Ch 6 Cells

What are the main differences between prokaryotic and eukaryotic cells?

• Prokaryotes: No nucleus (DNA in an unbound nucleoid region) and no membrane-bound organelles.

• Eukaryotes: do have nucleus, DNA inside a double-membrane nucleus and contains specialized membrane-bound organelles.

What is the fundamental, simplest unit of life?

The cell. All organisms are made of cells, and all cells come from pre-existing cells.

What four basic cellular components are shared by ALL cells (prokaryotic and eukaryotic)?

• Plasma membrane = outer barrier controlling what enters and exits

• Cytosol = jelly-like fluid holding cell components

• Chromosomes (DNA) = structures made of DNA carrying genetic info

• Ribosomes =structures that make protein

Many Cells Do Rock

Or can many cells crank rock?

Why are cells so small? (Surface Area-to-Volume Ratio)

As a cell grows, its volume increases faster than its surface area. Smaller cells have a higher surface area-to-volume ratio, allowing faster exchange of nutrients, wastes, and gases across the membrane.

What is the function of the nucleus, nuclear envelope, and nucleolus?

• Nucleus: Stores most of the cell's genetic material (DNA). (the og) located within the nucleus and is the site of ribosomal RNA

• Nuclear Envelope: Double membrane with pores that control what enters and exits the nucleus. (Think of the mailing process)

• Nucleolus: Dark region inside the nucleus where ribosomal RNA (rRNA) and ribosome subunits are made.

What is the difference between free ribosomes and bound ribosomes?

• Free Ribosomes: Float in the cytosol and make proteins that function within the cytosol.

• Bound Ribosomes: Attached to the ER or nuclear envelope and make proteins for membranes, packaging, or export (secretion) out of the cell.

What are the primary functions of the Smooth ER vs. Rough ER?

• Smooth ER: Lacks ribosomes (rna & protein) ; synthesizes lipids, metabolizes carbs, detoxifies drugs/poisons, and stores calcium ions. (builds fats and cleans up toxins)

• Rough ER: Has ribosomes; produces proteins/glycoproteins and packages them into transport vesicles. (builds and packages proteins)

What is the main function of the Golgi Apparatus?

It acts as the "shipping and receiving" center—it modifies, sorts, packages, and routes proteins and lipids arriving from the ER. (its the amazon warehouse)

consists of flattened membranous sacs called cisternae

What is a lysosome, and what are phagocytosis and autophagy?

• Lysosome: A membranous sac of hydrolytic enzymes that breaks down macromolecules in an acidic environment. (The cell's garbage disposal and recycling center. It is a tiny, fluid-filled bag with strong digestive juices that break down waste, old cell parts, and invading germs)

• Phagocytosis: Digestion of foreign food particles or substances taken into the cell.

• Autophagy: The process of recycling the cell's own damaged organelles and materials.

Cytoskeleton

A network of protein fibers in the cytoplasm that organizes structures cell shape and activities in the cell (a cells skeleton made of protein, with special abilities)

• composed of three types of molecular structures

  • Microtubules → will be brought up more frequently hollow rods

  • Microfilaments→ solid rods

  • Intermediate filaments → fibers with diameters in a middle range

Microtubules

The thickest cytoskeletal fibers (~23 nm) are made of tubulin; they shape the cell, move vesicles, separate chromosomes, and form cilia/flagella. (Physical tubes made of protein inside the cell help hold up the cell…)

Microfilaments

The thinnest cytoskeleton fibers (~7 nm) made of actin; they support cell shape and aid in muscle contraction and movement.

Intermediate Filaments

Medium-sized cytoskeleton fibers (~10 nm); permanent structures that reinforce cell shape and fix organelles in place.

Plant Cell Wall

A rigid outer layer made of cellulose that protects plant cells, maintains shape, and prevents bursting from excessive water.

Extracellular Matrix (ECM)

A network of proteins (like collagen) outside animal cells that holds cells together and relays signals.

• Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM)

Integrins

Cell-surface receptor proteins that attach animal cells to the Extracellular Matrix and transmit signals.

Tight Junctions

Animal cell connections that press neighboring membranes together tightly to prevent fluid leakage.

Desmosomes

Anchoring junctions in animal cells that fasten cells together into strong sheets like rivets.

Gap Junctions

Communicating junctions in animal cells that form open channels for water, ions, and molecules to pass between cells.

Plasmodesmata

Channels through plant cell walls that connect adjacent plant cells, allowing water, nutrients, and cytosol to pass through.

Organisms are either

• Single-celled, such as most prokaryotes and protists or

• Multicelled, such as plants, animals, and most fungi

Chromatin

the loose, uncoiled form of DNA and protein that fills the cell's nucleus when the cell is performing its everyday functions

(Each chromosome contains one DNA molecule associated with proteins, called chromatin )

chromosomes

the tightly packed, X-shaped packages that DNA rolls into only when the cell is ready to divide.

Ribosomes

Protein Factories

• complexes made of ribosomal RNA and protein

cellular machines responsible for making proteins in all living cells

They take genetic instructions from DNA and link amino acids into chains, creating the essential proteins the body needs to function.

Ribosomes carry out protein synthesis in two locations:

• The cytosol (free ribosomes)

• On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

Endomembrane system

• nuclear envelope

• ER

• Golgi

• lysosomes

• vacuoles

• Plasma membrane

components are either continuous or connected via vesicles

endoplasmic reticulum

a large, network-like organelle in eukaryotic cells that acts as a major manufacturing, processing, and transportation system for proteins and lipids

Vacuoles

Large vesicles derived from the ER and Golgi apparatus are essentially large, custom-made bubble wrap pouches inside a cell used for storing and moving materials.

Food vacuoles

formed by phagocytosis hold and transport food

Central vacuoles

found in many mature plant cells, hold organic compounds and water

Mitochondria

• The sites of cellular respiration, a metabolic process that uses oxygen to generate ATP

basically tiny power plants inside your cells that turn food and oxygen into usable energy

Chloroplasts

Found in plants and algae, they are the sites of photosynthesis

Mitochondria and chloroplasts change

energy from one form to another

Mitochondria and chloroplasts similarities with bacteria

• Enveloped by a double membrane

• Contain free ribosomes and circular DNA molecules

• Grow and reproduce somewhat independently
  in cells

(Endosymbiont theory)

Most eukaryotic cells have mitochondria

which extract energy from food

What organelle do photosynthetic eukaryotes use to capture sunlight and produce food?

Chloroplast

Function: Uses sunlight to produce food (glucose/energy) for the cell via photosynthesis

Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis

ECM is made up of…

glycoproteins (proteins attached to sugar chains) such as collagen, proteoglycans, and fibronectin

Three main junctions

Tight junctions: membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

Desmosomes (anchoring junctions) fasten cells together into strong sheets

Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells