Cell Structure and Membrane Concepts

Flashcards covering key vocabulary related to cell structure, membrane function, and cellular connections.

Plasma Membrane

A selectively permeable barrier that surrounds the cell, allowing certain substances to pass through while keeping others out. Transports proteins, glycprotiens, large and charge.

Extracellular Matrix (ECM) In animals

A network of proteins and carbohydrates outside the cell that provides structural support.

-Most synthesized in rough ER

-Major components:

Collagen and Proteoglycans

Peptidoglycans

The substance forming the cell wall of certain bacteria, consisting of a polymer of sugars and amino acids.

Plant Cell walls: Primary Cell wall

Primarily composed of cellulose, bundled together as microfibrils are cross-linked via hydrogen bond to other polysaccharide filaments

-The spaces between microfilaments are filled with pectin (polysaccharide/sugar)

Microfibrils

Bundles of cellulose fibers that provide structural support to the primary cell wall in plants.

Turgor Pressure

Flaccid = isotonic

Turgid= Hypotonic

The pressure of the cell contents against the cell wall, helping maintain plant rigidity.

Tight Junctions

Cell junctions that create watertight seals between adjacent cells, preventing leakage of fluids.

-Waterproof

-Found in epithelial cells like stomach lining and intestines

-Can loosen or tighten

Desmosomes

Anchoring junctions that connect the cytoskeletons of adjacent cells, providing mechanical stability.

-Found in muscle cells

-Analogous to rievets

-Use linking proteins and cytosolic anchoring proteins

Gap Junctions

Intercellular channels that allow for the direct transfer of ions and small molecules between neighboring cells.

-Communication portals

-Can be found in our muscle cells of the heart to coordinate contractions

Plasmodesmata (Direct Attachment) only plants

-Plasma membrane and cytoplasm of two plant cells are continuous

-Communication

-Symplast and Apolast

Symplast

-Continuous network of cytoplasm (direct way)

Apolast

Region outside the plasma membrane (cell walls, middle lamella, air spaces)
-Pathway (goes outside the cell to apolast

Secondary Cell Wall

-Makeup varies depending on the plant cell and its function

-For those that form wood, the secondary cell wall contains lignin

-Helps withstand forces of gravity and wind

Collagen

its the first image

-Fibrous component of ECM dominated by glycoprotiens

Proteoglycans

2nd image

-Glycosylated proteins found in the ECM

Cell-Cell attachments: Indirect

-Middle lamella (gelatinous pectins) serves as a glue to adjacent cell walls

Cell-Cell Attachments: Direct

-Tight Junctions

-Desmosomes

-Gap junctions

Signal Reception in Multicellular Organisms

• How cells can receive chemical signals, like hormones to communicate with each other.

Three main steps:

-Reception

-Transduction

-Response

Three types of signaling pathways

• Steroid Hormone Pathway

• G protein Coupled Receptor (GPCR)

• Receptor Tyrosine Kinases (RTK)

Steroid Hormone Pathway

Reception (first half) and response (bottom)

-Only for lipid soluble molecules like hormones (estrogen, cortisol, etc)

-Receptor in cytoplasm

-NO transduction for this

-Diffuses through membrane

G protein coupled receptors (GPCR)

• G protiens- Peripheral membrane proteins

• Second messengers

• Calcium ions

• Cyclic AMP

• Cyclic guanosine monophosphate (cGMP)

• Diacylglycerol (DAG)

• Inositol Triphosphate (IP3)

-Kinases —> enz that add phosphates

Receptor Tyrosine Kinase (RTK)

1.) Response —> GDP is peripheral protein and signal molecule passes integral mem.

4 &5.) Transduction —> triggers response

-Catalyzing a reaction within the cell

-Triggers a phosphorylation cascade

-Commonly involves mitogen-activated protein kinases (MAPK)

Causes of signal Deactivation

• Concentration of signaling molecules

• Amount of active receptors

• Phosphatases- takes off phosphate groups

• Phosphodiesterases - convert active second messengers into inactive ones

Cross-Talk Key points

1. One pathway may inhibit steps in a second pathway

2. One pathway may stimulate steps in a second pathway

3. Presence of multiple steps provides a series of points where crosstalk can regulate the flow of information

   -Allows response to different signals at same time

Signaling in Unicellular Organisms

• Quorum Sensing: signaling molecules are released into the environment

-Can move