Chapter 25 - Metabolism and Nutrition Flashcards
What are the three main fates of food molecules that are absorbed by the GI tract?
- Supply energy
- Serve as building blocks
- Stored for future use
What does metabolism refer to?
All of the chemical reactions that occur in the body
What is catabolism?
Chemical reactions that break down complex organic molecules into simpler ones
Are catabolic reactions exergonic or endergonic?
Exergonic
- produce more energy than they consume
What is anabolism?
Chemical reactions that combine simple molecules to form complex structural and functional components
Are anabolic reaction exergonic or endergonic?
Endergonic
- consume more energy than they produce
What is the function of ATP?
Participates in energy exchanges in living cells
What happens during oxidation reactions?
Electrons are removed from an atom or molecule
- results in a DECREASE in the potential energy of the atom of molecule
What happens during reduction reactions?
Electrons are added to an atom or molecule
- results in an INCREASE in the potential energy of the molecule
What is phosphorylation?
The addition of a phosphate group to a molecule
What are the three mechanisms of phosphorylation to generate ATP?
- Substrate-level phosphorylation
- Oxidative phosphorylation
- Photophosphorylation
What is the formula involving ADP, ATP, energy and a phosphate group (P)?
ADP + P + energy –> ATP
What is the body’s preferred source for synthesizing ATP?
Glucose
What are the four possible rates of glucose in the body?
- ATP production (glucose is oxidized to produce ATP)
- Amino acid synthesis
- Glycogen synthesis (glucose monomers are combined to form the polysaccharide glycogen)
- Triglyceride synthesis (hepatocytes transform glucose to glycerol and fatty acids)
How is glucose absorption accomplished in the GI tract?
Via secondary active transport
- Na+ glucose symporters
How is glucose absorption accomplished in the body (other than GI tract)?
GluT molecules (via facilitated diffusion) - insulin increases insertion of GluT into the plasma membrane, therefore, rate increases
What is the oxidation of glucose to produce ATP known as?
Cellular respiration
glucose catabolism
What are the four sets of reactions involved in cellular respiration?
- Glycolysis
- Formation of acetyl coenyzme A
- Krebs cycle
- Electron transport chain
What happens during glycolysis?
One glucose molecule is oxidized and it produces two molecules of pyruvic acid, two molecules of ATP and two (NADH + H+)
- ANAEROBIC CELLULAR RESPIRATION
What is anaerobic cellular respiration?
A way to produce ATP without oxygen
What happens during the formation of acetyl coenzyme A?
Pyruvic acid is prepared for entrance into the Krebs cycle
- also produces energy-containing NADH + H+ and carbon dioxide
What happens during the Krebs cycle reaction?
Oxidize acetyl co enzyme A and produces carbon dioxide, ATP, NADH + H+ and FADH2
What happens during the electron transport chain reaction?
NADH + H+ and FADH2 are oxidized, and transfer their electrons through a series of electron carriers
What are the two sets of reaction that require oxygen during cellular respiration?
Krebs cycle and electron transport chain
What is pyruvate dehydrogenase?
An enzyme
- converts pyruvic acid to a 2-carbon fragment called an acetyl group
Where does the Kerbs cycle occur?
In the matrix of mitochondria
- a series of oxidation-reduction reactions and decarboxylation reactions release CO2
Where does the electron transport chain reaction occur?
In the inner mitochondrial membrane
What is the overall reaction of cellular respiration?
Glucose (C6H12O6) + 6 oxygen molecules (6O2) + 36 or 38 Phosphate groups + 36 or 38 ADP –> 6 carbon dioxide molecules (6CO2) + 6 water + 36 or 38 ATP!
What happens if glucose is not needed immediately? What does it get made into?
Combines with other molecules to form glycogen
What is glycogenesis?
What hormone stimulates it?
Synthesis of glycogen
- insulin (from pancreatic beta cells) stimulates hepatocytes and skeletal muscles
Is glycogenesis catabolic or anabolic?
