Begin, euk, pro

Origin and Early Life

• Earth is approximately 4.6 billion years old.

• Early Earth had conditions conducive to the creation of life.

• Evidence of life dates back to 3.5 billion years ago (organisms found in rocks in Australia).

• Early atmosphere primarily composed of ammonia and methane with little oxygen.

• No ozone layer.

• Theory: Atmospheric events (volcanic eruptions, storms, lightning) led to the merging of specific atoms and molecules to create life.

Molecular Basis of Life

• Key atoms for life: carbon, hydrogen, nitrogen, and oxygen.

• Combining these elements led to the creation of larger molecules: purines, pyrimidines, sugars, and amino acids.

• These molecules form the building blocks of DNA, RNA, and proteins.

• Examples of molecules found in cells: proteins (polymers of amino acids), DNA, and RNA (polynucleotides).

• The combination of these molecules creates the cell.

• Compartmentalization within cells is key for proper function.

Cell Compartments and Plasma Membrane

• Plasma membrane: Found in both eukaryotic and prokaryotic cells.

• Surrounds the cell and maintains homeostasis.

• Homeostasis: Maintaining equilibrium of chemicals and substances moving in and out of the cell.

• Selectively permeable: Controls what enters and exits the cell.

• Involved in cell communication with the environment.

• Promotes adhesion between cells.

Cell Theory

• All cells are fundamental units of life.

• Organisms are composed of cells.

• All cells come from preexisting cells.

• Historical contributions from Schleiden, Schwann, and others.

• Schleiden: All plants are made of cells.

• Schwann: Cause of nutrition and growth resides in cells.

Early Cell Observation

• Robert Hooke (1665): Described cells using a rudimentary microscope.

• Observed thin slices of cork.

• Coined the term "cellular" (cells) based on the resemblance to monks' living quarters.

• Anton van Leeuwenhoek (1674): Described algae (Spirogyra) and identified their basic cellular structure.

Microscopy

• Microscopes are essential for viewing cells.

• Human eyes can typically see objects no smaller than 0.2 mm (200 micrometers).

• Microscopes enhance the ability to discriminate objects.

• Resolution: The ability to make closely situated objects visible.

Light Microscopes

• Use light to visualize objects.

• Allow you to see cells, plasma membrane, nucleus, and some organelles.

Electron Microscopes

• Provide more detailed views of cell ultrastructure.

• Allow you to see structures like the plasma membrane and mitochondria in greater detail.

Fluorescence Microscopy

• Uses specific stains that bind to cell structures.

• Stains are excited by specific wavelengths, emitting light.

• Different stains emit different colors, enhancing visualization of specific cell compartments.

Cell Size and Shape

• Cell shape is related to its function.

• The surface area to volume ratio is crucial for cell function.

• Surface Area = 4[pi]r^2

• Volume = [frac{4}{3}] [pi] r^3

• The ratio affects exchange efficiency.

• Larger cells have smaller surface area to volume ratios.

• Cells adapt their shape to facilitate required exchanges.

• Examples: Neurons, epithelial cells, red blood cells.

Cell Types

• Three main types: Bacteria, Archaea, and Eukarya.

• Bacteria (prokaryotic cells): Unicellular.

• Archaea: Intermediate between prokaryotic and eukaryotic cells.

• Eukarya (eukaryotic cells): More complex and compose more complex organisms.

Prokaryotic Cells

• Lack a nucleus.

• Do not have membrane-bound compartments or specific organelles.

Eukaryotic Cells

• Have a nucleus surrounded by a plasma membrane.

• Contain organelles.

Prokaryotic Cell Structure

• Plasma membrane.

• Nucleoid region (not a nucleus).

• Ribosomes.

• Cytoplasm.

• Size: Typically 0.2 to 2.0 micrometers.

• Cell wall: Composed of peptidoglycan, providing defense.

• Cell wall composition is used to discriminate different bacteria.

• Gram staining (pinkish or purplish) reacts with components in the cell wall to differentiate bacteria.

• Antibiotics target and disrupt the cell wall.

• Mycoplasma: Bacteria without a cell wall; antibiotics may not work.

Specialized Prokaryotic Cells

• Cyanobacteria: Contain organelles for photosynthesis.

• Flagella: Locomotory structures enabling movement.

• Pili: Involved in transferring genetic information and promoting adhesion.

Bacterial Shapes and Classification

• Rod-shaped: Bacillus.

• Spherical: Cocci.

• Spiral-shaped: Spirilla.

• Replication: Binary fission.

Inclusions in Prokaryotic Cells

• Deposits within the cytoplasm for storing lipids, starch, or glycogen.

Endospores

• Dormant structures that allow bacteria to survive extreme conditions.

• Enable bacteria to come back to life when conditions becomes favorable.

Prokaryotic Cell Habitats

• Found in various environments including hot, cold, acidic, alkaline, and salty conditions.

• Estimated 3 x 10^{28} bacteria in the ocean.

• Found on skin, saliva, and ocean sediments.

Prokaryotic vs. Eukaryotic Cells: Key Similarities

• Both have DNA, plasma membrane, and ribosomes.

• Exhibit similar metabolic functions.

• Vary in shape.

Prokaryotic vs. Eukaryotic Cells: Key Differences

• Eukaryotic cells have a nucleus and membrane-bound organelles, while prokaryotic cells do not.

