SECTION 06: METABOLISM AND ENERGY MOLECULES

Q: What do DNA, RNA, and protein all require for their synthesis and regulation?

A: Energy.

Q: How do enzymes help with energy usage?

A: They make reactions more favorable and can couple reactions to the breakage of high-energy bonds.

Q: What is the most common high-energy molecule in the cell?

A: ATP (Adenosine Triphosphate).

Q: What are two other high-energy molecules used in cells?

A: NADH (Nicotinamide Adenine Dinucleotide) and FADH₂ (Flavin Adenine Dinucleotide).

Q: What is the role of ATP in metabolism?

A: Acts as the cell’s energy currency—used to power cellular processes.

Q: What will this section of the course explore?

A: How cells create and use energy through metabolic processes.

Q: What is metabolism?

A: An integrated network of chemical reactions where the product of one reaction becomes the substrate for the next.

Q: What molecules are involved in metabolic synthesis and breakdown?

A: Carbohydrates, lipids, and amino acids.

Q: What will you learn by the end of BCHM 270?

A: How metabolic pathways interact to provide energy and nutrients, and what happens when something goes wrong.

Q: What does Module 04 cover?

A: Carbohydrate metabolism:

• Glycolysis (↓ arrows)

• TCA cycle

• Gluconeogenesis (↑ arrows)

• Glycogen synthesis/degradation

• Pentose phosphate pathway

Q: What does Module 05 focus on?

A: Lipid metabolism, including:

• Energy storage

• Cell membrane components

• Hormones & signaling molecules

Q: What is covered in Module 06?

A: Metabolism of amino acids, urea, and nucleotides.

Q: What is homeostasis in metabolism?

A: It's the balance of metabolic activities to maintain stable nutrient and energy levels in the body.

Q: What does the figure with flasks and tubes represent?

A: The interconnected pathways that maintain nutrient balance between proteins, carbs, lipids, and tissues.

Q: What are the 3 main ways metabolic processes are regulated?

1. Amount of enzymes (controlled by synthesis/degradation)

2. Enzyme activity (controlled by cofactors, allosteric regulation, covalent modification, etc.)

3. Substrate accessibility (controlled by compartmentalization)

Q: What is an example of substrate accessibility?

A: Opposing reactions like fat breakdown vs. fat synthesis occur in different places (compartments) to prevent interference.

Q: What is the goal of all these regulations?

A: To keep blood glucose stable and ensure each tissue gets the right fuel at the right time.

Q: Where is DNA & RNA made in the cell?

A: In the nucleus – the cell’s genetic library.

Q: Which metabolic processes happen in the cytosol?

A:

• Glycolysis

• Pentose phosphate pathway

• Fatty acid synthesis

• Protein synthesis

Q: What do proteosomes do and where are they found?

A: They’re in the cytosol and break down damaged proteins into amino acids.

Q: Which processes occur in the mitochondria?

A:

• TCA cycle

• Electron transport chain (ETC)

• ATP production via oxidative phosphorylation

• Beta-oxidation of fatty acids

Q: What happens in the Golgi apparatus?

A: Glycosylation of proteins (adding sugar chains to proteins).

Q: What’s the role of the endoplasmic reticulum (ER)?

A:

• Rough ER: Protein synthesis

• Smooth ER: Long-chain fatty acid synthesis

Q: What is the function of the lysosome?

A: It breaks down large or damaged structures (e.g., organelles, proteins, DNA) into basic building blocks.

Q: What is cellular metabolism?

A: It's the sum of all reactions in a cell that build or break down molecules.

Q: What are the two main types of metabolic reactions?

A:

1. Anabolism

2. Catabolism

Q: What is anabolism?

A:

• Builds larger molecules from smaller ones

• Uses ATP

• Example: Gluconeogenesis (makes glucose from smaller molecules)

Q: What is catabolism?

A:

• Breaks down large molecules (e.g., carbs, fats)

• Releases energy

• Energy is stored as ATP

• First example you’ll study: Glycolysis

Q: What is metabolism?

A: Metabolism is all the chemical reactions in your body. It includes two opposite processes: anabolism (building molecules) and catabolism (breaking molecules down).

Q: What are anabolic reactions?

A: Anabolic reactions build large molecules from small ones (like proteins from amino acids) and use energy (ATP).

Q: What are catabolic reactions?

A: Catabolic reactions break down large molecules (like glucose or fat) into smaller ones and release energy, which is stored in ATP.

Q: What is ATP and why is it important?

A: ATP is the main energy currency of the cell. It powers all processes that require energy, like muscle contraction or protein synthesis.

Q: What are the six essential nutrients your body needs?

A: Water, vitamins, minerals, carbohydrates, lipids (fats), and proteins.

