Carbohydrate Metabolism, TCA AND ETC - WEEK TWO

Flashcards on lecture material for week two

What is glucose?

Glucose is a simple monosaccharide sugar and the principal energy source for both the brain and the body. Carbs in foods are all ultimately broken down in the body into glucose

What does fructose along with glucose create?

Fructose along with glucose forms the commonly eaten 'table sugar' or sucrose that we are all familiar with

What is galactose?

Galactose is a simple ‘monosaccharide’ sugar naturally occurring in milk.

What does galactose joined with glucose form?

Joined with glucose, it forms lactose, the principal sugar in milk and dairy foods.

What is lactose important for?

It is particularly important in early human development.

Where is galactose not found?

Compared with glucose and fructose, galactose is not found in high quantities in any food.

Where is sucrose mainly found?

Sucrose is mainly found in plants and is the primary component of most granulated sugars we use in baking

What is starch and where is it found?

Starch is the most common form of carb and typically found in staple grains like rice, wheat, and corn.

What does starch consist of?

It consists of amylopectin (branched starch) and amylose (straight starch).

Whatbis dietary fibre essential for?

Dietary fiber or "roughage" is an essential nutrient required for proper digestion of foods and helping you feel full.

What are soluble fibers?

•Soluble fiber easily dissolves in water and is broken down into a gel-like substance in the part of the gut known as the colon.

What are insoluble fibers?

•Insoluble fiber does not dissolve in water and is left intact as food moves through the gastrointestinal tract.

How does our body use glycogen?

Your body mainly uses the store of glycogen in your liver to help regulate your blood glucose (sugar) levels.

In cases when the body needs a quick boost of energy or when the body isn't getting glucose from food, what happens with glycogen?

glycogen is broken down in the liver to release glucose into the bloodstream to be used as fuel for the cells.

What does FODMAP stand for and what are they?

•FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols, which are short-chain carbohydrates (sugars) that the small intestine absorbs poorly.

What are dextrins, what are they produced by?

Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. They are mixtures of polymers of D-glucose units

What is secreted in the mouth?

Salivary a-amylase is secreted in the mouth and its activity increases ~4 times in presence of Cl-. It has an optimum PH ~ 6.7.

What does salivary a-amylase do?

It “hydrolyzes” (breaks down) straight” (amylose) α(1→4) glycosidic bonds.

What happens to the salivary a-amylase when it gets to the stomach?

Salivary a-amylase will be inactivated in the stomach due to low PH ~3 (acidic environment).

Digestion in the stomach is mainly what by doing what movements?

Digestion in the stomach is mainly mechanical by constant moving of partially broken products – not chemical

How long is the small intestine?

Small intestine (~ 7 meters long, 3.5 times the length of body):

Where is the cholecystokinin CKK hormone secreted?

•Cholecystokinin (CKK) (hormone), secreted in the small intestine

What is the cholecystokinin CKK hormone stimulated by?

stimulated by presence of fat and glucose,

What with the cholecystokinin CKK hormone stimulate?

will then stimulate the “pancreatic juice” (among other e.g. bile salts) to be moved to the small intestine (amylase, protease, lipase) to continue digestion.

Where is the secretin hormone secreted?

•Secretin (hormone) secreted in the small intestine the intestinal lumen 

What does the hormone secretin stimulate?

Stimulates bicarbonate secretion, thus making PH higher (more alkalic/basic) for enzymes to function optimally.

What is pancreatic a-amylase?

•Pancreatic a-amylase is an isomer of salivary a-amylase.

What is the difference between pancreatic a-amylase and salivary a-amylase?

Main difference is it is secreted in the pancreas and “travels” to the small intestine where it gets active in in presence of Cl-. It has an optimum PH ~ 7.1

What does maltase do?

Maltase “hydrolyses” (breaks down) only “straight” (amylose) α(1→4) glycosidic bonds.

What does sucrase (iso-maltase) do?

Sucrase (iso-maltase) “hydrolyses” (breaks down) both “straight” (amylose) α(1→4) glycosidic and “branched” (amylopectin) α-1,6-glycosidic bonds.

