🧬 AP BIO TRI 1 MIDTERM FLASHCARDS

Why is water a polar molecule?

Oxygen is more electronegative than hydrogen, creating partial negative and positive charges.

What type of bond holds the hydrogen and oxygen atoms together within a water molecule?

Polar covalent bonds.

What is a hydrogen bond?

A weak attraction between a partially positive hydrogen and an electronegative atom, usually oxygen or nitrogen.

What is cohesion?

Attraction between molecules of the same substance. In water, hydrogen bonds cause water molecules to stick together.

What is adhesion?

Attraction between different substances, such as water molecules sticking to the walls of a xylem vessel.

What causes water's high specific heat?

Hydrogen bonds absorb substantial energy before water molecules increase in temperature.

Why is high specific heat important to organisms?

It helps organisms and environments resist rapid temperature changes.

What is the relationship between cohesion and surface tension?

Cohesion creates surface tension at the air-water interface.

Why is ice less dense than liquid water?

Hydrogen bonds hold water molecules farther apart in the crystalline structure of ice.

Why is water an effective solvent?

Its polarity allows it to surround and separate ions and other polar molecules.

What are the four elements that make up most of living matter?

Carbon, hydrogen, oxygen, and nitrogen.

Why is carbon especially important to life?

Carbon can form four covalent bonds, allowing enormous molecular diversity.

What is a covalent bond?

A bond formed when atoms share electrons.

What is an ionic bond?

An attraction between oppositely charged ions after electrons are transferred.

What is electronegativity?

An atom's attraction for shared electrons.

What makes a bond polar?

Electrons are shared unequally between atoms with different electronegativities.

What is an isotope?

An atom of an element with the same number of protons but a different number of neutrons.

What is a functional group?

A specific group of atoms attached to a carbon skeleton that gives a molecule particular properties.

What are the four major biological macromolecules?

Carbohydrates, lipids, proteins, and nucleic acids.

What is a monomer?

A smaller molecular subunit that can be linked to form a polymer.

What is a polymer?

A large molecule made from repeating smaller subunits.

What reaction joins monomers together?

Dehydration synthesis, also called a condensation reaction.

What reaction breaks polymers apart?

Hydrolysis.

What are carbohydrates primarily used for?

Energy, energy storage, and structural support.

What is the monomer of carbohydrates?

Monosaccharides.

Give examples of monosaccharides.

Glucose, fructose, and galactose.

What are starch and glycogen?

Polysaccharides used for energy storage.

What is cellulose?

A structural polysaccharide found in plant cell walls.

What is chitin?

A structural polysaccharide found in arthropod exoskeletons and fungal cell walls.

What are lipids generally characterized by?

They are largely hydrophobic and do not mix well with water.

Are lipids true polymers?

No. They are large biological molecules but aren't constructed from repeating monomer units like proteins and nucleic acids.

What are the components of a triglyceride?

One glycerol and three fatty acids.

Saturated vs. unsaturated fats?

Saturated fats have no C=C double bonds; unsaturated fats have one or more.

What is the main structural component of cell membranes?

Phospholipids.

Why are phospholipids amphipathic?

They have a hydrophilic head and hydrophobic tails.

What are proteins made of?

Amino acids.

How many standard amino acids are commonly used to build proteins?

20.

What bond connects amino acids?

Peptide bonds.

What determines a protein's amino acid sequence?

Genetic information encoded in DNA.

What are the four levels of protein structure?

Primary, secondary, tertiary, and quaternary.

What is primary protein structure?

The amino acid sequence.

What is secondary protein structure?

Local folding into structures such as α-helices and β-pleated sheets.

What is tertiary structure?

The overall three-dimensional shape of a single polypeptide.

What is quaternary structure?

The arrangement of multiple polypeptide chains into one functional protein.

What can cause a protein to denature?

Changes in temperature, pH, salt concentration, or other environmental conditions.

Does denaturation necessarily break peptide bonds?

No. It often disrupts weaker interactions that maintain the protein's three-dimensional shape.

What determines a protein's function?

Its specific three-dimensional structure.

What are nucleic acids made of?

Nucleotides.

What are the three components of a nucleotide?

