Cell and Molecular Biology

In eukaryotic cells, protein synthesis takes place at the

1. nucleus

2. mitochondria

3. chloroplasts

4. ribosomes

5. lysosomes

(D) Protein synthesis takes place at the ribosomes of eukaryotic cells. The nucleus of eukaryotic cells (A) contains DNA, packaged into distinct chromosomes, which governs the physical and biochemical properties of the cell. Cellular respiration takes place in the mitochondria of eukaryotic cells (B), while photosynthesis takes place in the chloroplasts of plant cells and some bacterial cells (C). Lysosomes (E) use hydrolytic enzymes to breakdown macromolecules in the cells of some eukaryotic organisms.

Diversity of Life

Which of the following organisms is NOT classified as a protist?

1. chlamydia

2. amoeba

3. paramecium

4. green alga

5. slime mold

(A) Chlamydia are bacteria and, thus, are prokaryotic organisms classified as Monera in the five-kingdom system of classification. Amoebas (B) and paramecia (C) are animal-like protists, green algae (D) are plant-like protists, and slime molds (E) are fungal-like protists.

Vertebrate Anatomy and Physiology

In vertebrate organisms, oxygen and carbon dioxide are transported throughout the body by binding to

1. water molecules in the blood

2. hemoglobin in white blood cells

3. hemoglobin in red blood cells

4. lymph in white blood cells

5. lymph in red blood cells

(C) Hemoglobin is a blood pigment that gives red blood cells their characteristic color. Hemoglobin consists of four subunits, each of which contains an iron molecule that can bind to oxygen for transport throughout the body. Hemoglobin also binds and transports carbon dioxide and serves to buffer the blood, preventing harmful fluctuations in blood pH.

Developmental Biology

The ability of embryonic cells to retain the potential to develop into any part of the organism is referred to as

1. cell fate

2. pattern formation

3. polarity

4. totipotency

5. determination

(D) Totipotency refers to the ability of some embryonic cells to develop into any part of the organism. In some organisms, only the zygote is totipotent. In mammals, the embryonic cells (blastomeres) remain totipotent through the eight-celled stage.

Genetics

Most cells in the human body contain proto-oncogenes that can be stimulated to become cancerous (oncogenes) through mutations. The normal function of proto-oncogenes in human cells is to

1. stimulate protein synthesis

2. repair damaged regions of DNA

3. produce antibodies against invading pathogens

4. control normal cell growth and division

5. splice introns from mRNA during RNA processing

(D) Proto-oncogenes are normal genes present in the human genome that code for proteins that regulate cell growth and cell division. Mutations (either spontaneous mutations, or those caused by exposure to radiation, cancer-causing chemicals, and certain viruses) occurring in the proto-oncogenes may cause them to no longer regulate normal cell growth and division. Uncontrolled cell growth and division may lead to cancer.

Evolution, Ecology, and Behavior

The evolutionary history of a species, or groups of related species, is referred to as

1. phylogeny

2. speciation

3. the fossil record

4. paleontology

5. pedigree analysis

(A) Phylogeny traces the evolutionary history of species or related groups of species. Reconstructive phylogeny is part of the discipline of systematics, the study of biological diversity on a global evolutionary scale.