Biochemistry and Cellular Respiration: Molecules, Enzymes, and Energy Transfer

What is diabetes and how is it diagnosed?

Diabetes is characterized by the body's inability to properly regulate blood glucose levels. Type 1 diabetes is treated with insulin due to the pancreas failing to produce it, while Type 2 diabetes involves insulin resistance.

How do enzymes facilitate catalysis?

Enzymes are mostly proteins that bring substrates together or hold them in an unstable transition state, lowering the activation energy required for chemical reactions.

What is the lock-and-key model of enzyme function?

The lock-and-key model implies a rigid fit between enzyme and substrate.

What is the induced fit model of enzyme function?

The induced fit model demonstrates that the enzyme changes shape slightly as the substrate binds to optimally hold it in the transition state.

What are the components of a reaction progress curve?

On a Gibbs free energy graph, reactants are at the starting energy level, the transition state is the peak, activation energy is the difference between reactants and peak, and products are at the final energy level.

In a reaction progress curve, which has more energy: a reactant/substrate or a product?

In a catabolic reaction, the reactants possess a higher potential energy than the products.

What is an example of structure relating to function in proteins?

The shape of the GLUT-1 transporter allows it to shift and carry glucose into the cell.

How does polarity relate to nutrient molecules?

Polarity is determined by the uneven pulling of electrons; molecules with abundant oxygen and nitrogen are polar, while those made of C-H bonds are non-polar.

What processes enable digestion?

Digestion involves mechanical breakdown and chemical breakdown, where specific enzymes cleave large polymers into monomers and dimers.

Which molecules diffuse easily in an aqueous environment?

Polar molecules like glucose and amino acids diffuse easily in the aqueous bloodstream.

Which molecules require transporters to cross cell membranes?

Polar molecules require protein transporters to cross non-polar cell membranes.

What is the structure of carbohydrates?

Carbohydrates, like glucose, have ring structures containing O and OH groups.

What is the structure of lipids?

Lipids, like fatty acids, have long hydrocarbon chains with very few oxygens.

What is the structure of amino acids?

Amino acids contain a central carbon, an amino group (NH2), a carboxyl group (COOH), and a variable R group.

What is the structure of nucleotides?

Nucleotides contain a nitrogenous base, a five-carbon sugar, and a phosphate group.

How does a glucose transporter facilitate glucose movement?

The GLUT-1 transporter binds to glucose outside the cell, undergoes a conformational change, and releases glucose inside the cell.

What are the types of protein structure?

Primary (1°) is the linear sequence of amino acids; Secondary (2°) is local folding (alpha-helices and beta-sheets); Tertiary (3°) is the complete 3D structure.

What can be learned from different protein models?

An amino acid sequence model shows which amino acids are present; a ribbon model shows secondary structure; a space-filling model shows overall tertiary structure.

What happens when a mutation disrupts a molecular transporter's function?

A genetic mutation in the primary amino acid sequence alters the tertiary structure, destroying its function.

Why are lipids transported in chylomicrons?

Lipids are highly non-polar and repel water, so they must be packaged inside chylomicrons for transport in the aqueous bloodstream.

How do transport and transduction solve the membrane barrier problem?

Transport provides a channel for large or polar molecules to cross the membrane; transduction allows a hormone to send a signal across the membrane without entering.

What determines if a hormone can cross a membrane?

Small, highly non-polar molecules can diffuse across the membrane, while large or highly polar molecules require a receptor or transporter.

What is the difference between autocrine, paracrine, and endocrine signaling?

Endocrine hormones travel through the bloodstream to distant targets; paracrine targets nearby cells; autocrine targets the cell that secreted it.

What are the events during signal transduction?

A hormone binds to a receptor, the receptor is activated, a signaling cascade is triggered, and the cell executes a response.

What do transport and signal transduction have in common?

Both rely on transmembrane proteins.

How do insulin and glucagon function to maintain blood glucose levels?

Insulin promotes glucose uptake and storage after meals; glucagon promotes glycogen breakdown and glucose release during fasting.