What are beta b pancreatic cells and what hormone do they produce and release?

•Beta (β) pancreatic cells are cells in the pancreas that produce and release the hormone insulin.

What does insulin help with?

Insulin helps control blood sugar, or glucose, levels in the body. 

When blood sugar increases — for example, after eating — What do the beta cells do?

Beta cells respond by releasing stored insulin and continuing to make more of it.

What is glucagon?

•Glucagon is a hormone that works with other hormones and bodily functions to control glucose levels in the blood.

Where does glucagon come from?

It comes from alpha (α) cells found in the pancreas and is closely related to insulin-secreting beta cells, making it a crucial component that keeps the body's blood glucose levels stable.

When blood sugar drops — for example, after long period of fasting or when we utilize blood sugar to cells for energy. How do alpha cells respond?

Alpha cells respond by releasing stored glucagon to release glucose from the liver to increase blood glucose levels

How are galactose and glucose absorbed?

Galactose and glucose are absorbed via active transport using sodium (Na) glucose linked transporters (SGLT1) and Na/K ATPase enzyme (3 Na ions: 2 K ions) across the membrane (2 Na ions : 1 glucose molecule).

What do GLUT2 transporters do?

Then GLUT2 transporters use facilitated diffusion further the absorption from the inner of the enterocyte to the bloodstream

How is fructose absorbed?

Fructose is absorbed via carrier-mediated facilitated diffusion – no energy required (ATP). This happens due to transporter GLUT5. Thus, the absorption rate of fructose alone from the small intestine is slower than that of glucose.

What is 50% of energy used by the brain attributed to?

50% of energy used by the brain is attributable to Na⁺/K⁺-ATPase! Of major importance for the function of brain, heart & kidney!

From what point of the body is fructose absorbed at a slower rate and where is it transported?

Fructose is absorbed at a slower rate from the lower part of duodenum and jejunum predominantly passively (in some cases actively) by the brush-border membrane transporter 5 (GLUT-5) and transported into blood also by GLUT2 and GLUT 5

What are GLUT transporters primarily made up of?

GLUT transporters are primarily made up of 13 multiple homologous proteins (GLUT 1–12 and 14)

Where are GLUT transporters located and what do they exhibit?

They are located throughout the body often exhibiting tissue specificities

The slower absorption and prolonged contact time of fructose with the luminal intestinal wall would be expected to result in what?

The stimulation of regulatory and satiety signals and release of hormones from enteroendocrine cells; yet  fructose will generally produce smaller insulin excursions upon consumption because it does not stimulate the secretion of insulin from pancreatic beta cells.

Define cellular respiration?

the process by which organisms use oxygen to break down food molecules to get chemical energy for cell functions.

Where does cellular respiration take place?

Cellular respiration takes place in the cells of animals, plants, and fungi, and also in algae and other protists

What do the stages of cellular respiration include? 

glycolysis, pyruvate oxidation, the citric acid or Krebs cycle, and oxidative phosphorylation

What are the two types of cellular respiration?

1. Anaerobic

2. Aerobic

Define oxidative phosphorylation?

Oxidative phosphorylation is the process by which ATP synthesis is coupled to the movement of electrons through the mitochondrial electron transport chain and the associated consumption of oxygen

What is oxidative phosphorylation made up of?

is made up of two closely connected components

•Oxidative phosphorylation is made up of two closely connected components. What are they?

•Electron Transport Chain

•Chemiosmosis

Define the Electron Transport Chain?

electrons are passed from one ETC complex to another, and energy released in these electron transfers is used to form an electrochemical gradient.

Define Chemiosmosis?

the energy stored in the gradient is used to make ATP via the ATP synthase pump.

What is cellular respiration?

●Cellular respiration is a series of chemical reactions that break down glucose to produce ATP, which may be used as energy to power many reactions throughout the body.

How many main steps are there of cellular respiration?

There are three main steps of cellular respiration

There are three main steps of cellular respiration, what are they?

●glycolysis, the citric acid cycle, and oxidative phosphorylation

What is the ATP yield from NADH is dependent on?

