Unit V Review Flashcards
Chapter 25 What is metabolism
All the chemical reactions that take place in an organism
What is cellular metabolism
Chemical reactions within cells, which create energy
What is catabolism
The breakdown of organic molecules
What is anabolism
Synthesis of new organic molecules
What are the four reasons why cells synthesize new organic components
- Maintenance and repair 2. Support growth 3. Produce secretions 4. Store nutrient reserves
Which fuel source is used first by a cell that has an excess of fats, carbohydrates, and proteins? Why?
Carbohydrates. Glucose is the most efficient energy source, as fats and proteins must first be converted to other things before they can be used. (Fats are second choice, and protein is third)
Which step in the catabolism of glucose takes place in the cytosol of the cell
Glycolysis
What is the difference between aerobic and anaerobic metabolism
Aerobic = uses O2, anaerobic = does NOT use O2 Note: Glycolysis is ANAEROBIC, while reactions inside the mitochondria are aerobic
What is glycolysis
Catabolism of one glucose (6 carbon) to two pyruvate (3 carbon). (Glucose –> Pyruvic Acid –> Pyruvate)
Where does glycolysis take place in the cell
In the cytosol
Why is glycolysis considered to be an anaerobic process
It doesn’t use oxygen
How many carbon, hydrogen, and oxygen atoms are found in one molecule of glucose
C6 H12 O6
How many molecules of pyruvic acid are produced from the catabolism of one glucose molecule
Two
What is pyruvate
At the normal pH inside cells, each pyruvic acid (C3H4O3) molecule loses a hydrogen ion and exists as a negatively charged ion (called pyruvate - C3H3O3)
Which atoms in a glucose molecule are “harvested” and used to drive the process that synthesizes ATP from ADP
Hydrogen (pyruvate = C3H3O3)
In order for pyruvate to enter the citric acid cycle, what gas has to be available
O2
The citric acid cycle takes place in which organelle
Mitochondria
How is acetyl-CoA produced
NAD and coenzyme A react with pyruvate (C3H3O3) to yield: 1x acetyl-CoA (CH3CO) 1x carbon dioxide (CO2) 1x NADH
What is the main function of the citric acid cycle
To remove hydrogen atoms from organic molecules and transfer them to coenzymes
What acid binds to the acetyl group carried by CoA to form citric acid
Oxaloacetic acid (4 carbons: C4H4O5)
What enzymes are responsible for “harvesting” the hydrogen atoms in the citric acid cycle
NAD or FAD
What is oxidative phosphorylation and where does it take place
Produced more than 90% of ATP used by bodily cells. Takes place in the ETS (electron transport system - a series of integral and peripheral proteins in the inner mitochondrial membrane)
What compound is a byproduct of ATP synthesis
The basis of oxidative phosphorylation is the formation of water, a very simple reaction: 2(H2) + O2 = 2(H2O)
Why is oxidative phosphorylation considered an aerobic process
It uses oxygen [2(H2) + O2 = 2(H2O)]
What is the net gain in ATP molecules from the complete catabolism of one glucose molecule
36 molecules of ATP: 2 from glycolysis 4 from the NADH generated in glycolysis 2 from the citric acid cycle (by means of GTP) and 28 from the ETS
What is gluconeogenesis
The synthesis of glucose from noncarbohydrate precursors, such as lactate, glycerol, or amino acids
What precursor molecules are used in gluconeogenesis
Lactate, glycerol, or amino acids Note: Fatty acids cannot be used for gluconeogenesis, because their catabolic pathways produce acetyl-CoA!
