3.3: Nutrition and energy systems 1
3.3: Nutrition and energy systems
Ultrastructure of a generalized animal cell
a) nucleus
contains the dna, has the instructions of the fucntioning cell
b) cytoplasm
matrix or fluid that is inside the cell.
where most chemical reactions take place.
lactic acid system and glycolysis take place here
c) cell membrane
outer wall of the cell. protects and isolates the cell from external environment.
controls movement of substances in and out of a cell
d) Mitochondrion
involved in aerobic prod. of ATP
*it’s present in all human cells e) Ribosomes
involved in protein synthesis.
bound to a membrane that forms the rough endoplasmic reticulum but can also be through the cell, wandering
f) Rough endoplasmtic reticulum involved in protein synthesis
g) Smooth endoplasmic reticulum
produces vesicles to transport proteins around the cell
involved in lipid synthesis h) Golgi apparatus
processing and packaging of proteins and fats i) Centrioles (Centrosome)
involved in organizing the cell during cell division
j) Lysosomes
digestion and breakdown of food particles,
“old” organelles and bacteria
Ultrastructure of a generalized mitochondrion
a) cristae
b) inner membrane c) outer membrane d) intermembrane space e) ribosome 70S and naked loops of DNA
f) matrix
Cell respiration
cell respiration: the controlled release of energy in the form of ATP (adenosine triphosphate) from the catabolism of organic compounds in the cell
it can be either aerobic or anaerobic (depends on the intensity and duration of the exercise)
Cell respiration (includes aerobic glycolysis, Krebs cycle and electron transport chain)
3.3: Nutrition and energy systems 3
ATP
Catabolic reactions convert biochemical energy from organic compounds into a way available for cells to consume: adenosine triphosphate (ATP)
It contains 3 inorganic phosphate groups (energy-rich) attached to each other
Hydrolysis (catabolic reaction) of ATP releases one of the 3 phosphate groups, and that releases energy.
After this process, we have left ADP (adenosine diphosphate)
ATP —— hydrolysis——> ADP+ Pi
We can extract more energy by removing another phosphate group, and then we would have AMP (adenosine monophosphate)
ADP——hydrolysis——> AMP+Pi
phosphorylation of ADP/AMP: consists of adding 1 inorganic phosphate to ADP to synthesize ATP. (the inverse process of ATP hydrolysis)
ADP——phosphorylation (+Pi) ——> ATP
*ATP is a temporary store of energy (it’s not stable for a long time). Cells can have glycogen and lipids as a long store enrgy, and if needed they are broken down into ATP through cell respiration.
role of ATP in muscle contraction
when ATP is broken into ADP, it releases a phosphate molecule, that provides energy for the contractile proteins (actin and myosin) to drive the contraction process.
*muscle cells require a lot of energy, but they only have ATP for 2 seconds of contraction. The rest comes from catabolic reactions that generate ATP (fermentation, Kreb cycle, ETC, glycolysis...)
catabolic reactions that generate ATP depend on the duration and intensity of the activity.
Anaerobic
doesn’t require oxygen
non-oxygen conditions (high-intensity exercise/just started to exercise)
only burns carbohydrates
strengthens tendons, ligaments, and joint functions
elevates good cholesterol
ATP-CP system (creatine phosphate system) Lactic acid system
Aerobic:
requires oxygen
muscles can contract repeatedly without fatigue burns carbohydrates and fats
reduces resting HR and increases number of RBC
aerobic system
ATP-CP system
Anaerobic system
creatine phophate: a high-energy compound that can be used to regenerate the ATP inside the muscle cells.
Creatine phosphate + ADP + H+ <——>Creatine + ATP
This reaction takes place really quickly so it supplies energy when we begin to exercise and in hard exercise (sprinting).
Used when there’s a rapid change in energy demand
It’s the fastest system (just has one reaction so supplies energy quickly) but it is very short-lived (10s) HOWEVER... it can be recovered during periods of steady exercise (at rest, the ATP generated by the aerobic system can be used to regenerate CP)
Lactic acid system
Anaerobic glycolysis
takes place in the cytoplasm of the cell without oxygen.
it uses glucose as fuel (glycolysis).
After glycolysis, the final products are 2 pyruvates.
