Cell Structure, Membrane Transport, and Protein Synthesis in Human Cells

What are the three basic parts of a human cell?

Plasma membrane, nucleus, and cytoplasm.

What is the structure of the plasma membrane?

A phospholipid bilayer with embedded proteins, having a dynamic fluid structure and is selectively permeable.

What percentage of the plasma membrane is composed of phospholipids?

75% phospholipids.

What role do glycolipids play in the plasma membrane?

They assist in cell identification.

What is the function of cholesterol in the plasma membrane?

It increases membrane stability.

What are integral proteins?

Proteins that are firmly inserted in the membrane, often spanning the membrane.

What are peripheral proteins?

Proteins that are loosely attached to integral proteins on either side of the membrane.

What is the glycocalyx?

A fuzzy, sticky covering at the cell surface made of glycolipids and glycoproteins that acts as a cell identification marker.

What are tight junctions?

Impermeable junctions that prevent molecules from passing through the intercellular space.

What are desmosomes?

Anchoring junctions that prevent separation of cells and withstand mechanical stress.

What are gap junctions?

Communication junctions that allow small molecules to pass from cell to cell.

What is diffusion?

The movement of molecules down their concentration gradient.

What is osmosis?

The diffusion of water through a selectively permeable membrane.

What is tonicity?

The ability of a solution to change the cell's internal water volume.

What happens to a cell in a hypertonic solution?

The cell loses water and shrinks (crenates).

What happens to a cell in a hypotonic solution?

The cell gains water and may swell or lyse.

What is active transport?

The process that uses energy (ATP) to move substances against their concentration gradient.

What is vesicular transport?

The use of membranous sacs called vesicles to transport particles, macromolecules, and fluids across the plasma membrane.

What is endocytosis?

The transport of substances into the cell.

What is exocytosis?

The transport of substances out of the cell.

What is the resting membrane potential (RMP)?

The condition in which the inside of the cell membrane is negatively charged compared to the positively charged outside.

What primarily determines the resting membrane potential?

The concentration gradient of potassium ions (K+).

What are the three major parts of the cytoplasm?

Cytosol, organelles, and inclusions.

What is the function of mitochondria?

They produce most of the ATP via aerobic respiration.

What is the role of ribosomes?

They are the site of protein synthesis.

What are the two types of endoplasmic reticulum?

Rough ER (with ribosomes) and Smooth ER (without ribosomes).

What is the function of the Golgi apparatus?

It modifies, concentrates, and packages proteins and lipids made at the ER.

What are lysosomes?

Membranous sacs containing digestive enzymes that digest worn-out organelles and ingested materials.

What is the function of the cytoskeleton?

It supports cellular structures and aids in cell movement.

What are the three types of cytoskeletal elements?

Microfilaments, intermediate filaments, and microtubules.

What is the role of the nucleus?

It contains DNA, which determines the kinds of proteins the cell will synthesize.

What is the function of the nucleolus?

It acts as the ribosome factory of the cell.

What is the difference between meiosis and mitosis?

Meiosis produces gametes (sperm and oocytes), while mitosis produces identical daughter cells for growth and repair.

What are the two main periods of the cell cycle?

Interphase (G1, S, G2) and mitotic phase.

What is transcription in protein synthesis?

The process where DNA information is coded into mRNA.

What is translation in protein synthesis?

The process where mRNA is decoded to assemble a polypeptide.