Biochemistry Section D

What are our bodies made of?

Compounds found in the foods we eat

What are macromolecules?

The chemical building blocks for our cells

What are the three types of macromolecules?

Proteins, carbohydrates, and lipids.

What do proteins provide to the body?

essential nitrogen, carbon, electrons, and amino acids that the body cannot synthesize that we need for function.

What do carbohydrates provide to the body?

carbons and electrons, these are not essential

What do lipids provide to the body?

carbons, electrons, and essential lipids that the body cannot synthesize that we need for signaling molecules.

How is a person able to grow from an infant to an adult?

The accruing of macronutrients such as fats and proteins

How does the accretion of proteins and lipids allow our bodies to grow?

Through a process known as metabolism

What are the two most fundamental metabolic states?

Fed state and Fasted state

What is the fed state? How long does it last?

The absorptive state; last for a variable amount of time depending on composition of the meal (usually 2-4 hours after the meal)

What is an example of fast fed state? Slow?

A sugary soda; a lot of protein and fat

When does the fed state end?

When the last nutrient has been absorbed into the intestine. Doesn't mean all were absorbed, refers to the last nutrient that gut was able to absorb.

When the fed state is over, what occurs then?

The fasted state

What is the fasted state? How long does it last?

The post-absorptive state; until food is consumed

What is the driving hormone in the fed state? What does it do?

Insulin; facilitates how the meal will be assimilated and stored for later use. Lowers blood glucose by increasing its uptake into insulin-responsive tissues

When food is passed into the intestine, what is directly absorbed into portal circulation?

Glucose and amino acids

Where do glucose and amino acids first pass into?

The liver

What does the liver do with glucose and amino acids?

Glucose will replenish glycogen and oxidize ATP in the liver

Amino acids make liver proteins and energy metabolism

What does the liver do if there are too many carbohydrates in the meal?

Create lipids

After passing through liver, where do glucose and amino acids go?

Enter the circulatory system and are taken up by other tissues. Insulin will signal tissues to absorb these nutrients.

What two tissues will take up glucose and amino acids?

Skeletal muscles and adipose tissue

How is dietary fat taken up differently?

Not water soluble, enters through lymphatics to adipose tissue in the gut

What are the driving hormones in the fasted state? What do they do?

Glucagon and adrenaline; move energy substrates around the body (mobilize stored nutrients)

What does the liver do during the fasted state?

Produces glucose either by breaking down glycogen or by stimulating gluconeogenesis.

It also oxidizes fatty acids that will create ketones

What is gluconeogenesis?

production of glucose from non-carbohydrate sources; always anabolic

What does adipose tissue do during the fasted state?

Giving up stored fat in the form of glycerol or fatty acids

Most go to liver and some go to heart/muscles for energy source

What is a key feature of glycerol?

It is a non-carbohydrate source that can be used in gluconeogenesis to make glucose.

Because insulin is low in fasted state, what do the skeletal muscles do?

Release amino acids that travel to the liver than can be used in gluconeogenesis

How is the CNS related to glucose regulation?

The brain will only use glucose for energy, generates a lot of regulatory processes for it

What are carbohydrates converted to for intermediate metabolism? Proteins? Fats?

Glucose; Amino acids; Glycerol and fatty acids

What can glucose be used to make?

Acetyl CoA via glycolysis (breakdown of glucose)

What can amino acids be used to make?

Acetyl CoA and gluconeogenic precursors

What can glycerol and fatty acids be used to make?

Glycerol: gluconeogenic precursors

Fatty acids: Acetyl CoA

What can gluconeogenic precursors be used to make?

Glucose (precursors to feed into gluconeogensis to create glucose)

What does Acetyl CoA feed into?

The Krebs Cycle (citric acid cycle)

What do the macronutrients ultimately get turned into?

CO2, H2O, and ATP

What is metabolism?

the chemical processes that occur within a living organism in order to maintain life, provides energy

What are the processes of metabolism regulated by?

Extracellular signals that signal a cell to change. When a cell changes function, it needs to change metabolism to support that function.

