Metabolism I: Cells and Energy Systems

Flashcards covering cell metabolism, ATP systems, enzymes, substrates, and the chemical pathways of energy production (ATP-PCr, Glycolysis, Krebs Cycle, and Oxidative Phosphorylation) as presented in the lecture notes.

Metabolism

The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life, categorized into catabolism and anabolism.

Adenosine triphosphate (ATP)

The primary energy currency of the cell, consisting of adenine, ribose, and three linked phosphates.

ATP Synthesis

The chemical reaction where adenosine diphosphate combines with inorganic phosphate to form ATP: $ADP + Pi \rightarrow ATP$.

ATP Breakdown

The hydrolysis reaction that releases energy for cellular work: $ATP \rightarrow ADP + Pi + \text{Energy}$ via the enzyme ATPase.

Enzymes

Catalysts that regulate the speed of chemical reactions by lowering the energy of activation; their activity is regulated by temperature and pH.

Lock-and-key model

A model describing the specific interaction between enzymes and their substrates.

Carbohydrate (CHO) fuel stores

Substrates stored as glucose or as glycogen in the muscle and liver.

Fat fuel stores

Substrates stored as free fatty acids (FFA) or as triglycerides in muscle and fat cells.

ATP-PCr System Power and Capacity

Energy system with a power of $3.6 \text{ mM ATP/min}$ and a capacity of $0.7 \text{ Total mol ATP}$.

Glycolytic System Power and Capacity

Energy system with a power of $1.6 \text{ mM ATP/min}$ and a capacity of $1.2 \text{ Total mol ATP}$.

Aerobic System Power and Capacity

Energy system with a power of $1.0 \text{ mM ATP/min}$ and a capacity of $90.0 \text{ Total mol ATP}$ (from glycogen).

Phosphocreatine (PCr or CP)

A rapid source of ATP that undergoes hydrolysis to make ATP via the reaction: $PCr + ADP \rightarrow ATP + Cr$ mediated by Creatine kinase.

Glycolysis

An anaerobic process occurring in the cytoplasm where glucose is broken down into 2 pyruvate or 2 lactate, producing a net of 2 ATP and 2 $(NADH + H^+)$ molecules.

Lactate

The conjugate base of lactic acid produced during glycolysis.

Anaerobic pathways

Energy systems (ATP-PCr and Anaerobic glycolysis) that do not use oxygen, occur in the cytosol, and produce relatively quick but lesser amounts of energy.

Krebs Cycle

A series of aerobic reactions in the mitochondrial matrix involving the oxidation of the carbon skeleton of fuel to $CO_2$ and the formation of $(NADH + H^+)$, $FADH_2$, and some ATP.

Nicotinamide adenine dinucleotide (NAD)

A reducing equivalent that exists in an oxidized form ($NAD^+$) and a reduced form ($NADH$), playing an important role in electron transfer.

Flavin adenine dinucleotide (FAD)

A reducing equivalent that exists in an oxidized form ($FAD$) and a reduced form ($FADH_2$), playing an important role in electron transfer.

Electron transport system (respiratory chain)

Reactions in the inner mitochondrial membrane where electrons from $(NADH + H^+)$ and $FADH_2$ are transported to $O_2$ to form $H_2O$.

Oxidative phosphorylation

Aerobic reactions in the inner mitochondrial membrane where ATP synthesis is coupled to electron transport, mediated via $H^+$ through ATP synthase (chemiosmotic hypothesis).

Oxidative phosphorylation yield

The specific ATP yield where 1 $(NADH + H^+)$ yields 3 ATP and 1 $FADH_2$ yields 2 ATP.

Glucose ATP Yield

The total ATP production from the complete oxidation of one glucose molecule: $C_6H_{12}O_6 \rightarrow 6 CO_2 + 6 O_2 + 36-38 \text{ ATP}$.