General Biology Exam 2

What are the basic structural and functional units of all living organisms?

Cells

What types of nucleic acids do cells contain that carry hereditary information?

DNA and RNA

What essential processes do cells carry out?

Use energy, respond to environmental changes, reproduce, and pass on hereditary information

How do cells direct the manufacture of cellular molecules?

By using the information carried in DNA and RNA

What is the primary purpose of microscopy in biology?

To see cells and the structures within them.

What type of microscope uses light to illuminate the specimen?

Light microscope.

What type of microscope uses electrons to illuminate the specimen?

Electron microscope.

What is the primary structure of the plasma membrane?

A bilayer made of lipids with embedded protein molecules.

What is the function of the lipid bilayer in the plasma membrane?

It acts as a hydrophobic barrier to water-soluble substances.

How do selected substances penetrate cell membranes?

Through transport protein channels.

What does selective transport of ions and water-soluble molecules maintain?

The specialized internal environments required for cellular life.

What is the central region of all cells that contains DNA?

The central region contains DNA molecules, which store hereditary information (genes).

What is found in the cytoplasm of a cell?

The cytoplasm contains the cytosol and cytoskeleton.

What is cytosol?

Cytosol is an aqueous solution containing ions, various organic molecules, and organelles.

What is the role of the cytoskeleton in a cell?

The cytoskeleton maintains cell shape and plays key roles in cellular functions.

What is a key characteristic of the nucleoid region in prokaryotes?

The nucleoid region has no boundary membrane.

How do the internal membranes of many bacteria compare to those of eukaryotes?

Many species of bacteria have few internal membranes, while eukaryotes have extensive membrane systems that form organelles.

What separates the true nucleus from the surrounding cytoplasm in eukaryotes?

The true nucleus is separated by membranes.

Which domains do prokaryotes belong to?

Prokaryotes belong to the domains Bacteria and Archaea.

What domain do eukaryotes belong to?

Eukaryotes belong to the domain Eukarya.

Where is DNA located in prokaryotic cells?

In the nucleoid

What is the structure of DNA in most prokaryotic species?

A single, circular molecule known as the prokaryotic chromosome

What is the role of messenger RNA (mRNA) in protein synthesis?

mRNA carries information from DNA to ribosomes in the cytoplasm

What do ribosomes do with the information from mRNA?

They assemble amino acids into proteins

What surrounds the plasma membrane in cells?

A rigid external cell wall coated with polysaccharides, known as the glycocalyx.

What is the difference between a slime layer and a capsule in relation to glycocalyx?

A slime layer is loosely associated with the cells, while a capsule is firmly attached.

What is the primary function of the molecular systems in the plasma membrane?

To metabolize food molecules or light energy into the chemical energy of ATP.

What structure do many bacteria and archaeans use for movement?

Long flagella

How does the bacterial flagellum facilitate movement?

It rotates in a socket and pushes the cell through a liquid medium.

What are pili and what is their function?

Hairlike pili attach the cell to surfaces or other cells.

What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have a true nucleus enclosed by membranes.

What role do membranous organelles play in eukaryotic cells?

They are specialized to carry out functions of energy metabolism, molecular synthesis, storage, and transport.

What is the function of the cytosol in eukaryotic cells?

The cytosol participates in energy metabolism and molecular synthesis and supports cell motility.

What components are found in the cytoplasm of eukaryotic cells?

The cytoplasm contains a system of membranous organelles and the cytosol.

What is the function of channel proteins in the eukaryotic plasma membrane?

Channel proteins transport substances in and out of cells.

What role do receptor proteins play in the plasma membrane?

Receptors recognize and bind specific signal molecules, triggering internal responses.

How do immune system proteins function in relation to cells?

Immune system proteins label cells as 'self' to help the immune system distinguish between the body's own cells and foreign invaders.

What separates the nucleus from the cytoplasm?

The nuclear envelope, which consists of two membranes.

What reinforces the nuclear envelope in animal cells?

A network of protein filaments called lamins.

What type of proteins reinforce the nuclear envelope in protists, fungi, and plants?

Other specific proteins (not specified) that vary by organism.

What is the function of nuclear pore complexes?

They regulate the transport of proteins and RNA molecules between the nucleus and cytoplasm.

What is the short amino acid sequence that proteins need to enter the nucleus?

Nuclear localization signal

What role does the specific protein in the cytosol play in nuclear import?

It recognizes and binds to the nuclear localization signal and moves the protein to the nuclear pore complex.

Where does the transport of proteins into the nucleus occur?

At the nuclear pore complex.

What is the liquid within the nucleus called?

Nucleoplasm

What does the nucleus contain that is a combination of DNA and proteins?

Chromatin

How is DNA organized in eukaryotes?

Each DNA molecule is linear and organized with proteins into specific eukaryotic chromosomes.

What structures are formed around the genes coding for rRNA in the eukaryotic nucleus?

Nucleoli

Where are ribosomal subunits formed in a eukaryotic cell?

In the nucleoli

How do ribosomal subunits exit the nucleus?

Through nuclear pore complexes

What do ribosomal subunits join with in the cytoplasm to form ribosomes?

mRNAs

How is gene expression regulated in eukaryotic cells?

