carbohydrate Flashcards
MOST important member of the sugar family
One of the main sources of calories
- Can cross blood-brain barrier and nourishes the brain
GLUCOSE
one sugar molecule
Monosaccharide
2 sugar molecules
Disaccharide
3 to 9 sugar molecules
Oligosaccharide
10 or more sugar molecules (most abundant
carbohydrate in food)
Polysaccharide
breakdown large polysaccharides (e.g., starch)
Amylases
breakdown lactose
Lactase
breakdown sucrose
Sucrase
breakdown maltose
Maltase
found in honey, fruits, and root vegetables
fructose
The individual __________that result from the digestion of larger carbohydrate molecules will cross the gut lining and get into
bloodstream to get used by the body.
monosaccharides
milk sugar.
only found in nature when it is links with glucose to form lactose
galactose
found in milk of mammals
cow milk and breast milk
lactose (beta 1-4 glycosidic bond)
fructose + glucose
table sugar
sugar cane and sugar beets
sucrose (alpha 1, 2 glycosidic bond)
found in molasses
used to ferment beer
maltose (alpha 1-4, glycosidic bond)
healthy diet:
45-65% of calories from the carbohydrates
fiber - 28g (2cal/1g) = 56cal (3%)
sugars - 100g -> 400cal (20%)
added sugars 100 cal (5%)
natural (f, v, g) 300 cal (15%)
STARCHES 160g 640 cal (32%)
0.55 (2000) = 1100 cal
mono and di that body can readily absorb
simple sugars
polysaccharide that takes longer to absorb
starches
can only partially absorb with gut bacteria
fibers
When glucose level in blood increases after eating,
pancreas releases ________ which helps move glucose into the cells for energy
insulin
helps stimulate the liver to store glucose as
glycogen (process is glycogenesis)
promotes fat and protein synthesis
Insulin
In the liver, metabolism of galactose has an initial step where an enzyme in the liver converts galactose into ________
(flipping the OH orientation of the 4th carbon)
glucose
In the liver, fructose is usually broken down into two 3-carbon molecules will be used in glycolysis to help generate energy.
what molecule is this?
two molecules of glyceraldehyde-3-phosphate (G3P)
When energy is needed, monosaccharides are metabolized through ___
glycolysis – citric acid cycle – oxidative phosphorylation
is the first step in the breakdown of glucose or other monosaccharides.
It takes place in the CYTOPLASM of the cell and does not require oxygen.
a molecule of glucose is broken down into two molecules of PYRUVATE (a 3-carbon compound).
This process generates a small amount of ATP and NADH.
Glycolysis
In aerobic conditions (when oxygen is available), pyruvate (the product of glycolysis) is further metabolized.
It enters the MITOCHONDRIA, where it is converted into acetyl-CoA
This step releases more NADH.
Pyruvate Decarboxylation
Acetyl-CoA enters a series of enzymatic reactions that occur in the mitochondria.
During this cycle, acetyl-CoA is further broken down, releasing carbon dioxide and generating more ATP, NADH, and FADH2.
Citric Acid Cycle (Krebs Cycle)
The NADH and FADH2 produced in glycolysis, pyruvate decarboxylation, and the citric acid cycle are used in the ___________
This chain is located in the inner mitochondrial membrane and is involved in the final stages of energy production.
Electron Transport Chain (ETC)
As electrons move through the ETC, they create a proton gradient, and this gradient is used to generate ATP
Oxidative Phosphorylation
The final result of these processes is the production of a significant amount of ATP, which is the cell’s primary energy source.
ATP can be used by the cell for various energy-requiring processes, such as muscle contraction, active transport, and biochemical reactions.
ATP Production
is the major regulator of both storage and
distribution of glucose towards the peripheral tissue.
In particular, to the glucose dependent tissues such as the BRAIN and ERYTHROCYTES.
liver
Both our muscle and liver store glucose in the form of __________
Glycogen
only the LIVER can break down the glycogen to glucose in order to provide for the _________
systemic circulation
Once the carbohydrate is broken down into simple sugar, it is absorbed in our intestine and distributed ___________.
systemically
Our liver provides __________ of glycogen per kilogram of liver tissue.