On how the electrons from the cytoplasmic (glycolytic) NADH are transported into the mitochondria

Remember: NAD⁺ & NADH Co-enzymes derived from what?

Niacin (vit B3)

What does the cellular respiration processes of all living cells make use of?

The coenzyme Nicotinamide adenine dinucleotide (NAD).

The cellular respiration processes of all living cells make use of the coenzyme Nicotinamide adenine dinucleotide (NAD). What does it play a key role in?

It plays a key role in energy metabolism by accepting and donating electrons (and protons – hydrogen ions).

•Nucleosides vs Nucleotides

“Nucleosides” contain only sugar and a base whereas “Nucleotides” contain sugar, base and a phosphate group.

When does the nucleotide occur?

A nucleotide is what occurs before RNA and DNA,

When does the nucleoside occur?

the nucleoside occurs before the nucleotide itself.

Where does glycolysis take place?

In the cytosol

What is the entry product of glycolysis?

Glucose

What is the end product of glycolysis?

2 X Pyruvate with 3 Carbons each

What is the net direct energy for glycolysis?

2 ATP

What is the net indirect energy for glycolysis?

2 NADH

What is the equation for glycolysis?

1 glucose (6C) + 2 NAD+ + 2NAP + 2Pi = 2 Pyruvate (3C) + 2NADH + 2H+ + 2ATP

Where does the Krebs cycle take place?

Mitochondrion

How many H2O are produced after glycolysis?

2 H20

What are the 3 phases of glycolysis?

1. Investment

2. Cleavage

3. Energy Harvest

What do we need to invest during glycolysis?

Energy: ATP

How many steps do we have in glycolysis?

10

How many missions does glycolysis have and what are they?

1+2 missions

• Provide pyruvate X2

• +

• Yield some ATP

• Re-generate NADH

What is the main reason we want NADH?

It carries electrons and protons

For one molecule of glucose how many pyruvate do we get in the end?

2

Describe steps 1, 3 and 10 of glycolysis?

• Irreversible

• Regulatory

• Rate limiting steps

What happens after step 5 of glycolysis?

Everything doubles

What is packed in NADH?

Electrons

Define Lactate Dehydrogenase?

An enzyme that the body uses during the process of turning sugar into energy for your cells to use

What is lactate production?

A consequence of cellular acidosis and not the cause of acidosis

What does lactate do?

Lactate is a temporary neutralizer or buffer to the cells elevated accumulation of protons during high intensity exer

Investment Phase - How many reactions does it have?

3

Investment Phase - How many reactions are irreversible/ reversible?

• 2 irreversible

• 1 reversible

Investment Phase - How many ATP do we use and at which steps?

Use 2 ATP (Steps 1 and 3)

Which steps are in the investment phase?

Step 1 - Step 3

Investment Phase - What is the rate limiting enzyme?

Phosphofructokinase - 1 PFK1

Investment Phase - What is the rate limiting enzyme phosphofructokinase 1 promoted by?

ADP (Di) or AMP (MONO) phosphate

Investment Phase - What is the rate limiting enzyme phosphofructokinase inhibited by?

• ATP

• Citrate

Cleavage Phase - How many reactions does it have?

2

Cleavage Phase - Are the reactions reversible or irreversible?

reversible

Cleavage Phase - Why DHAP (Dihydroxyacetone phosphate)?

It is a precursor of TG synthesis

Cleavage Phase - Why do we need GAP (glyceraldehyde - phosphate)?

When it increases it inhabits conversion

Cleavage Phase - What does the enzyme aldolase do?

Splits fructose 1,6 biphosphate into two sugars that are isomers of each other

• One called glyceraldehyde 3 phosphate

• the other called dihydroxyacetone phosphate

Cleavage Phase - Why is the conversion of DHAP to Gap extremely important?

For efficient conversion of glucose to energy

Cleavage Phase - What would happen if DHAP were not converted to GAP?

Half the energy available from glucose would be lost as an unstable by product

Energy Harvest Phase - How many reactions does it have?

5

Energy Harvest Phase - How many reactions are reversible or irreversible?

• 1 irreversible

• 4 reversible

Energy Harvest Phase - How many ATP are gained?

4