Who first used the term cell and what was he looking at?
Robert Hooke used this term when looking at cork under the microscope
What are the 3 points in the cell theory
- All living things are made up of one or more cells and their products
- The cell is the simplest unit that can carry out all life processes
- All cells come from pre-existing cells
Who are the scientists who developed the cell theory
Schleiden, Virchow, and Schwann
What are the defining characteristics of Eukaryotic cells
- contains a nucleus and other membrane-bound organelles
- have a cell membrane made up of a phospholipid bilayer
- may have a cell wall (plants and fungi)
- DNA is packaged as chromosomes
What is an organelle
a specialized structure within the cell… “little organs”
Cell membrane (structure & function)
Structure: a flexible matrix of phospholipids and protein
Functions:
*PROVIDES A BARRIER b/w the cell and its environment
* SELECTIVELY allows molecules in/out of the cell, thus maintaining HOMEOSTASIS
* ALLOWS COMMUNICATION b/w the cell and its environment and/or other cells
* ATTACHES CELLS to one another, forming tissues
What does the NUCLEUS do
contains and protects DNA, which controls all cell activities
What is the NUCLEAR ENVELOPE
- controls access to the nucleus
- outer connects to the ER
- provides protection
- contains nuclear pores & proteins that allow for communication
What is the NUCLEOPLASM
fluid within the nucleus
What is the NUCLEOLUS
- dense region of RNA, protein, and chromatin where ribosomes are produced
- seen as dark spheres.
Chromosomes vs Chromatin
Chromosomes: a complex of DNA and proteins for organization
Chromatin: single strands of DNA “used for protein making”
What is the ENDOPLASMIC RETICULUM
- 3D network of branching tubes and channels that transport materials throughout the cell
- extends throughout the cytoplasm and is continuous with the nuclear membrane and the cell membrane
- provides a huge surface area for chemical reactions to take place
- helps to subdivide the cytoplasm
- can be “smooth” or “rough”
What is the ROUGH ENDOPLASMIC RETICULUM
- is studded with ribosomes
- responsible for the transport of proteins
- ribosomes make proteins —> proteins enter the interior of the RER —> proteins fold —> pinch off in vesicles that travel to Golgi
What is the SMOOTH ENDOPLASMIC RETICULUM
- contains enzymes that make phospholipids, break down carbs, fatty acids, drugs, and poisons
- storage site for calcium
- special jobs depending on the cell type (in liver - detoxifies drugs/alcohol & in testes/ovaries - produce testosterone/estrogen)
What is the GOLGI APPARATUS
- complex of closely stacked membranous sacs
- receives products from RER and SER
- modifies proteins, clips off portions, adds fats or sugars
- proteins (now functional) collect in the vesicles that pinch off the end of the complex, still kept separate from the cytoplasm (protection)
- vesicles may stay in the cytoplasm (storage) or go to the cell membrane to be secreted
- manufactures lysosomes
What are the RIBOSOMES
- responsible for making cell proteins
- 2 subunits of rRNA and protein connect to form a sphere
- lack of membrane (meaning it is found in prokaryotes & eukaryotes)
- Ribosomes attached to the RER are responsible for making proteins that will become part of the cell membrane or are exported from the cell
- “free ribosomes” - those that are floating in the cytosol or attached to the cytoskeleton - are responsible for making proteins that will function within the cytosol
What does the ENDOMEMBRANE SYSTEM include
includes the RER, SER, Golgi, Vacuoles, Vesicles, Nuclear Membrane, Lysosomes, and Cell Membrane
–> all made up of the same “outer covering” (phospholipids), allowing easy exchange of materials b/w them
What are LYSOSOMES
- made by the Golgi complex
- contains enzymes that DIGEST nutrients, DESTROY harmful chemicals or foreign particles, and DEGRADE worn-out organelles
- “clean up crew” of the cell - when the cell is worn out or no longer needed, the lysosomes empty themselves into the cytoplasm, and the cell digests itself
LYSOSOMAL ENZYMES (how? why? what?)
- work best at pH 5
- organelle creates custom pH
HOW? Proteins in the lysosomal membrane pump H+ ions from the cytosol into lysosomes
WHY? Enzymes are sensitive to pH, and since enzymes are proteins, the pH affects the structure
Why evolve digestive enzymes that function at a pH different from the cytosol?
digestive enzymes won’t function well if some leak into the cytosol = don’t want to digest yourself
What happens when cells need to die
- Some cells have to die for proper development in an organism
- APOPTOSIS = programmed cell death, lysosomes break open & kill the cell
ex: tadpole tail gets reabsorbed when it turns into a frog
ex: loss of webbing b/w your fingers during fetal development
What are lysosomal disorders
- are often fatal
- digestive enzyme not working in lysosomes
- picks up biomolecules, but can’t digest
- fill up with/ undigested material
- grow larger until it disrupts cell and
organ function
Tay-Sachs Disease is a lysosomal disorder. Give a short description of the disorder
- genetic disorder (autosomal recessive) that results in a bad copy of an enzyme that breaks down a certain fat
- results in a buildup undigested fat in neurons of the brain and spinal cord, destroying then and causing symptoms
- muscles weaken, infants lose motoe skills, vision and hearing loss, usually die in early childhood
What are PEROXISOMES
- membrane enclosed sacs containing oxidative enzymes
- their enzymes are made by free ribosomes
- breakdown of fatty acids and amino acids
- a by-product of these reactions is H2O2 (which is toxic to the cell) therefore contain CATALASE
- in liver: breakdown alcohol and poisons and helps synthesize cholesterol and bile acids
