Weeks 4, 5 and 6 Flashcards
The only polysaccharide in the human body is:
Glycogen
The only lymphatic organ with both afferent and efferent lymphatic vessels is…
a lymph node
Tonsils promote memory of pathogens by…
trapping pathogens to develop immune cells with memory
Lymph transport is…
Sporadic and slow
Buboes are inflamed and swollen…
lymph nodes
Which of these lymphatic organs has a cortex and medulla? (I) spleen (II) lymphatic organs (III) thymus?
II and III only
Memory cells are responsible for tissue graft rejection. True or false?
False
Excess fluid drains from the central nervous system into…
The cerebrospinal fluid
Lymphatic System returns fluids that leaked from blood vessels back to blood.
True
Why is clonal expansion so important?
to increase the number of specific cells.
Nutrient: food substance needed for growth,
maintenance, repair
− Most nutrients used as metabolic fuel
− Some used for cell structures and molecular
synthesis (eg. hormones, enzymes, hemoglobin etc)
− Is water a nutrient?
Yes.
Three overall classes of nutrients
− Macronutrients – Carbohydrate, proteins, lipids, fibre
− Micronutrients (Essential) – Vitamins & Minerals
− other Essential Nutrients – some amino/fatty acids
Yes.
Conversion value:
1 “Calorie” ≈ 4.2 Kj
Yes.
Role of Carbohydrates, Lipids, and Proteins
Carbohydrates:
− basic units are simple sugars (ie glucose, fructose)
− Monosaccharides, Disaccharides, Polysaccharides
• Dietary sources & types
– Starch (a polysaccharide/complex carbohydrate) -
primarily from plants, mainly grains and vegetables.
– Sugars (mono- and disaccharides) in fruits, sugarcane,
sugar beets, honey, and milk
– Insoluble fiber: cellulose in vegetables → roughage
– Soluble fiber: pectin in apples and citrus fruits reduces
blood cholesterol levels
Glucose (G) Maltose (G-G) Glycogen (G-G-G……-G)
Yes.
Carbohydrates
Uses in body
– Glucose: fuel most used by cells to make ATP
− Neurons and RBCs rely almost entirely on
glucose
» Neurons die quickly without glucose
– Excess glucose is converted to glycogen or fat,
then stored
» Some cells use fat for energy (ie fatty acids)
Yes.
Carbohydrates
Dietary requirements
– Recommended daily intake: 45–65% of total
calories
• complex carbohydrates preferable (ie starch
from whole grains and vegetables)
– Simple carbohydrates should be limited
– High amounts of simple sugars can lead to obesity,
DM, as well as nutritional deficiencies
– Refined complex carbohydrates (bread, pasta)?
Yes
Carbohydrates
Glycemic Index
− measure of how food affects blood glucose levels
Yes
Lipids
Dietary sources
– Triglycerides (3 chain fatty acid derivatives)
o most abundant form of lipids
o “Saturated fats” found in meat, dairy foods, tropical
oils, or hydrogenated oils (trans fats)
o
“Unsaturated fats” found in seeds, nuts, olive oil, and
most vegetable oils
o Liver can convert some fatty acids into others, but
essential fatty acids must be eaten (examples: linoleic
and linolenic acid found in most oils)
– Cholesterol found in egg yolk, meats, organ
meats, shellfish, and milk products
o Liver makes ~85% cholesterol
Yes
Lipids
Uses in body
– Adipose tissue offers protection, insulation, fuel
storage
– Phospholipids essential in myelin sheaths and all
cell membranes
– Cholesterol stabilizes membranes; precursor of bile
salts, steroid hormones
– Prostaglandins contraction of some smooth muscle,
BP control, inflammation
– Lipids help absorb fat-soluble vitamins
– Major fuel alternative for hepatocytes, skeletal muscle
and nervous tissue
Yes
Lipids
American Heart Association recommendations
• Fats: 30% or less of total caloric intake
• Saturated fats: 10% or less of total fat intake
• Cholesterol: no more than 300 mg/day
(about 1-1/2 egg yolks)
– Goal is to keep cholesterol < 200 mg/dl
• Excess lipid in diet
• Increases risk* of cardiovascular disease
• Especially high intake of saturated/trans fats &
cholesterol
Yes
Proteins: Dietary sources
Animal products (eggs, milk, fish, most meats),
as well as soybeans, are complete proteins
− Contain all needed essential amino acids
• Legumes, nuts, and cereals contain incomplete
proteins (lack some essential amino acids)
– Legumes and cereal grains together contain all
essential amino acids
• Dietary needs reflect age, size, metabolic rate,
nitrogen balance
– Daily intake of 0.8 g per kg body weight
– High protein diet ????!!!!
