September, 29, 2023

Question 1

how does the increase of hydrogen ions inside muscle cells lead to a decrease in pH

Answer 1

The increase in hydrogen ions (H+) inside muscle cells leads to a decrease in pH because pH is a measure of the concentration of hydrogen ions in a solution.

When hydrogen ions accumulate in muscle cells, it means that there are more H+ ions present in a given volume of the intracellular fluid. This increase in H+ ions makes the solution more acidic, causing the pH to decrease.

In muscle cells, factors like lactic acid production during strenuous exercise, metabolic processes, and other cellular activities can contribute to an accumulation of H+ ions. This increased acidity can lead to a decrease in intracellular pH, which can affect muscle function and contribute to muscle fatigue and discomfort.

Question 2

how does the increase of hydrogen ions inside muscle cells lead to decreased force produced as a function of (Ca2+) -> fatigue

Answer 2

Muscle contraction is initiated by the release of calcium ions (Ca2+) from the sarcoplasmic reticulum, which binds to troponin, allowing actin and myosin to interact and generate force.

The concentration of Ca2+ in the muscle cell is a crucial regulator of muscle contraction. Higher Ca2+ levels lead to stronger contractions.

when muscle cells accumulate excess H+ ions, the intracellular pH decreases, making the environment more acidic.

At lower pH levels, the binding of Ca2+ to troponin is impaired as H+ competes with Ca2+ for troponin binding sites,

Competition means more calcium is needed to achieve the same force generation. Ultimately reducing the ability of the muscle fibers to generate force.

Therefore, the accumulation of hydrogen ions in muscle cells contributes to a decrease in intracellular pH, which, in turn, disrupts the normal function of proteins involved in muscle contraction. This disruption leads to reduced force production and muscle fatigue. This is why maintaining proper pH balance and reducing the buildup of H+ ions through efficient oxygen delivery and removal of waste products, such as lactic acid, is essential for prolonged muscle function during physical activity.

Question 3

how does H+ react with HCO3 in blood

Answer 3

In the bloodstream, hydrogen ions (H+) can react with bicarbonate ions (HCO3-) in a reversible chemical reaction that helps regulate blood pH. This reaction is important for maintaining the body’s acid-base balance and preventing drastic changes in blood acidity. The reaction can be summarized as follows:

H+ + HCO3- ⇌ H2CO3 ⇌ CO2 + H2O

Question 4

explain this reaction “H+ + HCO3- ⇌ H2CO3 ⇌ CO2 + H2O”

Answer 4

Formation of Carbonic Acid (H2CO3):

Hydrogen ions (H+) from various sources, such as metabolic processes or the breakdown of carbon dioxide (CO2), can combine with bicarbonate ions (HCO3-) in the blood.
The reaction between H+ and HCO3- forms carbonic acid (H2CO3), which is a weak acid.

Equilibrium with CO2 and Water:

Carbonic acid (H2CO3) can further dissociate into carbon dioxide (CO2) and water (H2O) in a reversible reaction.
This reaction is catalyzed by an enzyme called carbonic anhydrase, which is present in red blood cells.

Question 5

what catalyzes this reaction “H+ + HCO3- ⇌ H2CO3 ⇌ CO2 + H2O”

Answer 5

carbonic anhydrase

Question 6

Co2 and H+ in blood stimulate neurons in the brains stem to increase ventilation which leads to what?

Answer 6

this hyperventilation blows off the extra Co2 and prevents “hypercapnia”

Question 7

what is hypercapnia

Answer 7

When CO2 levels in the blood increase (hypercapnia)

Question 8

what is acidosis

Answer 8

an increase in H+ ions (acidosis)

Question 9

Can HCO3(bicarbonate ion) ingestion aid performance?

Answer 9

300mg/kg dose can delay fatigue in high intensity events

easy to detect based on urine pH and HCO3

Question 10

how does HCO3(bicarbonate ion) ingestion aid performance? (refer to page 45)

Answer 10

used to reduce the increase of H+ within muscle
(refer to page 45 for diagram)

but basically because there’s more HCO3 it draws hydrogen out of the muscle, keeping ph higher than normal, but you will blow off more CO2

Question 11

HCO3 increases the concentration gradient for H+ to move out of the cell. True or false

Answer 11

true

bicarbonate increase the concentration of H+ ions to move out of the cell by drawing more into the red blood cell

Question 12

explain how oxidation in muscle is determined by LDH isoform and mitochondria

Answer 12

LDH is an enzyme found in muscle cells that catalyzes the conversion of pyruvate to lactate in the absence of oxygen (anaerobic conditions) and the reverse conversion of lactate to pyruvate under aerobic conditions.

There are two major isoforms of LDH in muscle cells: LDH-4 or M-LDH (predominantly in fast-twitch glycolytic muscle fibers) and LDH-5 or H-LDH (predominantly in slow-twitch oxidative muscle fibers).

The presence of these LDH isoforms reflects the muscle fiber type and the type of metabolism that predominates in that muscle. Fast-twitch fibers rely more on anaerobic glycolysis, while slow-twitch fibers are adapted for oxidative metabolism.

Mitochondria are the “powerhouses” of the cell and play a central role in aerobic metabolism, where they produce energy (in the form of ATP) through the oxidative phosphorylation process.

Muscles with a high density of mitochondria are better equipped for sustained aerobic activity and are often associated with slow-twitch muscle fibers.

