AP Biology — Cell Structure & Function

What is a **desmosome**?

Desmosomes are structures that attach adjacent animal cells together, providing mechanical strength through **intermediate filaments**.

Explain the concept of **selective permeability**.

Selective permeability refers to the cell membrane's ability to allow certain molecules to pass through while blocking others, maintaining **homeostasis**.

What is the role of **cholesterol** in the cell membrane?

Cholesterol helps maintain membrane **fluidity and stability** by preventing the fatty acid chains of the phospholipids from sticking together.

What is the **cell membrane** composed of?

The cell membrane is composed of a **phospholipid bilayer** with embedded proteins, cholesterol, and carbohydrates.

Define **osmosis**.

**Osmosis** is the movement of water molecules across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.

What is the primary function of **mitochondria**?

Mitochondria are the powerhouses of the cell, responsible for producing **ATP** through cellular respiration.

Describe the function of **ribosomes**.

Ribosomes are responsible for **protein synthesis**, translating messenger RNA (mRNA) into polypeptide chains.

What is the role of the **nucleus** in a eukaryotic cell?

The nucleus houses the cell's **genetic material** (DNA) and coordinates activities like growth, metabolism, and reproduction.

What structures are involved in **protein transport** within a cell?

Proteins are transported by the **endoplasmic reticulum** and **Golgi apparatus**, often using vesicles.

What is the function of **lysosomes**?

Lysosomes contain **digestive enzymes** that break down waste materials and cellular debris.

Define **active transport**.

**Active transport** is the movement of molecules across a cell membrane from a region of lower concentration to higher concentration using energy, often in the form of ATP.

What is the role of **chloroplasts**?

Chloroplasts are responsible for **photosynthesis**, converting light energy into chemical energy stored in glucose.

Describe the structure of the **endoplasmic reticulum**.

The endoplasmic reticulum (ER) is a network of membranous tubules and sacs. It comes in two forms: **rough ER** (with ribosomes) and **smooth ER** (without ribosomes).

What is the **fluid mosaic model**?

The fluid mosaic model describes the cell membrane as a **dynamic and flexible structure** with proteins drifting in or on the fluid lipid bilayer.

What is the function of **peroxisomes**?

Peroxisomes contain enzymes that detoxify harmful substances and perform **beta-oxidation** of fatty acids.

What is **diffusion**?

Diffusion is the passive movement of molecules from an area of **higher concentration** to an area of **lower concentration** until equilibrium is reached.

What organelle is responsible for **cellular respiration**?

The **mitochondria** are responsible for cellular respiration, where they convert glucose and oxygen into ATP, carbon dioxide, and water.

Explain the function of the **cytoskeleton**.

The cytoskeleton provides **structural support** for the cell, plays a role in cell division, and facilitates cell movement and intracellular transport.

What is the **Golgi apparatus**?

The Golgi apparatus modifies, sorts, and packages proteins and lipids for **secretion or delivery** to other organelles.

What are **integral proteins**?

Integral proteins are embedded in the **phospholipid bilayer** and can span across the membrane, playing roles in transport and cell signaling.

Define **facilitated diffusion**.

Facilitated diffusion is the passive transport of molecules across a membrane through **transport proteins** without the use of energy.

What is the role of **vacuoles** in plant cells?

Vacuoles store nutrients, waste products, and maintain **turgor pressure** to provide structural support to plant cells.

What is **endocytosis**?

Endocytosis is the process by which cells take in materials by **engulfing them in a membrane**, forming a vesicle.

What is the primary function of the **smooth ER**?

The smooth ER is involved in the synthesis of **lipids**, metabolism of carbohydrates, and detoxification of drugs and poisons.

What is the **extracellular matrix**?

The extracellular matrix (ECM) is a network of proteins and carbohydrates outside the cell that provides **structural support** and facilitates cell signaling.

Define **exocytosis**.

Exocytosis is the process by which cells expel materials by **fusing a vesicle with the plasma membrane**, releasing its contents outside the cell.

What is the role of **plasmodesmata** in plant cells?

Plasmodesmata are channels between plant cell walls that allow for the **transport of substances** and communication between cells.

What is the **nucleolus**?

The nucleolus is a region within the nucleus responsible for **ribosomal RNA (rRNA) synthesis** and ribosome assembly.

Describe the process of **cell signaling**.

Cell signaling involves the reception of a signal molecule, transduction of the signal through a series of molecular changes, and a specific **cellular response**.

What are **microtubules**?

Microtubules are part of the cytoskeleton, composed of tubulin proteins, and play a role in maintaining cell shape, intracellular transport, and **cell division**.