Cell Biology: Structure & Function

What are the two major parts of a cell?

What is the historic scientific theory that living organisms are made up of cells called?

Which of the following scientists contributed to cell theory?

The cell is the basic unit of structure and organization of organisms.

Cells arise from pre-existing cells.

Energy flow (metabolism and biochemistry) occurs outside of cells.

All cells are basically the same in chemical composition in organisms of similar species.

What allowed the classification of cells into eukaryotes and prokaryotes?

Which of the following belong to the eukaryotes?

Prokaryotes have a typical nucleus and subcellular components.

A cell has three major components. Which of the following is NOT a component?

What is the thin membrane that envelops a cell called?

The plasma membrane defines the periphery of the cell separating the cell contents from the surrounding environment.

The plasma membrane is composed of a lipid bilayer and protein embedded in it.

The plasma membrane has highly permeable properties.

Receptor proteins on the membrane transmit signals into the cell.

What is the fluid portion of the cytoplasm in which particles are suspended called?

Which of the following is NOT an important organelle suspended in the cytoplasm?

The endoplasmic reticulum is a network of interconnecting membranes enclosing channels or cisternae.

The endoplasmic reticulum is continuous from the outer nuclear envelope to the inner plasma membrane.

The rough endoplasmic reticulum is where complex lipid and steroid are synthesized.

The rough endoplasmic reticulum appears rough due to the attachment of ribosomes.

Drug detoxification occurs in the endoplasmic reticulum.

The nucleus is the most important organelle.

All mammalian cells contain a nucleus except mature red blood cells (RBCs).

The nucleus is where the DNA, the genetic material of the cell, is stored.

The DNA consists of the complete set of genes (genome) of the organism only in prokaryotes.

The nucleus governs the cell because it contains the DNA which is the chemical basis of the genes.

The genetic material, DNA, forms chromatin by complexing with histone protein.

Chromatin is further organized into chromosomes.

The nucleolus is where protein synthesis takes place.

DNA replication takes place in the nucleolus.

Mitochondria are spherical oval or rod-shaped bodies in the cytoplasm.

Mitochondria are involved in the breakdown of food stuff and release energy.

Mitochondria store energy as ATP for the use of the cell in other metabolic processes.

Mitochondria have only one membrane.

The enzymes of the electron transport chain (ETC), where energy is trapped, are found in the inner membrane folds of mitochondria.

Cytochrome P450, involved in steroid synthesis, is found in the mitochondria.

Mature red blood cells contain mitochondria.

Mammalian cells have specific DNA called mitochondrial DNA, distinct from the DNA in the nucleus.

Lysosomes are large organelles where foreign particles are digested.

Lysosomes are comparable to incinerators where waste is burnt.

Enzymes released from lysosomes can cause tissue damage.

Lysosomes help in the destruction of bacteria and other foreign bodies and the removal of excessive secretory products in the cells of the glands.

The Golgi complex or Golgi apparatus is a network of flat, smooth membranes and vesicles.

The main function of the Golgi apparatus is to sort, package, mature, and release protein already synthesized.

The Golgi aparattus is present in all cells, including red blood cells.

Peroxisomes contain enzymes such as peroxidases and catalases, which are concerned with the metabolism of peroxides.

Peroxisomes are also capable of carrying out β-oxidation of fatty acids.

The cytoskeleton of eukaryotic cells contains networks of protein filaments.

The cytoskeleton helps fix organelles in the cell.

The cytoskeleton is a rigid permanent framework of the cell.

Which of the following is NOT a primary protein filament of the cytoskeleton?

Microfilaments are about 5 nm in diameter and are made up of protein actin.

Microfilaments form a meshwork just underlying the plasma membrane of cells, referred to as the cell cortex.

Microfilaments disappear as cell motility increases but do not reappear when motility stops.

Microfilaments help maintain the shape of the cell.

Microfilaments help cellular movement.

Microtubules are cylindrical tubes, 20 to 25 nm in diameter, made up of protein tubulin.

Microtubules are necessary for the formation and function of the mitotic spindle.

Microtubules prevent tubules of the endoplasmic reticulum from collapsing.

Microtubules are major components of axons and dendrites.

Intermediate filaments are so called because their diameter (10 nm) is intermediate between that of microfilaments (5 nm) and microtubules (25 nm).

