Metabolism Concepts Flashcards
Name the 3 typical fates of absorbed monosaccharides, amino acids, and monoglycerides.
- Most are oxidized (or “burned”) to supply energy for uphill life processes
- Some serve as building blocks for the synthesis of macromolecules
- Some are stored for future use (usually in the form of storage polymers - like glycogen or triglycerides
Contrast catabolism & anabolism in detail
Catabolism (or “breaking apart” processes) - downhill or exergonic
- Reactions release tiny little “puffs” of energy that need to be captured. Those little puffs of energy given off, are used to combine ADP and P to form ATP, which acts like a little storage battery
Anabolism (or building processes) - uphill or endergonic
- Requires a little burst of energy to happen. Splitting ATP back into ADP and P released tiny puffs of energy to lower the energetically uphill construction of macromolecules
Explain how ATP connects catabolism & anabolism. How does ATP, in this context, relate to cash money?
In catabolic reactions, the taking apart of simple molecules creates energy that’s stored in ATP
- You take the energy you made from catabolizing simple couples combine ADP and extra P and couple them together to create ATP
In anabolic reactions, complex molecules are being built, which take energy that is found in ATP
- Anabolic reactions will return ATP back to the two base products, ADP and P
Relating to cash money:
ATP is the currency of the cell
Contrast reduction & oxidation.
Reduction:
Adding H+ onto a molecule
Oxidation:
Stripping H+ off a molecule
Explain how redox reactions can also couple catabolism to anabolism.
The removal of H+ in oxidation (catabolism) is used to add H+ in reduction (anabolism).
When you catabolize a molecule, you oxidize it
Which coenzymes are typically put through redox reactions to couple cellular respiration (catabolism) to ATP synthesis (anabolism)
NAD (Nicotinamide adenine dinucleotide) is a critical coenzyme that’s frequently reduced to provide a source of energy
-The 2 H+ removed in oxidation is used to add 2H+ to NAD+ to create NADH + H+ (reduced form)
FAD is another important enzyme
-FAH to FADH2
How does the expression of glucose transporter on the cell membrane differ in hepatocytes and neurons – as compared to other body cells?
Hepatocytes and neurons have GluT’s that are always fully expressed and embedded in the membrane to allow for constant glucose uptake
Other body cells (like muscle cells) need to upregulate GluT 4 if they want to increase glucose
What hormone regulates the expression of glucose transporters
Insulin
Explain how phosphorylation of glucose works as “glucose trapping” inside a cell
Phosphorylation of glucose turns glucose to glucose 6-phosphate which creates a higher concentration of glucose outside the cell than inside, trapping glucose inside a cell
Describe Glycolysis – location, starting molecules, ending molecules, things produced, oxygen needed.
- Occurring in cytoplasm
- Taking one glucose molecule and splitting it into two pyruvate acids
- Oxygen NOT needed
- The end product is 2 ATP and 2 NADH
Explain how phosphofructokinase regulates glycolytic activity
- Controls how fast glycolysis goes
- High [ADP] stimulates Phosphofructokinase activity (glycolytic activity), cranking up the speed of glycolysis
Contrast the 2 paths of pyruvate, depending on whether oxygen is available.
O2
- Aerobically…pyruvate is converted to acetyl CoA and enters the Krebs Cycle (continuation of CR)
- The key factor is the presence of O2 to relieve NADH of its H’s. With O2 present, NADH can dump H’s into the Electron Transport Chain - which regenerates NAD+ for more glycolysis
No O2
- Anaerobically…pyruvate cannot continue CR - so it has to be oxidized to Lactic acids (which is “fermentation”)
- Without O2, the NADH made in glycolysis has to dump its H’s back onto pyruvate to make lactic acid, in order to free up NAD+
Describe the Haircut – location, starting molecules, ending molecules, things produced, oxygen needed.