Question 13

M-LDH is an isoform that converts _________

Answer 13

pyruvate to lactate
(anaerobic conditions)

Question 14

H-LDH is an isoform that converts _________

Answer 14

lactate to pyruvate
(aerobic conditions)

Question 15

Gluconeogenesis

Answer 15

the process by which the liver produce glucose from non-carbohydrate precursors

Question 16

when does Gluconeogenesis occur

Answer 16

This process occurs primarily during periods of fasting, low blood glucose, or during prolonged exercise when the body needs a steady supply of glucose to maintain energy levels.

Question 17

what are the Precursors for gluconeogenesis

Answer 17

glycerol (from fats)

lactate

alanine (from muscle)

Question 18

what are the enzymes involved in gluconeogenesis

Answer 18

H-LDH = Lactate to pyruvate

Alanine transaminase = alanine - pyruvate

Glucose-6-phosphatase = G3P to glucose

Question 19

gluconeogenesis(GNG) accounts for what percentage of glucose released by the liver at rest .. this contribution increase during exercise why?

Answer 19

25%

During exercise, several factors come into play that can increase the contribution of gluconeogenesis to the glucose released by the liver:

Depletion of Glycogen Stores: As exercise progresses, muscle glycogen stores may become depleted. When muscle glycogen is low, the liver compensates by increasing gluconeogenesis to provide a source of glucose for the muscles to use as fuel.

Increased Energy Demands: Exercise places higher energy demands on the body, requiring a greater supply of glucose to meet the energy needs of working muscles. Gluconeogenesis helps ensure a continuous supply of glucose for energy production.

Hormonal Changes: During exercise, hormonal responses, including the release of glucagon and epinephrine, stimulate gluconeogenesis. These hormones help increase the rate of glucose production in the liver.

Mobilization of Non-Carbohydrate Substrates: As exercise continues, the body may use up available glucose and glycogen stores. To maintain blood glucose levels, the liver increases the conversion of non-carbohydrate substrates, such as amino acids and glycerol, into glucose through gluconeogenesis.

Question 20

how does Mitochondria affect Lactate production and lactate threshold

Answer 20

Mitochondria are the primary sites of oxidative metabolism in muscle cells. They are responsible for the complete breakdown of glucose and other fuels in the presence of oxygen to produce ATP (adenosine triphosphate), which is the primary source of energy for muscle contraction.

When there is an adequate supply of oxygen, glucose is efficiently broken down within the mitochondria through a series of biochemical reactions, resulting in the production of ATP and carbon dioxide (CO2) as waste.

However, during intense exercise or when oxygen availability is limited (as in anaerobic conditions), mitochondria may not be able to keep up with the energy demands of the muscle cells.

Under these conditions, glycolysis (the breakdown of glucose) can continue in the absence of oxygen, leading to the formation of pyruvate and a buildup of NADH (a molecule involved in glycolysis). This situation can result in the conversion of pyruvate into lactate, a process known as lactic acid fermentation.

The lactate threshold is a point during exercise where the rate of lactate production exceeds the rate of lactate clearance. In other words, it is the point at which blood lactate levels begin to rise significantly.

The ability to delay the onset of the lactate threshold is influenced by several factors, including the efficiency of mitochondrial function. Well-trained athletes often have more efficient mitochondria, which can help them use oxygen more effectively and, in turn, delay the point at which lactate production significantly increases.

In summary, mitochondria indirectly affect lactate production by influencing the balance between aerobic and anaerobic metabolism. A high level of aerobic fitness can delay the onset of the lactate threshold, as more efficient mitochondria allow the body to rely on aerobic metabolism for longer, reducing the reliance on anaerobic glycolysis and lactic acid production during exercise.

Question 21

How does muscle fiber type composition affect lactate production and lactate threshold

Answer 21

different types of muscle fibers have distinct metabolic characteristics.

Slow-twitch muscle fibers are highly aerobic and rely on oxidative metabolism for energy production. They have a high density of mitochondria/H-LDH, which are responsible for efficient aerobic respiration.

Due to their aerobic nature, slow-twitch fibers produce very little lactate, even at high exercise intensities. They are fatigue-resistant and have a high lactate threshold.

Fast-twitch muscle fibers have lower mitochondrial density and lots of M-LDH and are more reliant on glycolytic metabolism for energy production. They produce ATP through glycolysis, which can lead to lactate production.

Type II fibers produce more lactate than Type I fibers, particularly during intense exercise. They have a lower lactate threshold, and their lactate production increases rapidly as exercise intensity rises.

Individuals with a higher proportion of slow-twitch muscle fibers tend to have a higher lactate threshold because these fibers are well-adapted to sustain aerobic exercise without producing excessive lactate.

In contrast, individuals with a higher proportion of fast-twitch muscle fibers may have a lower lactate threshold, as these fibers tend to rely more on glycolytic metabolism and produce lactate at lower exercise intensities.

Question 22

how does training affect lactate production and the lactate threshold in regards to muscle fiber type composition

Answer 22

The muscle fiber type composition can be influenced by genetics, but it can also be modified through training. Endurance training, for example, can increase the proportion of slow-twitch fibers and improve the lactate threshold.

High-intensity training, on the other hand, may lead to some adaptations in fast-twitch fibers that can increase their oxidative capacity and potentially raise the lactate threshold.