Bio Exam 2
In addition to the information below, be sure to review the corresponding in-class worksheets,
weekly homeworks, and the figures in the study slides posted on Canvas.
Eukaryotic Cells (Chapter 5.3 & 5.5)
❑ Label in a diagram and describe the structure and function of the eukaryotic structures discussed
in class: nucleus, plasma membrane, ribosomes, lysosomes, mitochondria, chloroplasts, rough
endoplasmic reticulum, smooth endoplasmic reticulum, and Golgi apparatus.
❑ Describe the components of the endomembrane system in eukaryotic cells and how materials are
moved between these components. - - - -
System likely originated from infolding of plasma membrane
Network of membranes and organelles that work together to modify, package, and
transport lipids and proteins
Includes nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes,
vesicles, endosomes, and plasma membrane
Plasma membrane: common to all cells, phospholipid bilayer with proteins and other
molecules embedded
❑ Describe the role of vacuoles in plant cells. -
Storage, maintaining turgor pressure, regulating pH, and supporting overall plant growth
and development
❑ Describe the function of peroxisomes, chromoplasts, and leucoplasts. -
Peroxisomes: detoxification and metabolism - -
Chromoplasts: pigment synthesis, storage, coloration, nutrient storage, protection
Leucoplasts: storage (starch, lipids, proteins), biosynthesis
❑ Describe the three types of protein filaments that comprise the cytoskeleton and the basic
function(s) of each. - - -
Microfilaments:
~Functions: muscle contraction, amoeboid movement, cytoplasmic streaming, cell
shape
~Structure: actin monomers, which can form long, double helices
~For movement: actin can elongate to form pseudopods, actin interacts with a
myosin (a motor protein) to contract cell shape
Intermediate filaments:
~Functions: anchor cell structures in place, provide rigidity
~Structure: tough, ropelike protein assemblages
Microtubules:
~Functions: rigid internal skeleton for some cells, framework/pathway for motor
proteins
~Structures: long, hollow, unbranched cylinders, made from tubulin which is a
dimer
❑ Describe the structure of eukaryotic cilia and flagella. -
Made of microtubules in a “9+2” array - -
Cilia: short, usually many present, beat stiffly in one direction
Flagella: longer, found singly or in pairs, snake-like movement
❑ Explain the functions and roles of the motor proteins myosin and kinesin. -
Undergo reversible shape changed powered by ATP hydrolysis
-
Kinesin: “drives” vesicles along microtubules, binds to a vesicle and “walks” it along by
changing shape -
Myosin: binds to actin filaments and generates force
❑ Explain how the nucleus and endomembrane system likely evolved. -
An ancient prokaryotic cell has no internal membranes - -
The cell membrane folds inward, many modern-day prokaryotes have membrane
infoldings
further membrane infoldings begin in the formation of the ER, creating a segregated
compartment, the ER surrounds the nucleoid and forms the nuclear envelope
❑ Describe the endosymbiosis theory for the origin of mitochondria and chloroplasts. -
Mitochondria and plastics likely originated from prokaryotes engulfed by larger cells →
endosymbiosis theory - -
An ancestral eukaryotic cell endocytoses a photosynthetic cyanobacterium
The endocytosed cyanobacterium loses most of its genetic material to the host nucleus but
retains the ability to photosynthesize, it is now a plastid
Cell Membranes (Chapter 6)
❑ Describe the general structure of the plasma membrane (fluid mosaic model).
o Phospholipid bilayer embedded with proteins
❑ Distinguish between saturated and unsaturated fatty acids in phospholipids. -
Unsaturated fatty acids: tails contain kinks at double bonds, packing of phospholipids is
loose -
Saturated fatty acids: tails are relatively straight (no double bonds), packing of
phospholipids is tight
❑ Describe the three ways that phospholipids can vary. -
Fatty acid chain length (# of carbons) - -
Degree of unsaturation (# of double bonds)
Polar (phosphate-containing) groups present
❑ Explain how the fluidity of the membrane can be affected by temperature, the amount of saturated
versus unsaturated fatty acids, fatty acid tail length, and the presence and amount of cholesterol (in
animals). -
❑ List and describe the four types of proteins found in the plasma membrane and whether they would
contain hydrophobic, hydrophilic, and/or both regions/domains.