The excess glycogen is converted into fatty acid and
stored in an adipose tissue,
65 grams
During the postabsorptive state in our body, our LIVER becomes the primary source of glucose.
However, most of our muscles rely on fatty acids from the ________
adipose tissue
An active muscle may deplete its own and glycogen and they start to be dependent on the ________
Liver-glycogen
After 48hrs of fasting, our liver shifts from glycogenesis to ____________
gluconeogenesis
The _________ is depleted the reason why our liver would shift from glycogenesis to gluconeogenesis
hepatic glycogen
The substrate for gluconeogenesis is mostly the ______
amino acids (specifically the alanine)
The alanine is derived from muscle breakdown and
glycerol form adipose tissue become the __________.
substrate
in a prolonged fasting, the fatty acids are β-oxidized in the liver.
This would result to the release of the ___________ which will became the primary source of fuel for the brain
ketone bodies
The transition of in and out of these various metabolic state and regulation of carbohydrate metabolism are influenced by glucose concentration in _______ & __________
sinusoidal blood and hormonal cells
During anaerobic metabolism, our liver uses LACATE, that is converted into pyruvate that enters the __________ in order to produce glucose.
gluconeogenic pathways
Lactate helps in producing more glucose.
This process in known as the _____
Cori Cycle
is an abnormal glucose intolerance
Liver cirrhosis
will ensue when too much liver tissue
is destroyed when gluconeogenesis fails.
Hypoglycemia
breakdown fuel molecules that transfer high energy
compounds like ATP, Guanosine Triphosphate, flavine, reduced adenine dinucleotide phosphate.
Cellular Respiration
The breakdown starts from the digestion of the food in the gastrointestinal tract and followed by the absorption of the carbohydrates component by
ENTEROCYTES by the form of monosaccharide
Cellular Respiration
The monosaccharides are transferred into the cells for anaerobic and aerobic respiration through _________ , _______, & _________ to be used during the starvation state
glycolysis,
citric acid cycle, and
pentose phosphate pathway
the muscle and the liver cells store monosaccharide in a form of glycogen
Normal state
the extra glucose is converted into triglycerides
through lipogenesis and stored as lipid droplets in the adipocytes
Obesity state
the lipid droplets of other tissues such as the liver,
skeletal muscle, and pancreatic beta cells also
accumulate triacylglycerol.
Lipotoxicity state
Access of pathogenesis of most metabolic
dysregulation such as insulin resistance, metabolic
syndrome, and diabetes
Lipotoxicity state
is a 6-carbon molecule that is used to make energy
in the form of ATP.
➢ Excessed of this are stored in both skeletal muscle cells and liver cells in the form of Glycogen.
Glucose
is a polymer that is made up of glucose
molecules linked together via glycosidic bond creating branched chains.
➢ This branching allows it to be compact and capable of rapid addition and removal of glucose.
Glycogen
4 Main Steps in Glycogen Synthesis
Step 1: Attaching Uridine Diphosphate (UDP) to Glucose
Step 2: Attaching Glucose to Glycogen Primer Called as Glycogenin
Step 3: Adding more Glucose to the Primer
step 4: adding more branches
an enzyme known as _________________moves
from the phosphate of the 6th carbon to the 1st carbon creating Glucose-1-phosphate
(comes in the form of Uridine triphosphate) step 1
Phosphoglucomutase
In the presence of Glucose-1-phosphate and UTP, an enzyme called ________________ cuts 2 molecules of phosphates off UTP leaving:
1 Phosphate attached to uridine and added with phosphate from the Glucose-1-phosphate.
UDP-Glucose Pyrophosphorylase
step 2 results to a molecule known as ________-
UDP Glucose
An enzyme known as ________ catalyzes the attachment of glucose the part of the UDP Glucose to another glucose residue at the end of the glycogen branch that forms an α-1,4 glycosidic bond.