When there’s no oxygen available, pyruvate is converted into lactic acid (lactate)
This process generates little ATP but really quickly, so it’s the best for high-intensity exercise or when the ATP-CP system starts to decade. However, it also lasts a short amount of time (more or less 3 mins, depending on intensity and kind of exercise)
*The accumulation of lactic acid limits long-duration exercise because it makes the muscle pH more acidic (reduces the ability to contract so it slows down)
This system will dominate if the athlete increases the intensity of the exercise above 90% of max HR.
Acidosis: when blood becomes more acidic due to the accumulation of hydrogen ions (protons) that come from the breakdown of an ATP molecule for energy.
Aerobic system
Aerobic glycolysis
production of ATP with oxygen
it involves three processes: glycolysis (cytoplasm), Kreb cycle, and electron transport chain (mitochondria)
It can produce energy from carbohydrates, lipids, and proteins (only in cases of starvation) and can generate up to 38 molecules of ATP
It’s the slowest way to resynthesize ATP but lasts the longest.
Glycolysis: net production of 2 ATP
3.3: Nutrition and energy systems 5 glucose is phosphorylated (uses 2 ATP)
then it’s split into 2 pyruvate molecules, which creates:
4 ATP (2 for each molecule) 2 NADH (1 each)
glucose —(2ATP used)—> fructose 1-6 biphosphate —(2 NADH + 4 ATP added)—> Pyruvate
*NADH is a coenzyme that carries electrons and hydrogens released during the reaction to the electron transport chain.
Kreb cycle: net production of 2 ATP per glucose (takes place in the matrix of the mitochondria) Pyruvate (from glycolysis) enters mitochondria and is converted into Acetyl CoA
Acetyl CoA enters the Kreb cycle, which produces 1 ATP molecule per cycle.
Since there were 2 pyruvate molecules, 2 ATP molecules will be produced per glucose.
Kreb cycle releases CO2 and hydrogen ions (carried to the electron transport chain by NADH and Fadh2)
pyruvate —(releases NADH)—> Acetyl CoA ——>Kreb cycle
Electron transport chain: net production of 34 ATP per glucose molecule takes place in the inner membrane of the mitochondria
Electrons released in the previous processes (glycolysis and kreb cycle) are transported by NADH and FADH2 and enter the ETC
Hydrogen ions are also released into the ETC
In this process, oxygen is needed to accept the electrons and “bind them” to the hydrogen ions to create water.
Production of ATP from fatty acids
Fatty acids (from tryglicerides) are broken down by ß-oxidation and catabolized into Acetyl CoA Acetyl CoA enters the Kreb cycle
Electrons released from kreb cycle and ß-oxidatin are incorporated into the ETC
Fats produce the triple amount of energy than carbohydrates (aroung 100-150 ATP molecules) Waste products: Water (h2o) and carbon dioxide (co2)
Fats can’t be used anaerobically
Glucose is consumed before fats because its more easily mobilized.
Advantages and disadvantages of aerobic system Advantages
-produces more ATP than an anaerobic system (38 molecules)
Disadvantages
-complex system that can’t be used right away. It takes a while to get enough oxygen to become available.
-there are no fatiguing by-products (just h2o and co2)
-large storage sites of glycogen and triglyceride=
exercise can last for a long time)
-fatty acid transportation to muscles is low, and it takes 15% more oxygen to break them down than glycogen.
Creatine Phosphate
system Lactic acid system Aerobic system
Fuel source Phosphocreatine Carbohydrates (blood glucose and glycogen)
Fatty acids (stored in adipose tissue and skeletal muscle) and carbs (blood glucose and glycogen)
Duration 2 seconds 20 seconds to 3 minutes very long
Intensity Maximal High Moderate-low
Amount of ATP Low but rapid (2ATP) Low but rapid (2ATP) High but slow (34 ATP) By-products Creatine Pyruvate and lactic acid co2, h2o, acetyl CoA
Oxygen deficit and oxygen debt
Oxygen deficit: as exercise begins, breathing rate increases →oxygen deficit occurs. Body initially uses ATP stores, PCr, and lactic acid system. Aerobic system takes more time to be activated, so when exercise starts, the oxygen needed and the oxygen supply don’t match at the first moment of exercise.
Initial stages of exercise: Oxygen demand >oxygen supply
Since oxygen demand is higher than the oxygen supply, it cannot be met by the aerobic system and ATP will be supplied via anaerobic pathways
Oxygen deficit may further increase as a result of increasing the intensity of the activity.
