Intro to Cells: Structure, Theory, and Classification

• Cells are fundamental to biology, acting as the smallest unit of living things and carrying out all life processes.
• Nasal sinus cells, onion cells, and Vibrio tasmaniensis bacterial cells share basic cell structure characteristics across different organisms.
• Microscopy is used to visualize cells; light microscopes and electron microscopes have different visualization capabilities

Discovering Cells

• Robert Hooke saw the first cells in 1965, these first cells were cork cells.

Cell Theory

• All living things consist of one or more cells
• The cell is the basic life unit in all living things
• All cells come from the division of pre-existing cells

Classifying Cells

• Eukaryotic Cells: Plants, Animals, Fungi, and Protists/Protoctists
• Prokaryotic Cells: Bacteria and Archaea

Cell Similarities

• All cells contain the following:
• Cell/Plasma membrane: outer covering separating the cell's interior from its surroundings
• Cytoplasm: jelly-like cytosol which holds cellular components
• Hereditary material (DNA): genetic material
• Ribosomes: synthesize proteins

Cell Sizes

• Relative sizes are measured on a logarithmic scale

Characteristics of Prokaryotic Cells

• Include bacteria
• Do not have a nucleus
• Have long circular DNA
• No membrane-bound organelles
• Ribosomes for producing proteins
• Most have a peptidoglycan cell wall
• Rod-shaped, spherical, or spiral

Prokaryotic Reproduction

• Asexual: binary fission, where DNA is duplicated and the organism divides, giving a DNA copy to each new organism
• Conjugation: an exchange of DNA between bacterial cells

Prokaryotic Classifications

• Eubacteria: commonly found
• Archaea: live in extreme environments like hot springs, salt lakes, and submarine volcanic habitats
• Halophiles
• Methanogens
• Thermoacidophiles

Beneficial Prokaryotics

• Bioremediation: organisms are added to water to convert toxic pollutants into harmless substances
• Food Production: includes butter, cheese, yogurt, sauerkraut, beer, pickles, olives, chocolate, coffee, soy sauce, and meats
• Decompose dead organisms
• Digest food
• Fix Nitrogen for Plants

Harmful Prokaryotics

• Food Spoilage
• Cause plant and animal diseases
• Produce Toxins

Eukaryotic Cells

• More complex and larger than prokaryotes
• Have membrane-bound organelles and a nucleus
• More DNA than prokaryotes; linear DNA
• Include animals, plants, and fungi

Eukaryotics for Unicellular Organisms

• Movement for unicellular eukaryotes like the Protist
• Flagella: tail projections
• Pseudopod: false-foot
• Cilia: finger-like projections, may or may not be motile

Structure of Eukaryotic Cells

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

The Major Groups of Organic Molecules

• Carbohydrates
• Nucleic acids
• Proteins
• Lipids

Proteins

• Proteins are the most diverse and complex macromolecules
• Proteins are used for structure, function, and information
• Composed of linearly arranged amino acid residues and folded into active regions

Types and Functions of Proteins

• Enzymes: Catalyze covalent bond breakage or formation (e.g., Amylase)
• Structural: Collagen, elastin, keratin
• Motility: actin, myosin, tubulin
• Regulatory: bind to DNA to switch genes on or off
• Storage - ovalbumin, casein
• Hormonal: insulin, nerve growth factor (NGF)
• Receptors - hormone and neurotransmitter receptors
• Transport - carries small molecules or ions
• Special purpose proteins - green fluorescent protein

Lipids

• Hydrophobic molecules for energy storage
• Used in membranes, and are signaling molecules
• Include triglycerides (fat), phospholipids, waxes or sterols

Fats (Lipids)

• Lipids are macromolecules composed of fatty acid monomers
• Function as structural support, provides energy storage, and cell signaling
• Lipids are typically nonpolar in nature and does not interact with water, though some exceptions exist
• Types: triglycerides, phospholipids, steroids or waxes

Saturated and Unsaturated Fatty Acids

• Saturated Fat features meat, dairy products, eggs, coconut oil, and palm oil
  • Solid at room temperature
  • Raises LDL cholesterol and TAG levels
  • Increases insulin resistance
• Unsaturated Fat features avocados, nuts, seeds, olives, natural nut butters, and plant oils
  • Liquid at room temperature
  • Lowers LDL cholesterol and raises HDL cholesterol
  • Decreases insulin resistance

Carbohydrates

• Sugars that help with storage (glycogen, starch)
• Structural polymers(cellulose and chitin)
• Major substrates of energy metabolism

Nucleic acids

• DNA (deoxyribonucleic acid)
• RNA encode genetic information for protein synthesis
• Building blocks of life

Eukaryotic Cell Structure: Plasma Membrane

• Properties:
  • Made of hydrophobic and hydrophilic components
  • Semi-permeable, allowing some materials to pass while excluding others
  • Fluid-like phospholipid bilayer
• Functions:
  • Selectively isolates the cell content and cell's organelles from the external environment
  • Regulates substance exchange between the cytoplasm and the external environment, controlling molecules, ions, water, oxygen, and CO2
  • Communicates with other cells

