Cellular Level of Life - Key Concepts (Lecture Notes)

Question-and-answer flashcards covering cell structure, organelles, and membrane transport based on the lecture notes.

What is the basic unit of life, and can cells have different structures while sharing common characteristics?

Cells are the basic units of life; although they can have different structures and functions, they share common features such as a plasma membrane, cytoplasm, genetic material, and organelles.

What organelle is the powerhouse of the cell and the main site of ATP synthesis?

Mitochondria.

Where are ribosomes located and what is their function?

Ribosomes synthesize proteins; they can be free in the cytoplasm or attached to the rough endoplasmic reticulum.

What is the difference between the rough endoplasmic reticulum and the smooth endoplasmic reticulum?

Rough ER has ribosomes and synthesizes/modifies proteins; smooth ER lacks ribosomes and synthesizes lipids and detoxifies.

What is the Golgi apparatus responsible for?

Modifies, packages, and distributes proteins and lipids produced by the ER; secretory vesicles bud from the Golgi.

What are secretory vesicles and what do they do?

Small membrane-bound sacs that transport and store materials; they fuse with the plasma membrane to release contents outside the cell (exocytosis).

What are lysosomes and what process occurs there?

Lysosomes contain hydrolytic enzymes for intracellular digestion; autophagy is the digestion of degraded organelles and cellular components.

What are peroxisomes and what is their role?

Peroxisomes contain enzymes that break down fatty acids and detoxify hydrogen peroxide.

What are proteasomes?

Large protein complexes that digest some proteins.

What is the cytoskeleton and what are microtubules used for?

The cytoskeleton provides structural support and organizes cell components; microtubules help in cell division and form components like cilia and flagella.

What are cilia, flagella, and microvilli?

Cilia move substances over cell surfaces; flagella propel cells (e.g., sperm); microvilli increase surface area for absorption and do not move.

What is the plasma membrane and what is its major composition?

The outer boundary of the cell, primarily a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrate chains; it is selectively permeable.

What are hydrophobic tails and hydrophilic heads in the plasma membrane?

Hydrophobic tails are water-repelling; hydrophilic heads are water-loving.

What is a receptor molecule in the plasma membrane?

A molecule that binds specific ligands to initiate a cellular response.

What is the nucleus and what does it contain?

A large membrane-bound organelle containing DNA; it controls cell structure and function and houses chromosomes.

What is the nucleolus and what is its function?

A diffuse region inside the nucleus that produces ribosomal RNA to form ribosomal subunits.

What are chromosomes and how many do humans have?

Thread-like DNA-protein structures that carry genetic information; humans have 46 chromosomes (23 pairs).

What is trisomy 21?

A genetic condition in which there is an extra copy of chromosome 21.

Where is DNA located and what is a gene?

DNA is located in the nucleus; a gene is a region of DNA that specifies an RNA molecule.

What is endoplasmic reticulum and its two types?

Endoplasmic reticulum is a network of membranes; rough ER has ribosomes and synthesizes proteins; smooth ER lacks ribosomes and synthesizes lipids and detoxifies.

What are the cis and trans faces of the Golgi apparatus?

The cis face receives vesicles from the ER; the trans face sorts and ships vesicles to final destinations.

What is the role of secretory vesicles in the cell?

Secretory vesicles transport and release materials outside the cell via exocytosis.

What is tonicity and the three types of solutions?

Isotonic: equal solute and solvent; no net water movement. Hypertonic: higher external solute causes cell to shrink. Hypotonic: lower external solute causes cell to swell.

What is osmosis?

Diffusion of water across a selectively permeable membrane.

What is passive transport and what are its components?

Passive transport does not require ATP and includes diffusion, facilitated diffusion (carriers), and osmosis.

What is active transport and examples?

Active transport requires ATP and moves substances against their concentration gradient; examples include membrane pumps (e.g., Na+/K+ ATPase) and endocytosis/exocytosis.

What are endocytosis and exocytosis?

Endocytosis is uptake of materials by vesicle formation (phagocytosis and pinocytosis); exocytosis is secretion of materials by vesicle fusion with the plasma membrane.