.

What are some exotic compounds that can be produced by fermentation?

Exotic compounds produced by fermentation can include butyric acid and acetone.

What is ischemia?

Inadequate blood flow to an organ, such that the rate of oxygen delivery is insufficient to maintain aerobic respiration.

What can cause myocardial ischemia?

Myocardial ischemia may occur if the coronary blood flow is occluded by atherosclerosis, a blood clot, or by an artery spasm.

What are the symptoms of myocardial ischemia?

Severe pain in the chest and left arm area.

What is associated with pain during myocardial ischemia?

Increased blood levels of lactic acid produced by the ischemic heart muscle.

What is glycogenesis?

The process by which the liver collects extra glucose from the portal vein and converts it into glycogen.

Which organs primarily store carbohydrates in the form of glycogen?

The liver, skeletal muscles, and heart.

What is the first step in glycogenesis involving glucose?

Glucose is converted to glucose 6-phosphate by utilizing the terminal phosphate group of ATP.

What is glucose 6-phosphate converted into during glycogenesis?

Its isomer, glucose 1-phosphate.

What role does glycogen synthase play in glycogenesis?

It removes phosphate groups as it polymerizes glucose to form glycogen.

glycogenolysis

conversion of glycogen to glucose 6-phosphate by enzyme glycogen phosphorylase

What is glycogenolysis in the liver?

The process by which glycogen stored in the liver is converted to glucose-1-phosphate and then into glucose-6-phosphate.

What can glucose-6-phosphate be used for in most tissues?

It can be respired for energy through glycolysis or used to resynthesize glycogen.

What unique function does glucose-6-phosphate serve in the liver?

It can be used to produce free glucose for secretion into the blood.

What enzyme in the liver removes the phosphate from glucose-6-phosphate?

Glucose 6-phosphatase.

How does the liver contribute to blood glucose levels?

By secreting glucose into the blood after converting glycogen.

What is the role of liver glycogen?

It can supply blood glucose for use by other organs.

What is glycogenolysis in skeletal muscle?

Glycogenolysis in skeletal muscle is the process by which skeletal muscles break down glycogen to generate glucose-6-phosphate for glycolytic needs.

Can skeletal muscles secrete glucose into the blood?

No, skeletal muscles cannot secrete glucose into the blood because they lack the ability to remove the phosphate group from glucose-6-phosphate.

What hormone is released from the pancreas in response to low blood glucose?

Glucagon

What hormone is released from the adrenal glands in response to stress?

Epinephrine

What is the role of glucagon and epinephrine in glycogenolysis?

Both hormones stimulate glycogen phosphorylase to begin glycogenolysis and inhibit glycogen synthetase to stop glycogenesis.

Gluconeogenesis

- Liver uptakes lactic acid, fatty acid, amino acid, and glycerol to convert into neoglucose

What is the Cori cycle?

The Cori cycle is the two-way traffic of lactic acid and glucose between skeletal muscles and the liver.

What happens to lactic acid produced by skeletal muscles during exercise?

Some of the lactic acid is transformed into blood glucose through gluconeogenesis in the liver.

How does the new glucose produced in the liver serve the body during and after exercise?

The new glucose can serve as an energy source during exercise and help replenish depleted muscle glycogen after exercise.

How long does it take for depleted skeletal muscle glycogen to be stored through the Cori cycle?

It can be stored within 48 hours.

krebs cycle

removes carbon dioxide molecules from glucose in a stepwise fashion to release energy

What is the end goal of the Krebs cycle?

The end goal is to convert citric acid to oxaloacetic acid.

What are the products of the Krebs cycle in terms of carbon and oxygen?

The Krebs cycle eliminates two carbons and four oxygens as two CO2 molecules.

What is removed during the Krebs cycle?

Hydrogens are removed during the Krebs cycle.

mitochondria

-smooth outer membrane

-cristae (formed by outer & inner membrane)

-two membranes create two compartments, namely the intermembrane space (the compartment between the membranes), and the matrix (the very interior of the mitochondria)

What is the electron transport system?

A series of molecules that serve as an electron-transport system during aerobic respiration.

What are the main components of the electron transport chain?

Complexes I, II, III, and IV, plus coenzyme Q and cytochrome c.

Where does the electron transport chain occur?

In the membranes of cristae.

What do the electron acceptors in the electron transport chain do?

They accept high energy electrons from NADH and FADH2.

What are the coenzymes involved in the electron transport chain?

FAD and NAD

What do FAD and NAD do in the electron transport chain?

They reduce electrons and hydrogen ions in the cytoplasm of the cell.

Where do FAD and NAD transport hydrogen ions and electrons?

Through the matrix part of the mitochondria.

What happens to the electrons released by FAD and NAD?

They pass through the cristae membrane.

What occurs to hydrogen ions after they are released by the coenzymes?

They move from the matrix to the outer compartment of the mitochondria.

What is the term for the increase of hydrogen ions in the outer compartment of the mitochondria?

Chemiosmosis (osmotic pressure is higher)

What happens to hydrogen ions when they move back into the matrix?

They pass through ATP synthase channels.

What two products are formed as a result of the electron transport chain?

H2O and ATP

What combines with oxygen molecules to form water in the electron transport chain?

Hydrogen ions

What combines with inorganic phosphate (P) to create ATP?

ADP

chemiosmosis

- protons diffuse from the outer compartment (high concentration) through ATP Synthase in the Cristae to the Matrix (low H+ Concentration)

- energy in the protons as they pass is used by ATP synthase to create 32 ATP

What is lipolysis?

The breakdown of fat.

What enzyme is responsible for hydrolyzing triglycerides during lipolysis?

Lipase.

What are the products of triglyceride hydrolysis in lipolysis?

Glycerol and free fatty acids.

What role do glycerol and free fatty acids play after lipolysis?

They serve as blood-borne energy carriers for aerobic respiration.

What is the structure of most fatty acids?

A long hydrocarbon chain with a carboxyl group (COOH) at one end.

What is the process called that removes two-carbon acetic acid molecules from fatty acid chains?

Beta-oxidation.

When is the amount of brown fat greatest in the body?

At the time of birth.

What is the major site for thermogenesis in newborns?

Brown fat.

Where is brown fat located in the body?

Around the kidneys and adrenal glands, and around the blood vessels of the chest and neck.

What unique protein does brown fat produce?

A unique uncoupling protein.

What effect does the uncoupling protein have on H+ in brown fat?

It causes H+ to leak out of the inner mitochondrial membrane.

What is the consequence of lower ATP concentrations in brown fat?

The electron-transport system becomes more active and generates more heat from the respiration of fatty acids.