Chapter 25 Flashcards
Metabolism
All the chemical reactions that occur in the body
Catabolism
Exergonic reactions that produce more energy than they consume releasing the chemical energy stored in organic molecules
Anabolism
Chemical reactions that combine simple molecules and monomers to form the bodies complex structural and functional components; endergonic reactions Consuming more energy than they produce
What happens to the energy released in catabolism?
40% is used for cellular functions
The rest is converted to heat which helps maintain normal body temperature
Oxidation
Removal of electrons from an atom or molecule the result being a decrease in the potential energy of the atom or molecule
Dehydrogenation reactions
The loss of hydrogen atoms, which happens in most biological oxidation reactions
Reduction
Addition of electrons to a molecule, result in an increase in the potential energy of the molecules
What are the two enzymes that are commonly used by animal cells to carry hydrogen atoms?
- Nicotinamide adenine dinucleotide (NAD), Derivative of the B vitamin niacin
- Flavin adenine dinucleotide (FAD), Derivative of B2 (riboflavin)
Oxidation-reduction or redox reactions are what?
Paired reactions that are coupled such as: When one substance is oxidized (exergonic reaction) another is simultaneously reduced
Phosphorylation
The addition of a phosphate group to a molecule which increases its potential energy
What are the three mechanisms of phosphorylation that organisms use to generate ATP
- Substrate level phosphorylation
- Oxidative phosphorylation
- Photophosphorylation
Substrate level phosphorylation
Generate ATP by transferring a high energy phosphate group from an intermediate phosphorylated metabolic compound-a substrate-directly to ADP. in human cells this process occurs in the cytosal
Oxidative phosphorylation
Removes electrons from organic compounds and passes them through a series of electron acceptors called electron transport chain, to molecules of oxygen. this process occurs in the inner mitochondrial membrane of the cells
Photophosphorylation
Occurs only in the chlorophyll-containing plant cells or in certain bacteria that contain other light- absorbing pigment
What is the body’s preferred source for synthesizing ATP
Glucose
What are the different fates of glucose?
- ATP production - Body cells that require immediate energy glucose is oxidized to produce ATP
- Amino acid synthesis - Cells throughout the body can use glucose to form several amino acids which can then be incorporated into proteins
- Glycogen synthesis - hepatocytes and muscle fibres can perform glycogenesis in which hundreds of glucose monomers are combine to form the polysaccharide glycogen
- Triglyceride synthesis - When glycogen storage areas are filled up hepatocytes can transform the glucose to glycerol and fatty acids that can be used for lipogenesis the synthesis of triglycerides, triglycerides are then deposited in adipose tissue which has virtually unlimited storage capacity
What are the four sets of reactions in cellular respiration?
- Glycolysis - in which one glucose molecule is oxidized and then two molecules of pyruvic acid are produced the reactions also produce two molecules of ATP in to energy containing NADH + H+
- Formation of acetyl Coenzyme A - A transition step that prepares pyruvic acid for entrance into the Krebs cycle also produces energy containing NADH + H+ plus carbon dioxide
- Krebs cycle reactions these reactions oxidize acetyl CoA and produce CO2, ATP, NADH + H +, and FADH2
- Electron transport chain reactions - these reactions oxidize NADH + H+ and FADH2 and transfer the electrons through a series of electron carriers
Aerobic
With oxygen
Anaerobic
Without oxygen
Aerobic respiration
Reactions that require oxygen such as the Krebs cycle and electron transport chain
Glycolysis does not require oxygen which makes it what kind of reaction?
It can occur under aerobic or anaerobic conditions
Anaerobic glycolysis
When glycolysis occurs by itself under anaerobic conditions
Glycolysis
Chemical reactions split a six carbon molecule of glucose into two 3 carbon molecules of pyruvic acid, Consumes to ATP molecules it produces for ATP molecules for a net gain of two ATP molecules for each glucose molecule that is oxidized
What is the fate of pyruvic acid?
