CELS191 LECTURE 3 - Plasma Membrane & Organelles

These flashcards cover key concepts related to cell functions, membrane structure, and transport mechanisms.

What must a cell do?

Manufacture cellular materials, obtain raw materials, remove waste, generate energy, control all of the above.

Plasma membrane

A semi-permeable barrier that allows passage of oxygen, nutrients, and waste, controlling movement of substances in and out of the cell.

Phospholipid bilayer

A double layer of phospholipids forming the plasma membrane with embedded or attached proteins.

Saturation in membrane fluidity

Saturated lipids are packed tightly together and have less fluidity.

What role do membrane proteins play?

Membrane proteins determine the function of the membrane, and can have multiple roles, including signal transduction and cell recognition, intercellular joining, and linking cytoskeleton to ECM.

Signal transduction

Membrane proteins relay messages from the body/ environment into the cell — grow, divide, move, make something, die, etc.

Cell Recognition

Involves glycoproteins with added sugars.

Intercellular joining

Connections formed by proteins that provide long-lasting links between cells.

Linking cytoskeleton and extracellular matrix

Allows cell to physically connect with protein structures outside the cell ECM.

Passive transport

Molecules move down their concentration gradient and thus do not require energy.

Facilitated diffusion

Movement of molecules requires membrane proteins called channels and carriers to aid the movement of specific substances down their concentration gradient. Passive Transport (no energy).

Osmosis

The movement of water across a cell membrane through channels called aquaporins, from high water (low solute) concentration to low water (high solute) concentration. Passive Transport (no energy).

Active transport

Movement of substances against their concentration gradient using energy (ATP).

Co-transport

Indirect active transport where one substance is pumped across the membrane. The concentration gradient is used to power the movement of a second substance against its concentration gradient.

Organelles

Specialized structures within a cell that provide specific conditions for processes, keep incompatible processes apart, concentrate substances, and package them for transport.

Key organelles in eukaryotic cells

Nucleus, Golgi apparatus, mitochondrion, endoplasmic reticulum (ER).

Organelle(s) specific to animal cells

Lyosome.

Organelle(s) specific to plant cells

Central vacuole and chloroplast.

Active transport - Direct

Directly uses ATP as energy to move energy up their gradient.

Active transport - Indirect

Uses the energy gained as other molecules move down their gradient to power the transport.

Unsaturation in membrane fluidity

Unsaturated lipids prevent tight packing and have more fluidity.