BSC 2085 Lesson 2 + 3

Vocabulary flashcards covering key terms and definitions from Chapter 3: Cellular Form and Function, including cell theory, membrane structure, membrane transport mechanisms, and vesicular transport.

Robert Hooke

The English scientist who made improvements to the compound microscope, was the first to see and name cells.

Somatic Cells

All cells in the human body except reproductive cells created by meiosis; examples include neurons, osteocytes, muscle cells, and epithelial cells.

Plasma Membrane

A membrane composed of lipids and proteins that surrounds a cell, regulating transport, providing support, and responding to chemical signals.

Phospholipids

$75\%$ of membrane lipids, hydrophilic phosphate heads facing water and hydrophobic tails directed toward the center, avoiding water

Cholesterol

$20\%$ of plasma membrane lipids that hold phospholipids still and regulate membrane stiffness and fluidity.

Glycocalyx

The carbohydrate coating on the external surface of the plasma membrane that protects the plasma membrane from physical and chemical injury

Other functions:

cell protection, immunity, cancer defense, cell adhesion, and fertilization.

Peripheral Proteins

Proteins that temporarily attach to the outside or inside surface of the cell membrane.

Leak Channels

Transmembrane channel proteins that remain constantly open, allowing hydrophilic solutes and water to pass freely across the membrane.

Gated Channels

Transmembrane channel proteins that open and close to let ions pass through only when they receive a specific signal. chemical (ligand), electrical (voltage), or mechanical stimuli.

Cell-Adhesion Molecules (CAMs)

Membrane proteins that mechanically link one cell to another cell or to extracellular material.

Simple Diffusion

down concentration gradient from an area of higher concentration to lower concentration, no energy

Osmosis

The net flow of water across a selectively permeable membrane from an area of higher water (lower solute) concentration to lower water (higher solute) concentration.

Osmotic Pressure

The pressure required to completely stop osmosis, the flow of water, which increases as the concentration of nonpermeating solutes rises.

Tonicity

How a solutions affects fluid volume and pressure inside a cell by causing water to move in or out of it.

Transport Maximum ($T_m$)

The maximum rate of carrier-mediated transport achieved when solute concentration rises to a level where all carrier proteins are fully saturated.

Symport

A carrier protein that transports two or more solutes simultaneously in the same direction across the membrane (cotransport).

Antiport

A carrier protein that transports two or more solutes in opposite directions across the membrane (countertransport).

Facilitated Diffusion

Carrier-mediated transport that moves solutes down their concentration gradient across the membrane without consuming ATP energy.

Primary Active Transport

Carrier-mediated transport where a carrier uses ATP energy directly to move solutes across a membrane up their concentration gradient.

Secondary Active Transport

Carrier-mediated transport where a solute moves up its concentration gradient using energy from an ion (Na+)

Sodium-Potassium Pump ($Na^+-K^+$ Pump)

moves 3 Na+ out of cell and brings 2 K+ into cell, keeps K+ concentration higher and Na+ concentration lower

within the cell

Phagocytosis

“cell eating”, cell intakes solid particles

Pinocytosis

('cell drinking') cell intakes liquids

Receptor-Mediated Endocytosis

when a cell takes in specific substances from outside the cell using receptor proteins on its cell membrane.

Transcytosis

transport of material across the cell by capturing it on one side and releasing it on the other

Microfilaments

Thinnest fibers; made mainly of actin proteins

Interacts with cytosolic proteins to adjust liquidity of cytosol

• If it makes dense interactions, cytosol becomes dense and gelatinous

• If it makes dispersed interactions, cytosol becomes more fluid

Microfilaments also play a key role in muscle contraction and cell division.

Intermediate filaments

Provide strength and stability; help hold organelles in place and strengthen cells

ex: keratin fibers

Microtubules

Maintain cell shape, act as tracks for moving materials, help separate chromosomes during cell division, and form structures such as cilia and flagella

Microvilli VS Cilia

Microvilli	Cilia

Cytoskeleton

Made of microfilaments (actin)

Made of microtubules (tubulin)

Main job

Increase surface area

Move substances across the cell surface

Movement

Generally do not move on their own

Actively move back and forth

Where found

Intestinal cells, kidney cells

Airways, parts of the reproductive system

Ribosomes

Tiny structures made of rRNA and proteins; make proteins

Proteasomes

large protein complexes inside cells that break down unneeded, damaged, or misfolded proteins into small peptide pieces

Rough & Smooth ER

Rough ER: Makes, folds, and begins processing proteins that will be secreted, inserted into membranes, or sent to certain organelles

Smooth ER: Makes lipids, helps detoxify substances, and stores/releases calcium in some cells

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids into vesicles for transport

Lysosomes

Break down waste, damaged cell parts, and substances brought into the cell

Lysosomes

Break down waste, damaged cell parts, and substances brought into the cell

• Primary lysosome – formed by the Golgi complex. Enzymes

inside are inactive

• Secondary lysosome – formed when primary lysosome fuses to

an endosome (transport vesicle containing materials to be digested)

or fuses with damaged organelle

Peroxisomes

Break down certain fatty acids and harmful substances; produce and break down hydrogen peroxide