Yes.
Proteins
Digested/absorbed as individual amino acids
− “Reconstructed” into a variety of proteins within body
• Uses in body
– Structural materials
• Examples: cell membranes, keratin (skin),
collagen and elastin (connective tissue)
and muscle proteins
– Functional molecules
• Example: enzymes, some hormones, antibodies,
hemoglobin
Yes.
Proteins
Uses in body (cont.)
Three factors help determine whether amino acids are used to
synthesize proteins or burned as fuel:
1. All-or-none rule
• All amino acids needed must be present for protein synthesis
to occur; if all not present, then amino acids used for energy
2. Adequacy of caloric intake
• Protein is used as fuel if insufficient carbohydrate or fat is
available
3. Hormonal controls
• Anabolic hormones (GH, sex hormones) accelerate protein
synthesis and growth
• Adrenal glucocorticoids (released during stress) promote
protein breakdown and conversion of amino acids to glucose
Yes
Role of Vitamins and Minerals
Vitamins
• Organic compounds that are crucial in helping body use
nutrients
• Many function as coenzymes (eg B12)
• Most must be ingested, except:
– Vitamin D (some made in skin)
– Some B vitamins and K synthesized by intestinal
bacteria
– Beta-carotene (e.g., from carrots) converted in body to
vitamin A
• No one food group contains all vitamins
• Some vitamin deficiencies → serious problems
Yes
Vitamins
Two types of vitamins based on solubility
– Water-soluble vitamins BC
• B complex and C are absorbed with water
• B12 absorption requires intrinsic factor
• Not stored in the body
– Any not used within 1 hour are excreted
– Fat-soluble vitamins ADEK
• A, D, E, and K are absorbed with lipid digestion
products
• Stored in body, except for vitamin K
– Excessive consumption can cause health problems
Yes
Minerals
Seven minerals are required in moderate
amounts:
– Calcium, phosphorus, potassium, sulfur, sodium,
chlorine, & magnesium
• Others are required in trace amounts (Fe, Se)
• Involved in a range of body activities
− CVS, muscle, nerves, heme, antioxidants
• Uptake and excretion are balanced to prevent
toxic overload
Yes.
Metabolism Metabolism: sum of all biochemical reactions in body to provide energy or to make new materials • Anabolism: synthesis of large molecules from small ones • synthesis of proteins from amino acids • Glucose → glycogen • Catabolism: breakdown of large molecules to smaller ones – often for energy • glucose → CO2 + H2O; proteins → amino acids • Both processes can occur at the same time within a cell Catabolic reactions @2013 Pearson Education, Ltd. Anabolic reactions Glycogen PROTEINS Proteins Triglycerides CARBOHYDRATES Glucose FATS Amino acids Glucose and other sugars Glycerol Fatty acids Pyruvic acid Acetyl CoA Infrequent NH3 H ATP ATP ATP CO2 O2 H2O Oxidative phosphorylation (in electron transportchain) Citric acid cycle Glycolysis Figure 24.3 Three stages of metabolism of energy-containing nutri
Yes
Energy release, energy capture and ATP (Adenosine Triphosphate) Chemical reactions and energy − Many chemical reactions need external energy to occur (cooking) − Other reactions give out internal energy - often as heat • Batteries store energy − Chemical reaction releases energy (electricity/heat) − Some batteries can be recharged – but require energy ADP + P ATP Requires energy Gives out energy • ATP stores energy in the body (phosphorylation)
Yes
Energy in the human body
Cellular respiration: Catabolic breakdown of food
fuels where energy is captured to form ATP in cells
− Cellular respiration traps chemical energy in ATP
− Energy can also be stored longer term in glycogen and
fats, which can be broken down later
• Phosphorylation:
− Primarily captures energy in ATP
− enzymes shift high-energy phosphate groups within
ATP to other molecules
− Phosphorylated molecules become activated to
perform cellular functions
Yes
Cellular Respiration and ATP production
Two mechanisms make ATP from captured energy liberated
during cellular respiration
1. Substrate-level phosphorylation
• Occurs during Glycolysis (cytosol)
• And during the Citric Acid Cycle (mitochondria)
2. Oxidative Phosphorylation (O2
required)
• Very complex and occurs in mitochondia
• Produces most ATP thru a chemiosmotic process
• Electron energy harnessed from Glycolysis & Citric Acid Cycle
pumps H+
ions across inner mitchondrial membrane to “outside”
• As H+
ions flow back into mitochondria energy is harnessed by ATP
synthase - to produce ATP
Yes.
