Test 2 Flashcards
Lipid definition
substances that are generally insoluble in water, but soluble in organic solvents
Simple lipids
fatty acids, tri,di, and mono-acylglcerols, waxes (sterol esters, nonsterol esters, etc)
Compound lipids
phospholipids, glycolipids, lipoproteins
derived lipids
hydrolysis of lipids in group 1-2
ethyl alcohol
one lipid classification
-similar as lipid metabolism
Short chain FA
2-4
won’t be found in diet
from gut bacteria
medium chain FA
6-10 C, not found in diet
Long chain FA
12-24, found in diet
Why do most FA have even number?
most generated from acetyl coA (2 C chain)
FA are amphipathic
true
monounsaturated FA
one double bond between carbon usuall non-essential but may be 1/3 of total FA intake such as oleic acid
Polyunsaturated FA
multiple double bonds (up to six)
Which FA will be solid at room temperature?
Saturated FA
Polyunsaturated FA are trans or cis form?
Cis
Where does Trans fat come from?
Created industrially in partial hydrogenation of plant oils -higher melting point for baking and extends shelf-life
Omega 6 FA
Linoleic Acid (18:2)
essential
Omega 3 FA
alpha-Linolenic Acid (18:3)
essential
**What are the most prevalent saturated FA in average US diet?
Palmitic and stearic acid
Where does beta-oxidation happen?
Mitochondria
Where is FA stored?
cytosol
What helps transfer FA from cytosol to mitochondria?
Acyl-CoA (requires 2 ATP)
-transport of acyl-CoA into mitochondria via an acyl-carnitine intermediate
**What is formed when FA are oxidized in the mitochondria?
acetyl CoA
FA synthesis
uses acetyl CoA (in mitochondria) to make FA in cytosol
how does acetyl CoA move from mitochondria to cytosol?
Oxaloacetate to citrate which can pass membranes then reverts back to oxaloacetate…
Key enzyme that controls FA synthesis
acetyl-CoA carboxylase
Most carboxylation uses what as a coenzyme?
Biotin
**What is the primary FA synthesized that can then undergo elongation and/or unsaturation to yield other FA?
palmitate (16:0)
If fat is entirely excluded from the diet what happens?
-retarded growth
-dermatitis
-kidney lesions
-early death
Why is omega-6 (linoleic acid) essential?
Our body cannot produce it and uses it to produce arachidonic acid
What is omega-3 (alpha linolenic acid) a precursor for?
n-3 PUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)
**Which fatty acid is considered essential and must be consumed by the diet?
alpha-linolenic acid
linoleic acid
Significance of arachidonic acid
Precursor to eicosanoids
-prostoglandins
-thromboxanes
-leukotrienes
Eicosanoids produce a wide range of biological effects on….
inflammatory responses
pain and fever
reproductive function
regulating blood pressure
platelet aggregation
thrombosis
Dietary sources of PUFA
animal fats are largely saturated, pig/poultry have less saturated FA and some PUFA, fish and plant oils are highly unsaturated
Fish vs plant omega 3
fish = EPA/DHA
plant = ALA (short chain omega 3)
Glycerol can be used directly in every tissue except..
adipose
What do adipocytes use for triacylglycerol synthesis?
dihydroxyacetone phosphate from glycolysis
When used for energy, FA are released as free FA by lipases (A1-3) in adipose tissue cells, then transferred by what protein to other tissue cells for oxidation?
albumin
cholesterol is stored in cells has
cholesterol esters
The majority of cholesterol is endogenous
true (about 2/3)
How much cholesterol in our body per day
1 g/day
Nearly all tissues can synthesize cholesterol from…
acetyl coA
What is the rate controlling enzyme in cholesterol synthesis?
HMG-CoA reductase
**Humans build about ____ mg of cholesterol each day.
700 mg
Cholesterol is important membrane structure and precursor for the synthesis of:
-steroid hormones
-bile acids
-adrenocortical hormones
-vitamin D
Primary bile acids come from….
cholesterol in the liver
Primary bile acids:
chenodeoxycholic acid (45%)
cholic acid (31%)
How are secondary bile acids formed?
primary bile acidds are acted upon by gut bacteria to form secondary bile acids
Secondary bile acids
deoxycholate, lithocholate (from chenodeoxycholate)
Where in small intestine is dietary TAG mostly digested?
upper jejunum (70-90%)
Can intact TAG be absorbed?
