Introduction to Cell Biology

Introduction to Cells

• A cell is the smallest unit of a living thing that can carry on all life processes.
• Different organisms have different types of cells, yet all share certain characteristics of basic cell structure.

Microscopy for Visualizing Cells

• Light microscopes and electron microscopes are used for visualizing cells
• Salmonella enteritidis bacteria can be viewed with a light microscope, transmission electron microscope, and scanning electron microscope with different degrees of focus and zoom
• Light microscope, transmission electron microscope and scanning electron microscope can be used to view bacteria

History of Cells

• Cork cells were the first cells seen in 1665 by Robert Hooke

Cell Theory

• All living things are composed of one or more cells.
• The cell is the basic unit of life in all living things.
• All cells come from existing cells.

Classification of Cells

• Eukaryotic cells are found in plants, animals, fungi, and protists/protoctists
• Prokaryotic cells are found in bacteria and archaea.

Similarities of All Cells

• All cells contain a cell/plasma membrane, which is an outer covering that separates the cell's interior from its surrounding environment.
• All cells contain cytoplasm, consisting of a jelly-like cytosol within the cell in which other cellular components are found.
• All cells contain hereditary material (DNA), which is genetic material of the cell.
• All cells contain ribosomes that synthesize protein

Cell Sizes

• Cells can be studied using electron microscopes or light microscopes
• Some cells can be seen with the naked eye

Prokaryotic Cells

• These include bacteria
• They do NOT have a nucleus
• They have long circular DNA
• They have no membrane-bound organelles
• They contain ribosomes which make proteins
• Most prokaryotes have a peptidoglycan cell wall
• These are rod-shaped, spherical, and spiral

Reproduction in Prokaryotic Cells

• Usually, reproduction is asexual
• Binary Fission: an organism duplicates its DNA and then divides into two parts, with each new organism receiving one copy of DNA.
• Conjugation involves the exchange of DNA between bacteria, which is not asexual

Classification of Prokaryotic cells

• Prokaryotes are classified as either eubacteria and archaea
• Eubacteria are commonly found
• Archaea live in extreme environments such as hot springs, salt lakes, and submarine volcanic habitats
• Archaea are either Halophiles, methanogens or thermoacidophiles

Prokaryotic Cells: The Good Ones

• Through Bioremediation, organisms are added to water to convert toxic pollutants, such as oil, into harmless substances.
• Prokaryotes are used in the production of butter, cheese, yogurt, sauerkraut, beer, pickles, olives, chocolate, coffee, soy sauce, and meats
• Decompose dead organisms
• Help in digestion
• Help fix nitrogen for plants

Prokaryotic cells: The Bad Ones

• Can cause food spoilage
• Can cause disease in plants and animals
• Can produce toxins

Eukaryotic Cells

• More complex and larger than prokaryotes
• These have membrane bound organelles and a Nucleus
• Eukaryotic cells have more DNA than prokaryotes
• The DNA is linear
• Animal, plant, fungi, are examples of Eukaryotic cells

Movement

• Movement for Unicellular Eukaryotes (like the Protist) is accomplished through flagella, pseudopods and Cilia

Structure

• The Plasma Membrane
• The Cytoplasm
• Organelles
• The Nucleus
• Ribosomes
• Mitochondria
• Peroxisomes
• Vacuoles and Vesicles

Organic Molecules of the Cell

• Carbohydrates are used in granules in chloroplasts
• Nucleic acids form chromosomes
• Proteins create polypeptide structures
• Lipids create adipose cells

Protein Structure

• Proteins are the most diverse and complex macromolecules in the cell
• They are used for structure, function and information
• They are made of linearly arranged amino acid residues that are "folded" up with "active" region

Types and Function of Proteins

• Enzymes catalyze covalent bond breakage or formation; amylase
• Structural function includes collagen, elastin, and keratin
• Motility includes actin, myosin, and tubulin
• Regulatory function includes when it binds to DNA to switch genes on or off
• Storage includes ovalbumin, casein, etc.
• Hormonal function includes insulin, Nerve Growth Factor (NGF)
• Receptors - hormone and neuotransmitter receptors
• Transport - carries molecules or irons
• Special purpose - green fluorescent protein.

