chapter 3 material
List the four emergent water properties that contribute to Earth’s fitness for life and describe
how each is related to the water molecule’s polarity.
Water’s polarity enables hydrogen bonding, which gives rise to cohesion, temperature moderation, expansion upon freezing, and solvent versatility
What property of carbon accounts for its unparalleled ability to form large, complex, and diverse molecules?
Carbon has four valence electrons, allowing it to form four covalent bonds with other atoms.
Tetravalence
define monomer vs polymer
Monomers are small molecular units, while polymers are large molecules composed of many repeating monomers bonded together.
What cell features are unique to eukaryotic cells? prokaryotic cells?
Eukaryotic cells contain a membrane-bound nucleus and membrane-bound organelles, whereas prokaryotic cells lack a nucleus and membrane-bound organelles and instead have DNA in a nucleoid region.
Proteins associated with membranes are what?
Proteins associated with membranes are integral (transmembrane) proteins and peripheral proteins, where integral proteins are embedded in or across the lipid bilayer and peripheral proteins are loosely attached to the membrane surface.
For every one-unit change in the pH of a solution, how much does the H+ concentration change?
hydrogen ion (H⁺) concentration changes by a factor of 10.
What is a hydrocarbon?
A hydrocarbon is an organic molecule composed only of carbon and hydrogen atoms. (CH4)
List the four important large molecules of living things.
Which of the four can be considered macromolecules?
The four major classes of large biological molecules are carbohydrates, lipids, proteins, and nucleic acids, and of these, carbohydrates, proteins, and nucleic acids are considered macromolecules.
What is a mitochondrion? What is its function?
A mitochondrion is a membrane-bound organelle found in eukaryotic cells, and its function is to carry out cellular respiration, converting energy stored in food molecules into ATP, the cell’s usable energy source.
What does solidification mean with respect to a membrane? Why is it detrimental to the cell?
Solidification of a membrane refers to the loss of membrane fluidity when phospholipids pack tightly together (often at low temperatures), making the membrane rigid; this is detrimental because reduced fluidity disrupts membrane protein function, transport processes, and overall cell signaling, threatening cell survival.
define hydrophilic and hydrophobic
Substances that have an affinity for water
Substances that do not have an affinity for water
What is an isomer? What is the difference between a structural and cis-trans isomer?
An isomer is one of two or more compounds that have the same molecular formula but different structures or arrangements of atoms, resulting in different properties.
Structural isomers differ in the arrangement of covalent bonds, while cis–trans isomers differ in the spatial arrangement of atoms around a double bond despite having the same bonds.
What is a lipid? What two types of smaller molecules are fats constructed from?
A lipid is a hydrophobic nonpolar molecule, and fats are built from one glycerol molecule bonded to three fatty acids.
What are the three major components of cilia and flagella?
The three major components of cilia and flagella are microtubules (arranged in a 9+2 pattern), dynein motor proteins, and a basal body that anchors the structure to the cell.
Describe the six major functions performed by membrane proteins?
The six major functions of membrane proteins are transport of substances across the membrane, enzymatic activity catalyzing reactions, signal transduction by receiving and relaying chemical signals, cell–cell recognition through identification markers, intercellular joining that connects adjacent cells, and attachment to the cytoskeleton and extracellular matrix to maintain cell shape and stabilize protein position.
What is the specific heat of a substance? What accounts for the relatively high heat of water?
The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 gram of that substance to change its temperature by 1°C.
Heat energy is used to break hydrogen bonds before the water molecules can increase their motion (temperature), so water can absorb a large amount of heat with only a small change in temperature.
What is an enantiomer? What type of carbon atom is required to form an enantiomer?
An enantiomer is a non-superimposable mirror-image molecule, and it forms when a molecule contains a chiral (asymmetric) carbon bonded to four different groups.
What are the two functional groups found in all amino acids?
What determines the properties of an amino acid?
All amino acids contain an amino group (–NH₂) and a carboxyl group (–COOH), and the unique properties of each amino acid are determined by its R group (side chain).
What is the function of plasmodesmata? Why are they particularly important for plant cells?
Plasmodesmata are cytoplasmic channels that connect adjacent plant cells, allowing direct transport of water, ions, nutrients, signaling molecules, and RNA; they are especially important in plants because rigid cell walls prevent direct cell-to-cell contact, making plasmodesmata essential for communication and coordination across tissues.
What is a transport protein? a channel protein? a carrier protein?
A transport protein is a membrane protein that helps specific ions or molecules cross the cell membrane, a channel protein forms a hydrophilic passageway that allows substances to diffuse across the membrane, and a carrier protein binds a specific molecule and changes shape to move it across the membrane.
What is a buffer and how does it function?
A buffer is a substance (or combination of substances) that minimizes changes in pH by resisting sudden increases or decreases in hydrogen ion (H⁺) concentration.
What are the seven functional groups discussed in class?
Hydroxyl (–OH)
Polar; forms hydrogen bonds
Characteristic of alcohols (e.g., sugars)
Carbonyl (–C=O)
Can be an aldehyde (end of chain) or ketone (within chain)
Found in many sugars
Carboxyl (–COOH)
Acts as an acid (can donate H⁺)
Found in organic acids and amino acids
Amino (–NH₂)
Acts as a base (can accept H⁺)
Found in amino acids and proteins
Sulfhydryl (–SH)
Forms disulfide bonds that stabilize protein structure
Found in some amino acids
Phosphate (–OPO₃²⁻)
Contributes negative charge and energy transfer
Found in ATP, nucleic acids, phospholipids
Methyl (–CH₃)
Nonpolar; affects gene expression and molecular shape
Found in fats and modified DNA
List the two major types of nucleic acids and explain how they differ from one another.
DNA: it contains the sugar deoxyribose, is double-stranded in a double-helix structure, and uses the nitrogenous bases adenine, thymine, cytosine, and guanine.
RNA: it contains the sugar ribose, is single-stranded, and uses the bases adenine, uracil, cytosine, and guanine, with uracil replacing thymine.
Distinguish among tight junctions, desmosomes, and gap junctions. Which is analogous to the plasmodesmata of plant cells?
Tight junctions seal adjacent animal cells together to prevent leakage of substances,
desmosomes anchor cells to one another to provide mechanical strength,
gap junctions form channels that allow ions and small molecules to pass directly between cells;
gap junctions are analogous to plasmodesmata in plant cells because both enable direct cell-to-cell communication.
What is exocytosis? endocytosis? List the three distinct types of endocytosis
Exocytosis is the process by which a cell exports materials by fusing vesicles with the plasma membrane, while endocytosis is the process by which a cell takes materials into itself by forming vesicles from the plasma membrane; the three types of endocytosis are phagocytosis (engulfing large particles), pinocytosis (uptake of extracellular fluid), and receptor-mediated endocytosis (selective uptake via receptor binding).