Lipid Metabolism
Lipids are the most concentrated source of energy.
•Most products of fat digestion absorbed as
“chylomicrons” and transported in lymph.
• Enzymes (lipases) in capillary endothelium act on
chylomicrons releasing fatty acids and glycerol.
•Oxidation of ‘fatty acids’ and ‘glycerol’ occurs
separately
• Three steps in Lipid Metabolism:
• Beta oxidation
• Lipolysis
• Lipogenesis
Yes.
Lipolysis and Lipogenesis
• Lipolysis provides fatty acids and glycerol (especially
for liver, cardiac muscle and resting skeletal
muscles)
• When carbohydrates are deficient, lipid oxidation is
incomplete and acetyl CoA accumulates… leading to
formation of ketone bodies
• Lipogenesis occurs when cellular ATP and glucose
levels are high
•In addition to their functions as energy substrate,
lipids are important for:
• Maintenance of the integrity of lung alveoli (surfactant)
• Solubilisation of non-polar substances in body fluids
Yes.
Clinical – Homeostatic Imbalance
Too much lipolysis may result in accumulation of ketone
bodies.
• When ketone bodies accumulate in the blood, ketosis
results and large amounts of ketone bodies are excreted
in urine.
• Ketosis is a common consequence of starvation,
extreme dieting, and diabetes mellitus.
• Ketosis leads to metabolic acidosis… if untreated,
patient may become comatose or even die
Yes.
Protein Metabolism
Amino acids are derived from dietary proteins or
they come from break down of existing proteins in
the body.
• Amino acids are recycled into new proteins or
other N-containing compounds.
• Proteins are not stored in body
– When dietary proteins are in excess, amino
acids are:
• Oxidized for energy or
• Converted to fat for storage
Yes.
Degradation of Amino Acids
Goal is to produce molecules that can be used for
energy in citric acid cycle or converted to glucose
•Before amino acids can be oxidised or converted,
they must be deaminated (NH2 group is removed),
then they are converted into:
• Pyruvic acid or
• One of keto acid intermediates of citric acid cycle
• Three events of amino acid degradation:
• Transamination
• Oxidative deamination
• Keto acid modification
Yes.
Protein Synthesis
Amino acids are most important anabolic nutrients.
• Form all proteins as well as bulk of functional molecules.
•Protein synthesis that occurs on ribosomes is
hormonally controlled (example: growth hormone,
thyroid hormone, sex hormones).
• Synthesis requires complete set of amino acids
• Essential amino acids must be acquired in diet.
•If essential amino acids are lacking in diet, body
protein is broken down to supply these, and negative
nitrogen balance results.
Yes.
Metabolic States of the Body
Catabolic-Anabolic Steady State
• Dynamic state in which organic molecules (except
DNA) are continuously broken down and rebuilt.
• Body uses nutrient pools(stores of amino acids,
carbohydrates, and fats)
– Pools are interconvertible because pathways are
linked by common intermediates.
– Amount and direction of conversion are directed by
liver, adipose tissue, and skeletal muscle.
Yes.
Catabolic-Anabolic Steady State
Two major differences between carbohydrate/fat
pools and amino acid pool:
• Fats and carbohydrates are oxidized directly to produce
energy
• Amino acids must first be converted to a citric acid cycle
keto acid
• Excess carbohydrate and fat can be stored as such.
Amino acids are not stored as proteins.
Yes.
Absorptive State
Also called fed state, lasts for ~4 hours after eating,
when absorption of nutrients is occurring
•Anabolism exceeds catabolism
• Excess nutrients are stored as fats if not used
Yes.
