energy, catalysis, and biosynthesis in cell metabolism

What do catabolic pathways do?

They break down food molecules, releasing energy, mostly as heat.

What is the role of anabolic pathways?

They build complex molecules needed for cell structure and function.

How do cells utilize energy?

Cells convert energy from one form to another, powering metabolic processes.

What is the significance of photosynthesis?

Photosynthetic organisms use sunlight to synthesize organic molecules, providing energy for life.

What occurs during the light capture stage of photosynthesis?

Light energy splits water, releasing oxygen and producing ATP and NADPH.

What happens during the sugar manufacture stage of photosynthesis?

Using ATP, NADPH, water, and carbon dioxide, plants synthesize sugars for energy storage.

How does cellular respiration relate to photosynthesis?

Cellular respiration uses oxygen to break down sugars, releasing energy and returning CO₂ and H₂O to the environment.

What is oxidation in terms of electron transfer?

Oxidation occurs when an atom loses electron density, becoming more positive.

What is reduction in terms of electron transfer?

Reduction occurs when an atom gains electron density, becoming more negative.

How do enzymes affect activation energy?

Enzymes lower the activation energy needed to initiate spontaneous reactions.

What is the difference between uncatalyzed and catalyzed reactions?

Uncatalyzed reactions require a large energy input, while catalyzed reactions proceed faster with lower activation energy.

What is the ATP cycle?

ATP is synthesized from ADP and phosphate, and hydrolysis of ATP releases energy for cellular processes.

What is the directionality of DNA and RNA chains?

DNA and RNA chains have a 5′ end with a phosphate group and a 3′ end with a hydroxyl group.

What is the composition of a bacterial cell?

A bacterial cell is about 70% water and 30% chemicals, including proteins, RNA, polysaccharides, phospholipids, and DNA.

What are macromolecules made of?

Macromolecules like polysaccharides, proteins, and nucleic acids are polymers built from small monomeric subunits linked by covalent bonds.

How do proteins and RNAs maintain their structure?

They fold into stable 3D shapes maintained by weak noncovalent bonds.

What role do noncovalent bonds play in macromolecular interactions?

Noncovalent bonds allow macromolecules to interact, with good shape matches forming strong bonds.

What is the relationship between disorder and energy in biological systems?

The natural tendency toward disorder can be reversed only by energy input, which increases overall universal disorder through heat release.

What is the free-energy change (ΔG) for a reaction?

A negative ΔG indicates an energetically favorable reaction that can occur spontaneously.

How can an energetically unfavorable reaction proceed?

It can proceed if coupled to a favorable reaction, resulting in a negative overall free-energy change.

What is the primary purpose of photosynthesis?

To capture solar energy to make sugars and oxygen (O₂).

What is the primary function of respiration?

To use sugars and oxygen to release energy and return carbon dioxide (CO₂) to the atmosphere.

Which process evolved first, photosynthesis or respiration?

Photosynthesis evolved before respiration.

Define oxidation in the context of electron density.

Oxidation is the loss of electron density, making a molecule less electronegative.

Define reduction in the context of electron density.

Reduction is the gain of electron density, making a molecule more electronegative.

What role do enzymes play in chemical reactions?

Enzymes lower the activation energy required to start reactions, making them proceed faster.

How can lowering the activation-energy barrier be analogized?

It is like lowering a dam so that substrates can flow over more easily, enabling reactions.

What is the significance of enzymes at pathway branch points?

They control which reactions occur, guiding molecules through specific metabolic routes.

Describe the enzyme catalytic cycle.

Enzymes bind substrates, convert them to products, and release the products unchanged, ready to catalyze new reactions.

What does a negative ΔG indicate about a reaction?

It indicates that the reaction occurs spontaneously and increases disorder.

What is reaction coupling?

It is when an unfavorable reaction can proceed if linked to a strongly favorable reaction, resulting in a net negative ΔG.

What occurs at chemical equilibrium?

Reactions proceed until forward and reverse rates balance, resulting in constant concentrations of reactants and products.

What does it mean if there are twice as many X molecules as Y at equilibrium?

It means the X → Y reaction is not strongly favorable, as a significant amount of X remains.

What does it indicate if there are 25 times more Z molecules than Y at equilibrium?

It indicates that the Y → Z reaction is highly favorable, producing much more Z than Y.

How does the Y → Z reaction affect the X → Y reaction when coupled?

The highly favorable Y → Z reaction 'pulls' the X → Y reaction forward, driving the conversion of X to Z.

What is the role of ATP in cellular reactions?

ATP transfers stored energy to power cellular reactions, and its hydrolysis releases inorganic phosphate.

How can ATP hydrolysis drive an energetically unfavorable reaction?

The energy released from ATP hydrolysis is greater than the energy needed for the synthesis of the product.

What is NADPH and its role in redox reactions?

NADPH is an electron carrier produced when NADP⁺ gains electrons, which can then be transferred to reduce another molecule.

What are activated carriers?

Activated carriers are molecules that temporarily store and transfer energy or chemical groups in cells.

What does ATP carry?

ATP carries phosphate groups.

What do NADH, NADPH, and FADH₂ carry?

They carry electrons and hydrogens for redox reactions.

What does Acetyl CoA carry?

Acetyl CoA carries acetyl groups for biosynthetic reactions.

What does carboxylated biotin carry?

Carboxylated biotin carries carboxyl groups for carboxylation reactions.

What does S-adenosylmethionine carry?

S-adenosylmethionine carries methyl groups for methylation reactions.

What does uridine diphosphate glucose carry?

Uridine diphosphate glucose carries glucose for carbohydrate synthesis.