Cellular Metabolism Study Guide

Front 1

Define energy.

Back 1

Energy is the ability to do work.
Cells capture, store and transport free energy in a chemical form.

Front 2

What do cells use to produce energy?

Back 2

Cells use oxygen and the breakdown products of the foods we eat to produce energy.

Front 3

What is the major carrier of chemical energy in all cells?

Back 3

Adenosine Triphosphate (ATP) is the major carrier of chemical energy in all cells.
ATP carries energy between metabolic pathways by serving as a shared intermediate that couples endergonic and exergonic reactions.

Front 4

What do cells need energy for?

Back 4

Cells need energy for (1)muscle contraction, (2) transport of ions and molecules, and (3)synthesis of enzymes, hormones and other macromolecules

Front 5

What is energy metabolism?

Back 5

Energy metabolism is the processes by which fats, proteins, and carbohydrates are converted into energy or complex energy sources in the cell.

Front 6

What are the two phases of metabolism? Define each.

Back 6

Catabolism is the breaking down of stored nutrients and body tissues to create energy. Anabolism is a constructive process in which more complex molecules are formed from simpler ones.

Front 7

What are the three fuels used for metabolism?

Back 7

The three fuels used for metabolism are fats, proteins, and carbohydrates.

Front 8

Define hydrolysis. What does it mean when a substance is hydrolyzed?

Back 8

Hydrolysis is a chemical reaction or process in which a chemical compound is broken down by reaction with water.

Front 9

Define oxidation and reduction.

Back 9

Oxidation describes the loss of electrons by a molecule, atom or ion. Examples: NADH --> NAD+
FADH --> FAD+

Reduction describes the gain of electrons by a molecule, atom or ion. Examples:
NAD+ --> NADH
FAD+ --> FADH

Front 10

What is the major carrier of chemical energy in all cells?

Back 10

ATP, the "energy currency" of the cell.

Front 11

What is ATP?

Back 11

Adenosine triphosphate: adenine, a nitrogenous base; ribose, a five-carbon sugar, and 3 phosphate groups, two of which are attached with high-energy bonds. ATP is the result of reduction of ADP. Cells need continuous ATP to function. Large amounts of energy are released when ATP is hydrolyzed to form ADP.

Front 12

What is ADP?

Back 12

ADP is adenosine diphosphate, the result of ATP hydrolysis (loses Pi). When phosphorylated, adding a high energy bond and third Pi forms ATP.

Front 13

Large amounts of energy are released when ___ is hydrolyzed to form ___.

Back 13

Large amounts of energy are release when ATP is hydrolyzed to form ADP.

Front 14

Formation of ATP involves the addition of a high energy bond to ADP through a process called ____.

Back 14

Oxidative phosphorylation.

Front 15

Compare and contrast aerobic and anaerobic metabolism.

Back 15

Aerobic metabolism produces energy without the use of oxygen. It occurs in the cytoplasm and uses glycolysis, the process whereby energy is liberated from glucose. This process is comparatively inefficient, yielding just 2 ATP molecules from each one molecule of glucose. When oxygen is present, pyruvate moves into the aerobic mitochondrial pathway. Aerobic metabolism occurs in the cell's mitochondria and involves the citric acid cycle and oxidative phosphorylation.

Front 16

The end product of anaerobic metabolism is ___.

Back 16

pyruvate

Front 17

The end product of aerobic metabolism is ___ and ___.

Back 17

CO2 and H2O

Front 18

Where in the cell does oxidative phosphorylation take place.

Back 18

In the mitochondria.

Front 19

Although many tissues and organ systems are able to use other forms of fuel, what organ and system relies almost exclusively on glucose as a fuel source?

Back 19

The brain and CNS.

Front 20

What organ regulates the entry of glucose into the blood?

Back 20

The liver.

Front 21

Excess glucose is stored in two forms. What are they?

Back 21

(1) excess glucose can be converted to fatty acids and stored in fat cells as triglycerides
(2) it can be stored in the liver and skeletal muscle as glycogen. Small amounts of glycogen are also stored in the skin and in some of the glandular tissues.

Front 22

What pathway is an anaerobic pathway?

Back 22

Glycolysis is an anaerobic pathway.

Front 23

What is glycolysis? Where in the cell does this process occur?

Back 23

Glycolysis is the process by which energy is liberated from glucose. It occurs in the cytosol of the cell. It is an important energy provider for cells that lack mitochondria, the cell organelle in which aerobic metabolism occurs. Glycolysis also provides energy in situations when delivery of oxygen to the cell is delayed or impaired.

(anaerobic glucose catabolism yielding 2 pyruvate and 2 ATP)

Front 24

Glycolysis involves a sequence of reactions that converts ____ to ____ with the concomitant production of ATP from ADP.