- If oxygen is scarce, Then pyruvic acid is reduced via an anaerobic pathways by the addition of two hydrogen atoms to form lactic acid. Lactic acid rapidly diffuses out of the cell and enters the blood the hepatocytes remove lactic acid from the blood and convert it back to pyruvic acid
- In aerobic conditions most cells convert pyruvic acid to acetyl coenzyme A, this molecule links glycolysis which occurs in the cytosol with the Krebs cycle which occurs in the matrix of the mitochondria pyruvic acid enters the mitochondrial matrix with the help of a special transporter protein
How can red blood cells produce ATP because they lack mitochondria?
The only way for red blood cells to produce ATP because their lack of mitochondria is through glycolysis
Coenzyme A
Derived from pantothenic acid a B vitamin
Acetyl CoA
Formed when the acetyl group attaches to the Coenzyme A After pyruvic acid has undergone decarboxylation
Krebs cycle
Known as the citric acid cycle, occurs in the matrix of mitochondria and consists of a series of oxidation reduction reactions and decarboxylation reactions that release CO2.
Electron transport chain
A series of electron carriers, integral membrane proteins in the inner mitochondrial membrane, cristae that increases its surface area accommodating thousands of copies of the transport chain in each mitochondrion each carrier in the chain is reduced as it picks up electrons and is oxidized as it gives up electrons
Chemiosmosis
The mechanism of ATP generation links chemical reactions with the pumping of hydrogen ions
Oxidative phosphorylation
Chemiosmosis and the electron transport chain together
What are the different electron carriers?
- Flavin mononucleotide (FMN) - Flavoprotein derived from riboflavin (vitamin B2)
- Cytochromes - Proteins with an iron containing group capable of existing alternately in a reduced form and then oxidized form
the cytochromes involved in the electron transport chain includes cytochrome b, cytochrome C1, cytochrome C, cytochrome a, and cytochrome a3 - Iron and sulphur centres - contain either two or four iron atoms bound to sulphur atoms that form an electron transfer centre within a protein
- Copper atoms - bound to two proteins in the chain also participate in electron transfer
- Coenzyme Q - is a non-protein low molecular weight carrier that is mobile in the lipid bilayer of the inner membrane
Glucose anabolism reactions
Glycogen and new glucose molecules from some of the products of protein and lipid breakdown
Glucose storage: glycogenesis
If glucose is not needed immediately for ATP production it combines with other molecules of glucose to form glycogen: the only stored form of carbohydrate in the body
insulin from pancreatic beta cells stimulates hepatocytes and skeletal muscle cells to carry out glycogenesis
The body can store 500 g of glycogen 75% in skeletal muscle fibres and the rest in the liver
Glucose release: glycogenolysis
When ATP is required glycogen stored in hepatocytes is broken down into glucose and released into the blood to be transported to cells where it will be catabolized by the process of cellular respiration
Formation of glucose from proteins and fats: gluconeogenesis
 When the glycerol part of triglycerides , lactic acid, and certain amino acids are converted in the liver to glucose it is called gluconeogenesis (when glucose is formed from non-carbohydrate sources)
Glucose is not converted back from glycogen but is newly formed
60% of the amino acids in the body can be used for gluconeogenesis
Stimulated by cortisol and by glucagon from the pancreas
Lipids
Nonpolar and therefore very hydrophobic
such as triglycerides
they do not dissolve in water
can combine with proteins produced by the liver and intestine which can create Lipo proteins
Lipoproteins
Spherical particles with an outer shell of proteins, phospholipids, and cholesterol molecules surrounding an inner core of triglycerides and other lipids
Each has a different function but all are essentially transport vehicles
Four major classes of lipoproteins are chylomicrons, Very low density lipoproteins (VLDL’s), low density lipoproteins (LDL’s), and high density Lipo proteins (HDL’s)
Apoproteins (apo)
Proteins in the outer shell of Lipo proteins that are designated by the letters a A, B, C, D, and E plus a number
they help solubilized the lipoprotein
Chylomicrons
form in mucosal epithelial
ells of the small intestine,
transport dietary (ingested) lipids to adipose tissue for storage.
