unit 2 clin chem

carbs

organic compounds (sugar, glycogen, starch), stored as glycogen in liver, primary source of energy, excess converted to fat and stored in adipose tissue

monosaccharides- carb structure

simple sugars (single sugar molecule), glucose, fructose, galactose, ribose, deoxyribose

disaccharides- carb structure

monosaccharide + monosaccharide, glucose + glucose = maltose, glucose + galactose= lactose, glucose + fructose= sucrose

polysaccharides- carb structure

poly is more than 10 monosacch, (3-10 monosac = oligosaccharide), exogen(eat) or endogen(make), storage or structure (starch- plants, glycogen-us, cellulose-plants)

carb metabolism

polysacc consumed broken down my salivary amylase and pancreatic amylase > limit dextrins, maltose, lactose, sucrose; maltase lactase sucraase breaks down > monosac- glucose fructose galactose enter bloodstream (intestinal mucosa, port vein, liver converted to glucose)

mono to glucose is used for energy

now- glycolysis, later today- glycogen, future- triglycerides, building supplies- keto acids, amino acids, nucleic acids

cellular respiration

glycolysis > citric acid cycle > oxidative phosphorylation (electron transport chain (ETC), chemiosmosis)

aerobic

glycolysis = Embden-Meyerhoff pathway (EMP)

uses 2 ATP, makes 4 ATP = net gain 2 ATP

glucose makes NADH + pyruvate + 2ATP

citric acid cycle

NADH + pyruvate + 2ATP converts to NADH + FADH2 + CO2 + 1 ATP

oxidative phosphorylation

NADH + FADH2 + CO2 + 1 ATP converts to NAD+ +FAD+ H2O+ ~28 ATP

NAD+ and FAD

electron carrier

1 glucose makes

30 ATP

fermentation

NAD recycled back to be used in glycolysis

pyruvate + NADH becomes lactate + NAD+ (anaerobic process)

uses 2 ATP, makes 4 ATP = net gain 2 ATP

hexose monophosphate pathway (HMP) aka pentose phosphate pathway (PPP)

glucose converts to ribose and NADPH (for anti-oxidant function in cells, removes free radicals) for nucleotides in DNA and RNA

glycogenesis

conversion of glucose to glycogen in the liver (and skeletal muscles) for storage

glycogenolysis (now, fasted, exercise)

convert glycogen back to glucose to use energy, breakdown of glycogen to

provide fuel between meals

liver: regulate blood glucose between means; glycogen > glucose-6-phosphate > glucose by glucose-6-phosphatase to enter bloodstream and help body

muscle: fuels muscle contractions, glycogen > G6P >glycolysis > ATP, directly helps muscles does not need to go all the way to glucose

gluconeogenesis (now, long-term faster)

glucose formed from non- carb sources (glycerol from triglycerides, amino acids, lactate)

ketone bodies

produced by the liver during prolonged fasting or low-carb diet as alternative fuel from catabolism of fatty acids (ketosis), transported to tissues, converted to acetyl-CoA to enter the citric acid cycle

ketosis

catabolism of fatty acids creating ketone bodies during fasting or low carb diet

three major ketones

acetone 2%, acetoacetic acid 20%, beta - hydroxybutyric acid BOHB (more stable) 78%

urine ketones

reference range: neg, reagent strip for acetoacetic acid= sodium nitroprusside

ketone- serum/plasma

reference range: <1 mg/dL, spectrophotometry for beta - hydroxybutyrate BOHB

hormones effects on glucose

insulin lowers, raised by counterregulatory hormones- glucagon, epinephrine, cortisol, growth hormone, T4/T3 (increase metabolic rate)

insulin

“fed state - use and store fuel” post eating, synthesized by beta cells of islets of Langerhans in pancreas, responsible for glucose entry into cell, ONLY hypoglycemic agent

glucagen

“fasted state - release fuel”, synthesized by alpha cells of islets of Langerhans in pancreas, responsible for increasing serum glucose, hyperglycemic agent, may be increased by stress and exercise

insuline alone stimulates and inhib

s- glycolysis, glycogenesis, and liposgenesis

inhib- glycogenolysis, gluconeogenesis

low insuline+ glucagon inhib and stim

i- glycolysis, glycogenesis, and liposgenesis

st- glycogenolysis, gluconeogenesis, lipolysis

catabolic vs anabolic state

c- breakes down, a- builds up muscles

serum/plasma ref range

fasting- 74-100, post prandial (eating) <140

hypoglycemia <40

hyperglycemia >500

serum/plasma specimen requirements

8-10 hr fast under 16 hrs, separated with 1 hr of collection (glycolysis will decreasing glucose), grey top tube (sodium fluoride preventing glycolysis, used if delayed centrifugation)

whole blood ref range

about 10% lower than plasma

urine ref range

<15 or negative

glucosuria= any present

csf ref range

about 60-70% of plasma, 40-70

hypoglycorrhachia <40

glucose oxidase- peroxidase aka trinder rxn

1. glucoe + O2 + H2O with glucose oxidase= gluconic acid + H2O2

   1. if stop here read by glucometer

2. H2O2 + reduced chromogen with peroxidase= oxidized chromogen + H2O

   1. color change, read by reflectance photometer, dipstick

older less precise, false decrease due to uric acid, bilirubin (icterus), ascorbic acid, false increase due to bleach