Lipids

• Lipids are hydrophobic molecules
• They are used for energy storage, membrane components and signal molecules
• Lipids are made up of triglycerides (fat), phospholipids, waxes, and sterols

Lipid Structures

• Triglycerides
• Phospholipids
• Steroids and Waxes

Carbohydrates

• Sugars, storage (glycogen, starch),
• Composed of structural polymers (cellulose and chitin)
• Major substrates of energy metabolism

Carbohydrates and Glycolysis

• Breakdown of carbohydrates

Nucleic Acids

• DNA (deoxyribonucleic acid) encodes genetic information
• RNA encodes genetic information for the synthesis of all proteins
• These are building blocks of life

Structure of Eukaryotic cells: Plasma Membrane

• Components include phospholipid, Glycolipid, Peripheral protein, Glycoprotein, Cholesterol, and Integral protein

Plasma Membrane - Properties

• Made of hydrophobic and hydrophilic components
• It is semi-permeable, which allows some materials to pass while excluding others
• Fluid-like phospholipid bilayer
• Functions by selectively isolating the content of the cell of the external atmosphere, enclosing cell and cell organelles
• Regulates the exchange of substances between the cytoplasm and the external environment
• Communicates with other cells

Eukaryotic: Cytoplasm

• The cytoplasm is the entire region of a cell between the plasma membrane and the nuclear envelope
• It is made up of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals
• The cytoplasm consists of 70 to 80 percent water
• Site for metabolic reactions

Organelles of an animal and plant cell

• Structures of the cell

Eukaryotic Cells: Nucleus

• Properties include the Nuclear membrane, Chromosomes, the Nucleolus and Ribosomes
• Functions by housing the cell's DNA and directs the synthesis of ribosomes and proteins

Mitochondrion properties and functions

• Are oval-shaped and of double membrane
• Have their own ribosomes and DNA
• The inner membrane has folds called cristae that increase surface area
• Responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule, this function makes them cell 'powerhouses'

Eukaryotic Cells: Peroxisomes

• Peroxisomes are small, spherical organelles enclosed by single membranes
• Many of these oxidation reactions release hydrogen peroxide, H2O2; enzymes safely break down the H2O2 into oxygen and water
• They carry out oxidation reactions that break down fatty acids and amino acids
• They also detoxify many poisons that may enter the body; Alcohol

Eukaryotic Cells: Lysosomes

• Lysosomes are small, spherical compartments that function as the digestive and organelle-recycling facility of animal cells.
• The enzymes in lysosomes are called acid hydrolases because they catalyze hydrolysis reaction and their optimal pH is around 4.5.
• They contain hydrolytic enzymes that digest non-functioning organelles, macromolecules, and pathogens (disease-causing organisms).

Lysosomes and Peroxisomes - Importance

• Lysosomes, the cell's recycling centers, use acid hydrolases to break down waste into reusable parts.
• Peroxisomes protect cells by isolating and breaking down harmful hydrogen peroxide into water and oxygen.
• These organelles ensure efficient and safe cellular function.

Eukaryotic Cells: Vesicles and Vacuoles

• The term "vacuole" means "empty space".
• Vesicles and vacuoles are membrane-bound sacs that function in storage and transport.
• Vacuoles are larger than vesicles
• They can store food or other nutrients required by a cell to survive
• They also store waste products and prevent the entire cell from contamination
• Contractile vacuoles contract to expel water from the cell
• Vacuoles in plant cells help maintain water balance

Endoplasmic Reticulum (ER)

• A series of interconnected membranous sacs and tubules
• Rough Endoplasmic Reticulum (RER) is named so because ribosomes attached give it a studded appearance, viewed through an electron microscope; bound ribosomes are in the process of translating proteins directly into the lumen
• Smooth Endoplasmic Reticulum (SER) is continuous with the RER but has few or no ribosomes; it is a site of synthesis of carbohydrates, lipids, phospholipids, and steroid hormones and detoxification of medications and poisons

Endoplasmic Reticulum (ER) - Functions

• Provides the site for protein and lipid synthesis
• The SER is generally used for the synthesis or storage of lipids and steroids
• The RER plays a significant role in the synthesis of various proteins

Golgi Apparatus (GA) - Properties

• The GA is a series of flattened membranes, each forming a separate compartment

Golgi Apparatus (GA) - Functions

• Vesicles that contain proteins and lipids bud from the ER and transport their contents to it
• In the GA, proteins and lipids are sorted, packaged, and tagged so that they wind up in the right place
• It’s referred to as the cell's "post office"

Plant vs Animal cells - Differences

• Cell wall, Chloroplast and Large Central Vacuole are found in plant cell but not animal cell
• Lysosomes are found in animal cells but not Plant cells

Cell wall in plant cell

• It is made up of cellulose and is a structure external to the plasma membrane
• The cell wall is a rigid covering that protects the cell, provides structural support, and gives shape to the cell

Chloroplast in plant cell functions

• Carry out photosynthesis
• Series of reactions that use carbon dioxide, water, and light energy to make glucose and oxygen

Large Central Vacuole in plant cell functions

• Plays a key role in regulating the cell's concentration of water in changing environmental conditions
• Also supports the expansion of the cell

Lysosomes in animal cell

• Act as cell's "garbage/recycle disposal."
• Enzymes inside lysosomes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles.

This quiz covers the fundamental concepts of cell biology, including cell theory, cell types (prokaryotic and eukaryotic), cellular components, and basic cell processes. It tests understanding of cell structure, function, and the significance of cells in biology.