The by-product of this reaction known as UDP.
Glycogen Synthase
The glycogen synthase only elongate an already existing glycogen chain that is at least 4 glucose molecules long.
However, if the chain do not have at least 4 glucose
molecules, the glycogen synthase would need to have __________-.
Glycogenin
__________ would fool the glycogen synthase through binding to the glucose molecules, looking like an old glycogen molecule
Glycogenin
The branching enzyme goes to the end of the chain and shortened it to about 68 glucose residues in length. The cut chain attaches to the side of the linear glycogen strand by_______
α-1,6 glycosidic bond
Once the chain is shortened, the glycogen synthase will elongate it again. This would then result to a glycogen tree of __________
stored energy
low glucose levels
pancreas secrete glucagon
adrenal glands secrete epinephrine to increase heart rate
glucagon tells the liver cells to _____
break down glycogen to individual glucose molecules
epinephrine tells skeletal muscle to
break down glycogen
- begins w/ branches
- glycogen phosphorylase
- debranching enzyme
glycogen breakdown
cleaves alpha 1, 4 bonds
- catalyzes the transfer of phosphate group
- release 1 glucose-1-phosphate
- leaves 4 glucose
glycogen phosphorylase
cuts of branches
debranching enzyme: 4-alpha-glucanotransferaase
cleave alpha 1, 6 bond
release free glucose
debranching enzyme: alpha 1,6 glucosidase
in liver, ___________ removes phosphate
- release free glucose in bloodstream for other organs to use
glucose-6-phosphatase
muscles do not have glucose-6-phosphatase but uses glucose-6-phosphatase to:
make glycolysis pathway
and help you provide energy when you run
transfer 3 glucose molecules off the
branch and reattach them to the linear glycogen, extending it as a result
4-alpha-glucotransferase
For each glucose that’s removed via phosphorylases There’s a glucose 1-phosphate that gets liberated and it’s converted to glucose-6-phosphate by __________
phosphoglucomutase
2 regulation of glycogen metabolism
- insulin
- glucagon
active without phosphate
glycogen synthase
(makes active, glycogen synthesis)
active with phosphate
glycogen phosphorylase
(makes inactive, glycogen breakdown)
Insulin will attach to _____________ receptor,
which will activate a protein phosphatase that removes phosphates from the glycogen
synthase making it active
and glycogen phosphorylase, making it inactive
Tyrosine kinase
glucagon on the liver cells bind to G-protein coupled receptor on the cell surface which activates _________
adenylyl cyclase
converts ATP to cyclic AMP
adenylyl cyclase
cyclic AMP activates ______
kinase A
kinase a adds a phosphate to _______________ which activates it
glycogen phosphorylase kinase
Glycogen phosphorylase kinase adds a
phosphate to _________________ increasing its activity and promoting glycogen breakdown.
glycogen phosphorylase
Kinase a also adds a phosphate to the _______________ decreasing its activity and therefore decreasing glycogen synthesis
glycogen synthase
the “Energy Currency” of the Body.
Adenosine Triphosphate
containing two high energy phosphate bonds.
each of these phosphate bonds is approximately 12,000 calories under conditions found in the body.
ATP
ATP is present in the ___________ & _______________
cytoplasm and nucleoplasm of all cells.
Essentially all of the physiological mechanisms that require energy for operation obtain this energy directly from __________
ATP or GTP
Normally,_________ or more of all the carbohydrates used by the
body are used for this purpose.
90 percent
The final products of carbohydrate digestion🡪
glucose, fructose, and galactose.
To enter the cell, these monosaccharides combine with protein carriers in the membrane that allow them to pass through the membrane via _________________ into the cell
facilitated diffusion
The rate of carbohydrate utilization by the body is controlled to a great extent by the rate of ____________ secretion from the pancreas and the sensitivity of the various tissues to insulin’s effects on glucose transport.
insulin
Phosphorylation of glucose is almost completely irreversible,
except in Liver cells, Renal tubular epithelium, and Intestinal epithelial cells,
where ____________ is available for reversing the reaction.
glucose phosphatase
serves to capture glucose in the cell.
