Chapter 4 Bio: A Tour of The Cell

Cell theory

• all living things are composed of cells, and all cells come from other cells

Eukaryotic cells

• have a defined nucleus and several types of membrane-bound organelles

  • suspended in gel-like cytoplasm

• also has a plasma membrane, cytoplasm, DNA, and ribosomes

• much larger than prokaryotic cells usually

prokaryotic cells

• have a plasma membrane, cytoplasm, DNA, and ribosomes

• smaller than eukaryotic

Cell Structures Are Grouped by 4 Main Functions

• Genetic Control (flow of information DNA – protein): nucleus, ribosomes

• Manufacturing, Distribution, Breakdown: endoplasmic reticulum (rough and smooth), Golgi apparatus, lysosomes, vacuoles

• Waste management

• Energy Processing: mitochondria, chloroplasts

• Structural Support, Movement, Communication: cytoskeleton, plasma membrane, extracellular matrix, cilia/flagella, cell junctions, cell wall

Chromatin

• combination of DNA and histone proteins that it wraps tightly around

nucleus

• contains DNA (instructions to make proteins)

nucleolus

• site of ribosome synthesis

Rough Endoplasmic Reticulum (ER)

• coated with ribosomes

• site for protein creation, folding, and packaging

Smooth Endoplasmic Reticulum (ER)

• Site for lipid creation (including phospholipids)

• Storage and release of calcium ions

• Drug detoxification: how does smooth ER play a role in “tolerance”?

  • An increase in production by Smooth ER the more you intake

  • Get tolerance because the amount of Smooth ER keeps increasing but the more intake causes more damage with all of this breakdown

Ribosomes

• help make proteins

• Large and small subunits

  • Free ribosomes: cytosol

  • Bound ribosomes: rough ER

Golgi Aparatus

• receives proteins (packaged in vesicles) from Rough ER ribosomes

• proteins are modified, including signals that determine where the protein goes (within the cell or outside cell)

vesicles

• lipid bilayer protecting proteins traveling to Golgi apparatus

cell membrane

• separates the inside of the cell from the outside

• Composed of a phospholipid bilayer

• (hydrophobic inner tails, hydrophilic outer head)

• Selectively permeable, meaning only certain materials can enter or leave

lysosomes

• contain digestive enzymes that aid in the breakdown and recycling of old organelles

• Why is this adaptive?

  • There may be items present that can be reused or redistributed

• also involved in Apoptosis: “programmed cell death” for cells damaged beyond repair

  • immune response: destroy viruses and bacteria

mitochondria

• produce ATP, the major energy transferring molecule used for cellular activities

• Powerhouse of the cell

chloroplasts

• specific to organisms that photosynthesize

• Convert solar energy to chemical energy

Endosymbiont Theory

• Mitochondria and chloroplasts were once free-living prokaryotic organisms that were either “eaten” by, or infected, a larger nucleated cell, and over time a mutually beneficial interaction developed

• Same size as prokaryotes

• Have their own DNA, ribosomes & protein synthesis

• Replicate the same way

Mitochondrial DNA Forensic Application

• Mitochondrial DNA is maternally inherited

Cytoskeleton

• protein-based filaments that maintain cell shape and provide paths for movement and transport

• 3 major components:

  • Microfilaments: thinnest; muscle movement

  • Intermediate filaments: anchor organelles

  • Microtubules: thickest -rigidity; tracks for movement

Cilia

• propulsion (single celled organisms); sweep mucus out of lungs

flagella

• propulsion (single celled organisms, sperm)

Extracellular Matrix (ECM)

• Hold tissue cells together

• Protect and support the plasma membrane

Collagen

• strong network outside cell

• Accounts for 40% of your protein!

tight junctions

• animal cells

• prevent fluid leakage

Anchoring junctions/Desmosomes

• animal cells

• fasten cells together in strong sheets

gap junctions

• animal cells

• allow the flow of molecules for communication

cell wall

• protection and support that keeps plants upright