Introduction to Cells: BIO 101

Introduction to Cells

• Cells will be studied from BIO 101 lectures 4 and 5.
• Supplementary reading is recommended for more detailed explanations.
• The link is https://rwu.pressbooks.pub/bio103/chapter/introduction-to-cells/

Cell Overview

• Although nasal sinus cells, onion cells, and Vibrio tasmaniensis bacterial cells are from vastly different organisms, they share certain characteristics of basic cell structure.
• A cell represents the smallest unit of a living thing, capable of independently performing all life processes.

Microscopy

• Light microscopes and electron microscopes are used for visualizing cells.
• Salmonella enteritidis bacteria can be viewed using light, transmission electron, and scanning electron microscopes.

History of Cells

• In 1665, Robert Hooke discovered cells while observing cork cells.

The Cell Theory

• All living things consist of one or more cells.
• The cell constitutes the basic unit of life in all organisms.
• All cells originate from pre-existing cells.

Classifications of Cells

• Eukaryotic Cells include Plants, Animals, Fungi, & Protists/Protoctists
• Prokaryotic Cells include Bacteria and Archaea.

Similarities Between Cells

• Every cell has a cell/plasma membrane -- an outer boundary separating the interior from the environment.
• Every cell has cytoplasm -- jelly-like cytosol with cellular components.
• Every cell has hereditary material (DNA).
• Every cell has ribosomes.
• Ribosomes synthesize proteins inside a cell.

Prokaryotic Cells

• Consist of bacteria.
• Lack a nucleus.
• Have long, circular DNA.
• Do not have membrane-bound organelles.
• Contain ribosomes for making proteins.
• Most possess a peptidoglycan cell wall.
• They are rod-shaped, spherical, or spiral.
• Prokaryotes typically reproduce asexually.
• Binary fission happens when an organism duplicates its DNA and divides into two, each getting one copy of DNA.
• Conjugation is the exchange of DNA between bacteria (not asexual).
• Prokaryotes can be classified as eubacteria or archaea.
• Eubacteria are commonly found.
• Archaea are live in extreme environments, such as hot springs, salt lakes, and submarine volcanic habitats.
• Halophiles, methanogens, and thermoacidophiles are specific for archaea

Applications of Prokaryotic Cells

• Bioremediation uses prokaryotes added to water to convert toxic pollutants into harmless substances.
• Food production relies on Butter, Cheese, Yogurt, Sauerkraut, Beer, Pickles, Olives, Chocolate, Coffee, Soy sauce, meats, etc.
• Importance for decomposition.
• Aids in digestion.
• Helps in nitrogen fixation for plants.
• Prokaryotes can cause food spoilage and disease in plants/animals and produces toxins.

Eukaryotic Cells

• Are more complex and larger than prokaryotes.
• Have membrane-bound organelles.
• Possess a nucleus.
• Contain more DNA than prokaryotes.
• Have linear DNA.
• Examples: animals, plants, and fungus. Movement in unicellular eukaryotes involves several mechanisms.
• Flagella are tail-like projections.
• Pseudopods are referred to false-feet.
• Cilia are finger-like projections (some non-motile).
• Eukaryotic cells have a plasma membrane, cytoplasm, and organelles.
• Organelles: nucleus, ribosomes, mitochondria, peroxisomes, vacuoles, and vesicles.

Organic Molecules

• Key organic molecules are carbohydrates, nucleic acids, proteins, and lipids.

Proteins

• Represent very diverse and complex macromolecules.
• Play roles in structure, function, and information.
• Proteins consist of linearly arranged amino acid residues.
• Primary Protein Structure is the amino acid sequence
• Secondary Protein Structure is the helix
• Tertiary Structure is polypeptide chains
• Quaternary Structure is aggregation of two or more polypeptides

Protein Types and Function

• Enzymes catalyze covalent bond breakage or formation, such as amylase.
• Structural proteins include collagen, elastin, and keratin.
• Motility proteins are actin, myosin, and tubulin.
• Regulatory proteins bind to DNA to switch genes on or off.
• Storage proteins include ovalbumin and casein.
• Hormonal proteins are insulin and nerve growth factor (NGF).
• Receptors are hormone and neurotransmitter receptors.
• Transport proteins carry small molecules or irons.
• Special purpose proteins are green fluorescent protein.
• Proteins sources include both Plants such as Soya Beans, Lentils etc and animal products such as eggs.

Lipids

• Are hydrophobic molecules used for: energy storage, membrane components, and signaling.
• Types: triglycerides (fat), phospholipids, waxes, and sterols.

Types of lipids

• The main lipids are Triglycerides, Phospholipids, Steroids and Waxes
• Lipids can both Saturated and Unsaturated

Carbohydrates

• Includes sugars, storage (glycogen, starch), and structural polymers (cellulose and chitin).
• Major substrates of energy metabolism.

Nucleic Acids

• DNA (deoxyribonucleic acid) encodes genetic information.
• RNA encodes genetic information for protein synthesis.
• They are building blocks of life.

Eukaryotic Cell - Plasma Membrane

• Components: Phospholipids, Cholesterol, Integral protein, Glycolipid, Peripheral protein, and Glycoprotein
• Characterized by hydrophobic/hydrophilic components and a fluid-like phospholipid bilayer.
• Allows selective isolation of cell contents.
• It regulates substance exchange with (organic molecules, ions, water, oxygen, CO2 etc) and communicates.

Eukaryotic Cells - Cytoplasm

• Consists of the space between the plasma membrane and the nuclear envelope.
• Made of organelles suspended in gel-like cytosol, cytoskeleton, and various chemicals.
• The cytoplasm is about 70% to 80% water.
• The sits for metabolic reactions

Eukaryotic Cells - Nucleus

• Properties: Nuclear membrane, chromosomes, nucleolus, and ribosomes.
• Functions: Houses DNA and directs ribosomes.
• Mitochondria are oval-shaped, double-membrane organelles, and contain their own ribosomes and DNA. These are responsible for making ATP
• Peroxisomes are small, spherical organelles enclosed by single membranes.

Lysosomoes

• Are small, spherical compartments that function as the digestive and organelle-recycling facility of animal cells.
• Hydrolytic enzymes with an pH of 4.5 break down non-functioning organelles and pathogens,

Vacuoles and Vesicles

• Are membrane-bound sacs that function in storage and transport.
• Vacuoles store food and may expel water

Endoplasmic Reticulum

• Are a series of interconnected membranous sacs for protein (RER) and lipid(SER) synthesis.
• The Golgi Apparatus proteins and lipids bud to be packaged/ sent like "the poster office " of the cell

Plant vs Animal Cells

• Plant cells have a cell wall (cellulose), chloroplasts, and a large central vacuole.
• The cell wall in plant cells is external to the plasma membrane and the rigid covering that protects the structure and gives shape

Chloroplasts

• Plant cells organelles that carry out Photosynthesis to makes glucose and oxygen

Lysosomes

• Animal cells (not plants) have lysomomes for garbage/ recycle disposal