Intermediate filaments are formed from fibrous proteins which varies with different tissue type.

Intermediate filaments play a role in cell-to-cell attachment.

Intermediate filaments help stabilize the epithelium.

Intermediate filaments provide strength and rigidity to axons.

The cytoskeleton gives cells their characteristic shape and form.

The cytoskeleton provides attachment points for organelles, fixing their location in cells.

The cytoskeleton makes communication between parts of the cell possible.

The cytoskeleton helps separate chromosomes during cell division.

The internal movement of cell organelles and cell locomotion would be possible without the cytoskeleton.

The cytoskeleton acts as a track on which cells can move organelles, chromosomes, and other things.

One of the functions of the plasma membrane is to regulate the passage of a variety of small molecules across it.

Biological membranes are permeable membranes.

The movement of molecules across a membrane is restricted because of size, charge, or solubility.

The permeability of substances across the cell membrane is dependent on their solubility in lipids and not on their molecular size.

Water-soluble compounds are generally permeable and do not require carrier-mediated transport.

An important function of the membrane is to withhold unwanted molecules while permitting the entry of molecules necessary for cellular metabolism.

Transport mechanisms are classified into two types. Which of the following is NOT a transport mechanism?

Passive transport requires energy in the form of ATP.

The direction of passive transport is always from a region of higher concentration to one of lower concentration.

Active transport is always from a region of lower concentration to one of higher concentration.

Active transport is classified into two types according to the source of energy used.

Primary active transport is directly coupled with hydrolysis of ATP.

Secondary active transport uses an energy generated by an electrochemical gradient.

Secondary active transport is classified into two types: co-transport and counter-transport.

Co-transport is when both substances move simultaneously across the membrane in the same direction.

Counter-transport is when both substances move simultaneously across the membrane in opposite directions.

The process by which cells take up large molecules is called exocytosis, and the process by which cells release large molecules from the cells to the outside is called endocytosis.

There are two types of endocytosis: pinocytosis (cellular drinking) and phagocytosis (cellular eating).

Pinocytosis is the only process by which most macromolecules, such as proteins, polysaccharides, and polynucleotides, can enter cells.

Molecules first attach to specific receptors on the surface of the membrane before undergoing pinocytosis.

Phagocytosis involves the ingestion of large particles such as viruses, bacteria, cells, tissue debris, or a dead cell.

Phagocytosis only occurs in specialized cells, such as macrophages and white blood cells.

Phagocytosis occurs in the same way as pinocytosis.

To obtain purified preparations of organelles, tissue is first carefully broken up in a homogenizing apparatus using a hypertonic solution.

Sucrose solution is used because it is not metabolized in most tissues.

Sucrose solution does not pass through membranes readily.

Sucrose solution does not cause interorganelles to swell.

The homogenate is centrifuged at a series of increasing centrifugal force.

The subcellular organelles, which differ in size and specific gravity, sediment at different rates and can be isolated from the homogenate by differential centrifugation.

The dense nuclei are sedimented last, followed by the mitochondria.

After all the particulate matter has been removed, the soluble remnant is the cytosol.

Organelles of similar sedimentation coefficients can be easily separated by differential centrifugation.

Mitochondria isolated by this method are not contaminated with lysosomes and peroxisomes.

Organelles can be separated by isopycnic centrifugation technique.

The purity of isolated subcellular fractions is assessed by analyzing marker enzymes.

Marker enzymes are the enzymes located exclusively in a particular fraction.

Analysis of marker enzymes confirms the identity of the isolated fraction and indicates the degree of contamination with other organelles.

Isolated mitochondria have a high specific activity of cytochrome oxidase, but low catalase and acid phosphatase.

The low activity of catalase and acid phosphatase in isolated mitochondria is due to contamination with peroxisomes and lysosomes.

The plasma membrane contains a variety of enzymes, including 5'-nucleotidase and Na+-K+ ATPase.

The nucleus contains DNA polymerase, RNA polymerase, and protein synthesis enzymes.

The endoplasmic reticulum contains high levels of glucose-6-phosphatase.

Golgi bodies contain galactosyl transferase.

Lysosomes contain high levels of acid phosphatase.

Mitochondria contain succinate dehydrogenase and cytochrome C oxidase.

Peroxisomes contain high levels of catalase.

The cytosol contains lactate dehydrogenase and glucose-6-phosphate dehydrogenase.