What is glycogen and in which two organs is it mainly stored
Main form of glucose storage in the body. Stored primarily in the liver (400 calories) and muscles (800-1200 calories)
What is glycogenesis
Conversion of glucose to glycogen
What is glycogenolysis
Breakdown of glycogen
What atoms make up lipid molecules
Carbon, hydrogen and oxygen
What are the products of triglyceride catabolism
Glycerol and free fatty acids (FFA)
What is glycerol converted to in the cytosol
Pyruvate
What is beta oxidation
A sequence of reactions which converts FFA to 2-carbon acetic acid fragments, which are then converted to acetyl-CoA and enter the citric acid cycle
How many ATP molecules are synthesized when an 18 carbon fatty acid molecule is catabolized
144 ATP
Why do cells prefer to use carbohydrates for the synthesis of ATP during periods of high energy demand
Lipids cannot provide ATP as quickly as carbohydrates (glucose)
Why can almost any organic substrate be used in lipogenesis
The synthesis of most types of lipids begins with acetyl-CoA, and lipids, amino acids, and carbohydrates can be converted to acetyl-CoA
What is the most common form in which lipids circulate through the bloodstream
Most lipids circulate through the bloodstream as lipoproteins
Which cells are major users of free fatty acids
Liver cells, cardiac muscle cells, skeletal muscle fibers, and many other body cells can metabolize free fatty acids
What are lipoproteins
Lipid–protein complexes that contain large insoluble glycerides and cholesterol
What is the major constituent of chylomicrons and what is its main function
About 95 percent of the weight of a chylomicron consists of triglycerides
What are the major constituents of Low-Density Lipoproteins (LDL) and what is its function
Cholesterol, phospholipids, and few triglycerides They deliver cholesterol to peripheral tissues
Why is LDL referred to as “bad cholesterol”
Because the cholesterol may wind up in arterial plaques
What are the major constituents of High-Density Lipoproteins (HDL) and what is its function
Equal amounts lipid (cholesterol and phospholipids) and protein Transports excess cholesterol from peripheral tissues back to the liver for storage or excretion in the bile
How many amino acids are responsible for the synthesis of the hundreds of thousands of different proteins in the human body
20 amino acids
What is transamination
Attaches the amino group of an amino acid to a keto acid. This transfer converts the keto acid into an amino acid that can enter the cytosol, where it can be used for protein synthesis. In the process, the original amino acid becomes a keto acid that can be broken down in the citric acid cycle.
What is deamination
Prepares an amino acid for breakdown in the citric acid cycle
Why is the urea cycle important for the maintenance of homeostasis
Deamination produces toxic ammonium ions, which are neutralized into urea in the urea cycle
Why is protein catabolism an impractical source for quick energy
- More difficult to break apart than carbohydrates 2. Produces toxic ammonium ions 3. Proteins are vital components of cells
What are essential amino acids
10 amino acids which must come from diet and cannot be synthesized by the body
What are nonessential amino acids
Can be synthesized by the body on-demand
What is the role of the liver in metabolic regulation
The liver is the focal point of metabolic regulation: 1. Converts many enzymes to breakdown or synthesize needed carbs/lipids/amino acids 2. Large blood supply to monitor and adjust nutrient composition 3. Large energy reserves in glycogen
How are lipids stored in adipose tissue
Triglycerides
What is the role of skeletal muscles in energy storage and utilization
- Muscle contains substantial glycogen reserves 2. Contractile proteins can be broken down for amino acids to use as energy
What is unique about the energy needs of neural tissue
- Neural tissue has no reserves of carbs, lipids or amino acids. 2. Neurons need glucose (only), and cannot break down other molecules for energy Without glucose, the CNS will fail, and the person will fall unconscious
What is the absorptive state
Following a meal, cells absorb nutrients to be used for growth, maintenance, and energy reserves
What is the post-absorptive state
Metabolic reactions are focused on maintaining blood glucose levels that meet the needs of neural tissue
How are ketone bodies formed
Byproduct of fatty acid metabolism produced in the liver
How do peripheral tissues utilize ketones
Cells in peripheral tissues absorb ketone bodies and reconvert them to acetyl-CoA for breakdown in the citric acid cycle
What causes ketoacidosis
During prolonged starvation, ketone levels rise, and eventually buffering capacities are exceeded and a dangerous drop in pH takes place
How does the liver stabilize blood glucose levels in the post-absorptive state
First by the breakdown of glycogen reserves and later by gluconeogenesis
What are complete proteins
Proteins which provide all the essential amino acids (Some foods in the dairy and protein groups—specifically, beef, fish, poultry, eggs, and milk—provide all the essential amino acids in sufficient quantities. They are said to contain complete proteins.)
