bio exam #2

Matter

Everything and all stuff. Anything that has mass and takes up space. Made of atoms, and atoms have mass.

Energy

The ability to bring about change or to do work. Exists in many forms: heat, light, chemical, electrical, kinetic, and potential.

Chemical Energy

A form of potential energy defined as the energy stored in the bonds between atoms in a molecule.

First Law of Thermodynamics

The total amount of energy in the universe is constant and conserved; energy cannot be created or destroyed.

Second Law of Thermodynamics

Energy can be transformed or transferred, and energy is lost to the surroundings (often in the form of heat energy) in the process. Sustaining energy in a system requires energy inputs.

Law of Conservation of Mass

Matter cannot be created or destroyed, but it can be transformed from one state to another (solid, liquid, gas). Atoms cannot be created or destroyed, but can be rearranged.

Energy & Mass Relationship

Energy is not made of anything, so it does NOT have mass. Energy does not transform into matter, and matter does not transform into energy.

Absolute Zero

An idea, not a real thing you can achieve. The state where molecules are completely stopped, with no molecular motion whatsoever. Scientists have gotten within 1,000th of a degree Celsius, but cannot quite get there.

Sources of Matter for Organisms

Living organisms get atoms from food, soil, water, and air.

Sources of Energy for Organisms

Light energy from the sun (not all organisms can use this) and chemical energy from food (all organisms use this).

Solid

Molecules are moving slowly but packed close together. Atoms are moving relatively slowly (e.g., solid steel vs. liquid steel).

Liquid

Molecules are moving a little faster. Atoms are moving relatively faster (e.g., liquid steel vs. solid steel).

Gas

Molecules are moving very fast; they are wild.

Phase Change Requirement

Pure energy is always required to change a solid to a liquid to a gas. Takes energy to change phase.

Cooling/Freezing

To turn a liquid into a solid, energy (heat) must be taken away. When molecules slow down, they get closer and closer together.

Biological Molecules

Large molecules necessary for life, built from smaller organic molecules. 'Organic' means they contain carbon-hydrogen and/or carbon-carbon bonds.

Food (Biological Definition)

Carbohydrates like glucose and starch. Used by organisms for energy and matter/mass to build physical parts.

Photosynthesis (BIG IDEA)

Energy and matter are transformed, making the original food (glucose) for all living organisms.

Photosynthesis Equation

$\mathbf{6CO_2} + \mathbf{6H_2O} + \text{light energy} \rightarrow \mathbf{C_6H_{12}O_6} \text{ (glucose)} + \mathbf{6O_2}$.

Role of Chlorophyll

A pigment found in chloroplasts.

Light Dependent Reactions (LDR)

Energy is transformed: light energy → chemical energy stored in ATP and NADPH. Water is split into hydrogen, electrons, and oxygen. Oxygen gas (O₂) is released as a waste product; it comes from the splitting of water molecules. Carbon dioxide and glucose are NOT involved.

Light Independent Reactions (Calvin Cycle)

Energy and matter are transformed: Chemical energy in ATP and NADPH → chemical energy stored in sugars (food). Carbon atoms are 'fixed' (put together) from CO₂ to form sugar molecules. Each sugar molecule stores energy that originated from the LDR. Glucose is made.

Ultimate Product of Photosynthesis

G3P (Glyceraldehyde 3-Phosphate), which plants convert into carbohydrates like glucose (short term energy storage), cellulose (structure), and starch (long-term storage).

Biomass Source

The majority of plant dry biomass comes from the carbon (49%) and oxygen (47%) atoms found in cellulose, which originates from atmospheric CO₂ and H₂O used in photosynthesis.

Cellular Respiration (BIG IDEA)

The process of transferring the chemical energy stored in the bonds of food (glucose) into a different, usable type of chemical energy stored in the bonds of ATP.

Respiration Equation

C₆H₁₂O₆ + O₂ → CO₂ + H₂O + ATP.

ATP

Adenosine triphosphate. The energy currency needed by cells. The main energy source for cellular functions, very efficient at storing and releasing energy.

Glycolysis (Step 1)

Glucose (6-C) splits in half to form two pyruvate (3-C) molecules. Produces a little ATP and forms NADH.

Transition Reaction (Step 2)

Pyruvate is converted to Acetyl Co-A (2-C). One carbon atom is lost as carbon dioxide (exhaled). NADH is formed.

Citric Acid Cycle (Krebs Cycle, Step 3)

Energy from Acetyl Co-A is transferred to energy carrier molecules (NADH and FADH₂) and some ATP. All remaining carbon is lost as carbon dioxide (exhaled).