hexokinase

1. glucose + ATP with hexokinase= glucose-6-PO4 + ATP

2. glucose-6-PO4 + NADP with G-6-PD= NADPH + 6-phosphogluconate

   1. change in UV absorbance by spectrophotometer (340 nm)

serum/plasma gold standard, csf, urine rarely, false decrease due to gross hemolysis and icterus

clinitest

Cu2 with reducing substance= Cu1O

obsolete, replaced by newborn screening tests for inborn errors of metabolism

lipids

water insoluble, cholesterol, triglyceride, phospholipid, glycolipid, used for life processes like energy storage, cell membrane components, bile salt precursor for digestion, steroid hormone precursor

fatty acids

linear chains of C-H bonds ending in carboxyl (-COOH), plasma ones found in triglycerides or phospholipids, short 4-6 C, med 8-12 C, long 12-18 C, v long >20 C, sat (cis) vs unsat (trans, db bond), synthesized from carbs, polyunsat fats for membrane struc and func

fatty acids that cannot be synthesized from carbs

linoleic LA= omega-6 and alpha-linolenic acid ALA= omega-3=essential (need in diet)

tryglycerides

3 fatty acids bound to glycerol by ester bond, non-polar = hydrophobic= water insoluble

phospholipids

2 esterified fatty acids and a hydrophilic phosphate group bound to glycerol (sphingosine), 1 sat and 1 unsat FA tail, amphipathic (phobic and philic), self-assemble into bilayers, liposomes, and micelles

glycolipids

in animals, glucosphingolipid= sphingosine + FA + carb chain, amphipathic, cell-cell rec, ABO antigens, cellular receptors

amphipathic

hydrophob and hydrophilic, water fear and love

cholesterol

amphipathic unsat lipid, polar head, 4 C rings, single C-H side chain, part of lipid bilayer membrane, precursor to steroid hormones bile acids, sythesized by animals from acetyl CoA

lipoproteins transport lipids

lipid + protein = apolipoprotein, deliver fuel, external layer- cholesterol and phospholipids, cargo or core- hydrophobic and neutral triglycerides and cholesteryl esters

apolipoprotein

protein part, maintain structure of lipoprotein, ligand for cell receptors, activator or inhibitor for enzymes modifying lipoproteins, contains amphipathic alpha helix, abnormalities cause atherosclerosis, cardi disease CVD, and Alzheimers

lipoproteins transport lipids size

correlates with neutral lipid cargo, larger = more lipid to protein = less dense, (classified by separation in ultracentrifugation, chylomicrons, VLDL v low d, LDL low den, HDL high

chylomicrons

largest, least dense, scatters light (turbidity in post-prandial specimens), creamy top-layer if sits/refrigerated, produced in intestine from dietary lipids, enter circulation and are hydrolized to chylomicron particles in liver

VLDL

produced by liver, transports liver-produced triglycerides to other tissues during fasted states, create turbidity in fasting hyperlipidemic specimen (no cream layer, less buoyant than chylomicrons)

LDL

contains Apo B100, more cholestrol-rich, “bad“ cholesterol bc smaller infiltrate vessel wall extracellular space, can be oxidized and macrophaged, can be foam cells (precursor to atherosclerotic plaques), small, dense, better marker for CVD risk

HDL

synthesized by liver and intestine, sleans up excess cholesterol from peripheral cells (reverse cholesterol transport), good cholesterol

metabolic pathways

absorption, exogenous, endogenous, reverse cholesterol transport

lipid absorption pathways

dietary lipids are digested in small intestine by liver bile acids then packaged into chylomicrons

exogenous pathway

dietary lipids are digested in small intestine by liver bile acids then packaged into chylomicrons delivering triglycerides to tissues, remnants are taken up by liver

endogenous pathway

during fasted state liver packages triglycerides and cholesterol into VLDL for circulation, as triglycerides are removed VLDL become intermediate density lipoprotein (IDL/VDL), remnants are cleared by liver or lose more triglycerides to be converted to LDL delivering cholesterol to cells

reverse cholesterol transport path

HDL collects excess chol from pheripheral tissues and macrophages in bv walls and transports back directly to liver or transfers to other lipoproteins, liver excretes chol into bile or bile acids (fat digesting part of bile)

lipid and lipoprotein specimen

serum or plasma, 12 hr fasted

lipid panel

total chol, LDL, HDL, trig

lipid and lipoprotein methodology

chol and trig- enzymatic colorimetric

HDL- homo, enzymatic colorimetric

LDL- friedewald calc, direct LDL is homo and enzymatic colorimetric and expensive

other- electrophoretic methods

friedewald calc

LDL= total chol - HDL - VLDL

VLDL= tri/5 if under 400

assay standardization

lipid results guide CVD risk assessment and treatment, results must be comparable between labs, lipoproteins are complex particles making accurate measurement challenging, CDC reference laboratories establish and maintain reference methods for chol testing

Gold standard ref system

most accurate method available, manufacturers and labs continuously compare test systems against ref methods to ensure accuracy