What are incomplete proteins
Proteins deficient in one or more of the essential amino acids
What is protein complementarity
Combining two or more foods with incomplete proteins, to form complementary proteins, can provide adequate amounts of all the essential amino acids - Beans and rice - Bread and peanut butter
Which essential vitamin is not found in the plants that we consume
B12, which is only obtained from animal products
What are minerals
Inorganic ions released through the dissociation of electrolytes
List some of the important minerals in the body
Sodium, potassium, chloride, calcium, phosphorus, magnesium
What are the four fat-soluble vitamins
A, D, E, K
List some of the important water-soluble vitamins
B and C vitamins
What is the main difference between fat-soluble and water-soluble vitamins
Fat-soluble vitamins can be stored in the liver and adipose tissue, and as a result normal metabolic function can continue without consuming them for several months. With water-soluble vitamins, only B12 and C are stored in significant quantities.
What is calorimetry
The process of calorimetry measures the total amount of energy released when the bonds of organic molecules are broken
What are a calorie and a kilocalorie
calorie (small c) - the amount of energy required to raise the temperature of 1 g of water 1 degree Celsius K-cal, or Calorie (big C) - the amount of energy needed to raise the temperature of 1 kilogram of water 1 degree Celsius
What is the caloric value of fats, carbohydrates, and proteins in Calories per gram
Carbs - 4 (4.18) Proteins - 4 (4.32) Fats - 9 (9.46) ** Alcohol - 7
What is metabolic rate
The sum of all the Calories being used by the various anabolic and catabolic processes taking place in your body at any given time
What is basal metabolic rate (BMR)
The minimum resting energy expenditure of an awake, alert person
What factors can influence BMR
These factors include age, gender, physical condition, body weight, and genetic differences Note: Energy use is proportional to oxygen consumption
Which hormone has a strong influence on the BMR
Thyroid hormones (thyroxine)
How is obesity defined
Body weight more than 20 percent above the ideal weight for a given individual
How do the hormones lepton and gherkin affect appetite
Lepton binds to CNS neurons to influence emotion and hunger
(Chapter 10) What is an epimysium
A dense layer of collagen fibers that surrounds the entire muscle
What is a perimysium
Divides skeletal muscle into a series of compartments
What is a fascicle
Each compartment of the muscle contains a bundle of muscle fibers (called a fascicle)
What is an endomysium
Surrounds the individual skeletal muscle cells, called muscle fibers, and loosely interconnects adjacent muscle fibers
What makes up tendons
At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium come together to form either a bundle known as a tendon (The sausage case extends past the end of the meat lol)
How are individual muscle fibers supplied with blood and innervated by nerves
Within the endomysium, arterioles supply blood to a capillary network that services the individual muscle fiber
Why are skeletal muscles multinucleated
The genes in these nuclei control the production of enzymes and structural proteins required for normal muscle contraction. The more copies of these genes, the faster these proteins can be produced.
What is the sarcolemma of a muscle fiber or muscle cell
The plasma membrane
What is the sarcoplasm of the muscle fiber or muscle cell
The cytoplasm of a muscle fiber
What are transverse tubules?
Narrow tubes whose surfaces are continuous with the sarcolemma and extend deep into the sarcoplasm. Able to conduct electrical impulses, and as a result, electrical impulses conducted by the sar colemma also travel along the T tubules into the cell interior
What are myofibrils
Each muscle fiber contains hundreds to thousands of cylindrical structures called myofibrils. A myofibril is 1–2m in diameter and as long as the entire cell. Branches of the T tubules encircle each myofibril. The active shortening of myofibrils is responsible for skeletal muscle fiber contraction.
What are myofilaments? What are the two types of contractile myofilaments in skeletal muscles
Myofibrils consist of bundles of protein filaments called myofilaments. 1. Thin filaments 2. Thick filaments
What is the sarcoplasmic reticulum
In skeletal muscle fibers, a membrane complex called the sarcoplasmic reticulum (SR) forms a tubular network around each individual myofibril, fitting over it like lacy shirtsleeves
What important cation that is required for muscle contraction is stored in the terminal cisternae
Ca2+ (calcium)
What are sarcomeres
Repeating functional units of myofilaments
What are the components of sarcomeres
(1) thick filaments (2) thin filaments (3) proteins that stabilize the positions of the thick and thin filaments (4) proteins that regulate the interactions be tween thick and thin filaments
What causes striations in skeletal muscles
Differences in the size, density, and distribution of thick filaments and thin filaments
Which myofilament chiefly occupies the A band
Thick filament (myosin)
What is the M line
The center line of the A band. (M is for middle)
What is the H band
A lighter region on either side of the M line. Contains only thick filaments.
