Lecture 1

In 1839 the idea of ==Cell Theory ==was created;

1. All living organisms are composed of one or more cells
2. The cell is the most basic unit of life
3. All cells arise from pre-existing cells \n

How can we study these cells? - this will be further discussed is Lecture 4

• Microscopy Techniques
• Biochemistry tools
• Genetic tools
• Cell culture
• “Model” organisms 

Model Organisms Includes

Yeast, Alga, Roundworm, Fruit Fly, Planarian, Zebrafish, Mouse, and Plants

• These organisms have an evolutionary conservation of genes, proteins, organelles, cell types etc.
• Discoveries found from one model organism often applies to other organisms

Organism -> Organs -> Tissue -> Cells -> Organelles -> Molecules \n

Diversity in cell types arise due to differences in generic programs, context, and environment.

^^VIRUSES ARE NOT CELLS^^ because they are not self sufficient and needs a QR code to survive

Virus membranes (when they have membranes) are stolen from cells

Can infect cells and cause cell death / mis-regulation

Viruses are made of capsid proteins surrounding nucleic acids

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Cells are SMALL, atoms < macromolecules<cells (bacterium) < cells (frog egg)

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Cells are organized and packed. They are very ordered and intentional.

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==6 main functions of a cell :==

• Obtain Food/Energy - Finding it, Taking it in, converting it into something usable

• Adjust and adapt to the Environment - Keep bad things out and good things in. Getting enough oxygen. Response to pH changes. Preventing dehydration

• Reproduction: Requires a lot more energy, getting the correct content into the daughter cells

• Fulfill specializes functions: neurons send/receive signal. “Knowing” what to do

• Communication: within the cells and with other cells. Coordination between cells

• Maintenance/Repair: of various parts of the cells. Remove trash.

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The functions of a cell is encoded in its genes, and carries out by different macromolecules especially proteins 

Cells are broadly classified into two types of cells: Prokaryotes and Eukaryotes

Prokaryotes

• Unicellular (think bacteria and archae)

  • Archae live in EXTREME environments
  • Thermophiles - cannot grow below 90C
  • Halophiles require high salt concentration
  • Evolutionarily closer to eukaryotes than bacteria

• Very small 1-2um

• No nucleus of membrane bound organelles

• Prokaryotes have: 

  • Circular DNA
  • Plasma membrane
  • Ribosomes
  • Cytoplasm
  • Cell Wall

• Can be of different shapes and sizes

• Reproduce by fission

• Some can carry out photosynthesis, through nitrogen fixation

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Eukaryotic cells

• Organisms that have cells that contain a well-defines nucleus and membrane bound organelles

• Protists, Fungi, PLants and Animals

• Can be unicellular (yeast) or multicellular

• About 10-100 um diameter (10-100x bigger than prokaryotic cells)

• Wide variety of shapes

• Some can undergo sexual reproduction

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Organelles to know and to be discussed later

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Cell membrane 

• Forms the boundary of the cell
• Holds things together and separates the inside of the cell from outside
• Has two layers (phospholipid bilayer)
• Composed of lipids, proteins, and carbohydrates
• Selectively allows molecules in and out of the cell

Nucleus

• Chromatin- Generic material + associated proteins (histones)
• Nucleolus - site of ribosomal RNA synthesis and assembly of ribosome components
• Nucleoplasm - non nucleolar regions of nucleus
• Nuclear matrix - composed of intermediate filaments called lamin and associated proteins - provides structural support
• Bound by two membranes - the inner and outer membrane
  • The outer membrane is connected to the endoplasmic reticulum
• Nuclear pore complex - through which materials move into and out of the nucleus

Endomembrane System 

• Series of interconnected, closed, membrane-bound vesicles

• Includes: nuclear envelope, ER, Golgi, Lysosome, Vacuoles, Vesicles, Endosomes, Plasms Membrane

• Works together to modify, package, and transport lipids and proteins

• Important in trafficking cellular content from one location to another

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Endoplasmic Reticulum

• A network of membranous tubules within the cytoplasm of a eukaryotic cell

• Continus with the nuclear membrance

• Acts as an intracellular transporting system or canal 

• Endoplasmic Recticulum has two types

  • Rough ER- studded with membrane bound ribosomes
  • Smooth ER - lacks ribosomes. Makes phospholipids and fatty acids

• Important in protein folding and quality control

• Held in place by cytoskeleton

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Golgi Complex

• Membrance bound organnele 

• Made up of a series of flattened, stacked pouches called cisternae 

• Responsible for modifying, sorting, and packaging proteins and lipids into vesicles for delivery to targeted destinations

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Lysosomes

• Membrance bound vesicles found exclusively in animal cells

• Contrains a group of enzymes (hydrolases) that degrade polymers into their monomeric subunits 

• The lumen of lysosomes have an acidic pH of 5

• The lysosomal hydrolases work most efficiently at acidic pH levels

  • Acidic pH also help to denature proteins, making them accessible to the action of the lysosomal hydrolases

• Lysosomes form closed compartments in which the composition of the lumen differs substantially from that of the surrounding cytosole

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Mitochondria

• Site of aerobic respiration ATP production

• Eukaryotic cells contain many mitochondria, up to 25% cytoplasmic volume

• Has two membranes that differ in composition and function

  • Outer - large pores allow molecules to move from the cytosol to the intermembrance space
  • Inner - many cristae infoldings into the central aqueous matrix compartment increase the membrane surface area

• Enzymes in the matrix and on cristae convert glucose to CO2 and H20 releasing ATP

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Cytosol/Cytoplasm

• 20-30% of cellular proteins are in the cytosol

• Also contains fat and carbohydrates

• Lot of interaction between these macromolecules happen in the cytosol

• Site of cellular metabolism, has ribosomes and proteasomes

• Contain a network of cytoskeletal proteins that are important for the structural integrity of cells anda cts as highways to move components 

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Cytoskeleton 

• Highway between the cells
• Three types:
  • Micrptubules
  • Microfilaments
  • Intermediate Filaments
• Functions to provide strength and rigidity, maintain cell shape, cell motility, intercallular motility of organelles and chromosomes during mitosis
• Cilia and flagella contain a bundle of microtubules
  • Enable sperm to swim, push egg through oviduct etc. 

Humans have more bacteria than actually human cells but the bacteria only makes up about 1-3% of body mas

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