Cell Biology Essentials: Understanding Structure and Functions

A cell is not a type of phone, a room for prisoners, or a battery compartment. It is the smallest unit capable of carrying out life processes.

Cell theory is a fundamental concept in biology that states all living organisms are composed of cells, cells are the basic units of structure and function, and cells can only come from the reproduction of existing cells.

The plasma (cell) membrane serves as the cell's outer boundary, covering its surface and acting as a barrier to regulate the passage of substances in and out of the cell.

The nucleus in a cell is responsible for housing the DNA and controlling various functions of the cell, such as gene expression and cell division. It is not involved in storing excess nutrients, protein synthesis, or cellular respiration.

Prokaryotes are single-celled organisms that lack membrane-bound organelles and a true nucleus. Their DNA is concentrated in a central region called the nucleoid.

Eukaryotes are characterized by having cells with a nucleus and organelles, distinguishing them from prokaryotes. This complexity is what sets them apart and allows for various functions within the cell.

Tissue refers to a group of similar cells that work together to perform a specific function in an organism.

Organs are specialized structures within living organisms that perform specific functions necessary for survival. They are made up of different types of tissues working together to carry out complex tasks.

An organ system is a collection of organs that work together to perform specific functions in the body, such as the digestive system or respiratory system.

Lysosomes are membrane-bound vesicles that contain digestive enzymes and are formed by the Golgi apparatus. They are responsible for breaking down cellular waste and recycling materials within the cell.

Microfilaments are primarily composed of actin protein, which forms long threads linked end to end and wrapped around each other. The incorrect options provided do not accurately describe the composition of microfilaments.

Centrioles are a pair of small, cylindrical structures found near the nuclear envelope in animal cells. They play a key role in cell division and organization of the mitotic spindle.

The cell wall is a rigid layer that provides structure and support to plant cells only, acting as a protective outer barrier.

The central vacuole is a large, fluid-filled organelle found in plant cells that stores various substances such as water, enzymes, and metabolic wastes. It plays a crucial role in maintaining turgor pressure and storing nutrients.

Chloroplasts are responsible for using light energy to carry out photosynthesis, converting carbon dioxide and water into carbohydrates.

Cytoplasm is the gel-like substance inside the cell membrane that holds all organelles except the nucleus. It plays a critical role in various cellular functions such as metabolism, protein synthesis, and intracellular transport.

Cytosol refers to the part of the cytoplasm that does not contain membrane-bound organelles like the nucleus, mitochondria, or endoplasmic reticulum. It is a crucial component of the cell where various metabolic processes occur.

During cell division, chromosomes condense to be more easily distributed to daughter cells, ensuring proper allocation of genetic material.

The nucleolus is a denser area in the nucleus where DNA is concentrated when making RNA. It is not a membrane-bound organelle responsible for protein synthesis, a subcellular structure containing digestive enzymes, or a pigment responsible for the green color of plant cells.

Ribosomes are cellular organelles responsible for protein synthesis by translating mRNA into amino acid sequences. They are not involved in waste disposal, energy production, or protein transportation within the cell.

The endoplasmic reticulum is responsible for various functions within the cell, including protein synthesis, lipid metabolism, and transport of molecules. It is composed of membranous structures and plays a crucial role in the cell's overall function.

The cytoskeleton is a dynamic network of protein filaments and tubules that give the cell its shape, provide mechanical support, facilitate cell movement, and help with intracellular transport. It plays a crucial role in various cellular functions such as cell division, cell signaling, and maintaining cell structure.

Microtubules are structures within cells that are composed of hollow tubes made of tubulin protein, providing structural support and serving as tracks for cellular transport.

Cilium refers to hair-like structures on the surface of a cell, not long thread-like structures inside the nucleus, gel-like substances between cells, or hard coverings of cells.

A flagellum is specifically defined as hair-like structures that assist in movement on the surface of a cell, making the other options incorrect.

Plastids are specialized organelles found in plant cells that are responsible for functions like photosynthesis and storage of pigments. They are similar to mitochondria in structure, being surrounded by a double membrane and containing their own DNA.

The nuclear envelope is a double membrane surrounding the nucleus, consisting of two phospholipid bilayers. It serves as a barrier between the contents of the nucleus and the cytoplasm. The incorrect options provided do not accurately describe the structure of the nuclear envelope.

The golgi apparatus is a system of flattened, membranous sacs found in eukaryotic cells, often likened to a warehouse or post office for cellular products. It plays a key role in modifying, sorting, and packaging proteins for secretion or for use within the cell.