Chapter 24 Study Guide
o What is a nutrient?
A nutrient is a substance that provides essential nourishment for growth, maintenance, and overall health in living organisms.
o What is the difference between an essential nutrient and a nonessential nutrient?
An essential nutrient must be obtained from the diet because the body cannot synthesize it in sufficient quantities, whereas the body can produce a nonessential nutrient in adequate amounts.
o What units are used to measure the energy provided by food?
The energy provided by food is measured in calories.
o Name the three macronutrients.
lipid
proteins
carbohydrates
o Define catabolism and anabolism. How are the two related?
anabolism: the synthesis of larger molecules from smaller molecules
amino acids → proteins
catabolism: is hydrolysis (breakdown) of larger molecules into smaller molecules
proteins→amino acids
o Define metabolism.
metabolism: the chemical reactions of cells that involve nutrients.
o What is cellular respiration (aerobic respiration)? What are the three metabolic pathways of cellular respiration?
cellular respiration: is a set of catabolic reactions that provides cellular energy.
three metabolic pathways of cellular respiration: from glycolysis and citric acid cycle, to oxidative phosphorylation.
o What is the main input of cellular respiration? What is the main output?
Main input: Glucose (C6H12O6) and oxygen (O2)
Main output: ATP (adenosine triphosphate), carbon dioxide (CO2), and water (H2O)
o Are hydrogen ions lost during oxidation?
oxidation: is loss of electrons
gain of oxygen or loss of hydrogen
o Are hydrogen ions gained during reduction?
reduction: is gain of electrons
loss of oxygen or gain of hydrogen.
o Are NAD+ and FAD the oxidized or reduced forms of their molecules?
NAD+ and FAD are oxidized forms.
o Are NADH and FADH2 the oxidized or reduced forms of their molecules?
NADH and FADH2 are reduced forms.
o Which two metabolic pathways utilize substrate-level phosphorylation?
glycolysis and citric acid cycle
o Where does oxidative phosphorylation occur?
Oxidative phosphorylation occurs only in the mitochondrial matrix.
o Which pathways of cellular respiration occur in the mitochondria? Which in the cytoplasm?
The citric acid cycle and oxidative phosphorylation occur in the mitochondria, while glycolysis occurs in the cytoplasm.
Additionally, the electron transport chain is also located in the inner mitochondrial membrane.
The stage that requires oxygen is oxidative phosphorylation, where oxygen acts as the final electron acceptor in the electron transport chain.
§ What is the starting input for glycolysis?
The starting input for glycolysis is glucose
§ What is the ending output of glycolysis?
x2 pyruvic acid
x2 ATP
x2 NADH+H+
§ How much (net) ATP is produced by glycolysis?
x2 of the net ATP is produced by glycolysis
§ Is NADH oxidized or reduced during glycolysis? How many molecules of NADH?
NADH is reduced during glycolysis, producing a total of 2 molecules of NADH.
§ Where will the NADH made during glycolysis be used later in cellular respiration?
NADH produced during glycolysis will later enter the electron transport chain, where it contributes to the production of ATP through oxidative phosphorylation.
§ After glycolysis, to what is pyruvate converted before moving to the citric acid cycle? Is NADH made during that reaction?
Pyruvate is converted to acetyl-CoA during the transition reaction, and in this process, one molecule of NADH is produced for each pyruvate.
§ What is the starting input for the citric acid cycle?
x2 pyruvic acid
2 CoA
x2 NAD+
§ Is NADH oxidized or reduced during the citric acid cycle? How many molecules of NADH?
NADH is reduced during the citric acid cycle, resulting in the production of three molecules of NADH for each acetyl-CoA that enters the cycle.
§ Is FADH2 oxidized or reduced during the citric acid cycle? How many molecules of FADH2?
FADH2 is oxidized during the citric acid cycle, resulting in the formation of one molecule of FADH2 for each acetyl-CoA that enters the cycle.
§ Where will the NADH and FADH2 made during the citric acid cycle be used later in cellular respiration?
These molecules will be used in the electron transport chain, where they will donate electrons to drive ATP synthesis through oxidative phosphorylation.
§ What is the role of NADH and FADH2 in the electron transport chain?
deliver electrons
water formed from protons and oxygen (required)
much energy released in steps
§ Where does the electron transport chain happen in the cell?
The electron transport chain occurs in the inner mitochondrial membrane, where a series of protein complexes facilitate the transfer of electrons.
§ What is the goal of the electron transport chain?
The goal of the electron transport chain is to create a proton gradient that drives the synthesis of ATP through oxidative phosphorylation.
§ What is the function of ATP synthase?
ATP synthase functions as a molecular turbine, allowing protons to flow back into the mitochondrial matrix, which energizes the enzyme to catalyze the conversion of ADP and inorganic phosphate into ATP.
§ From where does the energy for oxidative phosphorylation by ATP synthase come?
The energy for oxidative phosphorylation by ATP synthase comes from the electrochemical gradient of protons established by the electron transport chain, which drives the flow of protons through ATP synthase, ultimately producing ATP.
o Which organ plays a major role in regulation of plasma cholesterol levels?
The liver plays a major role in the regulation of plasma cholesterol levels by synthesizing and metabolizing cholesterol, in addition to producing bile acids that help in the digestion and absorption of dietary fats.
o Where in the body are most drugs and toxins metabolized?
Most drugs and toxins are metabolized primarily in the liver, where various enzymes break down these substances through processes such as oxidation, reduction, and hydrolysis.
o Which macronutrients and micronutrients are regulated by metabolic functions of the liver?
The liver regulates several macronutrients including carbohydrates, proteins, and fats, as well as various micronutrients such as vitamins and minerals, ensuring proper metabolic function and nutrient balance in the body.
o Name three types of molecules that are formed from cholesterol.
Steroid hormones: Including testosterone, estrogen, and cortisol.
Bile acids: Essential for the digestion and absorption of dietary fats.
Phospholipids: Key components of cell membranes, influencing cell signaling and fluidity.
o Name a structure of our cells that requires cholesterol for its functioning.
Lipid rafts: Membrane microdomains that enrich signaling molecules and play crucial roles in cell communication and receptor activity.
o What are LDLs? What are HDLs? Which one transports cholesterol to tissue and which one transports cholesterol to liver to be broken down?
IDL’s (low density lipoproteins): transport cholesterol to peripheral tissue for storage or hormone synthesis
HDL’s (high density lipoproteins): transport excess cholesterol from peripheral tissues to liver to be broken down and secreted into bile.
o What are generally considered healthy levels for HDL and LDL? Which one is considered “good cholesterol?”
Healthy levels for HDL are typically considered to be 60 mg/dL or higher, while healthy levels for LDL should be less than 100 mg/dL.
HDL is frequently referred to as "good cholesterol" because it helps remove cholesterol from the bloodstream.