Bio Exam 1 Cram

Levels of life's organizational hierarchy

Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere.

Characteristics that distinguish living things from nonliving things

Living things are made of cells, maintain homeostasis, require energy (metabolism), respond to stimuli, grow and develop, reproduce, and evolve.

Components of scientific inquiry

Observation → Question → Hypothesis → Prediction → Experiment → Data collection → Analysis → Conclusion.

Difference between a hypothesis and a theory

A hypothesis is a testable explanation or prediction. A theory is a well-supported explanation backed by extensive experimental evidence.

Chemical elements organisms require in large amounts

Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), and Sulfur (S) (CHNOPS).

Location of protons, neutrons, and electrons in an atom

Protons and neutrons are located in the nucleus; electrons occupy orbitals (electron cloud) surrounding the nucleus.

Relationship between mass number and atomic mass

Mass number equals the number of protons plus neutrons in one atom. Atomic mass is the weighted average mass of all naturally occurring isotopes of an element.

How valence electrons determine bonding

Atoms with incomplete valence shells gain, lose, or share electrons to achieve a stable outer shell, determining the number and type of bonds they form.

Importance of cohesion to life

Cohesion allows water molecules to stick together, creating surface tension and enabling water transport through plants by capillary action.

Difference between hydrophilic and hydrophobic molecules

Hydrophilic molecules are polar or charged and interact with water. Hydrophobic molecules are nonpolar and repel water.

How the different densities of ice and water affect life

Ice is less dense than liquid water, so it floats and insulates bodies of water, allowing aquatic life to survive beneath frozen surfaces.

How isotopes of the same element differ

Isotopes have the same number of protons but different numbers of neutrons, giving them different mass numbers.

Relationship among atoms, molecules, and compounds

Atoms are the smallest units of elements. Molecules consist of two or more bonded atoms. Compounds are molecules containing atoms of different elements.

Relationship between polar covalent bonds and hydrogen bonds

Polar covalent bonds create partial positive and negative charges, allowing hydrogen bonds to form between neighboring molecules.

How acids and bases affect H⁺ concentration

Acids increase the concentration of H⁺ ions in solution, while bases decrease H⁺ by accepting hydrogen ions or releasing OH⁻ ions.

Example of hydrogen bonding

A hydrogen atom covalently bonded to oxygen in one water molecule forms a hydrogen bond with the oxygen atom of another water molecule (H₂O···H₂O).

General structure of an amino acid

An amino acid contains a central (alpha) carbon bonded to an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom, and a variable R group (side chain).

How does water participate in the chemistry of life?

Water acts as a solvent, participates in hydrolysis and dehydration synthesis reactions, stabilizes temperature due to its high specific heat, and transports substances throughout organisms.

Relationship between hydrolysis and dehydration synthesis

Dehydration synthesis removes water to join monomers into polymers, while hydrolysis adds water to break polymers into monomers.

Main components of cell theory

1. All living things are composed of one or more cells. 2. The cell is the basic unit of life. 3. All cells arise from preexisting cells.

Significance of a protein's shape and how it can be destroyed

A protein's shape determines its function. Heat, extreme pH, high salt concentration, or certain chemicals can denature the protein and destroy its function.

Adaptations that increase the surface area-to-volume ratio in cells

Cells remain small, flatten their shape, or develop folds and projections such as microvilli to maximize exchange with the environment.

Difference between prokaryotic and eukaryotic cells

Prokaryotic cells lack a nucleus and membrane-bound organelles; eukaryotic cells possess both a nucleus and membrane-bound organelles.

How organelles contribute to efficiency in eukaryotic cells

Organelles compartmentalize cellular processes so multiple functions can occur simultaneously without interfering with one another.

How phospholipids form a bilayer in water

Their hydrophilic phosphate heads face water while their hydrophobic fatty acid tails face inward, causing a stable bilayer to form spontaneously.

Functions of the cytoskeleton

Provides structural support, maintains cell shape, positions organelles, enables intracellular transport, powers cell movement, and assists in cell division.

Functions of membrane proteins

Transport substances, receive signals (receptors), perform enzymatic reactions, recognize cells, attach to the cytoskeleton, and mediate cell adhesion.

How are cilia and flagella similar and different?

Both are microtubule-based structures used for movement. Cilia are short and numerous, moving fluid across cell surfaces, while flagella are long and few, propelling the entire cell.

Three types of junctions linking animal cells

Tight junctions prevent leakage; desmosomes provide strong mechanical attachment; gap junctions allow direct communication between adjacent cells.