What is the zone of overlap
A dark region where thin filaments are located between the thick fila ments. Here three thick filaments surround each thin fila ment, and six thin filaments surround each thick filament
What is the I band
A region of the sarcomere that contains thin fila ments but no thick filaments. It extends from the A band of one sarcomere to the A band of the next sarcomere
What are Z lines
Bisect the I bands and mark the boundary between adjacent sarcomeres. The Z lines consist of proteins called actinins
What four proteins are found in thin filaments
Actin (f-actin), nebulin, tropomyosin, troponin
What is the function of the active sites that are present on actin molecules
Provide a binding site for myosin
What is the function of tropomyosin
Cover actin to prevent binding of myosin and actin.
What is the function of troponin
Troponin binds to incoming Ca2+ and causes tropomyosin to “roll away”, exposing actin and allowing myosin binding
What are the components of thick filaments
Thick filaments are made up of 300 myosin molecules. They have a myosin tail, a hinge, and a myosin head (which attaches to actin)
How are cross-bridges formed
When the myosin heads interact with thin filaments during a contraction
In the sliding filament theory, which filaments stay put and which filaments move
The thick filaments in the A band stay put and the thin filaments in the I band move. The Z line approaches the A band.
What neurotransmitter is released at the neuromuscular junction
ACh
What is AChE and what is its role at the neuromuscular junction.
Acetylcholinesterase. Breaks down ACh at the neuromuscular junction
What happens when an action potential arrives at the sarcoplasmic reticulum
It triggers the release of calcium ions (Ca2+) from the terminal cisternae
Which filament covers the active sites on the actin filament in a resting muscle
Tropomyosin
What happens when calcium ions arrive at the zone of overlap
Ca2+ binds to troponin
What happens when calcium ions bind to troponin
Troponin pulls away tropomyosin and exposes the active sites of actin
What happens when the active sites on the actin filament are exposed
Myosin heads bind to the active sites (cross bridge formation). The sarcomeres shorten and pull the ends of the muscle fibers closer together
What causes myosin heads to detach from the active sites on the actin filament
When the action potential ends, tropomyosin recovers the active sites
What factors influence the duration of muscle contractions
- Period of stimulation at the neuromuscular junction 2. Level of calcium ions in the cytosol 3. Availability of ATP
What factors affect the tension produced by an individual muscle fiber
- The fiber’s resting length at the time of stimulation 2. The frequency of stimulation
What is a twitch in a single muscle fiber
A twitch is a single stimulus–contraction–relaxation sequence in a muscle fiber
Why is there a latent period between the arrival of a stimulus and tension generation in a muscle twitch
The latent period corresponds to the time needed for the conduction of an action potential and the subsequent release of calcium ions by the sarcoplasmic reticulum
What is treppe
If a skeletal muscle is stimulated a second time immediately after the relaxation phase has ended, the resulting contraction will develop a slightly higher maximum tension than did the first contraction. The increase in peak tension will continue over the first 30–50 stimulations.
What causes treppe
The rise is thought to result from a gradual increase in the concentration of Ca2+ in the cytosol, in part because the calcium ion pumps in the SR have too little time to recapture the ions between stimulations
What is wave summation
If a second stimulus arrives before the relaxation phase has ended, a second, more powerful con traction occurs
What is incomplete tetanus
A muscle producing almost peak tension during rapid cycles of contraction and relaxation is in incomplete tetanus (tetanos, convulsive tension)
What is complete tetanus
When a higher stimulation frequency eliminates the relaxation phase. Action potentials arrive so rapidly that the SR does not have time to reclaim the Ca2+.
