General Biology Exam #2 flashcards

Metabolism

The totality of an organism's chemical reactions, arising from interactions between molecules within the cell.

Metabolic pathways

A series of chemical reactions where each step is catalyzed by a specific enzyme. Begins with a specific molecule and ends with a product.

Catabolic pathways

Break down complex molecules to release energy (e.g., cellular respiration).

Anabolic pathways

Consume energy to build complex molecules (e.g., protein synthesis).

Energy

The capacity to do work.

Kinetic Energy

Energy of motion.

Potential Energy

Stored energy.

Heat energy measurement

1 calorie (cal): Energy needed to raise 1g of H₂O by 1°C. 1 kilocalorie (kcal) = 1000 cal.

Redox reactions

Oxidation: Loss of electrons. Reduction: Gain of electrons. Energy is transferred

First Law of Thermodynamics

Energy cannot be created or destroyed, only converted. Example: Photosynthesis converts sunlight into chemical energy.

Second Law of Thermodynamics

Disorder (entropy) in the universe is always increasing.

Gibbs free energy (G)

The energy available to do work. Formula: G = H - TS (H = enthalpy, S = entropy, T = temperature).

Endergonic reactions

Require energy input (ΔG positive).

Exergonic reactions

Release free energy (ΔG negative).

Activation energy

The extra energy needed to start a reaction.

Catalysts

Substances that lower activation energy without being consumed.

ATP

The energy currency of the cell.

Structure of ATP

Ribose (5-carbon sugar), Adenine (a nitrogenous base), Three phosphate groups.

Phosphates store energy

Phosphate groups are negatively charged and repel each other. Breaking the bond releases energy: ATP → ADP + Pi (inorganic phosphate) + Energy.

Enzymes

Biological catalysts that speed up reactions by lowering activation energy. Most are proteins, but some are RNA-based

How enzymes work

Bind to a substrate at an active site. This binding induces a better fit for catalysis.

Multienzyme complexes

Groups of enzymes working together to enhance efficiency.

Ribozymes

RNA molecules with catalytic properties

Factors affecting enzyme function

Temperature & pH: Each enzyme has an optimal range. Substrate concentration: Higher substrate levels can increase reaction rate.

Enzyme inhibitors

Competitive inhibitors: Bind to the active site, blocking the substrate. Noncompetitive inhibitors: Bind elsewhere, altering enzyme shape.

Allosteric enzymes

Exist in active or inactive states. inhibitors: Inactivate enzyme. activators: Activate enzyme.

Cofactors and coenzymes

Metal ions assisting enzyme activity. Organic molecules that help in redox reactions.

Feedback inhibition

A biochemical pathway where the end product inhibits an earlier enzyme to regulate activity.

Autotrophs

Organisms that produce their own organic molecules through photosynthesis.

Heterotrophs

Organisms that rely on organic compounds produced by other organisms for energy.

Cellular respiration

A process of breaking down organic molecules to release energy.

Oxidation

Loss of electrons.

Dehydrogenation

Electrons are lost with hydrogen atoms.

Redox reactions

Electrons carry energy from one molecule to another.

NAD+

An electron carrier that accepts 2 electrons & 1 proton to become NADH.

Aerobic respiration

Uses O₂ as the final electron acceptor.

Anaerobic respiration

Uses an inorganic molecule (not O₂) as the final electron acceptor.

Fermentation

Uses an organic molecule as the final electron acceptor.

General chemical equation for aerobic respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O; ΔG = -686 kcal/mol of glucose.

Stages of glucose oxidation

Glycolysis, Pyruvate oxidation, Krebs cycle, Electron transport chain & chemiosmosis.

Ways cells make ATP

Substrate-level phosphorylation and Oxidative phosphorylation.

Glycolysis location

In the cytoplasm.

Stages of glycolysis

Energy investment/priming, Cleavage reactions, Energy production.

Net products of glycolysis

2 pyruvate molecules, 2 ATP (net) via substrate-level phosphorylation, 2 NADH.

Fate of pyruvate after glycolysis

If oxygen is available, pyruvate is oxidized to Acetyl-CoA; if no oxygen, pyruvate is reduced to regenerate NAD+ in fermentation.

Pyruvate oxidation location

Mitochondria in eukaryotes; Plasma membrane in prokaryotes.

Enzyme complex for pyruvate oxidation

Pyruvate dehydrogenase.

Products of pyruvate oxidation

1 CO₂, 1 NADH, 1 Acetyl-CoA (2 carbons from pyruvate attached to coenzyme A).

Krebs cycle location

In the mitochondrial matrix.

First step of the Krebs cycle

Acetyl-CoA (2C) combines with oxaloacetate (4C) to form citrate (6C).