Phosphorylation
Once in the cell, the glucose does not diffuse out except from special cells that have the necessary _____________.
phosphatase
All cells of the body are capable of glycogenesis and storing some glycogen, but_____ & _______ can store LARGE quantities of it.
liver and muscle cells
Very large glycogen can molecular weights up to 5 million
This very large glycogen molecules precipitate to form __________
solid granules
In glycogenolysis, the glucose molecule on each branch of the glycogen polymer is split away by the process of _________
phosphorylation
When it is required to re-form glucose from glycogen, phosphorylase can be activated by the hormones _____________ & _________
epinephrine and glucagon.
The _____initiates a cascade of chemical reactions that activates the phosphorylase.
cAMP
Glycolysis occurs in ____ successive steps, while each step is being catalyzed by at least one specific enzyme.
10
The complete oxidation of 1 mole of glucose releases 686,000 calories of energy, but only _________ calories of energy are required to form 1 mole of ATP.
12,000
The energy in glucose is released in small packets to form ______
one molecule of ATP at a time
A total of ______ is formed for each mole of glucose used by the cells.
38 moles of ATP
During glycolysis, glucose is split to form two molecules of ________
pyruvic acid
Only 2 moles of ATP are formed for each mole of glucose used, which amounts to 24,000 calories of energy stored in the form of ATP.
The total amount of energy lost from the original glucose molecule is 56,000 calories, so the overall efficiency for ATP formation during glycolysis is _________
43 percent
The remaining _________ of the energy is lost as heat.
57 percent
after glycolysis, the next stage of degradation of glucose is:
Pyruvic Acid Is Converted to Acetyl-Coenzyme A.
During this reaction, 2 carbon dioxide molecules 4 four hydrogen atoms are released.
No ATP is formed
Pyruvic Acid Is Converted to Acetyl-Coenzyme A.
6 molecules of ATP are produced when the 4 hydrogen atoms are later oxidized via the process of
oxidative phosphorylation
Continued Degradation of Glucose Occurs in
the
Citric Acid Cycle
Acetyl portion of acetyl-CoA is degraded to carbon dioxide and hydrogen atoms.
Occur in the matrix of mitochondria.
Citric Acid Cycle
__________released are subsequently oxidized, liberating tremendous amounts of energy to form ATP.
Hydrogen atoms
No large amount of energy is released during the citric acid cycle,
however; for each molecule of glucose metabolized, _______ molecules of ATP are formed.
2
Formation of ATP by Oxidation of Hydrogen:
The Process of _________
Oxidative Phosphorylation
2 ATP molecules are formed in the glycolytic scheme, and another 2 molecules are formed in the citric acid cycle.
true
Almost __________________ of the total amount of ATP is formed during subsequent oxidation of the hydrogen atoms released during these
early stages of glucose degradation.
95 percent
The principal function of these earlier stages is to make the __________ of the glucose molecule available in a form that can be used for
oxidation.
hydrogen
The energy released as the electrons pass through the electron transport chain is used to create a _____________across the inner membrane of the mitochondria.
gradient of hydrogen ions
The high concentration of hydrogen across the
space is actually what we call as ___________________ across the membrane
electron potential difference
Hydrogen ions to flow into the mitochondrial matrix through a molecule called ____________
ATP synthetase
The energy derived from the _________ is used by ATP synthetase to convert adenosine diphosphate (ADP) to ATP.
hydrogen ions
For each 2 hydrogen atoms ionized by the ETC, up to ____ molecules of ATP are synthesized.
3
is a sequence of chemical reactions in which
the acetyl portion of the Acetyl Coenzyme A as a product of
glycolysis is degraded towards carbon dioxide and hydrogen atom.