Why are muscle twitches not useful in the production of sustainable muscle contractions
A single twitch is so brief that there isn’t enough time to activate a significant per centage of the available crossbridges
What is a motor unit
All the muscle fibers innervated by a single motor neuron
What is a fine motor unit
A small number of muscle fibers being controlled by a motor neuron
What is a gross motor unit
A large number of muscle fibers being controlled by a single motor neuron
What is recruitment
The smooth, but steady, increase in muscular tension pro duced by increasing the number of active motor units
What is muscle tone
In any skeletal muscle, some motor units are always active, even when the entire muscle is not contracting. Their contrac tions do not produce enough tension to cause movement, but they do tense and firm the muscle.
What is an isotonic contraction
Tension increases and the skeletal muscle’s length changes. There are two types of isotonic contractions: concentric and eccentric
What is a concentric contraction
The muscle tension exceeds the load and the muscle shortens
What is an eccentric contraction
The peak tension developed is less than the load, and the muscle elongates due to the contrac tion of another muscle or the pull of gravity
What is an isometric contraction
The muscle as a whole does not change length, and the tension produced never exceeds the load
What are the three factors that play a role in returning a contracted muscle to its original length
Elastic forces, opposing muscle contractions, gravity
What intensity and duration of physical activity can be sustained by CP stored in muscles
15 second all-out run
What is the main fuel of resting skeletal muscles
CP
What is the main fuel of active skeletal muscles
ATP
What causes muscle fatigue
(1) depletion of metabolic reserves within the muscle fibers (2) damage to the sarcolemma and sarcoplasmic reticulum (3) a decline in pH within the muscle fibers and the muscle as a whole (4) a sense of weariness and a reduction in the desire to continue the activity, due to the effects of low blood pH and sensations of pain
What happens to lactic acid during the recovery period
During the recovery period, when oxygen is available in abundance, lactate can be converted back to pyruvate
List the main characteristics of fast fibers
- Reach peak tension 0.01 sec after stimulation - Large in diameter - Densely packed myofibrils - Large glycogen reserves - Few mitochondria - “White muscles”
List the main characteristics of slow fibers
- Take 3x as long to reach peak tension - Half the diameter of fast twitch - Surrounded by a more extensive network of capillaries, for more oxygen - Contain more myoglobin - “Red muscles”
What is muscular hypertrophy
As a result of repeated, exhaustive stimulation, muscle fibers develop more mitochondria and larger glycogen reserves. Such muscle fibers have more myofibrils than do lessstimulated fibers, and each myofibril contains more thick and thin filaments.
What is muscular atrophy
A skeletal muscle that is not regularly stimulated by a motor neuron loses muscle tone and mass
Why is anaerobic activity only sustainable for only a very short period of time
Anaerobic activity is restricted by: 1. The reserves of ATP and CP 2. The amount of glycogen available for glycolysis 3. The tolerance of the muscle to lactic acid
List the main structural features of cardiac muscles
- Cardiac muscle cells are relatively small - Typical cardiac cell has a single nucleus - The SR of a cardiac muscle cell lacks terminal cisternae, and its tubules contact the plasma membrane as well as the T tubules
List the main functional characteristics of cardiac muscle cells
- Cardiac cells contract without neural stimulation - Nervous system can alter pace of contraction - Contract about 10x as long as skeletal muscle - Sarcolemma structure is different
(Chapter 11) What is the main characteristic of parallel muscles? Provide an example.
The fascicles (bundles of muscle fibers) are parallel to the long axis of the muscle, e.g., biceps brachii
What is the main characteristic of convergent muscles? Provide an example.
Muscle fascicles extending over a broad area come together, or converge, on a common attachment site, e.g., pectoralis muscles.
What is the main characteristic of a pennate muscle? Provide an example.
In a pennate muscle (penna, feather), the fascicles form a common angle with the tendon, e.g., extensor digitorum muscle.
Why are pennate muscles able to generate more tension than parallel muscles
A pennate muscle has more muscle fibers—and thus more myofibrils—than does a parallel muscle of the same size
What is the main characteristic of circular muscles? Provide an example.
Aka sphincter. The fascicles are concentrically arranged around an opening, e.g., obicularis oris.
What is an antagonist muscle
A muscle whose action opposes that of a particular agonist