(e.g: hiking 20 km in mountains, when the slope increases, more deficit is reached as the body cannot reach the demand)
That is way heart rate and breath rate increase.
3.3: Nutrition and energy systems 7 At a steady submaximal level, there will be a plateauing of breathing rate and heart rate
PC stores can be resynthesized during a steady state. For example, when the slope declines in the 20 km hike in mountains.
Oxygen debt (EPOC): At the end of the exercise the athletes breathing rate and heart rate remain elevated. After exercise, the body needs a greater supply of oxygen.
The greater the intensity of the race the greater the EPOC/oxygen debt.
What is this excess of oxygen required for:
ATP/ PC stores are replenished in the muscles
Myoglobin and hemoglobin are reoxygenated Phosphagen stores and myoglobin stores can be replenished within a few minutes of recovery.
Aerobically metabolize lactic acid. What happens is that lactate is resynthesized to glycogen.
Replacement of muscle and liver glycogen stores
The recycling of lactate and replenishment of glycogen stores may take several hours after exercise
Examples of the difference in recovery between the different types of exercise
Relative contribution of the three energy systems during different types of exercise
High intensity exercise → high rate of ATP needed →Fast metabolism → PCr (20 sec) and Lactic Acid System
Longer & Slower exercise → Aerobic metabolism: Glucose and Fat oxidation (slowest one)
Glucose (anaerobic and aerobic) metabolism is key across all intensities of exercise.
Unit 3.1: Nutrition 1
Unit 3.1: Nutrition
Nutrients: the energy needed for metabolic processes in the body and to maintain homeostasis (INSERT DEFINICIÖN DE HOMEOSTASIS)
Food: the combination of several nutrients that influence the function of the human body. When you eat, food is digested, absorbed, and then transported by the circulatory system to each cell, where it’s metabolized, providing a source of energy for cell function.
Macronutrients: nutrients needed by the body in large amounts to maintain health Most of them provide energy.
Micronutrients: are needed by the body in smaller amounts, but they play a very important role in several physiologic functions.
All of them are essential and the majority have to be supplied by food, but there are some that our body synthetizes.
Minerals: mainly found in meat, fish, dairy products, cereals, and green vegetables Ca: (calcium) essential for bone structure and muscle contraction
Fe: (iron) forms part of hemoglobin
-Inorganic compounds that have to be supplied through food and fluids
-Important role in releasing energy, maintaining healthy blood, teeth and bones, muscle function, and maintaining cellular fluid balance.
Vitamins: mainly found in fruit, vegetables, fish oil and some meats e.g: Vitamin C: important role in the healing process
-They play important roles, assisting the enzymes to break down carbs, fats and proteins -Important in healing the body, inmunuty, blood and bone health
-Two groups:
Water soluble: most of them are proteins. An excess can be removed easily through urine (e.g.:
Vitamin C)
Fat soluble: insoluble in water. Most of them are lipids. They can be stored in the adipose tissue (fat tissue) and build high concentrations, which is toxic (e.g.: Vitamin D)
Glucose:
It’s a monosaccharide composed of carbon, hydrogen, and oxygen (CHO) in a 1:2:1 ratio
*Lipids are made with the same elements (C, H, and O) but in a different ratio: very little oxygen and many carbon and hydrogen molecules.
Monosaccharides: the basic unit of carbohydrates.
Consists of one molecule and it’s what we commonly call sugar. Easily absorbed in the digestive system.
e.g.: glucose
Disaccharides: made by two monosaccharides e.g.: maltose
Oligosaccharide: carbohydrates with 3-9 monosaccharides
Polysaccharide: carbs with more than 10 monosaccharides.
Glucose molecules can combine to form disaccharides and polysaccharides through CONDENSATION
Condensation polymerization is a chemical process by which (2) molecules are joined to make a larger and more complex molecule.
This reaction involves removing a water molecule.
The Hydroxyl group (OH) from one molecule reacts with the hydrogen atom of another OH molecule and they join together (OH + H = H2O). There’s a free oxygen remaining, that joins both molecules together (O-bridge).
This is an anabolic reaction (creating large molecules from smaller ones by consuming ATP or energy).
Two monosaccharides (glucose) are joined together to form a disaccharide (maltose)
Unit 3.1: Nutrition 3 If we continued to add glucose to this molecule, we would have a polysaccharide (more than 10
monosaccharides) called glycogen (glycogenesis)
Glycogen: polysaccharide stored in the liver (to be used by the brain) and in the skeletal muscles (to be used by muscles in muscle contraction). Content is limited and short-term shortage.
