Science 8 Bioenergetics & Genetics Master Reviewer

5000 Practice Flashcards covering all units from Biogeochemical cycles to Genetics disorders based on the lecture transcript.

What do biogeochemical cycles represent?

The continuous, cyclical movement and transformation of chemical elements between living organisms and the physical environment.

What is the 'biotic phase' of a biogeochemical cycle?

The phase involving living organisms.

What is the 'abiotic phase' of a biogeochemical cycle?

The physical environment phase, including the atmosphere, lithosphere, and hydrosphere.

Which spheres are included in the abiotic phase?

The atmosphere, lithosphere, and hydrosphere.

Define the Hydrologic (Water) Cycle.

The continuous circulation of water throughout Earth's ecosystems, driven by solar radiation and gravitational forces.

What forces drive the Hydrologic Cycle?

Solar radiation and gravitational forces.

What is Evaporation?

The process where solar energy heats surface water, transforming liquid water into water vapor.

What is Transpiration?

The process where plants release excess absorbed water vapor into the atmosphere via microscopic leaf pores.

What are stomata?

Microscopic leaf pores through which plants release water vapor during transpiration.

Define Condensation in the water cycle.

The process where warm water vapor rises, cools, and transitions back into liquid water droplets or ice crystals, forming clouds.

How do clouds form?

Microscopic water droplets or ice crystals coalesce around dust particles.

What is Precipitation?

The process where condensed atmospheric droplets become too heavy for updrafts and are pulled to Earth by gravity.

What force pulls precipitation to the Earth's surface?

Gravity.

List four forms of precipitation mentioned in the text.

Rain, snow, sleet, or hail.

What is Runoff?

Precipitated water that moves across the surface of the land into bodies of water.

What is Infiltration?

The process where water sinks downward through soil and rock layers to replenish groundwater reserves.

What is Collection in the hydrologic cycle?

The accumulation of water in oceans, lakes, and rivers.

What is the Carbon Cycle?

The framework tracking how carbon moves between organic molecules in living systems and inorganic reserves in the air, sea, and crust.

How do autotrophic organisms like plants and algae use carbon dioxide ($CO_2$)?

They absorb it from the atmosphere and fix it into organic energy molecules like glucose ($C_6H_{12}O_6$) during photosynthesis.

What is the chemical formula for glucose?

$$C_6H_{12}O_6$$

What molecule is used for photosynthesis and absorbed from the atmosphere?

Carbon dioxide ($CO_2$).

What is Respiration in the carbon cycle?

The process where living organisms break down carbon compounds for energy, releasing $CO_2$ back into the atmosphere as a metabolic byproduct.

How is $CO_2$ released back into the atmosphere by organisms?

Through respiration as a metabolic byproduct.

What is Decay in the carbon cycle?

The process where decomposers (bacteria and fungi) break down organic remnants of dead organisms, releasing buried carbon.

Which organisms are primary decomposers in the carbon cycle?

Bacteria and fungi.

What is an 'Ocean Sink'?

Marine bodies that absorb immense volumes of atmospheric $CO_2$.

What do marine organisms manufacture from dissolved carbon?

Calcium carbonate ($CaCO_3$).

What is the chemical formula for calcium carbonate?

$$CaCO_3$$

Why do marine organisms need $CaCO_3$?

To manufacture protective shells and skeletal structures.

How are fossil fuels formed?

Dead organic matter compressed beneath massive structural layers undergoes intense heat and pressure over millions of years.

List three examples of carbon-dense fossil fuels.

Coal, oil, and gas.

What is a major sedimentary carbon deposit besides fossil fuels?

Limestone deposits.

What does the Oxygen Cycle track?

The distribution of oxygen throughout the atmosphere, biosphere, and lithosphere.

How is pure diatomic oxygen gas ($O_2$) produced biologically?

Phototrophic organisms split water molecules during light-driven reactions.

What is the primary byproduct of photosynthesis in the oxygen cycle?

Diatomic oxygen gas ($O_2$).

What is the role of $O_2$ in biological consumption?

It serves as the final electron acceptor during cellular respiration.

What is produced when aerobic organisms combine $O_2$ with hydrogen ions?

Water ($H_2O$).

Where is the largest reservoir of Earth's oxygen located?

The Lithosphere Vault.

How is oxygen stored in the lithosphere?

Permanently bound within silicate and oxide minerals in the earth's crust and mantle layers.

What is Photolysis in the oxygen cycle?

A non-biological source of oxygen where high-energy solar UV radiation splits atmospheric water vapor molecules.

What energy source drives photolysis?

Solar ultraviolet (UV) radiation.

What atoms are produced by photolysis of water vapor?

Free oxygen and hydrogen atoms.

What is the Sulfur Cycle?

The process regulating sulfur movement through rocks, waterways, and living tissue.

Why is sulfur essential for life?

It is needed for manufacturing vital structural proteins.

How does natural sulfur enter the atmosphere via geological emissions?

Volcanic eruptions, hydrothermal vents, and the weathering of sulfur-bearing rocks.

In what gaseous forms does sulfur enter the atmosphere naturally?

Sulfur dioxide ($SO_2$) or hydrogen sulfide ($H_2S$).

What is DMS?

Dimethyl Sulfide gas released by marine phytoplankton.

What happens when DMS oxidizes in the atmosphere?

It forms aerosols that act as seed particles for cloud condensation.

How do plants assimilate sulfur?

By absorbing dissolved inorganic sulfate ions ($SO_4^{2-}$) through their roots.