What are plasmodesmata?

Microscopic channels through plant cell walls that connect neighboring cells, allowing transport of water, nutrients, and signaling molecules.

Examples of potential and kinetic energy in your body

Potential energy: chemical energy stored in glucose, glycogen, fats, and ATP. Kinetic energy: muscle contraction, blood flow, nerve impulses, and movement.

Why does entropy in the universe always increase?

Every energy transfer increases disorder because some usable energy is converted into heat, consistent with the Second Law of Thermodynamics.

What are oxidation and reduction, and why are they linked?

Oxidation is the loss of electrons, while reduction is the gain of electrons. They always occur together because electrons lost by one substance are gained by another.

What do enzymes do in cells?

Enzymes are biological catalysts that lower activation energy, speeding up chemical reactions without being consumed.

How does an enzyme lower a reaction's activation energy?

Enzymes bind substrates at their active site, properly orient reactants, strain chemical bonds, and stabilize the transition state, reducing the energy needed for the reaction.

What is the role of negative feedback in enzyme production?

Negative feedback prevents overproduction by reducing enzyme synthesis or activity when sufficient product has accumulated, helping maintain homeostasis.

Why does it cost energy to maintain a concentration gradient?

Moving substances against their concentration gradient requires active transport, which uses ATP to pump molecules from low concentration to high concentration.

How do exocytosis and endocytosis use vesicles to transport materials across cell membranes?

Exocytosis exports materials by fusing vesicles with the plasma membrane, while endocytosis imports materials by forming vesicles from the plasma membrane.

How do differing concentrations of solutes in neighboring solutions drive osmosis?

Water moves across a selectively permeable membrane from the solution with lower solute concentration (higher water concentration) to the solution with higher solute concentration until equilibrium is reached.

Give examples of potential and kinetic energy in your body.

Potential energy: ATP, glycogen, fat, and glucose. Kinetic energy: muscle contraction, blood circulation, nerve impulses, and body movement.

Distinguish between simple diffusion, facilitated diffusion, and active transport.

Simple diffusion moves molecules directly through the membrane down their concentration gradient. Facilitated diffusion uses channel or carrier proteins to move substances down their gradient without ATP. Active transport uses ATP to move substances against their concentration gradient.

What is photosynthesis?

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored as glucose using carbon dioxide and water while releasing oxygen.

Describe the relationship among the chloroplast, stroma, grana, and thylakoids.

The chloroplast contains the stroma, a fluid-filled space. Suspended in the stroma are stacks of thylakoids called grana. Light-dependent reactions occur in the thylakoid membranes, while the Calvin cycle occurs in the stroma.

What happens in each of the two main stages of photosynthesis?

The light-dependent reactions capture sunlight to produce ATP, NADPH, and oxygen. The Calvin cycle uses ATP and NADPH to fix carbon dioxide into sugars.

Describe the events that occur after light strikes photosystem II, ending with the production of ATP.

Light excites electrons in Photosystem II. Water is split to replace the electrons, releasing oxygen. The energized electrons travel through the electron transport chain, pumping hydrogen ions into the thylakoid space. The proton gradient powers ATP synthase to produce ATP.

How do electrons pass from photosystem II to photosystem I?

Electrons travel through an electron transport chain consisting of carrier proteins, releasing energy that pumps hydrogen ions into the thylakoid lumen before reaching Photosystem I.

What are the roles of CO₂, ATP, and NADPH in the Calvin cycle?

CO₂ provides the carbon atoms used to build sugars. ATP supplies energy, and NADPH provides high-energy electrons for reducing carbon compounds into G3P.

Why is the Calvin cycle also called the C3 pathway?

The first stable product formed after carbon fixation is 3-phosphoglycerate (3-PGA), a three-carbon molecule.

Describe how a C4 plant minimizes photorespiration.

C4 plants first fix CO₂ into a four-carbon compound in mesophyll cells, then transport it to bundle sheath cells where CO₂ is concentrated around Rubisco, reducing photorespiration.

How is the CAM pathway like C4 metabolism, and how is it different?

Both minimize photorespiration by concentrating CO₂ around Rubisco. C4 plants separate carbon fixation by location (different cell types), whereas CAM plants separate it by time, fixing CO₂ at night and using it during the day.

Why do all organisms need ATP?

ATP is the cell's universal energy currency. It provides immediate energy for cellular work, including active transport, muscle contraction, biosynthesis, cell signaling, movement, and metabolism.