Cycle/ Kreb’s cycle
One important way in which ATP helps control energy metabolism is allosteric inhibition of the enzyme ___________.
phosphofructokinase
phosphofructokinase promotes formation of _________________ during the initial steps of glycolysis.
fructose-1,6-diphosphate
The net effect of excess cellular ATP is a _______________ to stop glycolysis
Which in turn stops almost all carbohydrate
metabolism
feedback mechanism
Conversely, ___causes the opposite allosteric change in this enzyme phosphofructokinase
ADP
The glycolytic process is the set-in motion
➢ When cellular storage of ATP is replenished, the enzyme is again ____________
inhibited
If oxygen becomes either unavailable or insufficient,
___________ of glucose cannot take place
cellular oxidation
The process of _______________ is extremely wasteful of glucose because only 24, 000 calories of energy are used to form ATP for each mole of glucose
This is only about 3% of the total energy of the glucose molecule
anaerobic glycolysis
This release of glycolytic energy to the cells can be
lifesaving measure for a few minutes when oxygen is unavailable -
Meaning if cells are not getting enough blood flow, it can undergo _________________
anaerobic glycolysis
Allow release of extra anaerobic energy
- Pyruvic acid and nicotinamide adenine dinucleotide (NADH) -> Lactic dehydrogenase -> lactic acid and NAD+
FORMATION OF LACTIC ACID DURING THE PROCESS OF ANAEROBIC GLYCOLYSIS
RELEASE OF ENERGY FROM GLUCOSE BY PENTOSE
PHOSPHATE PATHWAY
As much as 30% of glucose breakdown in the liver and fat cells is accomplished independent of glycolysis and citric acid cycle
Removes 1 carbon atom from a glucose molecule to
produce carbon dioxide and hydrogen during each turn of the cycle
The hydrogen produced eventually enters the oxidative phosphorylation pathway to form ATP
PENTOSE PHOSPHATE PATHWAY
Formation of carbohydrates from proteins and fats
also occurs in the process of
gluconeogenesis
When body store of carbohydrate decreases below normal levels, moderate quantities of glucose can be formed from amino acids and the glycerol portion of fat through
gluconeogenesis
Approximately _____ of the amino acids in the body proteins can be easily converted to carbohydrates, each amino acid is converted to glucose through a slightly different chemical process
60%
A ___________ and ______________ are the basic stimuli that increase the rate of gluconeogenesis
low level of carbohydrates in the cells
decrease in blood glucose
in between meals, when fasting, the body maintains glucose using _________________.
gluconeogenesis
a metabolic pathway to make glucose from amino acids, lactate & glycerol
➢ primarily in liver cells
➢ also happens in epithelial cells of kidney and intestine
➢ specifically, it takes place in the cytoplasm, mitochondria, and ER of the cells
GLUCONEOGENESIS
2 pathways that can contribute glucose
- Glycogenolysis
- Gluconeogenesis
- Liver breaks down glycogen into individual glucose
molecules - Only helps on 12-24 hours fasting because glycogen stores are finite
GLYCOGENOLYSIS
- Makes glucose from scratch
- You can keep going if you fast for more than a day - In the 12 hours of fasting, this is the main provider of glucose in the blood stream
GLUCONEOGENESIS
This process is the reverse of glycolysis
In glycolysis, you’re using 10 enzymatic reactions to
convert glucose to pyruvate to make ATP
In ________________, you’re working backwards, using ATP to convert pyruvate to make glucose
gluconeogenesis
7 of the reactions in glycolysis and gluconeogenesis
are __________, meaning they can go both in directions using the same enzymes
reversible
However the other 3 are _________
meaning the enzyme mediating the reaction can only go in the direction of glucose to pyruvate but not in the opposite
irreversible (1st, 8th, & 9th)
In gluconeogenesis, the 2 main source of pyruvate are:
- lactate
- amino acids (alanine)
byproduct of anaerobic respiration in RBC in exercising skeletal muscle cells
Lactate
enzyme that removes hydrogen from
lactate turning it to pyruvate
the hydrogen goes to nearby nicotinamide
dinucleotide (NAD+) which turns into NADH
Lactate Dehydrogenase
building blocks of proteins
- there are 20 of them - 18 of them (leucine and lysine exemption) are glucogenic amino
acids, meaning they can make glucose
Amino Acid
Lazy L’s
Leucine and Lysine
When fasting for a long time, the body breaks down protein in skeletal muscle cells into individual amino acids with the main
amino acid
ALANINE
enzyme that removes amino
group from alanine and turns it to pyruvate
the amino group attached to an acid called alpha
ketoglutarate which turns into regular glutamate
Alanine Transaminase (ALT)
ALT + Pyridoxine (Vitamin B6) is a
cofactor
When stranded in the woods, your body will start to breaking down fats which come in the form of _________–> ATP
triacylglycerides
______________ sense blood glucose decreasing so they release glucagon
Pancreatic α-cells
cause adipocytes or fat cells to stimulate hormone sensitive lipase or HSL (an enzyme that breaks down triacylglycerides into 3 fatty acid and glycerol
Low levels of insulin , epinephrine, ACTH
enter the bloodstream and hepatocytes mitochondria
and then broken down to AcetylCoA and ATP by Beta-Oxidation.
