Cell and Molecular Biology - Exam 1

One of the first scientists to elucidate the chemical structure and composition of a plant virus

Wendell Stanley

Which diseases did Robert Koch connect to specific bacterial pathogens using his experimental methods?

Anthrax, tuberculosis, and fowl cholera.

The production of human insulin using genetically modified microorganisms is primarily an application of what field?

Genetic engineering / biotechnology

All of the following attempted to prove or disprove the doctrine of spontaneous generation except...

Florence Nightingale

Who was the physician that believed that rats originate from wheat bran and old rags?

Baptista van Helmont

Which of the following scientists published the book called Micrographia, which contained a description of the microscope and its uses?

Robert Hooke

Why is immersion oil used with the 100× oil-immersion objective?

Immersion oil reduces the refraction of light between the slide and the objective, allowing more light to enter the lens and improving resolution.

Which of the following scientists was unsuccessful in disputing the theory of spontaneous generation?

John Needham

The __________________________ can be changed by pulling apart or pushing the oculars together

interocular distance

Who discovered the antibacterial effects of the first medically useful sulfonamide drug?

Gerhard Domagk

Saccharomyces cerevisiae is an example of what type of microorganism?

A fungus (yeast)

In a compound light microscope, what is the correct path of light from the light source to the eye?

Light source → condenser → specimen → objective lens → ocular lens → eye

What is bioremediation?

The use of microorganisms to break down or remove harmful chemicals and pollutants from the environment.

During microscopic observation of a specimen, the amount of light that is allowed to pass through the specimen is controlled by the

iris diaphragm

Ignaz Semmelweis showed that the transmission of disease could be interrupted by

hand washing in chlorine water

Which two domains consist of prokaryotic cells?

Bacteria and Archaea

What is the smallest known infectious agent that causes disease in plants and consists only of a short strand of RNA?

Viroid

The use of agar as the gelling agent in solid media was suggested by

Fannie Hesse

Which types of microorganisms contain a membrane-bound nucleus?

Eukaryotic microorganisms, including fungi and protozoa.

What is the purpose of the swan-shaped neck in Pasteur's flask experiment?

It allows air to enter while trapping airborne microorganisms and dust before they can reach the sterile broth.

The accomplishments of Koch include all of the following except

development of the rabies vaccine

The first medically useful antibiotic, penicillin, was originally produced by what type of organism?

A Penicillium mold

A cell is observed without a membrane-bound nucleus. What type of cell is it most likely to be?

A prokaryotic cell.

What is the total magnification when using a 10× ocular lens and a 100× oil-immersion objective?

1000x

Pasteur's swan-neck flask experiment is repeated, but bacterial growth appears after sterilization. What is the most likely explanation?

The broth was contaminated or was not completely sterilized.

What important antibiotic did Alexander Fleming discover?

Penicillin

Which discoveries or achievements are associated with Louis Pasteur?

He demonstrated that different microorganisms produce different fermentation products and developed vaccines against diseases including anthrax and fowl cholera.

Which of the following does not contain DNA or RNA

Prion

Which microscope component is adjusted to compensate for differences in focus between a person's two eyes?

Diopter adjustment on the ocular lens.

What was Paul Ehrlich's “magic bullet”?

Salvarsan (arsphenamine), a chemical antimicrobial used to treat syphilis.

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion occurs directly through the lipid bilayer without a transport protein. Facilitated diffusion moves substances down their concentration gradient using a membrane transport protein.

Where do nitrogen-fixing bacteria associated with plants commonly live, and where do cellulose-digesting microbes of ruminants live?

Nitrogen-fixing bacteria live in root nodules; many digestive microbes live in the rumen.

Which infectious agents can reproduce only inside living host cells and do not carry out independent metabolism?

Viruses

What were Koch's postulates designed to establish?

A causal relationship between a specific microorganism and a specific disease.

What does resolution mean in microscopy?

The ability to distinguish two closely spaced points as separate objects.

Which of the following is/are false about viruses?

Viruses use their own catabolic enzymes to metabolize nutrients

Which bacterial genus commonly fixes atmospheric nitrogen in plant root nodules?

Rhizobium

What major types of chemical bonds and interactions occur in biological systems?

Covalent bonds, ionic/electrostatic interactions, hydrogen bonds, and Van der Waals interactions.

What is ATP composed of?

Adenine + ribose + three phosphate groups.

What is tonicity?

Tonicity describes the relative solute concentration on opposite sides of a selectively permeable membrane and predicts the direction of water movement.

Why does a transmission electron microscope provide much better resolution than a light microscope?

Electrons have a much shorter wavelength than visible light

You want to examine the three-dimensional surface appearance of a cell. Which technique would be most useful?

SEM

Why can fluorescence microscopy identify particular structures within a cell?

Fluorescent substances can be attached to specific molecules

Which functional group commonly contributes negative charge to molecules such as ATP and nucleic acids?

Phosphate group

Why does water have unusually strong cohesion and a high specific heat?

Hydrogen bonding occurs between neighboring water molecules

When an ionic compound such as NaCl dissolves in water, what allows the ions to remain separated?

The polar water molecules interact with the charged ions

A molecule contains a polar region and a large nonpolar region. How would this molecule be classified?

Amphipathic

Why do phospholipids spontaneously form bilayers in water?