Q: What’s the main fuel your body uses for energy?

A: Glucose (a simple carbohydrate). It's critical for the brain and red blood cells.

Q: What happens to carbs if they’re not used right away?

A: They get stored as glycogen (short-term) or converted into fat (long-term storage).

Q: Why are fats important (besides storing energy)?

A: Fats cushion organs, store fat-soluble vitamins, insulate nerves (myelin), and are used to build hormones and cell membranes.

Q: What are essential fatty acids?

A: Fats your body can’t make (like omega-3 and omega-6). You must get them from food.

Q: What do proteins do in the body?

A: Proteins make up muscles, enzymes, cell channels, pumps, and many other functional molecules.

Q: Can the body make all the amino acids it needs?

A: No. There are 9 essential amino acids you must get from your diet.

Q: What’s the relationship between food and the body?

A: Your body constantly breaks food down into building blocks, then rebuilds those blocks into new body parts — like proteins and cell membranes.

Q: What are the 4 main tissues involved in energy metabolism?

A: Liver, adipose (fat), skeletal muscle, and brain.

Q: What does each metabolic tissue do?

• Liver: Makes, stores, and releases energy sources

• Adipose: Stores fat and releases fatty acids

• Muscle: Uses glucose and fat for movement

• Brain: Uses glucose (mostly) for energy

Q: How do these tissues interact?

A: They form a network and share energy molecules (substrates).

Q: What controls the coordination between tissues?

A:

• Hormones (especially insulin and glucagon)

• Nervous system signals

• Levels of circulating substrates in the blood

Q: What triggers hormone release for metabolic control?

A: Changes in blood energy levels — usually depending on when you last ate.

Q: What two main hormones control energy metabolism?

A: Insulin and Glucagon.

Q: Where is insulin made?

A: In β-cells (beta cells) of the pancreas, specifically in the Islets of Langerhans.

Q: When is insulin released and what does it do?

• Released after a meal when energy levels are high.

• Anabolic hormone → builds and stores:

  • Increases synthesis of proteins, fats, and carbs

  • Promotes energy storage

Q: When is glucagon released and what does it do?

A:

• Released when energy is low (fasting or low blood sugar).

• Catabolic hormone → breaks down stored molecules to release energy

  • Maintains blood glucose levels

Q: What other hormones help during stress or danger?

A: Catecholamines like epinephrine and norepinephrine (fight or flight response).

Q: What will be explored in the next modules of BCHM 270?

A: Major metabolic pathways and their regulation by key hormones.

Q: What kind of enzymes are regulated by hormones like insulin and glucagon?

A: Allosteric enzymes at key control points in metabolic pathways.

Q: Which hormones commonly regulate metabolic enzymes?

A:

• Insulin

• Glucagon

• (Also epinephrine, to a lesser extent)

Q: Why are these hormonal controls important?

A: They determine whether a pathway is activated or inhibited based on the body’s energy state.

Q: What are the main energy “currencies” used in metabolism?

A:

• ATP (adenosine triphosphate)

• GTP (guanosine triphosphate)

• NADH

• FADH₂

• NADPH

Q: What is ATP made of?

A: Adenosine + Ribose sugar + 3 phosphate groups

Q: What is the role of ATP in the cell?

A: It's the main energy source for most cellular processes.

Q: What is GTP and how is it different from ATP?

A: GTP is like ATP, but it has guanosine instead of adenosine.

Q: What are some functions of GTP?

A:

• Powers protein synthesis (peptide bond formation)

• Fuels gluconeogenesis

• Acts as backup energy when ATP is low

Q: When does the cell use GTP instead of ATP?

A: In specific reactions or energy-poor conditions

Q: What happens when ATP loses its 3rd phosphate group?

A: It becomes ADP and releases energy (~–7.3 kcal/mol).

Q: What happens when ADP loses a phosphate?

A: It becomes AMP and releases more energy (~–7.3 kcal/mol again).

Q: Why is ATP called a high energy molecule?

A: Because the bonds between phosphate groups store a lot of free energy (ΔG° = –7.3 kcal/mol per bond broken).

Q: What does Pi mean in biology?

A: Pi stands for inorganic phosphate (PO₄³⁻), released when ATP is broken down.

Q: What is Standard Free Energy (ΔG°)?

A: It’s the change in energy under standard conditions:

• Temp = 273.15 K

• Pressure = 1 atm

Q: Why is ATP called the "energy currency" of the cell?

A: Because it stores energy in its phosphate bonds and transfers that energy to power other reactions.

Q: How do enzymes use ATP to drive reactions forward?

A: Enzymes often transfer a phosphate group from ATP to the substrate or to themselves, which helps power the next step of the reaction.