Back 24

glucose; pyruvate

Front 25

Important end products of glycolysis are _____ and ___ + __.

Back 25

Pyruvate; NADH; H+

Front 26

Under conditions of circulatory shock, pyruvate is converted to ____, which diffuses out of the cell into extracellular space. What happens when oxygen supply is restored? In what organ does this process occur?

Back 26

Under conditions of circulatory shock, pyruvate is converted to lactic acid. When oxygen supply is restored, lactic acid is reconverted back to pyruvate and used directly for energy or to synthesize glucose. Much of this process occurs in the liver, but a small amount can occur in other tissues.

Front 27

Where does glycolysis take place in the cell?

Back 27

Glycolysis takes place in the cytosol.

Front 28

What are the two phases of glycolysis? What is the ATP gain?

Back 28

The two phases of glycolysis are the preparatory phase and the payoff phase. The ATP gain in the preparatory phase is -2 ATP. The ATP gain in the payoff phase is +4 ATP. The net yield of glycolysis is 2 ATP.

Front 29

What are the first and last steps of the preparatory phase of glycolysis?

Back 29

Preparatory phase first step: glucose --> Kinase --> glucose 6 phosphate

Preparatory phase last step: fructose 1,6 bisphosphate --> aldolase --> 2 glyceraldehyde 3-phosphates

Front 30

What are the first and last steps of the payoff phase of glycolysis?

Back 30

Payoff phase first step: 2 glyceraldehyde 3-phosphates + 2 Pi's --> Dehydrogenase --> (NAD+ --> NADH + H) --> 2 1,3 bisphosphoglycerates.

Payoff phase last step: 2 phosphoenolpyruvate + 2 ADP --> kinase --> 2 pyruvate and 2 ATP

Front 31

What are two other names for the citric acid cycle?

Back 31

The tricarboxylic acid cycle and the Krebs cycle.

Front 32

In what cellular structure does the citric acid cycle occur?

Back 32

The citric acid cycle occurs in the mitochondrial matrix.

Front 33

Cellular respiration occurs in three major steps; what are they?

Back 33

(1) organic fuel molecules are oxidized to 2-carbon acetyl-coenzyme A (Acetyl-CoA production)
(2) Acetyl-CoA is fed into the citric acid cycle
(3) electron transfer and oxidative phosphorylation

Front 34

Define oxidative phosphorylation. Where does it occur in the cell?

Back 34

Oxidative phosphorylation is ATP synthesis driven by electron transfer to oxygen. It occurs in the mitochondria. It involves the addition of a high-energy phosphate bond to ADP in order to produce ATP.

Front 35

Pyruvate is oxidized to ____ and ___.

Back 35

Pyruvate is oxidized to Acetyl-CoA and CO2.

Front 36

The citric acid cycle oxidizes ____ to __ and __.

Back 36

The citric acid cycle oxidizes Acetyl-CoA to CO2 and H2O.

Front 37

What is the inner membrane and the outer membrane of mitochondria?

Back 37

The inner membrane of the mitochondria:
(1) forms infoldings called cristae which enclose the mitochondrial matrix
(2) Most of enzymes for TCA cycle, the beta-oxidation of fatty acids and for mitochondrial DNA synthesis are found in the matrix
(3) ATP synthase (enzyme complex that generates ATP from ADP) and the protein complexes of the electron transport chain are embedded in the inner membrane.

The outer membrane of the mitochondria is permeable to small ions (while the inner membrane is impermeable).

Front 38

Oxidative phosphorylation involves the reduction of ___ to ___ with electrons donated by ___ and ___.

Back 38

Oxidative phosphorylation involves the reduction of O2 to H2O with electrons donated by NADH and FADH2.

Front 39

What are cytochromes?

Back 39

Cytochromes are iron-containing electron transfer proteins in the mitochondrial inner membrane.

Front 40

How many complexes are involved in oxidative phosphorylation?

Back 40

4 complexes (I through IV):
Complex I: NADH to ubiquinone
Complex II: succinate to ubiquinone
Complex III: Ubiquinone to cytochrome c
Complex IV: cytochrome oxidase (reduction of O2)

Front 41

Define gluconeogenesis.

Back 41

Gluconeogenesis is the biosynthesis of glucose (glucose anabolism). Carbohydrates are made from non-carbohydrates.
Gluconeogenesis operates in an anti-parallel pathway from glycolysis.

Front 42

Cells constantly make glucose from precursors. What are these precursors?

Back 42

(1) Lactate
(2) Pyruvate
(3) Glycerol
(4) most amino acids

Front 43

What hormones stimulate gluconeogenesis?

Back 43

Gluconeogenesis is stimulated by:
(1) glucagon
(2) thyroid hormone
(3) glucocorticoid hormones, including cortisol, from the adrenal cortex.