FATE OF FATTY ACIDS
used to make glucose in gluconeogenesis.
FATE OF GLYCEROL
Pyruvate enters the mitochondria and pyruvate carboxylase adds a carbon to it converting it to ______-.
oxaloacetate
The ____________enhances pyruvate carboxylase activity
AcetylCoA
3 COFACTORS OF PYRUVATE CARBOXYLASE:
1) ATP (from fatty acid oxidation)
2) Biotin
3) Carbon dioxide (CO2)
Since oxaloacetate is unable to go out of the mitochondria to continue gluconeogenesis,
___________________ aids by adding hydrogen and converts oxaloacetate to malate (can go out the
mitochondria) and enter the cytoplasm where it is converted by
Malate dehydrogenase back into oxaloacetate.
Malate dehydrogenase
PEPCK adds a phosphate group to oxaloacetate to turn it into PEP with the energy coming from ________________
Guanosine Triphosphate (GTP).
enhances the activity of PEPCK by induction, hence
speeding up gluconeogenesis.
Stress hormones
The goal is for PEP to be converted to ____________________
Dihydroxyacetone phosphate/
DHAP.
converts G3P to DHAP
glycerol-3-phosphate dehydrogenase
DHAP is then converted into fructose-1,6
Biphosphate by a reversible reaction catalyzed by the enzyme called
aldolase
The enzyme Phosphofructokinase-1 (PFK1) adds a phosphate group to fructose-6-phosphate making ______________
fructose-1,6-biphosphate.
In gluconeogenesis, fructose-1,6-biphosphatase removes a phosphate from the first carbon of fructose-1,6-biphosphate making __________-
fructose 6-phosphate (rate-limiting step).
Fructose-6-phosphate is converted to its isomer glucose-6 phosphate by the enzyme
isomerase
-An alternative Oxidative pathway for glucose -Concerned with the synthesis of glucuronic acid, pentoses, and vitamin, ascorbic acid (except in primates and guinea pigs)
-Synthesis of glycosaminoglycans (GAG).
URONIC ACID PATHWAY/ GLUCORONIC PATHWAY
-highly polar molecule which is incorporated into proteoglycans as
well as combining with bilirubin and steroid hormones.
It can also be combined with certain drugs to increase their solubility.
GLUCORONATE
normal metabolic intermediate of D-glucuronate breakdown
-enters the Uronic acid pathway to which it can participate in other metabolism
DIETARY XYLULOSE
EFFECT OF DRUGS ON URONIC ACID PATHWAY
Certain drugs like administration of phenobarbital, aminopyrine, antipyrine, chlorobutanol increases uronic acid pathway for synthesis of more glucoronate from glucose for conjugation
purposes
Uronic acid of glucose conversion to glucoronate begins with the conversion of glucose-6-phosphate to glucose-1-phosphate by phosphoglucomutase and then activated to UDP-glucose by UDP
glucose phosphorylase.
UDP-glucose is oxidized to UDP
glucoronate by NAD with the enzyme UDP-glucose dehydrogenase