Q: What happens when ATP is used in a reaction?

A: A phosphate is removed, releasing free energy (ΔG°) that pushes the reaction forward.

Q: What is a common intermediate step when ATP is used?

A: ATP forms a phosphorylated intermediate, which is more reactive and helps the reaction proceed.

Q: Can other molecules act like ATP?

A: Yes — molecules like GTP, NADH, FADH₂ also store and transfer energy in the cell.

Q: What is energy coupling in metabolism?

A: It’s when an unfavourable (endergonic) reaction is paired with a favourable (exergonic) one to make the overall process happen.

Q: Why do we need energy coupling?

A: Some important reactions (like protein synthesis) require energy and can’t happen on their own — they need help from reactions that release energy, like ATP hydrolysis.

Q: What is a common intermediate in energy coupling?

A: A molecule that is the product of one reaction and the reactant of the next, like D in the example.

Q: How does a common intermediate help with energy coupling?

A: It links two reactions, allowing the energy from the first (exergonic) to drive the second (endergonic).

Q: In this example, what is the common intermediate?

A: D is the common intermediate — it is made in Reaction 1 and used in Reaction 2.

🔁 Energy Coupling — ATP Drives Unfavorable Reactions

⚗ Example: Glutamine Synthetase Reaction

⚙ Allosteric Regulation by ATP

Q: What is an allosteric factor?

A: A molecule that binds to an enzyme outside the active site and changes the enzyme's shape and activity.

Q: How does ATP act as an allosteric factor?

A: ATP binds to certain enzymes and changes their shape → this can either activate or inhibit the enzyme's function depending on the enzyme.

Q: What happens if ATP is hydrolyzed to ADP?

A: The shape of the enzyme changes again, further modifying activity.

🔄 Sodium-Potassium Pump Example (You don’t need to memorize steps)

Q: What is the sodium-potassium pump?

A: An active transport protein that uses ATP to move ions across the cell membrane.

soddium potassium poump - Q: What ions are moved and where?

A:

• 3 Na⁺ (sodium) out of the cell

• 2 K⁺ (potassium) into the cell

sodium potassium pump - Q: How does ATP help?

1. 3 Na⁺ bind to the pump (inside cell)

2. ATP is used → phosphate attaches to the pump

3. This changes the pump shape → releases Na⁺ outside

4. 2 K⁺ bind from outside

5. Phosphate leaves → pump changes shape again

6. K⁺ released inside the cell

sodium potasssium pump - Q: What’s the key takeaway?

A: ATP powers the pump by binding and causing shape changes—this is allosteric regulation in action!

Q: What are two key high-energy electron carriers in the cell (besides ATP/GTP)?

A: NADH and FADH₂.

🧪 FAD (Flavin Adenine Dinucleotide)

Q: What reaction turns FAD into its high-energy form?

A: FAD + 2 e⁻ + 2 H⁺ → FADH₂

Q: What vitamin is used to make FAD?

A: Vitamin B2 (Riboflavin)

Q: What is FMN?

A: Flavin Mononucleotide, an intermediate made from B2 that can also help store energy.

⚡ NAD⁺ (Nicotinamide Adenine Dinucleotide)

Q: What reaction turns NAD⁺ into its high-energy form?

A: NAD⁺ + 2 e⁻ + H⁺ → NADH

Q: What vitamin is used to make NAD⁺/NADH?

A: Vitamin B3 (Niacin)

Q: What is NADPH used for?

A: NADPH is used in anabolic (building) reactions like gluconeogenesis and lipid synthesis.

Q: How is NADP⁺ different from NAD⁺?

A: NADP⁺ has one extra phosphate group (highlighted in green in the diagram).

Q: Does the extra phosphate on NADP⁺ affect the reaction chemistry?

A: No — it doesn’t change the redox chemistry but does affect enzyme binding.

Q: Why do cells use NADPH instead of NADH for some reactions?

A: The extra phosphate makes NADPH bind different enzymes that are specific to biosynthesis pathways.

Q: What do catabolic reactions do?

A: Break down molecules to release energy and produce ATP, NADH, FADH₂

Q: What do anabolic reactions do?

A: Build larger molecules and use energy (require ATP, NADPH, etc.)

Q: Which hormone triggers anabolism after a meal?

A: Insulin – promotes storage and synthesis when energy is high.

Q: Which hormones trigger catabolism when energy is low?

A: Glucagon and epinephrine – stimulate breakdown of stored fuel like fat.

Q: Why are NADPH and GTP important?

A: They support special energy-demanding reactions, especially when ATP is low or other pathways are active.

Q: What major processes will be studied next to understand ATP production?

A: Cellular respiration, TCA (Krebs) cycle, and oxidative phosphorylation.