Key outputs per Acetyl-CoA molecule in Krebs cycle

2 CO₂ released, 3 NADH produced, 1 FADH₂ produced, 1 ATP generated, Oxaloacetate is regenerated.

Total products after glycolysis, pyruvate oxidation, and Krebs cycle

6 CO₂, 4 ATP, 10 NADH, 2 FADH₂.

ETC location

In the inner mitochondrial membrane.

What happens in the ETC

Electrons from NADH and FADH₂ are transferred through protein complexes; Energy from electrons pumps protons (H⁺) across the membrane, creating a proton gradient.

Chemiosmosis

Protons diffuse back into the matrix through ATP synthase, driving ATP production.

ATP synthase

A membrane-bound enzyme that synthesizes ATP from ADP + Pi using the proton gradient.

Theoretical yield of ATP

38 ATP per glucose in bacteria.

Theoretical yield of ATP

36 ATP per glucose in eukaryotes.

Actual ATP yield

~30 ATP per glucose due to the inner membrane being 'leaky' and proton gradient being used for other processes.

Respiration regulation

Feedback inhibition controls key steps.

Inhibitors of glycolysis

ATP and citrate inhibit an enzyme

Inhibitors of pyruvate oxidation

High NADH levels

Inhibitors of the Krebs cycle

High ATP levels inhibit citrate synthase.

Anaerobic respiration

Cells switch to anaerobic respiration or fermentation if no O₂ is available.

Examples of anaerobic respiration

Methanogens: Use CO₂, produce methane (CH₄).

Examples of anaerobic respiration

Sulfur bacteria: Use SO₄²⁻, produce hydrogen sulfide (H₂S).

Regeneration of NAD+ in fermentation

Ethanol fermentation (yeast): Produces ethanol, CO₂, and NAD⁺.

Regeneration of NAD+ in fermentation

Lactic acid fermentation (muscles): Converts pyruvate to lactic acid.

Stages of aerobic respiration

Glycolysis, Pyruvate oxidation, Krebs cycle, ETC & chemiosmosis.

Main goal of cellular respiration

To harvest energy from glucose and convert it into ATP.

bacteria division

Binary fission (asexual reproduction).

Key steps in binary fission

Replication begins at the origin of replication and proceeds bidirectionally. New chromosomes move to opposite ends of the cell. A septum forms, dividing the cell into two.

Essential protein for septum formation

FtsZ protein, which forms a ring at the midpoint of the cell.

Why must chromosomes be condensed?

They are very long and must fit within the nucleus.

What is chromatin?

Uncondensed form of DNA.

What is a nucleosome?

DNA wrapped around 8 histone proteins.

Proteins that condense chromatin further

Scaffold proteins and condensin complex.

Heterochromatin and euchromatin

Inactive DNA and Active DNA (expressed genes).

What has the ENCODE project shown?

~80% of the human genome is active.

What is ploidy?

Refers to the number of chromosome sets: Haploid (n): One set. Diploid (2n): Two sets.

What is a karyotype?

A chromosomal 'map' of an organism. Humans: 2n = 46 chromosomes.

What must happen before cell division?

Chromosomes must be replicated.

Holds replicated chromosomes together

Cohesion proteins.

What are sister chromatids?

Two identical copies of a replicated chromosome.

replicated and non-replicated chromosome

(pre-S phase): 'I'-shaped (single). (post-S phase): 'X'-shaped (doublet).

Five main phases of the eukaryotic cell cycle

G1 (Gap 1): Cell growth. S (Synthesis): DNA replication. G2 (Gap 2): Organelle replication, preparation for mitosis. M (Mitosis): Division of genetic material. C (Cytokinesis): Division of cytoplasm.

Longest phase of the eukaryotic cell cycle

G1 phase.

Prophase

Chromosomes condense, centrioles move to opposite poles, spindle apparatus forms, and nuclear envelope dissolves.

Prometaphase

Chromosomes attach to spindle via kinetochores and microtubules pull chromosomes toward the center.

Motor proteins

Proteins that drive chromosome movement along with tubulin polymerization/depolymerization.

Metaphase

Chromosomes align at the metaphase plate.

Metaphase plate

An imaginary plane in the center of the cell.

Anaphase

Cohesion proteins break down, separating sister chromatids; A: Kinetochores move toward poles; B: Poles move apart.

Telophase

Spindle disassembles, nuclear envelope reforms, chromosomes uncoil, and nucleolus reappears.

Cytokinesis in animal cells

Actin filaments constrict the membrane, forming a cleavage furrow.

Cytokinesis in plant cells

Cell plate forms between nuclei.

Cytokinesis in fungi & protists

Mitosis occurs inside the nucleus.

G1/S checkpoint

At what check point does the cell decide whether to divide.

G2/M checkpoint

Commits to mitosis.

Spindle checkpoint

Ensures chromosomes are attached to spindle.