Absorptive State
Hormonal control of the absorptive state
• Absorptive state is controlled primarily by insulin
•Insulin secretion by beta cells of pancreas is stimulated
by:
• Elevated blood levels of glucose and amino acids
• Intestinal GIP (glucose-dependent insulinotropic peptide)
and parasympathetic stimulation
• When insulin binds to membrane receptors, it
facilitates diffusion of glucose into muscle and
adipose cells
• Brain and liver take up glucose without insulin
Yes.
Insulin
•Insulin binds to membrane receptors on its target
cells. This stimulates translocation of glucose
transporters to the plasma membrane, which
enhances facilitated diffusion of glucose into cells.
•Within minutes, the rate of glucose entry into cells
(particularly muscle and adipose cells) increases
about 20-fold.
•Brain and liver cells do not require insulin for
glucose uptake
Yes.
Clinical – Homeostatic Imbalance
Diabetes mellitus: inadequate insulin production or
abnormal insulin receptors
•Results in:
• Unavailability of glucose to most body cells
• Excessively high blood glucose levels
• Glucose loss in urine
• Fats and proteins are used for energy instead
•Can lead to metabolic acidosis, protein wasting, and
weight loss
Yes.
Postabsorptive State
•Postabsorptive state is also called fasting state,
when GI tract is empty and energy sources are
supplied by breakdown of body’s reserves
•Catabolism of fat, glycogen, and proteins exceeds
anabolism
•Goal is to maintain blood glucose between meals
by:
• Making glucose available to blood
• Promote use of fats for energy
•Glucose sparing saves glucose for organs that need
it most, such as brain
Yes.
Postabsorptive State
Sympathetic nervous system interacts with several
hormones to control events of postabsorptive state.
•Postabsorptive state is triggered by reduced insulin
release as blood glucose levels drop.
•Glucagon: hyperglycemic hormone is released in
response to declining blood glucose levels and rising
amino acid levels
•Glucagon promotes:
• Glycogenolysis and gluconeogenesis in the liver
• Lipolysis in adipose tissue, causing fatty acids and glycerol
to be released
Yes
In Summary
Metabolic pathways are dynamic, interrelated
networks.
• Catabolic and anabolic pathways are at least partially
reversible in response to the availability of fuel
substrates.
• The pathways intersect…
e.g., variation in the plasma concentration of glucose can
activate or inhibit pathways in lipid metabolism, and vice
versa.
• Metabolic intermediates can enter other pathways…
e.g., intermediates from glucose breakdown serve as
substrates for amino acid and fatty acid synthesis.
Yes
Cholesterol Metabolism
Cholesterol is not used as an energy source
•It is structural basis of bile salts, steroid hormones,
and vitamin D
•Major component of plasma membranes
• 15% of blood cholesterol is ingested, with rest made
in body, primarily by liver
• Lost from body when catabolized or secreted in bile
salts that are lost in faeces
Yes.
Cholesterol Transport
Lipoproteins: transport water-insoluble cholesterol
and triglycerides through blood
• The higher the percentage of lipids, the lower the
density
• Types of transport lipoproteins
• HDLs (high-density lipoproteins): highest protein content
• LDLs (low-density lipoproteins): highest cholesterol
content
• VLDLs (very low-density lipoproteins): contents are more
than half triglycerides, with low density of proteins
• Chylomicrons: have lowest density and consist almost
entirely of triglycerides
Yes
Regulation of Blood Cholesterol Levels
Recommended cholesterol, HDL, and LDL levels
– Maximum total cholesterol: 200 mg/dl or less
• Levels > 200 mg/dl linked to atherosclerosis
– More important to measure form in which
cholesterol is transported in blood
– HDL is thought to protect against heart disease
because it takes cholesterol out of blood
• >60 is good, <40 not good
– LDL cholesterol deposits cholesterol in vessels
• 100 or less is good, 130 or above not good
Yes.
Regulation of Blood Cholesterol Levels
• Liver produces cholesterol at a basal level regardless
of dietary cholesterol intake
• Restricting dietary cholesterol does not markedly reduce
blood cholesterol levels
•More important effect is relative amounts of
saturated and unsaturated fatty acids
• Saturated fatty acids stimulate liver synthesis of
cholesterol and inhibit cholesterol excretion from body
• Unsaturated fatty acids enhance excretion of cholesterol
into bile salts
Yes
Regulation of Blood Cholesterol Levels
• Trans fats can occur when healthy oils are
chemically transformed into solids (example:
margarine)
• Worse effect on cholesterol levels than saturated fats;
increase LDL and reduce HDL
•Unsaturated omega-3 fatty acids (found in coldwater fish) have lower proportions of saturated fats
and cholesterol
• Make platelets less sticky and help prevent spontaneous
clotting
• Have antiarrhythmic effects on heart
• Can lower blood pressure
Yes.