Why is insulin treatment used for Type 1 but not Type 2 diabetes?

Type 1 diabetes patients cannot produce insulin, so treatment replaces the missing signal; Type 2 patients have insulin resistance, making additional insulin ineffective.

How does ghrelin affect blood glucose regulation?

Ghrelin decreases insulin receptor sensitivity and increases glucagon, raising blood glucose.

What role does incretin play in blood glucose regulation?

Incretin triggers insulin release, which lowers blood glucose.

What are the downstream effects of insulin?

Insulin decreases gluconeogenesis and increases glycogenesis and glucose uptake.

What are the downstream effects of glucagon?

Glucagon increases gluconeogenesis and glycogenolysis to restore blood sugar.

Do insulin and glucagon operate in a positive or negative feedback loop?

They operate in a negative feedback loop, reversing high or low blood sugar.

What feedback loop does ghrelin operate in?

Ghrelin operates in a positive feedback loop, promoting higher blood sugar during fasting.

What is the input and output of glycolysis?

Input: 1 Glucose; Output: 2 Pyruvate + 2 ATP + 2 NADH.

What is the input and output of pyruvate processing?

Input: 2 Pyruvate; Output: 2 Acetyl CoA + 2 CO2 + 2 NADH.

What is the input and output of the Citric Acid Cycle?

Input: 2 Acetyl CoA; Output: 4 CO2 + 2 ATP + 6 NADH + 2 FADH2.

What is the input and output of the Electron Transport Chain and ATP Synthase?

Input: NADH/FADH2 + O2; Output: 25-30 ATP + H2O.

What is the role of glucose in cellular respiration?

Glucose is the initial energy and carbon source.

What are NADH and FADH2 in cellular respiration?

They are high-energy electron carriers.

Where does glycolysis occur in the cell?

Glycolysis occurs in the cytoplasm.

Where does pyruvate processing and the Citric Acid Cycle occur?

They occur in the mitochondrial matrix.

Where does the Electron Transport Chain and ATP Synthesis take place?

They take place across the inner mitochondrial membrane.

How is energy transformed through cellular respiration?

Chemical potential energy in glucose is transferred to NADH/FADH2, then to a proton gradient, and finally to ATP.

What oxidation and reduction reactions occur during cellular respiration?

Glucose is oxidized to CO2; oxygen is reduced to form H2O.

What is the higher energy form of glucose and CO2?

Glucose has higher potential energy than CO2.

What is the higher energy form of NADH and NAD+?

NADH has higher energy than NAD+.

What is the higher energy form of FADH2 and FAD?

FADH2 has higher energy than FAD.

How is carbon transformed through glycolysis?

Glucose (6 carbons) splits into two pyruvates (3 carbons each).

How is carbon transformed during pyruvate oxidation?

Each pyruvate loses one carbon as CO2 to form Acetyl CoA.

How is carbon transformed in the Citric Acid Cycle?

Acetyl CoA bonds to oxaloacetate, and remaining carbons are oxidized and exhaled as CO2.

Why is O2 consumption a good indicator of ATP production?

O2 is the final electron acceptor; without it, ATP synthesis halts.

What happens when cyanide blocks Complex IV?

The ETC stops, the gradient fails, and ATP production ceases.

What effect does DNP have on respiration?

It creates a leaky membrane, causing ATP production to drop and generating heat.

Why does NADH lead to more ATP production than FADH2?

NADH activates all proton pumps; FADH2 bypasses Complex I, pumping fewer protons.

Why can't CO2 be used as an energy source?

CO2 is fully oxidized and at its lowest potential energy state.

How is mass lost when people lose weight?

Carbon atoms from glucose are oxidized into CO2 and exhaled.

How do aerobic and anaerobic respiration differ?

Aerobic respiration uses O2 and yields 25-30 ATP; anaerobic respiration occurs without O2 and yields only 2 ATP.

How does localization of molecules contribute to cellular respiration?

ETC complexes are embedded in the inner mitochondrial membrane to create a proton gradient for ATP Synthase.