- Occurring in the mitochondria matrix
- Convert pyruvate into acetyl coenzyme A
- Oxygen needed
- The end product is CO2 and NADH
Describe the Krebs Cycle – location, starting molecules, ending molecules, things produced, oxygen needed.
- Occurring in the mitochondria matrix
- Starting with Acetyl Coenzyme A and ending with CO2
- Oxygen needed
- End product per glucose molecule: 6 NADH, 2 FADH2, 2ATP
Explain why the Krebs Cycle spins twice for every glucose molecule, and how that affects the yield
- Krebs Cycle spins twice for every glucose molecule because two molecules of Acetyl CoA are formed from one molecule of glucose during Glycolysis
- If each Acetyl CoA (1 spin) yields 3 NADH, 1 FADH2, and 1ATP…then… the yield per glucose molecule in the Krebs cycle (2 spins) creates 6NADH, 2FADH2, and 2ATP
Contrast substrate-level phosphorylation & oxidative phosphorylation in glorious detail.
Substrate-level phosphorylation
- Making ATP slow and low-yield
- Make 4 ATP
Oxidative phosphorylation
- Making huge amounts of ATP
- 7 times the production of ATP
Describe energy coupling and electronegativity, and apply energy coupling to the essential 4 steps of the Electron Transport Chain (ETC)
Energy coupling:
Each “downhill” step in CR releases a little burst of energy and each little burst of energy gets “coupled” to an uphill task
Electronegativity:
- The more electronegative you are, the more you’re going to get electrons
- Each successive protein in the chain is simply more electronegative than the previous one, meaning the electrons will move from one protein to another
Downhills = the electrons (H’s) from NADH and FADH2 jump from protein to protein within the Electron Transport Chain (ETC)
- Each “jump” is downhill and releases a little burst of energy that gets coupled to an uphill task
Explain the 4 key steps of chemiosmosis, focusing on the energetics, and the key role of oxygen in the process.
- NADH goes to the electron transport chain to dump its electrons into the chain and regenerates NAD+ so it can go back and continue the process
- Each time an electron moves from protein to protein, little bursts of energy pump protons from the mitochondrial matrix to the intermembrane space, charging the battery
- O2 comes and couples with H to make H2O and NAD+ goes away to continue its process
- There’s a greater concentration in the intermembrane space than compared to the mitochondrial matrix, so the protons flow down into the mitochondrial matrix through the ATP synthase
- Using the downhill energy released from the protons flowing through the ATP synthase, ADP and P are coupled to make ATP via oxidative phosphorylation
Oxygen is essential to this process because oxygen is the most electronegative of them all, so it’s the terminal electron acceptor that always accepts the elections at the end of the ETC
Discuss fermentation in an anaerobic context, focusing on the need to regenerate NAD+
- Pyruvates receive the elections (instead of oxygen) and create lactic acid (fermentation)
- This process frees NAD+ to go back into glycolysis and collect more electrons
Contrast Glycogenesis with gluconeogenesis, focusing on the locations of each and hormonal control
Glycogenesis:
- 75% of the glycogen in muscle cells and 25% in hepatocytes
- Stimulated by Insulin
Gluconeogenesis
- Hepatic conversion of other molecules into glucose
- Stimulated by cortisol and glucagon, and T3/T4
Describe the structure and function of lipoproteins
Lipoproteins encapsulate lipids and transport them
Outer lipid Hydrophilic, center core packed with true hydrophobic lipids
Name the 3 most likely fates of absorbed dietary lipids
- Jump into CR and oxidized to produce ATP
- Stored as triglycerides in adipose tissue and in the liver
- Used as building blocks to synthesize complex lipids
Name a couple of key complex lipids built anabolically from simple lipids
Phospholipids
Lipoproteins
Myelin sheaths
Detail the distribution of adipose tissue throughout the body – in the primary storage areas
50% in the SubQ layer of the integument
12% in kidneys
10-15% in omenta
15% in the genital area
10-15% in muscles, around eyes, heart, and intestine