A phosphate group, a five-carbon sugar, and a nitrogenous base.

What are the two major nucleic acids?

DNA and RNA.

What sugar does DNA contain?

Deoxyribose.

What sugar does RNA contain?

Ribose.

What bases are found in DNA?

Adenine, thymine, cytosine, and guanine.

What bases are found in RNA?

Adenine, uracil, cytosine, and guanine.

What bond connects nucleotides in a nucleic acid strand?

Phosphodiester bonds.

Why can changes in temperature affect protein function?

Temperature can disrupt interactions maintaining a protein's shape.

Why can extreme pH affect proteins?

It can alter the charges of amino acid side chains and disrupt interactions maintaining protein structure.

What does denaturation mean?

A change in protein structure that causes loss or alteration of function.

Why is protein shape so important?

A protein's shape determines how it interacts with other molecules.

What are the three parts of cell theory?

All organisms are made of cells; cells are the basic unit of life; cells come from preexisting cells.

Prokaryote vs. eukaryote?

Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have them.

What organisms are prokaryotic?

Bacteria and archaea.

What organisms are eukaryotic?

Animals, plants, fungi, and protists.

What does the nucleus contain?

Most of the cell's DNA.

What is the nucleolus?

The region where ribosomal RNA is produced and ribosome subunits are assembled.

What do ribosomes do?

Make proteins.

What is the rough ER responsible for?

Producing and processing proteins destined for secretion, membranes, or certain organelles.

Why is the rough ER 'rough'?

Ribosomes are attached to its surface.

What does the smooth ER do?

Lipid synthesis, detoxification, and calcium ion storage.

What does the Golgi apparatus do?

Modifies, sorts, and packages proteins and lipids.

What do lysosomes do?

Digest macromolecules and damaged cell components.

What do mitochondria do?

Carry out cellular respiration and produce much of the cell's ATP.

What do chloroplasts do?

Carry out photosynthesis.

What is the central vacuole's role in plant cells?

Storage and maintenance of turgor pressure.

What is the cytoskeleton?

A network of protein fibers involved in cell shape, movement, and intracellular transport.

Why can't cells simply grow indefinitely?

As a cell gets larger, its volume increases faster than its surface area, making exchange with the environment less efficient.

What happens to surface-area-to-volume ratio as a cell gets larger?

It decreases.

Why is a high surface-area-to-volume ratio advantageous?

It allows more efficient exchange of materials relative to the cell's volume.

What is the cell membrane primarily made of?

A phospholipid bilayer with proteins, cholesterol, and carbohydrates.

What does 'fluid mosaic' mean?

The membrane is fluid because components can move laterally, and mosaic because it contains many different components.

Which part of a phospholipid is hydrophilic?

The phosphate-containing head.

Which part is hydrophobic?

The fatty acid tails.

What does selectively permeable mean?

The membrane allows some substances to cross more easily than others.

What is diffusion?

Net movement of molecules from high concentration to low concentration.

What is passive transport?

Movement across a membrane that does not require cellular energy.

What is facilitated diffusion?

Passive movement through membrane proteins down a concentration gradient.

What is active transport?

Movement against a concentration or electrochemical gradient using energy.

What is osmosis?

Diffusion of water across a selectively permeable membrane.

What is a hypotonic solution?

A solution with lower solute concentration than the cell.

What happens to an animal cell in a hypotonic solution?

Water enters the cell, potentially causing it to swell and lyse.

What is a hypertonic solution?

A solution with higher solute concentration than the cell.

What happens to an animal cell in a hypertonic solution?

Water leaves the cell, causing it to shrink.

What is an isotonic solution?

A solution with the same effective solute concentration as the cell.

What happens to water in osmosis?

Water moves toward the side with the higher concentration of nonpenetrating solutes.

What is endocytosis?

The cell takes material into the cell by forming a vesicle from the plasma membrane.

What is exocytosis?

A vesicle fuses with the plasma membrane and releases its contents outside the cell.

Why do cells communicate?

To coordinate activities and respond to changes in their environment.

What is a signal molecule?

A molecule that carries information to a target cell.

What is a receptor?

A protein that specifically binds a signaling molecule.

What is signal transduction?

The process by which a signal is converted into a cellular response.