Cell Biology and Structure

Adult stem cells reside in various tissues of the fully developed organism, where they function to maintain, repair, and replenish dying cells in those specific tissues. Embryonic stem cells and totipotent cells are found in early-stage embryos and do not naturally perform ongoing repair in an adult body.

Multipotent stem cells are committed to a specific lineage and can only differentiate into the specialized cell types of the tissue in which they reside. For example, hematopoietic stem cells in the bone marrow can differentiate into various blood cells, but not into nerve or muscle cells.

Stem cells are unspecialized cells that have the unique ability to self-renew and differentiate into specialized cell types. Sex cells, embryos, and meiotic cells do not share this defining functional definition.

Cell differentiation is the process by which a less specialized cell becomes a more specialized cell type. Apoptosis refers to programmed cell death, and regulation refers to the control of cellular processes.

Totipotent stem cells have the highest differentiation potential and can differentiate into any embryonic or extraembryonic cell type, allowing them to construct a complete, viable organism. Pluripotent cells can form any cell type in the body but cannot form extraembryonic tissues like the placenta.

Cell differentiation is the process by which a less specialized cell becomes a more specialized cell type, determining its ultimate identity and function. Other options like interphase are part of the cell cycle, while indoctrination and reincarnation are not biological processes.

Glands, such as sweat glands, salivary glands, and endocrine glands, are formed by specialized epithelial cells known as glandular epithelium. These cells are highly adapted for synthesizing and secreting substances like hormones, sweat, and enzymes.

Animal cells contain a cell membrane, cytoplasm, vacuoles (usually small and temporary), a nucleus, and mitochondria. They do not contain chloroplasts, which are characteristic of plant cells.

A tissue is a group of similar cells working together to perform a specific function. Multiple tissues then organize to form an organ.

The four primary types of animal tissues are epithelial tissue, connective tissue, muscle tissue, and nervous tissue. The other options humorously list brands of household paper tissues.

Both single-celled and multi-celled organisms possess cell structures (such as membranes, ribosomes, and genetic material) to carry out life processes. Tissues, organs, and organ systems are only found in multicellular organisms.

The nucleus is typically located near the center of animal cells (and many plant cells, though often pushed to the side by a large vacuole in mature plant cells) and acts as the control center containing the cell's DNA.

The correct hierarchical organization of living things from simplest to most complex is: cells form tissues, tissues form organs, and organs work together to form organ systems.

Chloroplasts are organelles found in plant cells and algae that carry out photosynthesis. Animal cells do not perform photosynthesis and therefore lack chloroplasts.