Hydrophilic heads face water, while hydrophobic tails cluster away from water

Why are cellulose and starch structurally different even though both are polymers of glucose?

Their glucose units are arranged differently; in cellulose, every other glucose is inverted, producing a different structure and function from starch.

What chemical reaction forms a peptide bond between two amino acids?

A condensation reaction that releases water

A mutation replaces a hydrophobic amino acid located in the middle of a membrane-spanning region with a strongly charged amino acid. What would most likely happen?

Membrane insertion or protein folding could be disrupted

Phospholipids frequently move sideways within the same leaflet of a membrane, but spontaneous movement from one leaflet to the other is rare. Which enzyme assists this "flip-flop"?

Flippase

Compared with a membrane containing mostly saturated fatty acids, a membrane containing many unsaturated fatty acids would generally have:

A lower transition temperature

What are lipid rafts?

Specialized membrane domains enriched in cholesterol, saturated fatty acids, and proteins

Unlike simple diffusion, why does facilitated diffusion eventually reach a maximum transport rate?

Transport proteins become saturated

The Na⁺/K⁺ ATPase directly uses ATP. Which description therefore best classifies it?

Primary active transport

During one transport cycle of the Na⁺/K⁺ ATPase, what happens?

3 Na⁺ leave and 2 K⁺ enter

Which organelle would you expect to be particularly abundant in a cell that synthesizes steroid hormones?

Smooth ER

A cell has engulfed a damaged mitochondrion and is breaking it down for recycling. Which process is occurring?

Autophagy

During receptor-mediated endocytosis, which proteins are especially important for forming and releasing the vesicle?

Clathrin and dynamin

What are the major functions of lysosomes?

Lysosomes contain acid hydrolases and function in intracellular digestion, defense, and autophagy. Their interior is acidic, approximately pH 4–5.

Which microscope component concentrates and focuses light onto the specimen?

Condenser

How does cholesterol affect membrane fluidity at high and low temperatures?

At high temperatures, cholesterol makes the membrane less fluid. At low temperatures, it keeps the membrane more fluid and prevents gelling.

What is the difference between passive transport and active transport?

Passive transport moves substances down their concentration or electrochemical gradient; active transport moves substances against the gradient and requires energy

What are the major functional differences between rough ER and smooth ER?

Rough ER is mainly involved in protein synthesis and maturation; smooth ER is involved in lipid and steroid synthesis, carbohydrate metabolism, calcium storage, and detoxification.

What are the major functions of tight junctions, adherens junctions, and desmosomes?

Tight junctions: seal neighboring cells and regulate movement between them.
Adherens junctions: provide cell-cell adhesion and connect to the cytoskeleton.
Desmosomes: provide strong structural adhesion between cells.

What are the three major principles of Cell Theory?

All organisms consist of one or more cells; the cell is the basic structural unit of organisms; all cells arise from preexisting cells.

What is the approximate resolution limit of a light microscope?

0.2 µm

How does TEM differ from SEM?

TEM reveals high-resolution internal structure; SEM scans and shows specimen surfaces.

What distinguishes a bacterial cell from a typical eukaryotic cell?

Bacteria lack a nuclear envelope and membrane-bound organelles

What major structures distinguish plant cells from animal cells?

Plant cells have a cell wall, chloroplasts, and typically one large vacuole; animal cells lack a cell wall and chloroplasts

What makes a water molecule polar?

Oxygen carries a partial negative charge and the hydrogens carry partial positive charges.

What is a hydrogen bond?

An attractive interaction between hydrogen and an electronegative atom such as oxygen, nitrogen, or fluorine.

What do hydrophilic, hydrophobic, and amphipathic mean?

Hydrophilic interacts with water; hydrophobic avoids water; amphipathic contains both hydrophilic and hydrophobic regions

What structures can amphipathic lipids form in water?

Bilayers, micelles, and liposomes

How do starch, glycogen, and cellulose differ?

Starch is a glucose-storage polymer in plants; glycogen is a highly branched glucose-storage polymer in animals; cellulose is a structural glucose polymer with alternating glucose orientation

What determines the chemical properties of an amino acid?

The charge and polarity of its R group

What did Gorter and Grendel's experiment demonstrate about cell membranes?

Cell membranes contain a lipid bilayer

What is the general role of lipids versus proteins in biological membranes?

The lipid bilayer provides the barrier; membrane proteins perform many transport and signaling functions.

How do saturated and unsaturated fatty acids affect membrane fluidity?

Unsaturated fatty acids generally increase fluidity because double bonds prevent tight lipid packing.

What are the major functions of peroxisomes?

Peroxisomes carry out hydrogen peroxide metabolism, detoxification, fatty-acid oxidation, and metabolism of nitrogen-containing compounds.

What is osmosis?

The diffusion of water across a selectively permeable membrane.

What happens to an animal cell in hypotonic, isotonic, and hypertonic solutions?

Hypotonic: water enters and the cell may lyse; isotonic: no net water change; hypertonic: water leaves and the cell shrinks.

What is the difference between symport and antiport?

Symport moves two substances in the same direction; antiport moves them in opposite directions

What are the two major energy sources used for active membrane transport?

ATP and stored ion gradients.

What are the major components of the endomembrane system?

ER, Golgi apparatus, endosomes, and lysosomes.

What is the primary role of the Golgi apparatus?

Modification, sorting, and targeting of proteins and lipids for transport to their destinations.