They contain about 1-2% proteins, 85% triglycerides, 7% phospholipids, and 6-7% cholesterol, plus a small amount of fat soluble vitamins
Enter lacteals of intestinal villi and are carried by lymph intervenous blood and then into the systemic circulation
Very low density lipoprotein
form in hepatocytes,
contain mainly endogenous (made in the body) lipids.
Contain about 10% proteins, 50% triglycerides, 20% phospholipids,
d 20% cholesterol.
transport triglycerides synthesized in
patocytes to adipocytes for storage. Like chylomicrons, they lose
glycerides as their apo C-2 activates endothelial lipoprotein lipase,
the resulting fatty acids are taken up by adipocytes for storage
by muscle cells for ATP production.
As they deposit some of their
glycerides in adipose cells, VLDLs are converted to LDLs.
Low density lipoproteins (LDL’s)
contain 25% proteins, 5%
triglycerides, 20% phospholipids, and 50% cholesterol.
They carry about 75% of the total cholesterol in blood and deliver it to cells throughout the body for use in repair of cell membranes and synthesis of steroid hormones and bile salts.
contain a single apoprotein,
apo B100, which is the docking protein that binds to LDL receptors on The plasma membrane of body cells so that LDL can enter the cell via receptor mediated endocytosis
High density lipoproteins (HDL’s)
contain 40-45% proteins, 5-10% triglycerides, 30% phospholipids, and 20% cholesterol
move excess cholesterol from body cells and the blood and transport it to the liver for elimination.
prevent accumulation of cholesterol in the blood, a high HDL level is associated with Decreased risk of coronary artery disease.
known as “good” cholesterol.
Sources and significance of blood cholesterol
Sources of cholesterol in the body are foods, but most are synthesized by hepatocytes
Desirable levels of blood cholesterol are total cholesterol under 200 mg/dL
LDL cholesterol under 130 mg/dL
HDL cholesterol over 40 mg/dL
Fate of lipids
Oxidized to produce ATP, stored in adipose tissues throughout the body and liver, structural molecules, or to synthesize other essential substances like phospholipids, Lipoproteins, thromboplastin, and myelin sheath
To essential fatty acids that the body cannot synthesize are linoleic acid and Linolenic acid (Which include vegetable oils in leafy vegetables)
Triglyceride storage
Triglycerides stored in adipose tissue constitute 98% of all body energy reserves
Stored more readily than glycogen
Lipolysis
Triglycerides that are split into glycerol and fatty acids
catalyzed by the enzyme called lipases
Epinephrin and norepinephrine enhance triglyceride breakdown into fatty acids and glycerol
Beta oxidation
A series of reactions in the first stage of fatty acid catabolism
Acetoacetic acid are condensed by
Hepatocytes which take to acetyl-CoA molecules at a time as part of normal fatty acid Catabolism
What is some acetoacetic acids converted to?
Beta-hydroxybutyric acid and acetone
What are the three ketone bodies and what is the process called that makes them?
Acetoacetic acid beta-hydroxybutyric acid and acetones
ketogenesis
Lipogenesis
How liver cells and adipose cells synthesize lipids from glucose or amino acids
Stimulated by insulin
occurs when individuals consume more calories than Is needed to satisfy their ATP needs
What are proteins broken down into during digestion?
Amino acids
What are amino acids used for?
Oxidize to produce ATP or used to synthesize new proteins for body growth and repair they are not warehoused for future use or excreted in the urine or feces but instead are converted into glucose or triglycerides
What activates the transport of amino acids into the body cells?
Insulin like growth factors and insulin
What are the main functions of proteins?