It is carefully controlled according to the function of each cell.

What are the two subunits of a eukaryotic ribosome?

A large subunit and a small subunit.

Where can ribosomes be found in a eukaryotic cell?

Some ribosomes are freely suspended in the cytosol, while others are attached to membranes.

What happens to proteins made on free ribosomes?

They may remain in the cytosol, pass into the nucleus, or become parts of mitochondria, chloroplasts, cytoskeleton, or other cytoplasmic structures.

What is the fate of proteins made on ribosomes attached to the endoplasmic reticulum (ER)?

They follow a special path to other organelles in the cell.

What is the function of the endomembrane system in eukaryotic cells?

It divides the cell into functional and structural compartments.

How are the membranes in the endomembrane system connected?

They may be connected directly or indirectly by vesicles.

What are vesicles in the context of the endomembrane system?

Vesicles are small membrane-bound sacs that transfer substances between parts of the system.

Name three components included in the endomembrane system.

Nuclear envelope, endoplasmic reticulum, Golgi complex, lysosomes, vesicles, and plasma membrane.

What is the role of the nuclear envelope in the endomembrane system?

It surrounds the nucleus and is part of the endomembrane system.

What is the structure of the endoplasmic reticulum (ER)?

An extensive interconnected network of membranous channels and cisternae.

What forms the cisternae in the endoplasmic reticulum?

Each cisterna is formed by a single membrane that surrounds an enclosed space called the ER lumen.

What are the two forms of endoplasmic reticulum?

Rough ER and smooth ER.

What is the primary function of ribosomes on the Rough ER?

They synthesize proteins that enter the ER lumen.

What happens to proteins in the lumen of the Rough ER?

They fold into their final form and undergo chemical modifications.

What type of chemical modification occurs in the Rough ER lumen?

Addition of carbohydrate groups to produce glycoproteins.

How are proteins delivered from the Rough ER to other regions of the cell?

They are transported within small vesicles that pinch off from the ER.

Which cellular structure is a common destination for proteins delivered by the Rough ER?

The Golgi complex.

What is a key characteristic of Smooth ER membranes?

Smooth ER membranes have no ribosomes attached to their surfaces.

What does Smooth ER synthesize?

Smooth ER synthesizes lipids that become part of cell membranes.

How does Smooth ER function in the liver?

In the liver, Smooth ER converts drugs, poisons, and toxic by-products into substances that can be tolerated or more easily removed from the body.

What is the structure of the Golgi complex?

A stack of flattened, membranous sacs called cisternae.

How do proteins enter the Golgi complex?

Proteins made in the endoplasmic reticulum (ER) enter on the cis face, delivered by transport vesicles that fuse with the membrane.

What modifications occur to proteins in the Golgi complex?

Proteins are chemically modified by removing segments or adding functional groups, lipids, or carbohydrates.

From which face do modified proteins exit the Golgi complex?

Modified proteins exit from the trans face in vesicles that bud off from the membrane.

What is the primary function of the Golgi complex?

To tag proteins for sorting to their final destinations.

How are proteins secreted from the cell?

They are transported to the membrane in secretory vesicles, which release their contents by exocytosis.

What happens to the membrane of the secretory vesicle during exocytosis?

It fuses with the plasma membrane and becomes part of the plasma membrane.

What process brings molecules into the cell from the exterior?

Endocytosis

How do vesicles form during endocytosis?

The plasma membrane forms a pocket that bulges inward and pinches off into the cytoplasm.

What do endocytic vesicles carry materials to?

The Golgi complex or other destinations such as lysosomes in animal cells.

What is the role of endocytic vesicles in the cell?

They transport materials from the exterior of the cell to various internal destinations.

What are lysosomes?

Small, membrane-bound vesicles containing hydrolytic enzymes that digest complex molecules.

What is the primary function of lysosomes?

To digest complex molecules and recycle the subunits of these molecules.

In which type of cells are lysosomes found?

Lysosomes are found in animal cells but not in plant cells.

How are lysosomes formed?

Lysosomes are formed by budding from the Golgi complex.

Where are the hydrolytic enzymes of lysosomes synthesized?

The hydrolytic enzymes are synthesized in the rough endoplasmic reticulum (ER).

What is the pH level within lysosomes?

The pH level within lysosomes is acidic, approximately pH 5.

How does the pH of lysosomes compare to that of the cytosol?

The pH of lysosomes is significantly lower than that of the cytosol, which is around pH 7.2.

What types of substances do lysosomal enzymes digest?

Lysosomal enzymes digest food molecules, worn-out organelles (through autophagy), and break down bacteria or other cellular debris (during phagocytosis).

What occurs in lysosomal storage diseases?

In lysosomal storage diseases, one of the hydrolytic enzymes normally found in the lysosome is absent.

What are mitochondria?

Membrane-bound organelles where cellular respiration occurs.

What is cellular respiration?

The process by which energy-rich food molecules are broken down to water and carbon dioxide, capturing energy in ATP.

What do mitochondria require for cellular respiration?

Oxygen, which is supplied by breathing.

What is the main product of cellular respiration?

ATP (adenosine triphosphate), which captures energy.