ANABOLIC!
What is glycogenolysis?
Process of splitting glycogen into its glucose subunits
What is gluconeogenesis?
Process where glucose is formed from noncarbohydrate sources
- triglycerides, lactic acid, certain amino acids
What is gluconeogenesis stimulated by?
Cortisol
- the main glucocorticoid hormone of the adrenal cortex
Glucagon (in the pancreas)
What are lipoproteins?
Lipid and protein combinations
- make lipids able to be transported in blood
What are the two ways that cholesterol can be increased in the blood?
- A high intake of dietary fats stimulates reabsorption of cholesterol-containing bile back into the blood - less is lost in the feces
- Saturated fats are broken down in the body, hepatocytes use some of the breakdown products to make cholesterol
What happens to the risk of coronary artery disease as total cholesterol level increases?
INCREASES!
What are the fates of lipids in the body?
- Can be oxidized to produce ATP
- Stored in adipose tissue
- Used as structural molecules or to synthesize other essential substances
What is the major function of adipose tissue?
To remove triglycerides from chylomicrons and VLDLs and store them until they are need for ATP production in other parts of the body
- 98% of body energy reserves
What happens during lipolysis?
Breakdown of triglycerides into glycerol and fatty acids
- epinephrine and norepinephrine enhance lipolysis
What hormone inhibits lipolysis?
Insulin
How do liver cells and adipose cells synthesize lipids from glucose or amino acids?
Through lipogenesis
- stimulate by insulin
What happens when individuals consume more calories than are needed to satisfy ATP needs?
Lipogenesis
- excess carbohydrates, proteins, fats are all converted into triglycerides
What are proteins used for?
Amino acids (broken down from proteins) are used to:
- oxidized to produce ATP
- synthesize new proteins for body growth and repair
What happens to excess proteins?
Not excreted in urine or feces
- converted into glucose (gluconeogenesis) or triglycerides (lipogenesis)
What are the fates/functions of proteins in the body?
Function as enzymes, transportation, antibodies, clotting chemicals, hormones, contractile elements in muscle fibers
What happens during protein catabolism?
Proteins are broken down into amino acids
- amino acids are recycled
What happens during protein anabolism?
Formation of peptide bonds between amino acids to produce new proteins
How many amino acids are in the human body?
How many are essential?
20 amino acids in the body
- 10 are essential
What are essential amino acids?
Must be present in the diet, b/c we cannot create them
What are non-essential amino acids?
Amino acids that the body can synthesize
What is happening during the absorptive state?
Ingested nutrients are entering the bloodstream and glucose is readily available for ATP production
- exists about 12 hours a day
What happens during the post-absorptive state?
Absorption of nutrients from GI tract is complete
- energy needs must be met by fuels in the body
What are the absorptive state reactions?
- 50% of absorbed glucose used to produce ATP (glycolysis, Krebs cycle and electron transport chain)
- Glucose is converted to glycogen (in hepatocytes)
- Hepatocytes package most fatty acids and triglycerides to adipose tissue for storage
- Adipocytes convert glucose into triglycerides for storage
- Dietary lipids are stored
- Amino acids enter Krebs cycle or are used to synthesize glucose or fatty acids
- Some amino acids are used to synthesize proteins
- Amino acids are used to synthesize hormones/chemicals
What happens about 4 hours after your last meal?
- blood glucose starts to fall (it continues to leave bloodstream while none is being absorbed)
During the post-absorptive state, what helps maintain blood glucose level?
- glucose production
- glucose conservation
What are the post-absorptive state reactions?
that produce glucose
- Breakdown of liver glycogen
- Lipolysis
- Gluconeogenesis using lactic acid
- Gluconeogenesis using amino acids
What are the post-absorptive state reactions?
produce ATP withOUT using glucose
- Oxidation of fatty acids
- Oxidation of lactic acid
- Oxidation of amino acid
- Oxidation of ketone bodies
- Breakdown of muscle glycogen
What is the metabolic rate?