Eukaryotic Cell Structure: Cytoplasm

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

Eukaryotic Cell Structure: Nucleus

• Properties:
  • The Nuclear membrane
  • Chromosomes
  • The Nucleolus
  • Ribosomes
• Functions:
  • The nucleus houses the cell's DNA and directs the synthesis of ribosomes and proteins

Eukaryotic Cell Structure: Mitochondrion

• Properties:
  • Are oval-shaped,
  • Double membrane organelles
  • Have their own ribosomes and DNA.
  • The inner membrane has folds called cristae that increase surface area
• Functions:
  • powerhouses” or “energy factories" responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule

Eukaryotic Cell Structure: Peroxisomes

• Properties:
  • Small, spherical organelles enclosed by single membranes.
  • These oxidation reactions release hydrogen peroxide (H2O2), which the peroxisome is capable of safely breaking into oxygen and water.
• Functions:
  • They carry out oxidation reactions that break down fatty acids and amino acids
  • They also detoxify many poisons that may enter the body, for example,alcohol

Eukaryotic Cell Structure: Lysosomes

• Properties:
  • Small, spherical compartments that function as a digestive.
  • Lysosomes contain acid hydrolases enzymes to catalyze hydrolysis reactions and their optimal pH is around 4.5.

Lysosomes and Peroxisomes

• Break down waste into reusable parts.
• Ensure efficient and safe cellular function.
• Peroxisomes protect cells by breaking down harmful hydrogen peroxide into water and oxygen.

Eukaryotic Cell Structure: Vesicles and Vacuoles

• Vesicles and vacuoles are membrane-bound sacs that function in storage and transport, with vacuoles being larger
• They can store food or other nutrients required by the cell to survive
• They prevent the entire cell from contamination which could come from waste products from the cell
• Vacuoles in plant cells help maintain water balance
• Contractile vacuoles contract to expel water from the cell.

Eukaryotic Cell Structure: Endoplasmic Reticulum

• The endoplasmic reticulum (ER) is a series of interconnected membranous sacs and tubules
• Named because ribosomes attached to its cytoplasmic surface give it a studded appearance, called the rough endoplasmic reticulum (RER) and are in the translation process of proteins.
• Site for protein and lipid synthesis and the SER plays a significant role in the synthesis of various proteins
• The smooth endoplasmic reticulum (SER) is continuous with the RER without ribosomes, synthesizes carbohydrates, lipids, phospholipids, and steroid hormones, and is responsible for medications and poisons detoxification.

Eukaryotic Cell Structure: Golgi Apparatus (GA)

• A series of flattened membranes forming compartments
• Proteins and lipids are sorted, packaged, and tagged for the GA to wind up in the right place

Differences between plant and animal cells

• Cell Wall: Plant cell wall, not in animal cell

  • Structure external to the plasma membrane
  • Prokaryotics have peptidoglycan cell walls
  • Organic molecule in the plant cell wall is cellulose (polysaccharide made of made up of glucose units)
  • A rigid covering that protects the cell, provides structural support, and shape

• Chloroplast: Plant cell, but not in animal cell

  • Double membrane organelles with outer and inner membranes
  • Inner space enclosed by interconnected and stacked fluid filled membranes called thylakoids
  • Plant cell's organelles that carries out photosynthesis
  • Photosynthesis uses carbon dioxide, water, and light energy to make glucose and oxygen

• Large Central Vacuole: Plant cell, but not in animal cell

  • Plant cells have a large central vacuole that supports cell expansion
  • A key role is water concentration regulation to protect the cell in changing environments

• Lysosomes: found in Animal cells but not plant cells

  • aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and worn-out organelles
  • garbage and recycle disposal

Cellular Components

• Plasma Membrane: Separates cell from externalenvironment.

• Controls passage of organic molecules, ions, water, oxygen, and wastes in/out of the cell

• Cytoplasm: Provides turgor pressure to plant cells; Site of many metabolic reactions. Medium in which organelles are found

• Nucleus: Cell organelle that houses DNA and directs synthesis of ribosomes and proteins

• Nucleolus: Darkened area directs synthesis of ribosomes where ribosomal subunits are synthesized

• Ribosomes: Protein Synthesis

• Mitochondria: ATP production/cellular respiration

• Peroxisomes: Oxidizes and detoxifies

• Vesicles & Vacuoles: Storage and transport

• Centrosome: Cell division

• • Lysosome: macromolecule & organelle digestion

• Cell Wall: provides structural support and maintenance of cell shape

• Chloroplast: Helps with Photosynthesis

• Endoplasmic Reticulum: Modifies proteins and synthesizes lipids

• Golgi Apparatus: Modifies, sorts, tags, packages, and distributes lipids and proteins

• Cytoskeleton: Maintains cell's shape, secures organelles in positions, cytoplasmic and vesicle allowance to move within cell, promotes movement of unicellular organisms

• Flagella: Cellular locomotion

• Cilia: Movement of particles along membrane and filtration