*polysaccharides are too big and need to be broken down into monosaccharides (smaller) to be absorbed and transported to the organs. (hydrolysis)
Processes:
Glycogenesis: formation of glycogen from glucose
Glycogenolysis: removing glucose from glycogen (a catabolic reaction called hydrolysis but because we’re talking about glucose and glycogen it’s called glycogenolysis)
Triglycerol:
made by joining a molecule of glycerol with three fatty acids.
stored in the adipose tissue cells constitute the long-term energy storage (provide energy when the energy supply is not from the diet or the glycogen stores)
They are found in animal and plant sources, and the main dietary fats are triglycerides, phospholipids and steroids.
Main storage site: adipose tissue and skeletal muscles (but also in organs such as the heart and kidneys to act as protection)
*adipose tissue cells are specialized cells of connective tissue that store fat.
Chemical composition of a triglycerol molecule
During digestion, triglycerides (fats) are broken down into fatty acids and glycerol (releasing H2O because it’s a catabolic reaction) for energy metabolism.
Other functions of triglycerides:
-Heat insulation (layer of subcutaneous fat reduces heat loss) -Protection of vital organs
-Buoyancy (ability to float in water or other fluids) [ƒlotabilidad]
-Synthesis and transport of hormones
Fatty acids: saturated and unsaturated.
Fatty acids are a chain of 14-20 carbon atoms attached to hydrogen atoms. They have a methyl group on one end and a carboxyl group on the other end
There are two types: saturated and unsaturated
Unsaturated fatty acids
Some of them have double bonds between the individual carbons of the hydrocarbon chain.
Some carbons have hydrogen missing and those two carbons create a double covalent bond.
sources: olive oil, olives, avocado, peanuts, cashew nuts, canola oil, seeds, sunflower oil, rapeseed oil...
Saturated fatty acids (the “unhealthy ones”) They don’t have double bonds in the hydrocarbon chain.
All the carbons are attached to two hydrogens and have a simple covalent bond with the other carbons.
sources: red meat, poultry, full-fat dairy products, tropical oils (palm or coconut)
These fatty acids raise cholesterol.
Triglyceride broken down into fatty acids and glycerol by adding 3 molecules of water
Unit 3.1: Nutrition 5 Trans- and Cis-unsaturated fatty acids.
Cis (bent)
triglycerides that contain cis-unsaturated fats are loosely packaged
usually liquid when at room temperature (low melting points)
common in nature
e.g.: Omega 3 (first double bond between carbons 3-4) and Omega 6. They are really important in the inflammatory and immunological systems
Trans (not bent)
triglycerides that contain trans-unsaturated fats are loosely packaged
usually solid when at room temperature (high melting points)
rare in nature
e.g.: hydrogenated vegetable and fish oils, margarine, processed foods
*Trans fatty acids are to be avoided at all costs
Proteins:
They are formed by amino acids joined together by a peptide bond (a special kind of covalent bond) They are made of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N)
There are 20 amino acids, and they all follow the same structure, only changing in the side group (Radical group: R) which is responsible for the chemical and physical properties.
There are 8 essential amino acids that need to be provided by the diet since they can’t be synthesized them (the rest are non-essential)
source of the essential amino acids: meat, fish, processed soybean, bread, protein bars Functions of protein:
-structural function: muscle, skin, bone, cells
-enzymatic function: to catalyze chamical reactions
-transport: hemoglobin or myoglobin -hormonal communication (insulin) -inmune response (antibodies) -cellular transport
Unit 3.2: Fat Metabolism
3.2: Carbohydrates and fat metabolism
Metabolism: the chemical processes or reactions in living organisms required for the maintenance of life.
Metabolism includes catabolism and anabolism.
Catabolism
Chemical reactions that break down complex large organic compounds into simpler compounds.
Releases energy
Aerobic: uses oxygen
e.g.: triglycerides turn into glycerol and fatty acids
Anaerobic: doesn’t use oxygen e.g.: glucose turns into lactic acid ADP and phosphate are turned to ATP (phosphorylation)
Large molecules—>(ADP+Pi in—>ATP out)—>
smaller molecules
Small molecules are combined into larger molecules
Requires energy
Anabolism
e.g.: glucose molecules turn into glycogen (glycogenesis)
ATP is converted to ADP and phosphate (hydrolysis of ATP)
Small molecules—> (ATP in —> ADP+Pi out) —>
large molecules
Unit 3.2: Fat Metabolism 2
Glycogen:
It’s a polysaccharide of glucose. A short energy store.
