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82 Cards in this Set

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As general rule anarobic metabolism is associated with?
storage (how so?)

also glycolysis and lactic acid
formation for making ATP
metabolism is controlled by ?
1. hormones (e.g. insulin and glucagon)
2. sympathetic nervous system via epi.& nor.
3. energy available (ratio of ATP to ADP)
4. sometimes if not taken up intermediates or metabolites inhibit from going forward
are carbohydrates essential nutritients?

example of essential nutrient?
No, because can be convert to make carbs; our body can make

some amino acids
preferred energy source of tissues?
glucose
glucose dependent tissues?
NERVOUS SYSTEM including neurons, retina, RBCs,
retina, renal medulla, gonads, fetus, lactation (milk production)
first tissue/system to be affected by reduced glucose level?
nervous system most sensitive to reduced glucose levels
normal blood glc levels

at what lower level might have seizures? coma?
80-120 mg Glc/dl

<50mg = seizures
<20mg = coma
death (spp. differences exist)
process of releasing stored glucose
glycogenolysis
glycogenesis for ?
storing (as glycogen)
what happens if have insulinoma ?

common in what animal? why?
excess insulin secreted, all tissues use glucose, get hypoglycemic

common in ferrets, b/c inbred and fed excess carbs
Glucose enters cells via ?
facilitated diffusion
What unique about Glucose dependent tissues and Liver?
GLUTs are ALWAYS part of their cell membranes
= facilitated diffusion (glucose uptake) is always active
Are muscle,fat are examples of Glucose dependent tissues?
No
Where do Glucose independent tissues (eg muscle,fat) store/keep their GLUTs?
GLUTs are stored intra-cellular
What is required for GIT's (Glc. independent tissues) to express GLUTs on surface?
= facilitated diffusion only when INSULIN present
- GLUTs detach when Insulin is absent
What does insulin do?
* when insulin present ALL TISSUES have free pass to use glucose!
- allows GLUTs to fuse with cell membranes
- now GIT's can use Glc
Insulin is secreted in response to?
- Insulin is secreted in response to hyperglycemia
During Hypoglycemia what are insulin levels like in blood (or wherever it's secreted)?
LOW
Glucose Trapping : upon cell entry, glucose is ____?
phosphorylated to Glc-6-P ->
What's different about Glc-6-P...I mean in regard to its ability to move in and out cells of cells?

Is it reversible?
glucose cannot diffuse out of cells;

irreversible except in liver, kidney and GI cells
Fate of glucose depends on
the body’s energy situation:

What happens to GLUCOSE (which means Glu-6-P from now on unless otherwise stated) which has entered cells and O2 present?

Just give name of each cycle involved in order with major product/intermediate
Glycolytic pathway -> pyruvate -> converted to acetyl gp. (acetyl CoA) -> enters Kreb's Cycle -> H+ ions -> ETC -> ATP
What happens to GLUCOSE which has entered cells and w/o O2?
Glycolytic pathway -> pyruvate -> Lactic Acid cycle

get 2 ATP, 2 pyruvate
Why do we need Glycolytic pathway?
glucose too big to enter mitochondria

pyruvate can enter mitochondria
What happens to pyruvate as soon as enters mitochondria?
carbon taken off (C3->C2), get acetyl gp., cofactor added to get acetyl CoA (activated to enter Kreb's cycle)
Does Krebs Cycle have other functions aside from break down of glucose (pyruvate)?
yes, involved in making non essential A.A. / glc (gluconeogenesis), and combusting FA & A.A.
What happens to Citric Acid after going around cycle once?

What is lost?
In what form?
; Citric acid undergoes a sequence of decarboxylations and dehydrations ending again in OAA

- 2 carbons brought in are lost as CO2 (waste product)
Krebs cycle starts and
ends with ____?
OAA (OXALOACETATE)
What's OAA (OXALOACETATE) do?
C2 (Acetyl CoA) joined by C4 (OAA) to form Citric Acid = C6
After Kreb's Cycle turns once, what is produced?
1 ATP, and NADH2, FADH

~most important outcome making its energy-rich hydrogen ions (NADH, FADH2) available for ETC
How are NADH2 produced from aceyl CoA?
- energy of acetyl gp. transferred onto cofactor NAD, 8 H+ from each acetyl gp. loaded onto NAD, to form NADH2 (FADH also created)
where does ETC occur ?
on inner wall of mitochondria membrane, H+ pumped in intermembrane space
Where in metabolism is oxygen required ?
ETC, oxygen is required as proton acceptor
What kind of phosphorylation occurs in ETC?

Most important product?
oxidation phosphorylation


ATP
Aside from generating ATP, what is important function of ETC?
re-generate electron acceptors NAD+ (and FADH+) for glycolysis and Krebs cycle

w/o those cofactors Krebs (and glycolysis to lesser extent) cannot happen
How do anaerobic bacteria get rid of protons (cannot do ETC) to generate NAD+?
load onto proprionate and butyrate to make methane
What happens if O2 absent (overworked muscles) and NAD+ not generated by ETC?
TCA (Krebs) stops, acetyl gp. pileup -> pyruvate accumulates -> glycolysis stops as well
Can any ATP be generated in absense of O2?
Yes, use lactic acid pathway to generate 2 ATP and NAD+
How is pyruvate converted into lactic acid or lactate?

(skip until know everything else)
2 H+ loaded onto central carbon of pyruvate (3-C) -> lactate or lactic acid

central carbon is keto- gp.
How is lactate reabsorbed?

What does it form back into?
taken by cells that have oxygen

H+ removed to form pyruvate -> enters TCA
What enzyme responsible for converting lactate to pyruvate?