Enzymes, transportation, antibodies, clotting chemicals, hormones, contractile elements in muscle fibres, structural components of the body
Protein catabolism
Stimulated by cortisol from the adrenal cortex
Proteins from worn out cells are broken down into amino acids some are converted into other amino acids peptide bonds are reformed and new proteins are synthesized as part of the recycling process
The Hepatocytes convert some amino acids to fatty acids, ketone bodies, or glucose
A small amount of amino acids are oxidized to generate ATP via the kerbs cycle and the electron transport chain
Deamination
Amino group NH2 is removed from amino acids
Occurs in hepatocytes and produces ammonia
Protein Anabolism
The formation of peptide bonds between amino acids to produce new proteins and is carried out on the ribosome of almost every cell in the body directed by the cells DNA and RNA
Protein synthesis is stimulated by insulin like growth factors, thyroid hormones, insulin, estrogen and testosterone
What are the eight essential amino acids not found in the body?
Isoleucine, Lucein, lysine, Methionine, threonine, tryptophan, and valine
What are the two essential amino acids that are synthesized in the body?
Arginine and histidine
Complete protein
Contain sufficient amounts of all essential amino acids
beef, fish, poultry, eggs and milk contain complete proteins
Incomplete protein
Does not contain all essential amino acids
leafy green vegetables, legumes, and grains
Nonessential amino acids
Can be synthesized by body cells
are formed by transamination the transfer of an amino group from an amino acid to pyruvic acid or to an acid in the Krebs cycle
What three molecules play a pivotal role in metabolism?
Glucose 6-phosphate, pyruvic acid, and acetyl coenzyme A
What are the four possible fates that awake glucose six phosphate?
- Synthesis of glycogen
- Release of glucose into the bloodstream
- Synthesis of nucleic acids
- Glycolysis
Each six carbon molecule of glucose that undergoes glycolysis yields what?
Two 3 carbon molecules of pyruvic acid
What are the anaerobic and aerobic reactions of pyruvic acid?
- Production of lactic acid, anaerobic
- Production of alanine, anaerobic
- Gluconeogenesis, anaerobic
- Conversion to acetyl CoA, streams towards ATP producing reactions the Krebs cycle and electron transport chain
- Entry into the Krebs cycle
- Synthesis of lipids
Absorptive state of metabolism
Ingested nutrients are entering the bloodstream and glucose is readily available for ATP production
Postabsorptive state of metabolism
Absorption of nutrients from the G.I. tract is complete and energy needs must be met by fuels already in the body
a typical meal requires about four hours for complete absorption
Absorptive state reactions That promote the bodies energy needs or used to synthesize proteins?
- Catabolism of glucose
- Catabolism of amino acids
- Protein synthesis
- Catabolism of few dietary lipids
Absorptive state reactions That promote the use of nutrients stores?
- Glycogenesis
- Lipogenesis
- Transport of triglycerides from the liver to Adipose tissue
Why is homeostasis of blood glucose concentration especially important for the nervous system and red blood cells?
- The dominant fuel molecule for ATP production in the nervous system is glucose because fatty acids are unable to pass the blood brain barrier
- Red blood cells derive all of their ATP from glycolysis of glucose because they have no mitochondria so the Krebs cycle and electron transport chain are not available to them
What are the reactions of the postabsorptive state that produce glucose?
- Glycogenolysis in the liver
- Glycogenolysis in muscle
- Lipolysis
- Protein catabolism
- Gluconeogenesis
What are the reactions in the postabsorptive state that are glucose sparing, allowing there to be more glucose in the blood for the brain and red blood cells?
- Catabolism of fatty acids
- Catabolism of lactic acid
- Catabolism of amino acids
- Catabolism of ketone bodies
Regulation of metabolism during the postabsorptive state
Regulated by hormones and sympathetic division of the ANS
Sometimes called Auntie insulin hormones because the counter the fact of insulin during the absorptive state
Metabolism during fasting and starvation
Glycogen stores are depleted within a few hours of beginning a fast catabolism of storage triglycerides and structural proteins can provide energy for several weeks
the amount of adipose tissue the body contains determines the lifespan possible without food
Energy balance
The precise matching of energy intake to energy expenditure over time
When the energy content of food balances the energy used by all cells of the body body weight remains constant
Calorie
The amount of energy in the form of heat required to raise the temperature of 1 g of water 1°
Kilocalorie (kcal)
Often used to express the energy content of foods a kilo calorie equals 1000 cal that’s when we say that a particular food item contains 500 cal we are actually referring to kilo calories
Metabolic rate
The overall rate at which metabolic reactions use energy
What are the factors that affect the metabolic rate?