No; only hydrolytic TAG such as MAG and FFA
***What is the most active site of lipid digestion?
Upper jejunum
All lipids in the body are transported by 5 lipoproteins:
chylomicrons transport exogenous dietary lipids
-VLDL
-IDL
-LDL
-HDL
***The main function of lipoproteins is
To act as the carrier of lipids
***The main component of a HDL molecule is protein…
True
major function of chylomicrons
deliver dietary triacyglycerols to tissues and dietary cholesterol to the liver
Apolipoproteins of chylomicrons
apoB-48, apoA
LDL is often termed “bad cholesterol” b/c it has been linked to atherogenic fatty plaque formation…
true
Trans FA are now considered more atherogenic than saturated FA b/c they…
elevate serum LDL while decreasing HDL
Antiatherogenic Mechanisms of n-3 PUFA
-interfere w/platelet aggregation by inhibiting thromboxane production
-reduction of proinflammatory leukotrienes
-reduction of serum triacylglycerols
How much ALA will convert to EPA and DHA?
<5%
Statins
fungal HMG-CoA reductase inhibitors –>increased cellular uptake of LDL
Nicotinic acid (niacin)
reduces plasma VLDLs and LDLS by inhibiting hepatic VLDL secretion and FFA release from adipose tissue
olistat
derivative of lipstatin, potential inhibitor of gastric and pancreatic lipase
**The MOA of Orlistat
-to inhibit lipase activity
Rate limiting step in FA synthesis
-acetyl-CoA carboxylase (ACC)
ACC is inhibited by
palmitoyl-CoA and other long-chain acyl-CoAs
ACC is activated by…
citrate
Regulation of Lipid Metabolism
-other major target other than ACC
carnitine palymitoyl=CoA transferase-I
-prevents against FA oxidation
**Which hormone is considered to be an antagonist of lipolysis?
Insulin
From overflow of acetyl CoA (from fat catabolism) the liver cells can create…
ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone)
**Excessive ketone bodies may be accumulated due to reduced supply of cellular glucose and a concomitant _____ in FA oxidation.
increase
Two major pathways of oxidation of ethyl alcohol
-ADH- alcohol dehydrogenase (major)
-MEOS- microsomal ethanol oxidizing system (minor)
**What is the legally intoxicated amount of alcohol in the bloodstream?
-less than 10%
(it’s 0.08)
Ethanol intoxication causes cellular imbalance of NADH/NAD+
-in mitochondria leads to FA synthesis
-in cytosol leads to TAG synthesis
results in fatty liver syndrome
Epigenetics
modification of gene expression by mechanisms other than in the underlying DNA sequence (nutritional factors)
Nutrigenomic
nutrition interacts with genetics to influence health
**About ____ of the dry weight of a typical human cell is protein
one half
**Enzymes
decrease transition (activation) energy
Collagen is made up of
tropocollagen
Tropocollagen is made up of…
3 peptide chains that are cross-linked triple helix
Which AA does collagen have a large amt of?
glycine and proline
2 AA unique to collagen
Hydroxylysine
hydroxyproline
5 classes of plasma proteins by electrophoresis:
-albumin
-alpha1-globulins
-alpha2-globulins
-beta-globulin s
-gamma globulins
55% of total plasma proteins
Albumin
**Albumin functions:
-nonspecific transport protein (ex FA, CA, Zn, Vitamin B6)
-contribution to osmotic pressure of the blood
**Major role of alpha1-globulin
inhibit certain blood protease, contains alpha1-antitrypsin
-inhibitor of elastase that degrades elastin
***alpha2-globulins
ceruloplamin (copper transport protein)
haptoglobulin (binding free hemoglobin)
**The most important beta-globulin protein
transferrin and LDL apoprotein
***gamma globulins
immunoglobulins or antibodies
5 classes of immunoglobulins
IgG-70% (repeated exposure), can cross placenta
IgA-can secrete in milk (passive immunity)
IgM-largest, responds first
IgE-responsible for allergy
IgD
Protein domain
large functional sequences of AA that have unique three-dimensional shape
more than ____ human diseases can be traced to production of abnormal proteins
1500
Which AA are absolutely essential?
lysine
threonine
histidine
3 classes of AA
glucogenic
ketogenic
glucogenic and ketogenic
ketogenic AA
lycine, leucine
**A deficiency in which AA will result in Kwashiorkor, even though the diet may contain a large amount of protein?
Tryptophan
Three phases of protein digestion
- gastric (10-15%)
-pepsin hydrolyzes proteins to polypeptides - Intestinal (most important)
- Brush Border
Partially digested chyme in duodenum stimulates the release of…
secretin, CCK, and enteropeptidase
Proteins use ____ to absorb into enterocytes
Sodium-potassium pump
Which immunity function is associated with a significant uptake of intact protein in the small intestine?
