Unit 2: The Cell - Structure and Transport

Vocabulary terms and definitions covering cellular organelles, transport mechanisms, and surface area-to-volume ratio as presented in the Unit 2 lecture notes.

Nucleus

A double membrane (nuclear envelope) structure with pores that stores genetic information (DNA) and is the site of RNA synthesis and ribosome subunit assembly.

Ribosomes

Organelles composed of rRNA and protein, consisting of large and small subunits, that function in protein synthesis; they can be bound or free (cytoplasmic).

Rough ER

A membrane-bound structure composed of flattened sacs (cisternae) studded with ribosomes; it is the site of membrane-bound and secreted protein synthesis, cell compartmentalization, mechanical support, and intracellular transport.

Smooth ER

A folded, tubelike structure (cisternae) responsible for detoxification, calcium storage, and lipid synthesis.

Golgi Complex

A membrane-bound structure of flattened sacs (cisternae) that functions in the folding and chemical modification of synthesized proteins and packaging protein traffic.

Mitochondria

Double-membrane organelle (outer smooth, inner highly folded) with its own DNA and ribosomes; its matrix is the site of the Krebs Cycle, and its highly folded cristae are the site of oxidative phosphorylation.

Chloroplast

A double outer membrane organelle containing thylakoid sacs stacked into grana and a fluid called stroma; it is the site of photosynthesis (Light Reactions in thylakoids and Calvin-Benson Cycle in stroma).

Lysosome

Membrane-enclosed sacs containing hydrolytic enzymes used for intracellular digestion to recycle organic materials and carry out programmed cell death (apoptosis).

Vacuole

A membrane-bound sac for storage and release of macromolecules and waste; central vacuoles provide turgor pressure for water retention, and contractile vacuoles handle osmoregulation in protists.

Surface Area-to-Volume Ratio

A mathematical relationship where smaller cells typically have a higher ratio, allowing for more efficient exchange of materials with the environment.

Sphere Volume and Surface Area Formulas

V = rac{4}{3} imes ext{π} imes r^3 and $S = 4 imes ext{π} imes r^2$

Rectangular Prism Volume and Surface Area Formulas

$V = L imes W imes H$ and $S = 2LH + 2LW + 2WH$

Cube Volume and Surface Area Formulas

$V = s^3$ and $S = 6s^2$

Cylinder Volume and Surface Area Formulas

$V = ext{π} imes r^2 imes h$ and $S = 2 ext{π} imes r^2 + 2 ext{π} imes r imes h$

Hypertonic Solution

A solution with a HIGH solute concentration and LOW free water concentration that gains water from a hypotonic solution.

Hypotonic Solution

A solution with a LOW solute concentration and HIGH free water concentration that loses water to a hypertonic solution.

Isotonic Solution

A solution with EQUAL solute concentration and EQUAL free water concentration compared to another solution, resulting in equal water movement.

Simple Diffusion

Passive transport requiring no energy that moves small, nonpolar molecules (such as $CO_2$, $O_2$, $N_2$, and steroids) down their concentration gradient without a transport protein.

Facilitated Diffusion

Passive transport requiring no energy that moves small molecules down their concentration gradient through a transport protein (e.g., water, $Na^+$, $K^+$, $Ca^{2+}$).

Active Transport

Transport requiring the input of energy to move molecules (e.g., $Na^+$, $K^+$, $Ca^{2+}$, $H^+$) against their concentration gradient using a transport protein.

Osmosis

The movement of water across a semi-permeable membrane from high water potential to low water potential.

Plasma Membrane

The cell boundary composed of phospholipids, membrane proteins, glycolipids, glycoproteins, and cholesterol.

Phagocytosis

A type of endocytosis commonly known as cellular eating.

Pinocytosis

A type of endocytosis commonly known as cellular drinking.

Exocytosis

The bulk transport process for the export of materials, such as the pathway from the Rough ER to the Golgi complex to the plasma membrane.

Turgid

The state of a cell (specifically plant cells) when water enters by osmosis from a hypotonic solution.

Plasmolysed

The state of a cell when water leaves by osmosis into a hypertonic solution.