Front 44

Gluconeogenesis has reactions that occur in which structures?

Back 44

both in the cytosol and in the mitochondria.

Front 45

How many ATP molecules are used in gluconeogenesis?

Back 45

4 ATP molecules are used.

Front 46

Where does glycogen synthesis occur?

Back 46

Glycogen synthesis occurs in all tissues but is most prominent in the liver and skeletal muscle.

Front 47

What is the role of the liver and skeletal muscle in glycogen synthesis?

Back 47

This liver is a reservoir of glucose, to be converted to blood glucose and transported to other tissues.
Skeletal muscle: broken down by glycolysis to provide ATP energy for muscle contraction.

Front 48

Seven of the 10 steps of gluconeogenesis are in the reverse of what pathway?

Back 48

Glycolysis.

Front 49

Glycogenolysis and glycogen synthesis are controlled by which hormones?

Back 49

(1)Glucagon (liver more responsive)
(2)epinephrine (stimulates glycogen breakdown in muscle)
(3)insulin

Front 50

Dietary fats are emulsified by ___.

Back 50

bile salts

Front 51

Describe the process of emulsification.

Back 51

Bile acids play their first critical role in lipid assimilation by promoting emulsification. As derivatives of cholesterol, bile acids have both hydrophilic and hydrophobic domains (i.e., they are amphipathic). On exposure to a large aggregate of triglyceride, the hydrophobic portions of bile acids intercalate into the lipid, with the hydrophilic domains remaining at the surface. Such coating with bile acids aids in breakdown of large aggregates or droplets into smaller and smaller droplets.

Front 52

What are lipases?

Back 52

Lipases are enzymes that break the TGs into 3 fatty acids and a glycerol molecule.

Front 53

Which hormones stimulate the activation of lipases and subsequent mobilization of fatty acids?

Back 53

(1)epinephrine
(2)glucocorticoid hormones
(3)growth hormones
(4)glucagon

Front 54

Define chylomicrons apolipoproteins.

Back 54

Chylomicrons are large lipoprotein aggregates that travel in blood and lymph to tissues.

Apolipoprotein: lipid-binding protein in blood; responsible for transport of lipids between organs.

Front 55

Fatty acids are oxidized for fuel or reesterified for storage. What does this mean?

Back 55

ATP is generated from oxidation of fatty acids in the pathway of beta-oxidation. In beta-oxidation pathway, fatty acyl group is oxidized to yield FAD, NADH, and acetyl CoA.

Front 56

Fatty acid biosynthesis starts with ____ and the end product is ___.

Back 56

Fatty acid biosynthesis starts with 3-carbon molecule malonate and the end product is palmitate (16 carbon FA).

Front 57

Fatty acid oxidation involves the breakdown of ___ to ___ and takes place in ___ (cell structure).

Back 57

Fatty acid oxidation involves the breakdown of fatty acids to Acetyl-CoA and takes place in the mitochondria.

Front 58

What are the three sources of at?

Back 58

(1)Dietary
(2)Stored in cells
(3)Synthesized

Front 59

What situation mobilizes TG?

Back 59

Low blood sugar.

Front 60

What hormones mobilize stored TG?

Back 60

Epinephrine and glucagon.

Front 61

What are the 3 enzymatic reactions that occur to transport fatty acids across the mitochondrial inner membrane?

Back 61

(1)Fatty acyl group transferred to carnitine
(2) Carnitine-fatty acyl complex transported across membrane
(3) Fatty acyl group transferred from carnitine to CoA in matrix

Front 62

In what organ does protein metabolism occur?

Back 62

Protein metabolism occurs mainly in the liver.

Front 63

What is the primary source of protein under normal conditions?

Back 63

The diet

Front 64

What is the source of protein under conditions of starvation?

Back 64

Cellular proteins are utilized in starvation

Front 65

What is deamination of amino acids?

Back 65

Deamination is the removal of amino groups. This occurs mainly by transamination, which means transfer of the amino group to some acceptor substance.

Removal of the a-amino group (NH3) from glutamate, needed for excretion. Transfer of alpha-amino group to alpha-ketoglutarate.

Front 66

What enzymes are responsible for deamination of amino acids?

Back 66

ALT -- alanine aminotransferase GPT -- glutamate pyruvate transaminase)

Front 67

What is glutamate?

Back 67

Glutamate is the principle excitatory neurotransmitter in the nervous system.

Front 68

What is glutamine?

Back 68

An amino acid whose functions include serving as an amino radical storehouse.

Front 69

Ammonia is converted to ___ in the ____ cycle which starts in the ___ of hepatocytes and finishes in the ___ of hepatocytes.

Back 69

Ammonia is converted to urea in the urea cycle which starts in the mitochondria of hepatocytes and finishes in the cytosol of hepatocytes.