Passive immunity during infancy
At least ____ transporters have been found for extraintestinal AA absorption
4
Two diseases related to low-tryptophan levels
Hartnup-cell can’t uptake
Kwashiorkor-not enough
***A patient came to the ER complaining of severe abdominal pain. Labs revealed elevated dibasic AA in the urine. The patient’s pain subsided a few hours later after he passed a kidney stone. The most likely diagnosis is:
Cystinuria
AA Pool
AA not used by the intestinal cells are transported to the portal vein
**What % of AA are used to rebuild tissue protein?
75%
The remainder of AA are used for
synthesis of glucose, ketones, various products
What is the primary site for AA uptake?
liver
What % of AA will be catabolized in liver?
60%
Where are branched chain AA metabolized?
muscle
3 branched chain AA
leucine, valine, isoleucine
1st step in catabolism of AA
removal of AA via either deamination or transamination
Which vitamin is required for this step?
B6
Most transamination transfer AA into….
glutamate—which is then deaminated into ammonia
In humans, the major route of nitrogen transfer from AA into ammonia involves which of the following pairs of enzymes?
Glutamate dehydrogenase and transaminases
**Where is urea synthesized?
Liver (majority) and kidneys
Intestine AA catabolism
absorption
-oxidize glutamine as their major source of energy
-synthesize and release citrulline
Skeletal Muscle AA catabolism
BCAAs are transaminated into glutamate
Ammoniagenic organ
kidney
Primary function of protein
- replace body proteins
- synthesize N-containing products
Primary function of protein
- replace body proteins
- synthesize N-containing products
How much of total body protein is turned over each day?
about 1-2% (30-40g)
A deficiency in which AA will result in negative N balance, even though the diet may contain a large amount of protein?
Tryptophan
RDA allowance for protein is based on amt needed to maintain
Nitrogen balance
How much additional protein needed during pregnancy? Lactation?
30, 20
most common form of malnutrition
protein-calorie malnutrition
amt of protein required for hospitalized patient formula
protein intake (g/24 hr) = (g urinary urea + 4) x 6.25
Marasmus
not enough protein/or food
-progressive wasting and emaciation
***Pellagra-like symptoms may be induced by which condition?
-incomplete dietary protein such as corn protein
-inherited defects in neutral amino acid transporter
-niacin deficiency
Can FA be used to make glucose?
no
Fat gain from CHO and/or protein is due to
sparing lipolysis rather than direct lipogenesis
Fed state
last 3 hrs after meal
Post absorptive state
3-18 hrs after meal
Fasting state
18 hrs to 2 days w/o additional food intake
***How long does it take for a fasting state?
Up to 48 hours
Most liver glycogen is synthesized via
gluconeogenesis
Two organs that highly depend on glucose for energy
Red blood cells
Brain
During the post absorptive state, what is the major provider of glucose to the blood?
hepatic glycogenolysis
Nearly all liver glycogen and most muscle glycogen can be depleted within…
24-36 hrs
***How long do hepatic glycogen stores last before exhaustion is reached?
24-36 hrs
AA from muscle breakdown provide the chief substance for which metabolic process during fasting state?
gluconeogenesis
A protein-sparing shift in metabolism from gluconeogenesis to lipolysis occurs during which state?
starvation state
A protein-sparing shift in metabolism from gluconeogenesis to lipolysis occurs during which state?
starvation state
Metabolic syndrome requires 3 of the 5
-elevated waist circum.
-elevated triglycerides
-reduced HDL
-elevated blood pressure
-elevated fasting glucose
Red muscle
Type 1, high level mitochondria, aerobic….slow twitch
Red muscle
Type 1, high level mitochondria, aerobic….slow twitch
4 major sources of energy during exercise
-muscle glycogen
-plasma glucose
-plasma FA
-intramuscular TAG
**During EX, which contributes only minimally to the amt of ATP used by working muscles?
Amino Acids
**The predominant use of plasma free fatty acids for energy is at a low to moderate intensity ex and the prominant use of glucose is at high intenesity ex.
True
**What is the most important factor influencing the duration of endurance performance?
muscle glycogen stores at the start of exercise
**BMI is one way to estimate
appropriate weight for height
**In the reference man and woman, what % of body weight is fat?
15, 27