Electron Transport Chain & ATP Synthase (Step 4)

Energy carrier molecules (NADH/FADH₂) provide energy to create a proton gradient (potential energy) across the mitochondrial membrane. The flow of this gradient drives ATP synthase, producing LOTS of ATP (32-34 ATP in this step, 30-38 net ATP total per glucose).

Role of Inhaled Oxygen (O₂)

Oxygen gas is essential in the final step (ETC). It acts as the final electron acceptor, combining with two hydrogens to form water (H₂O), which is then exhaled.

Source of Exhaled Carbon Dioxide (CO₂)

The carbon atoms that make up the exhaled CO₂ come from the original glucose molecule, and are released during the Transition Reaction and the Citric Acid Cycle.

Fundamental Principles of Energy and Matter

These universal rules of physics dictate every chemical reaction that captures energy, builds structures, and sustains life, leading to the startling conclusion that the vast majority of the energy used on Earth ultimately comes from sunlight.

Relationship Between Energy and Matter in Biology

A critical distinction in biology is that energy does not transform into matter, and matter does not transform into energy. Rather, energy is a property that is stored within the chemical bonds between the atoms of matter.

Three Phases of Matter

Solid: Molecules are packed closely together and move slowly. Liquid: Molecules are still close but are moving faster and are able to flow past one another. Gas: Molecules are moving very fast and are far apart.

Determining Factor of Phase

Energy is the determining factor. Adding energy increases molecular motion, driving transitions from solid → liquid → gas. Removing energy slows molecular motion, causing transitions from gas → liquid → solid.

Example of Phase Changes: Water

Adding energy causes solid ice to melt into liquid water. Adding more energy causes liquid water to boil and become invisible water vapor (a gas).

Composition of Air

Earth's atmosphere is 78% nitrogen gas. This is the same invisible gas that surrounds us constantly and, in its liquid form at -196°C, is cold enough to make things boil using only the energy in the room.

Photosynthesis

Photosynthesis stands as the most critical biological process on Earth, the foundational mechanism that captures energy from the sun—the ultimate source of power for nearly all life. It takes inorganic carbon from the atmosphere and converts it into the organic matter that fuels entire ecosystems.

Purpose of photosynthesis

To convert light energy into chemical energy and store it in the bonds of a sugar molecule (glucose).

Balanced chemical equation for photosynthesis

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Light-Dependent Reactions

Take place in the thylakoids.

Calvin Cycle (Light-Independent Reactions)

Takes place in the stroma (the fluid-filled space outside the thylakoids).

Inputs of the Light-Dependent Reactions

Light Energy, Water (H₂O).

Outputs of the Light-Dependent Reactions

ATP and NADPH (chemical energy carriers), and Oxygen (O₂) as a waste product.

Core Function of the Light-Dependent Reactions

Transforms light energy into usable chemical energy.

Inputs of the Calvin Cycle

Carbon Dioxide (CO₂), ATP, and NADPH.

Outputs of the Calvin Cycle

Glucose (C₆H₁₂O₆) or its precursors.

Core Function of the Calvin Cycle

Uses the chemical energy from the light reactions to fix atmospheric carbon into organic sugar molecules.

Origin of oxygen gas released during photosynthesis

The oxygen gas (O₂) is a byproduct that comes from the splitting of water (H₂O) molecules during the light-dependent reactions.

Source of a plant's dry mass (biomass)

A plant's dry mass is primarily built from the carbon atoms acquired from carbon dioxide (CO₂) in the atmosphere.

Purpose of cellular respiration

To break down glucose to release its stored chemical energy and transfer that energy to molecules of ATP.

Balanced chemical equation for cellular respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (energy)

Glycolysis

Occurs in the cytoplasm.

Transition Reaction (Pyruvate Oxidation)

Occurs in the mitochondrial matrix.

Krebs Cycle (Citric Acid Cycle)

Also occurs in the mitochondrial matrix.

Electron Transport Chain & Chemiosmosis

Occurs on the inner mitochondrial membrane.

ATP production in Glycolysis and Krebs Cycle

Each produces only a small amount of ATP directly (a net of 2 ATP each).

ATP production in Electron Transport Chain

Produces the vast majority of ATP—an estimated 26-34 molecules per single molecule of glucose.

Origin of carbon dioxide (CO₂) exhaled by animals

The carbon atoms in the exhaled CO₂ originate from the breakdown of the glucose molecule (C₆H₁₂O₆) during the Transition Reaction and the Krebs Cycle.

Role of oxygen (O₂) inhaled by animals

Oxygen serves as the final electron acceptor at the end of the Electron Transport Chain.

Byproduct of oxygen combining with hydrogen ions

Forms water (H₂O) as a byproduct.

Do plants perform cellular respiration?

Yes. Plants perform photosynthesis to create their own glucose and then use cellular respiration to break down that glucose and produce the ATP needed to power their own growth, transport, and metabolic functions.