- Hormones
- Exercise
- Nervous system
- Body temperature
- Ingestion of food
- Age
- Other factors- Gender, climate, sleep, and malnutrition
Calorigenic effect
Thyroid hormones increase BMR by stimulating cellular respiration
Food induced thermogenesis
Ingestion of food raises the metabolic rate 10 to 20% due to the energy cost of digesting absorbing and stores nutrients
Basal state
The body in a quiet, resting, and fasting condition
Basal metabolic rate (BMR)
The measurement obtained under these conditions: Measuring the amount of oxygen used per kilo calorie of food metabolized
Total metabolic rate (TMR)
The total energy expenditure by the body per unit of time
What are the three components that contribute to the TMR?
- Basal metabolic rate, 60%
- Physical activity, 30-35%
- Food induced thermogenesis, 5-10%
Non-exercise activity thermogenesis (NEAT)
The energy cost for maintaining muscle tone, posture while sitting or standing, and involuntary fidgeting movements
Satiety
Feeling of fulness accompanied by lack of desire to eat
Leptin
Helps decrease adiposity, total body fat mass
Neuropeptide Y
released when leptin and insulin levels are low
a neurotransmitter that stimulates food intake
Milanocortin
Similar to melanocyte stimulating hormone
stimulated for released by leptin
and also acts to inhibit food intake
Ghrelin
Produced by endocrine cells of the stomach
plays a role in increasing appetite
stimulates the release of neuropeptide Y from the hypothalamic neurons
Mechanisms of heat transfer
- Conduction - heat exchange that occurs between molecules of two materials that are in direct contact with each other, 3% of body heat is lost this way heat can also be gained
- Convection - the transfer of heat by the movement of air or water between areas of different temperatures, 15% of body heat is lost to the air
- Radiation - the transfer of heat in the form of infrared rays between a warmer object and a cooler one without physical contact, 60% of heat loss
- Evaporation the conversion of a liquid to a vapour, 22% of heat loss
Insensible water loss
Water loss through the skin and mucous membranes of the mouth and respiratory system that we are not aware of
Preoptic area
A group of neurons located in the anterior part of the hypothalamus is the control centre that functions as the bodies thermostat
receives input from Thermo receptors in the skin and in the hypothalamus and generate action potential‘s at a higher frequency when blood temperature increases and a lower frequency when blood temperature decreases
propagates action potentials to two other parts of the hypothalamus the heat losing centre and the heat promoting centre
How do action potentials from the hypothalamus and TSH increase the core temperature to the normal values?
- Vasoconstriction - decreasing the flow of warm blood and thus the transfer of heat from the internal organs to the skin slowing the rate of heat loss allows the internal body temperature to increase as metabolic reactions continue to produce heat
- Release of epinephrine and norepinephrine increasing cellular metabolism which increases heat production
- Shivering
- Release of thyroid hormones
What are the six main types of nutrients?
Water, carbohydrates, lipids, proteins, minerals, and vitamins
Minerals
Inorganic elements that occur naturally in the earths crust
constitute 4% of total body mass
concentrated most heavily in the skeleton
Vitamins
Vitamins do not provide energy or serve as the bodies building materials most vitamins with known functions are co-enzymes
Fat soluble vitamins
Vitamin A, D, E, and K are absorbed along with other dietary lipids in the small intestine and package in the chylomicrons
Soluble vitamins
Several B vitamins and vitamin C are dissolved in body fluids excess of these are excreted in the urine
Antioxidant vitamins
Three vitamin C, E, and beta carotene
Inactiate oxygen free radicals
Protect against some kinds of cancers, reducing the buildup of atherosclerotic plaque, delaying some effects of ageing, and decreasing the chance of cataract formation in the lens of the eyes
