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, whereas unsaturated lipids prevent tight packing and have more 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.

Signal transduction

The process by which membrane proteins relay messages from the environment into the cell.

Glycoproteins

Proteins with added sugars that are often involved in cell recognition.

Intercellular joining

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

Linking cytoskeleton and extracellular matrix

A function of membrane proteins that allows a cell to connect with extracellular structures.

Passive transport

Movement of molecules across a membrane without energy, following the concentration gradient.

Facilitated diffusion

A type of Passive Transport (no energy). Movement of hydrophilic molecules across a membrane via protein channels or carriers, down their concentration gradient without energy.

Osmosis

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

Active transport

Movement of substances against their concentration gradient using energy (ATP), allowing different concentrations inside and outside the cell.

Co-transport

A mechanism where one substance is moved across the membrane, and its gradient powers the movement of a second substance against its 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.