Clinical – Homeostatic Imbalance
Risk factors for assessment of cardiovascular disease:
•Previously high cholesterol and LDL:HDL ratios were
used as predictors of potential disease
• Found not to be as reliable
•Now LDL levels and other risk factors are believed
to be more accurate
• Treatment for high LDL levels
• Statins: cholesterol-lowering drugs
• Estimated >10 million Americans take statins
Yes.
Energy Balance •Bond energy released from food must equal total energy output • Energy intake: • energy liberated during food oxidation (depends upon the type of food consumed) • Energy expenditure: • Lost as heat • Basal metabolic rate • Physical activity • Stored as fat or glycogen
Yes.
Daily energy expenditure
•Daily energy expenditure may be expressed as a
ratio to resting metabolic rate- the “physical activity
level” (PAL)
• Sedentary people have a PAL around 1.4
• Highly active people have PAL up to 2.5
• Elite endurance athletes (e.g., Tour de France cyclists)
may maintain a PAL value of 3 to 4
•If energy intake equals energy output, then a
person’s weight is stable. If not equal, there will be
gain or loss of weight
Yes.
Obesity
•Obesity is a problem because of its complications…
• Obese people have higher risk of atherosclerosis, type 2
diabetes mellitus, hypertension, heart disease, and
osteoarthritis.
• The causes of the high incidence of obesity in the
general population are probably multiple.
•Obesity can be determined by the body mass index
(BMI).
•Other parameters used are:
• Estimated body fat; skinfold thickness; arm
circumference; waist circumference and waist/hip ratio
Yes.
Regulation of Food Intake
•Areas of hypothalamus release peptides that
influence feeding behaviour
• Arcuate nucleus (ARC), lateral hypothalamic area (LHA),
ventromedial nucleus (VMN)
• Some ARC neurons release neuropeptide Y (NPY)
and agouti-related peptides that enhance appetite
•Other ARC neurons release pro-opiomelanocortin
(POMC) and cocaine-/amphetamine-regulated
transcript (CART), which suppress appetite
Yes.
Regulation of Food Intake
• Feeding behaviour and hunger regulated by:
• Neural signals from digestive tract
• Blood borne signals related to body energy stores
• Hormones
• Psychological factors
•Operate through brain thermoreceptors,
chemoreceptors, and others
• Food intake is subject to both short- and long-term
controls
Yes.
Short-term regulation of food intake
•Neural signals from digestive tract
• High protein content of meal increases and prolongs
afferent vagal signals
• Distension sends signals along vagus nerve that suppress
hunger center
•Nutrient signals related to energy stores
• Increased nutrient levels in blood depress eating
•Hormones
• Gut hormones (e.g., insulin and CCK) depress hunger
• Glucagon and epinephrine stimulate hunger
• Ghrelin (Ghr) from stomach stimulates appetite; levels
peak prior to mealtime
Yes.
Long-term regulation of food intake
• Leptin
• Hormone secreted by fat cells in response to
increased body fat mass
• Protects against weight loss in times of nutritional
deprivation
• Acts on ARC neurons in hypothalamus. Suppresses
secretion of NPY (a potent appetite stimulant)
• Rising leptin level causes some weight loss but is no
“magic bullet” for obese patients
• Obese people have high leptin levels but seem to be
resistant to its action
Yes.
In Summary…
• Liver is the metabolic powerhouse of the body
• Lipoprotein metabolism is important in maintaining
blood cholesterol levels
• Ratio and levels of various lipoproteins are important risk
factors for heart disease
• Energy intake and expenditure balance is important
to maintain healthy body weight and avoid
metabolic complications
Yes.
Metabolic Rate
• Metabolic rate: total heat produced by
chemical reactions and mechanical work of
body
– Can be measured:
• Directly: calorimeter measures heat liberated
into water chamber
• Indirectly: respirometer measures oxygen
consumption (directly proportional to heat
production)
Yes.