In humans, glycogen is made and stored primarily in the liver and muscles
Liver: supplies glucose to organs Muscles: supply glucose to the muscles.
Glucose is broken down by the body to provide energy through a process called glycolysis. Excess sugar is converted into glycogen in the liver and muscle cells. This condensation process of linking glucose to form glycogen is called glycogenesis. Glycogen is stored, but when the body needs energy quickly, glycogen can be transformed into glucose again to provide energy. The process of breaking down glycogen into glucose is called glycogenolysis.
Glycogenolysis: the breakdown of glycogen into glucose. It’s a hydrolysis reaction (consumes water)
The main enzyme responsible is phosphorylase, which removes glucose from glycogen by adding a phosphate group to carbon 1. This produces glucose-1-phosphate.
This process raises blood glucose levels and provides a rapid rate of production of glucose-6- phosphate.
Glucose removed from the liver glycogen will be used by all organs and will raise blood glucose levels
Glucose removed from the glycogen in muscles will be used by the muscle, where glycolysis takes place.
Hormones involved:
-glucagon: stimulates glycogenolysis
-adrenalin: stimulates glycogenolysis (involved in many other processes)
-insulin: inhibits glycogenolysis (stimulates glycogenesis)
Lipolysis: the breakdown of triglycerides into glycerol and fatty acids.
Glycerol will go to the bloodstream to be absorbed by the liver and kidneys (incorporated in the glycolysis process)
Fatty acids will be transported through the bloodstream to cells that require energy. They’re broken down into Acetyl CoA during a process called Beta (ß) oxidation.
Acetyl CoA is incorporated into the Kreb cycle (which happens in the mitochondria and needs oxygen to take place).
Lipolysis consumes water (3 molecules) because it’s a hydrolysis reaction
Hormones involved:
-adrenaline: stimulate lipolysis -glucagon: stimulate lipolysis -insulin: inhibits the process
Fructose and galactose absorbed by the digestive system can be transformed into glucose in the liver.
Insulin:
protein synthesized in the beta cells of the pancreas
released when blood glucose levels rise (e.g.:after eating) Exercise inhibits the release of insulin because your body needs sugar.
Promotes
glycogenesis (anabolic reaction)
uptake of glucose into fat cells (lipogenesis) Inhibits
gluconeogenesis glucagon lipolysis
Glucagon:
hormone synthesized by the alpha cells of the pancreas released when blood glucose levels fall below normal When released, it stimulates liver cells and accelerates the conversion of glycogen (in the liver) into glucose
Promotes
gluconeogenesis glycogenolysis glucose formation (from amino acids) lipolysis
Inhibits
glycovenesis lipogenesis insulin
Adrenaline:
a hormone secreted by the adrenal glands
plays several roles in the body (increase HR, cardiac output, contractility of the heart...) Increases vasodilation of blood vessels in the heart so more nutrients can arrive.
It’s synthesized during exercise to increase blood glucose levels for muscle contraction
requirement
Promotes
Glycogenolysis (in the liver and active muscles) lipolysis
Inhibits
glycogenesis
Unit 3.2: Fat Metabolism 4 Insulin and muscle contraction during exercise
Both insulin and muscle contraction stimulates glucose uptake from the blood into skeletal muscles.
However, insulin is released in response to high blood sugar levels and stimulates glucose uptake from the liver and muscle cells to be stored as glycogen (glycogenesis)
Muscle contraction stimulates glucose uptake from the blood into the skeletal muscles to be used (glucose molecule is phosphorylated by phosphorylases into glucose-6-phosphate)
Insulin production is inhibited during exercise
During exercise, adrenaline promotes glycogenolysis and lipolysis (catabolism of fatty acids). When glucose levels in blood drop during exercise, glucagon is also released to promote glycogenolysis and lipolysis.
GLUT-4
To enter the cells, glucose uses transporters. Muscle contraction stimulates vesicles that contain GLUT-4 to mobilise to the cell membrane. The number of GLUT-4 increases and this facilitates glucose uptake.