Is rxn reversible?
LDH

Yes, whichever is higher concentration determining direction
What tissue handle most of lactate accumulated?
heart muscle and liver

(muscles have alot of LDH)
What cells always in anaerobic conditions?
RBC, no mitochondria, TCA, or ETC

so depend on glycolytic pthwy for 99% of energy
why does glucose need to be stored as glycogen?
because if remained as glucose in cell would increase osmolarity dramatically; too much H2O would accumulate

if condensed as 1 huge molecule, not as osmotically active
Where can glycogen be made?

Which tissue produce/store most?
every tissue can make but very little

only liver (up to 6% of weight) and muscle (up to 1%) can store a lot
Structure of glycogen?
endless chains of glucose, mostly condensed as α1-4 with some branches of α1-6 side chains
enzyme encourages formation of glycogen?
insulin
What enzyme responsible for adding α1-6 chain?

What enzyme responsible for breaking off α1-6 chain?
Branching enzyme: adds 1-6 side chain to very long α1-4 linkage

Debranching enzyme
End product of glycogenolysis (w/debranching enzyme, etc)?
makes Glc-6-P

note: cannot leave cell w/P
process of synthesizing new glucose from precursors is
gluconeogenesis
Gluconeogenic precursors
* many gluconeogenic amino acids (w/amine gp. removed)
* lactate
* propionate out of
* fermentation
* glycerol (from triglyceride breakdown)
What happens to these precursors?
* usually have C4 or C5 backbone
* enter Krebs at half way point
Precursors in Krebs cycle are pulled out into cytoplasm
as ____ -> enter gluconeogenesis (except glycerol).
*OAA / Malate* pulled into cytoplasm to enter gluconeogenesis (except glycerol).
Why can't we go directly backwards e.g. from precursor -> acetyl CoA -> pyruvate -> Glu-6-P? Is this possible with any precursors?
- because some steps aren't reversible

- all precursor must enter TCA to form OAA/Malate w/exception of glycerol
Both liver and kidney contain
_____ and release free
glucose into circulation.

Which releases more glucose?
phosphatases

80% of glucose released into blood stream comes liver and 20% from kidney
Where does glycerol come from?


Where do other precursors come from?
According Dr. Zeigler:
* its precursor is one of products of glycolytic pathway

* often are A.A. precursors pulled from muscle tissue
* liver and kidney can also produce some
* proprionate (UFA) is major precursor in ruminants and hindgut fermenters
* lactate can be produced by any tissue
When Gluconeogenesis is very active which intermediate is in highest demand?
Malate (OAA can revert back to malate)

~this is major bottleneck in metabolism
Lack of phosphatase enzyme common in what animal?
dogs
What is triglyceride?
glycerol backbone + 3 FA's
What bile acids are produced from?
cholesterol
what are lipoproteins?
aggregations of lipids surrounded by a shell of hydrophilic proteins, phospholipids and specific receptor proteins = Apoproteins
Two classes of lipoproteins:
1. CHYLOMICRONS
2. VLDLs (Very Low Density Lipoprotein), e.g. after
production of new lipids
why do fats form lipoproteins?
combined with proteins so are soluble in water -> for transport in plasma
how do cells take up VLDLs?
cells have receptor which binds apoprotein in VLDLs

after BINDING subunit of receptor which enzyme known as LPL (lipoprotein lipase)
what does LDL do?
enters VLDL, going thru hydrophilic surface, and hydolyzes triglycerides inside
What happens to components of VLDL after LDL has finished?
FFA and glycerol components diffuse down concentration gradient into cell

if fat, components join again into triglyceride
What cells store triglycerides?
only fats cells
what term describe break down of fat or release from storage?
glycolysis or lipolysis
hydrolyzes stored triglycerides -> free fatty acids (FFAs) and glycerol diffuse back into circulation
Hormone-Sensitive Lipase (HSL)
chylomicrons are? what do they contain?
are lipoproteins, have apoproteins

dietary fats after absorbed by enterocyte and go into blood stream
lipoproteins (endogenous fats) made by liver cells known as ?
VLDLs - very low density lipids

are same as chylomicrons, aside from their origin; are endogenous
FFAs can originate from
1. NEFAs
2. VLDLs
3.Chylomicrons
FFAs that bind to plasma Albumin for transport.......are known as ?
Non-Esterified Fatty Acids = NEFAs, which deliver FFAs to active tissues for energy gain
after cell entry, FFAs enter mitochondria and undergo progressive release of C2 segments (Acetyl CoA) in process known as ???
β-OXIDATION
What happens to acetyl CoA after β-OXIDATION ?
Acetyl CoAs enter KREBS cycle for complete oxidation and ATP generation in the ETC
Where does glycerol go?
Diffuses into active tissues where can either:
1. enter glycolysis -> Krebs cycle -> ETC when ATP is needed
2. or enters GLUCONEOGENESIS when glucose is needed
Excess glucose and amino acids can be <converted into FFAs> = ?
LIPOGENESIS

glucose -> FFA
Where does lipogenesis occur?
(in Liver, Fat Tissue, Mammary Gland).
True OR False: Lipogenesis is activated when stores of ATP, Glycogen and Labile Protein are full and Glc and AAs are still available.
True
True OR False: LIVER is a fat storage site?
False *****!

LIVER: is not a fat storage site
What does liver do with excess fat?
Makes them into VLDLs, send into circulation for fat storage
During LIPOLYTIC phases, what organ takes up NEFAs (FFA) and makes them available to other tissues as (1) VLDLs and (2) Ketone Bodies
Liver
What occurs during lipogenesis?
* new fat made from excess glucose
* glucose enter TCA and leaves as citrate, which goes to F.A. production