What is the formula for the inorganic sulfate ion?

$$SO_4^{2-}$$

Name two sulfur-containing amino acids mentioned in the text.

Cysteine and methionine.

What human activities disrupt the sulfur cycle?

Burning coal and refining petroleum.

How is acid rain formed anthropogenically?

Excessive $SO_2$ from industrial activities reacts with water vapor.

What is the chemical formula for the acid rain mentioned in the notes?

$$H_2SO_4$$

What is the primary characteristic of the Phosphorus Cycle's phases?

It is an entirely sedimentary cycle lacking a gas or atmospheric phase.

How are inorganic phosphate ions ($PO_4^{3-}$) released from rocks?

Through weathering by rain, wind, and environmental fluctuations.

What is the formula for a phosphate ion?

$$PO_4^{3-}$$

What foundational molecules are built using phosphorus?

Nucleic acids (DNA/RNA) and cellular energy units (ATP).

How do heterotrophic animals acquire phosphorus?

By eating plants.

How is phosphorus returned to the soil from living organisms?

Decomposers break down organic matter from excreted waste or dead organisms.

Where is phosphorus geologically stored over eras?

In new sedimentary phosphate rock layers on ocean floors.

What mechanism moves sedimentary phosphate rock from ocean floors to land?

Tectonic uplift.

Why is atmospheric nitrogen ($N_2$) bio-unavailable to most plants?

It contains a highly stable triple covalent bond that plants cannot break.

What is Nitrogen Fixation?

The conversion of inert diatomic nitrogen ($N_2$) into bio-available ammonia ($NH_3$) or ammonium ($NH_4^+$).

Name a bacterium found in legume root nodules that fixes nitrogen.

Rhizobium.

Name a free-living bacterium that performs nitrogen fixation.

Azotobacter.

What are the first products of nitrogen fixation?

Ammonia ($NH_3$) or ammonium ($NH_4^+$).

Define Nitrification.

A two-step oxidation process performed by soil-dwelling bacteria converting ammonia/ammonium into nitrates.

What does Nitrosomonas bacteria do in the nitrogen cycle?

Converts toxic ammonia into nitrite ions ($NO_2^-$).

What does Nitrobacter bacteria do in the nitrogen cycle?

Oxidizes nitrite ions into stable nitrate ions ($NO_3^-$).

What is the formula for Nitrite?

$$NO_2^-$$

What is the formula for Nitrate?

$$NO_3^-$$

How do animals acquire organic nitrogen?

By consuming plants that have assimilated soil nitrates.

Define Denitrification.

The process where anaerobic bacteria convert soil nitrates back into gaseous nitrogen ($N_2$).

Where do denitrifying bacteria typically live?

In waterlogged or oxygen-depleted soils.

What type of process is Photosynthesis?

An anabolic process capturing radiant solar energy and converting it into chemical potential energy.

What is the complete chemical equation for Photosynthesis?

$$6CO_2 + 6H_2O + \text{Sunlight} \longrightarrow C_6H_{12}O_6 + 6O_2$$

In which organelle does photosynthesis occur?

The Chloroplast.

Where precisely in the chloroplast do Light-Dependent Reactions occur?

The Thylakoid Membrane.

Where precisely in the chloroplast does the Calvin Cycle (Light-Independent Reactions) occur?

The Stroma.

What is the primary function of the Light-Dependent Reactions?

The Energy-Harvesting Phase.

What are the inputs for Light-Dependent Reactions?

$$\text{Sunlight} + H_2O + \text{ADP} + P_i + \text{NADP}^+$$

What are the outputs of Light-Dependent Reactions?

$$O_2 + \text{ATP} + \text{NADPH}$$

Which specific wavelengths of light does chlorophyll absorb?

Specific wavelengths of blue and red light.

What is Photolysis in photosynthesis?

The enzymatic splitting of water molecules ($H_2O$) inside the thylakoid space.

What does photolysis produce as a byproduct?

Diatomic oxygen gas ($O_2$).

What generates the proton gradient during the light reactions?

The Electron Transport Chain (ETC) pumping hydrogen ions across the membrane.

Which enzyme uses the proton gradient to generate ATP?

ATP Synthase.

What is the final stage of the ETC in light reactions?

Electrons are captured by $NADP^+$ to form NADPH.

What is the function of the Calvin Cycle?

The Sugar-Building Phase.

What carbohydrate is directly fixed in the Calvin Cycle?

Carbon dioxide ($CO_2$).

To what 5-carbon sugar is atmospheric $CO_2$ attached during fixation?

Ribulose 1,5-bisphosphate (RuBP).

What enzyme drives the initial step of carbon fixation in the Calvin Cycle?

RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase).

What is G3P?

Glyceraldehyde 3-phosphate, a high-energy 3-carbon sugar.

How many molecules of G3P are needed to form one Glucose molecule?

Two molecules of G3P (resulting from six turns of the cycle).

What are the inputs for the Calvin Cycle?

$$CO_2 + \text{ATP} + \text{NADPH}$$

What are the outputs of the Calvin Cycle besides Glucose?

$$\text{ADP} + \text{NADP}^+$$

Define Cellular Respiration.

A multi-step metabolic pathway where cells break glucose bonds to convert harvested energy into ATP.

What is the complete chemical equation for Cellular Respiration?

$$C_6H_{12}O_6 + 6O_2 \longrightarrow 6CO_2 + 6H_2O + \approx 32\text{-}36\text{ ATP}$$

Where in the cell does Glycolysis occur?

The fluid Cytoplasm.