Overall rate at which metabolic reactions use energy
What is the basal metabolic rate (BMR)?
Metabolic rate when the body is quiet, resting and fasting
What is the core body temperature?
Temperature in body structures deep to the skin and subcutaneous layer
- near 98.6 degrees F or 37 degrees C
What is the shell body temperature?
Temperature near the body surface
- 1-6 degress C COOLER than core temperature
What are the factors that affect heat production?
- Exercise - increases heat production
- Hormones - increase heat production
- Nervous system - increase metabolic rate
- Body temperature - the higher the body temperature, the higher the metabolic rate
- Ingestion of food - raises metabolic rate
- Age - metabolic rate slows as you age
- Other factors (pregnancy, climate, sleeping, malnutrition)
What are the mechanisms of heat transfer?
- Conduction - heat exchange between two things that are in direct contact with one another
- Convection - transfer of heat by the movement of fluid (a gas or a liquid)
- Radiation - transfer of heat in the form of infrared rays between a warmer object and a cooler one withOUT physical contact
- Evaporation - conversion of a liquid to a vapor; evaporating water takes with it a LOT of heat
What is the function of the hypothalamic thermostat?
Sets the desired body temperature
What are two centers in the hypothalamus that regulate heat?
- Heat-losing center
2. Heat-producing center
Describe the negative feedback loop that conserves heat and increases heat production.
- Stimulus disrupts homeostasis by decreasing body temperature
- Skin and hypothalamus detect changes in temperature
- Send nerve impulses to preoptic area
- heat-promoting center, neurosecretory cells in hypothalamus and thyrotropes in anterior pituitary - Effectors - vasocontriction (decreases heat loss through skin), adrenal medulla releases hormones that increase cellular metabolism, skeletal muscles shiver, thyroid gland releases thyroid hormone (increases metabolic rate)
- Increase in body temperature
What happens if the body temperature rises above normal?
A negative feedback loop kicks in
- stimulates heat-losing center
- dilation of blood vessels in the skin
- metabolic rate decreases
- shivering does not occur
- high temperature stimulates sweat glands
What is energy homeostasis?
Matching of energy intake (in food) to energy expenditure over time
What three components contribute to total energy expenditure?
- Basal metabolic rate (60% of energy expenditure)
- Physical activity (voluntary exercise) and energy costs of maintaining muscle tone, posture, fidgeting
- Food-induced thermogenesis
What is satiety?
Feeling of fullness accompanied by lack of desire to eat
What are nutrients?
Chemical substances in food that body cells use for growth, maintenance, and repair
What are the six main types of nutrients?
- Water
- Carbohydrates - provide energy
- Lipids - provide energy
- Proteins - provide energy
- Minerals
- Vitamins
What are minerals?
Inorganic elements that occur naturally in the Earth’s crust
- calcium, phosphorus, potassium, sulfur, sodium, chloride, magnesium, iron, iodide, manganese, copper, etc
What is the main role of minerals in the body?
Help regulate enzymatic reactions
What are vitamins?
Organic nutrients required in small amount to maintain growth and normal metabolism
- most are co-enzymes
What are provitamins?
Substance that is converted into a vitamin within an organism
What is a fever?
An elevation of core temperature caused by a resetting of the hypothalamic thermostat
What is obesity?
Body weight more than 20% above a desired standard
- due to an excessive accumulation of adipose tissue
What are heat cramps?
Cramps that result from profuse sweating
- salt lost in sweat causes painful contractions of muscles
What is heat exhaustion?
(Heat prostration)
- core temperature is generally normal, skin is cool and moist due to profuse perspiration
- loss of fluid and electrolytes
What is heat stroke?
(Sunstroke)
- Exposure to high temperatures and high humidity
- body temperature rises sharply b/c of failure of the hypothalamic thermostat
- must immerse body in cool water
What is malnutrition?
Imbalance of total caloric intake or intake of specific nutrients
- inadequate or excessive