o Peripheral, integral (but not transmembrane), transmembrane, glycoprotein - - -
Peripheral membrane proteins: lack exposed hydrophobic groups, do not penetrate the
bilayer
Integral membrane proteins: have hydrophobic and hydrophilic regions or domains
~Some are partially embedded, some extend all the way through phospholipid
bilayer (transmembrane proteins)
Glycoproteins: carbohydrate + protein
❑ Briefly describe how diffusion of membrane proteins was determined by forming a heterokaryon
(human + mouse cell). - -
Mouse cell has a membrane protein that can be labeled with a green dye, human with red
dye
Cells are fused together to create a heterokaryon
-
Initially, the mouse and human membrane proteins are on different sides of the
heterokaryon -
After 40 minutes the mouse and human membrane proteins are intermixed
❑ Describe the basic structure and function of glycolipids and glycoproteins. - -
Glycolipids: carbohydrate + lipid
Glycoproteins: carbohydrate + protein
❑ Given a cross-section of the plasma membrane, be able to label the following parts: phospholipids,
cholesterol, integral and peripheral membrane proteins, glycoproteins, and glycolipids.
❑ Describe the three types of cell junctions (tight junctions, desmosomes, and gap junctions) and
their functions. - - -
Tight junctions: help ensure directional movement of materials
~Form a “quilted” seal, barring the movement of dissolved materials through the
space between epithelial cells
Desmosomes: provide mechanical stability to epithelial cells
~Link adjacent cells tightly but permit materials to move around them in
intercellular space
Gap junctions: allow communication
~Let adjacent cells communicate
❑ Explain how and why the plasma membrane is selectively permeable. -
Some substances can pass through unaided, other cannot -
Cells need to get nutrients into cell and waste out of cell
❑ List and describe the major types of membrane transport (simple diffusion, osmosis, facilitated
diffusion, and active transport).
o Does the process require energy? - - - - - - - - - - - - - - - - - -
Simple diffusion: no
Osmosis: no
Facilitated diffusion: no
Active transport: yes
o Does the process require a carrier or channel protein?
Simple diffusion: no
Osmosis: no, but can be facilitated by aquaporins
Facilitated diffusion: yes
Active transport: yes
o Do molecules move with or against the concentration gradient?
Simple diffusion: yes
Osmosis: yes
Facilitated diffusion: yes
Active transport: no
o What types of molecules are typically transported in this manner?
Simple diffusion: smaller nonpolar molecules such as O2 and CO2
Osmosis: water (H2O)
Facilitated diffusion: polar molecules such as Na+, K+, Cl-, glucose, amino acids,
nucleotides
Active transport: polar molecules such as Na+, K+, Cl-, glucose, amino acids, nucleotides
o What distinguishes primary active transport from secondary active transport?
Primary active transport: direct hydrolysis of ATP provides energy for transport
~Ex. Sodium – potassium pump
Secondary active transport: an already established concentration gradient allows a
different molecule to be transported against its own concentration gradient
❑ Explain how water moves into/out of a cell when its surrounding salt concentration changes.
o What will happen to a cell if placed in an isotonic vs. hypertonic vs. hypotonic solution? -
Isotonic: equal solute concentration inside and outside cell, water moves in and out evenly - -
Hypotonic: lower solute concentration on outside of cell than inside, water moves into the
cell and the cell swells
Hypertonic: higher solute concentration on outside of cell than inside, water moves out of
the cell and the cell shrinks
❑ Describe how the sodium-potassium pump is an example of primary active transport and what type
of transporter it is (antiporter).