What are some functions that require metabolism?

Survival, growth/division, differentiating, and death

What is the catabolic pathway?

release energy by breaking down complex molecules into simpler compounds, energy captured as ATP

What is the anabolic pathway?

consume energy to build complex molecules from simpler ones, energy input is ATP

What are the end products we normally get from catabolic pathways?

CO2, H2O, Nitrogen, ammonia, and Acetyl CoA

How do catabolic reactions pay for anabolic reactions?

Reactions that require energy (anabolic) can couple with reactions that produce energy (catabolic)

What is an example of a coupling reaction?

The formation of pyruvate (catabolic) is paired with the formation of ATP (anabolic) and the sum of their energy is negative (gives off energy, spontaneous, neg G)

What makes metabolism possible?

The coupling of favorable and unfavorable reactions

What reactions have the ability to be anabolic and/or catabolic?

Glycolysis and the Krebs Cycle

What is the catabolic pathway of glycolysis and the Krebs Cycle?

Glucose (6 carbons) to pyruvate (3 carbons) that can generate ATP and Acetyl CoA. Also, fatty acids to Acetyl CoA. Acetyl CoA enters the Kreb Cycle to make CO2, H2O, and more ATP.

When can the pyruvate make Acetyl CoA?

When it enters the mitochondria

What is produced when Acetyl CoA goes through Krebs Cycle?

CO2 and reducing agents

What is produced when reducing agents from the krebs cycle goes through the ETC?

H2O and ATP

What is the anabolic pathway of glycolysis and the Krebs Cycle?

Instead of sending glucose through glycolysis, we can send it on anabolic intermediate pathways.

Instead of generating ATP, CO2, and water through Krebs, we can generate anabolic products

What are the anabolic pathways of glycolysis and anabolic products of Krebs Cycle?

G: UDP-SUGARS, Ribose-5-Phosphate (NAD, nucleic acids), and Serine/sphingolipids

K: citrate, fatty acids, cholesterol, and amino acids

What do we need anabolic pathways for?

synthesis of new membranes, organelles, proteins, enzymes, and provides substrates for post-translational modification

What are some survival activities that require ATP?

(1)Maintenance of membrane gradients, (2) muscle contraction, (3) membrane trafficking and secretion, and (4) cellular turnover.

How does the brain rely on ATP?

(1 and 3) membrane fusion events that support neurotransmitter secretion and rectification of ion gradients during action potential propagation,

How does the heart and skeletal muscles rely on ATP?

(2) require high levels of ATP for muscle contraction

How does the liver rely on ATP?

for synthesis of plasma proteins and gluconeogenesis

How does the kidney rely on ATP?

for active transports of solutes when filtering the blood plasma.

How much ATP does each organ use a day? (moles/day)

liver: 18 resting skeletal muscle: 17 brain: 17 heart: 10 kidneys: 7

What dictates substrate selection in different organs/tissues?

Metabolic enzymes present in the tissue and nutrient transported needed to get onto cell surface

What organs prefer glucose and are not metabolically flexible?

Brain and kidney

What organs prefer either glucose or fat and are metabolically flexible?

Liver, heart, and skeletal muscles.

How do metabolically flexible organs know when to switch substrates?

Changes in insulin levels that will change nutrient transporters on surface of the cell.

What type of transporter is on the cell when insulin is high?

GLUT4 will create a pore in the membrane when insulin is high in the extracellular solution. This will allow influx of glucose into the cell when insulin binds to insulin receptor.

What type of transporter is on the cell when insulin is low?

GLUT4 will come back into the cell since insulin is no longer bound. New transporters that allow fat to cross the membrane will be used instead.

What pathways consume glucose?

Glycolysis, pentose phosphate pathway and glycogen synthesis all consume glucose (fed state)

What pathways produce glucose?

Glycogenolysis and gluconeogenesis both produce glucose (fasting and exercise stress).

What cofactors help transfer electrons, but do not provide the electrons?

NAD and FAD