• DNA in prokaryotic cells is located in the cytoplasm.

• Eukaryotic cell organelles are specialized for different functions.

Eukaryotic Cells

• Found in animals, plants, fungi, and protists.

• Larger than prokaryotic cells (approximately 10 times bigger).

• Have a plasma membrane, cytoplasm, and ribosomes.

• Possess a nucleus surrounded by a membrane.

• Contain organelles not found in prokaryotic cells.

• Have a cytoskeleton for structural support.

• Compartmentalization is essential for function.

Organelles in Eukaryotic Cells

• Each organelle has a specific role or function defined by chemical processes.

• Membranes protect the organelles.

• Examples: Nucleus, endoplasmic reticulum (rough and smooth), mitochondria, cytoskeleton, Golgi apparatus, lysosomes, peroxisomes, centrioles, and ribosomes.

Animal Cell Structure

• Figure include a nucleus, rough endoplasmic reticulum, mitochondria, cytoskeleton, Golgi apparatus, smooth endoplasmic reticulum, plasma membrane, peroxisome, centrioles, and ribosomes.

Electron Microscopy of Animal Cell

• Clearer estimation of organelles like nucleus, nucleolus, mitochondria, cytoskeleton, and rough endoplasmic reticulum.

Plant Cell Structure

• Similar structures to animal cells, but with additional organelles specific to plants.

• Also Include rough and smooth endoplasmic reticulum, plasma membrane, mitochondria, Golgi apparatus, nucleus, and ribosomes.

• Cell wall: Provides rigidity.

• Chloroplasts: Contain components for photosynthesis.

• Vacuoles: Large water tanks maintaining cell rigidity.

Nucleus in Detail

• Largest organelle in eukaryotic cells.

• Contains DNA (genetic material).

• Surrounded by a plasma membrane for protection.

• DNA replication occurs within the nucleus.

• Essential for decoding DNA information to produce proteins.

Nuclear Structure

• Double membrane with nuclear pores.

• Nuclear pores: Composed of subunits and involved in RNA and DNA exchange between the nucleus and cytoplasm.

Rough Endoplasmic Reticulum (RER)

• Approximately 10% of the cell's internal volume.

• Covered in ribosomes.

• Ribosomes synthesize proteins.

• Close proximity to the nucleus to receive RNA.

• Chemical modifications of proteins occur within the RER.

Smooth Endoplasmic Reticulum (SER)

• More tubular than RER.

• Lacks ribosomes.

• Involved in chemical modification of molecules and transport of drugs.

• Hydrolyzes glycogen into glucose.

• Synthesizes lipids and steroids (essential for the plasma membrane).

Ribosomes in Detail

• Site of protein synthesis.

• Found freely in the cytoplasm and on the rough endoplasmic reticulum.

• Bacterial ribosomes differ from eukaryotic ribosomes.

• Antibiotics can target bacterial ribosomes to inhibit protein synthesis.

Golgi Apparatus

• Composed of flattened membrane sacs called cisternae.

• Acts like a post office: receives, modifies, and sends proteins.

• Close to the rough endoplasmic reticulum.

Golgi Apparatus: Processing Protein

• Proteins move through the Golgi apparatus, receiving stamps for delivery.

• Cis face: Receives proteins from the rough endoplasmic reticulum.

• Trans face: Secretory site where proteins are enveloped into vesicles.

• Vesicles transport proteins to their destinations.

Golgi Apparatus Mode of Operation

• Rough endoplasmic reticulum passes down proteins encapsulated in vesicles.

• Vesicles merge with the cis region of the Golgi apparatus.

• Content is released, and stamps are added to proteins.

• Proteins move into the Golgi apparatus.

• A vesicle is generated to transport the proteins and releases content.

Golgi Apparatus and Lysosomes

• Not integrated but they merge and are recycled.

Lysosomes: Functionality and Description

• Vesicles containing digestive enzymes.

• Break down food and foreign materials.

Lysosome Production

• Golgi apparatus creates primary lysosomes containing digestive enzymes.

• Phagocytosis: Process of engulfing food particles by the cell.

• The plasma membrane creates a vesicle around food particles.

• Lysosomes merge with these vesicles, releasing enzymes to digest the contents.

Mitochondria

• Powerhouse of the eukaryotic cell.

• Produces energy in the form of ATP.

• Has its own DNA.

• Structures: Outer membrane, inner membrane, cristae, and matrix.

• Citric acid cycle and oxidative phosphorylation occur within the mitochondria.

• An ancient bacteria modified in order to became a mitochondria.

Plastids

• Found in plants and protists.

• Chloroplasts: Essential for photosynthesis.

• Structures: Outer membrane, intermembrane, inner membrane.

• Inner membrane surrounds the stroma.

• Thylakoids: Structures composed for photosynthesis.

Vacuoles in Plant Cells

• Have several functions: storage, structural support, reproduction, and digestion of molecules.

Summary of Eukaryotic and Prokaryotic Cells

• Summary of everything from what has been discussed.

• The whole message is the similarities and the differences between both prokaryotic and eukaryotic cells. The key difference that has to be remembered is the fact that eukaryotic cells have the nucleus, which is surrounded by the membrane, and organelles that are surrounded by membranes.