❑ Explain when glucose would be transported via facilitated diffusion versus secondary active
transport. - -
Diffusion for ions and water-soluble molecules (glucose) can move “down” their
concentration gradient
Channel proteins or carrier protein get molecules across
❑ Define endocytosis and distinguish between phagocytosis, pinocytosis, and receptor-mediated
endocytosis. - - - -
Endocytosis: 3 methods to move large molecules cell
Phagocytosis: cell membrane engulfs large particles, “cellular eating”
Pinocytosis: cell membrane brings in liquids and small particles, still with vesicle
formation, “cellular drinking”
Receptor-mediated endocytosis: uptake of specific materials, recognized on cell surface by
receptor proteins
❑ Define exocytosis and give some examples. -
Exocytosis: how cells release large molecules, secretory vesicles duse with plasma
membrane to release molecules outside the cell -
Ex. digestive enzymes in pancreas, neurotransmitters at the synapse
❑ If given a substance (e.g., ion, small molecule, large molecule, bacterium), be able to provide the
type of membrane transport used to enter/leave the cell (like on the membrane function worksheet).
Energy and Enzymes (Chapter 8)
❑ Explain the two types of energy and their role in biology. -
Potential: stored energy -
Kinetic: energy that does work, that makes things change
❑ Define metabolism. -
Metabolism: totality of all chemical reactions involved
❑ Describe the differences between anabolism and catabolism and be able to give examples of both
types of reactions (proteins to amino acids, etc.). - - -
Anabolism: anabolic reactions connect simple molecules to form more complex ones
~Ex. Amino acids → Proteins, Sugars → Polysaccharides, Fatty acids → Lipids,
Nitrogenous Bases → Nucleic Acids
Catabolism: catabolic reactions break down complex molecules into simpler ones
~Ex. Carbohydrates → CO2, Fats → H2O, Proteins → NH3
These two processes are often linked
❑ Define exergonic and endergonic reactions and how they relate to anabolism and catabolism. -
Exergonic: reactions release free energy
~Complex molecules → free energy + small molecules -
Endergonic: reactions consume free energy
~Free energy + small molecules → complex molecules
- -
Measured in Gibbs free energy = G
Catabolism and anabolism involve energy transformations, endergonic and exergonic
describe the energy changes associated with them
❑ Explain why ATP is the fuel molecule of the cell. -
Cells rely on adenosine triphosphate (ATP) for capture and transfer of free energy to do
work - -
Free energy from exergonic reactions is captured in the formation of ATP and from ADP
and inorganic Phosphate (Pi)
ATP can be hydrolyzed at sites in the cell to release energy to power endergonic reactions
❑ Describe the structure of an enzyme and how it binds its substrate. - - -
Shape of an enzyme active site allows a specific substrate to fit (lock-and-key)
Binding of substrate(s) to active site depends on hydrogen bonds, attraction and repulsion
of electrically charged groups, and hydrophobic reactions
Induced fit: enzymes change shape when they bind substrate
❑ Be able to label and understand energy graphs of catalyzed vs. uncatalyzed reactions.
❑ Describe three ways that enzymes lower the activation energy of a chemical reaction.
o Orientation -
Enzymes orient substrate molecules, bringing together the atoms that will bond
o Stretching/straining bonds in substrate molecule(s) - -
Enzymes can stretch the bonds in substrate molecules, making them unstable
o Temporary addition of chemical groups to substrates
Enzymes can temporarily add chemical charges to substrates
❑ Explain the induced-fit model of enzyme substrate binding. -
Induced fit: enzymes change shape when they bind substrate
❑ Describe how enzymes can be regulated by effectors.
o Explain the difference between irreversible, competitive, uncompetitive, & noncompetitive
inhibitors. -
Irreversible inhibition = inhibitor covalently bonds to enzyme’s active site
~Nerve gas, Sarin, VX, etc. - - - - -
Reversible inhibition = all bind noncovalently
Competitive → binds to active site; effect on enzyme activity determined by
concentrations of substrate and inhibitor
Uncompetitive → binds to enzyme-substrate complex
Noncompetitive → binds to enzyme away from active site, changing the enzyme’s shape
(this, allosteric regulation)
o Describe allosteric regulation of enzymes by activators or inhibitors.
Noncompetitive
binds to enzyme away from active site, changing the enzyme’s shape
(this, allosteric regulation)
❑ Describe how temperature, pH, and substrate concentration affect enzyme function.
(see graphs)