Cells as Basic Units

Cells as Basic Units

• Cells are the fundamental structural and functional units of the body
• Cells are measured in micrometers (µm)
• Differentiated cells have developed specialized characteristics
• Cell size and shape are varied and are related to their function

Composite Cell

• A composite cell illustrates components commonly found in most cells
• The three major parts of a cell are the nucleus, cytoplasm, and cell membrane
• Nucleus contains genetic material and directs cellular activities
• Cytoplasm consists of organelles in a liquid called cytosol
• Cell membrane encloses the cell

Cell (Plasma) Membrane Structure

• The cell membrane is the cell's outer boundary, maintaining its integrity
• It separates intracellular fluid (cytosol) from extracellular fluid
• Selectively permeable membrane regulates the entry and exit of substances
• Cell membrane permits signal transduction, enabling cells to receive and respond to messages
• The cell membrane consists mainly of lipids and proteins, with some carbohydrates

Cell Membrane Lipids and Proteins

• The phospholipid bilayer is the basic framework of the cell membrane
• Hydrophilic heads of phospholipids form surfaces and hydrophobic tails form interior
• The lipid bilayer is permeable to lipid-soluble, but not water-soluble, substances
• Cholesterol stabilizes the membrane and helps keep it impermeable to water-soluble substances
• Lipids and proteins can move within the membrane, giving it "fluid mosaic" properties
• Membrane proteins serve as pores, channels, receptors, enzymes, and cell adhesion molecules (CAMs)
• Carbohydrates play a role in cell recognition, interaction, and act as self marker

Membrane Protein Types

• Receptors respond to extracellular signals
• Pores, channels, and carriers transport small molecules and ions
• Enzymes catalyze chemical reactions
• Cell surface proteins establish self
• Cellular adhesion molecules enable cells to stick to each other

Faulty Ion Channels and Disease

• Mutations in Na+ channels cause inability to feel pain or extreme pain
• Mutations in K+ channels disrupt electrical activity of the heart and impair hearing
• Abnormal Cl- channels cause cystic fibrosis through thick mucus production

Cellular Adhesion Molecules

• CAMs guide cell movement
• Selectins coat white blood cells and anchor them to capillary walls, providing friction
• Adhesion receptor proteins bind to integrins, helping white blood cells leave capillaries
• Integrins direct white blood cells through capillary walls toward infection sites
• Other CAMs guide embryonic cells toward maternal cells and establish connections between nerve cells

Cytoplasm

• Cytoplasm consists of networks of membranes and organelles suspended in cytosol
• Cytoplasm is composed of cytosol and organelles
• Cytosol is the fluid portion of the cytoplasm
• Organelles are tiny solid structures with specific functions in the cell
• The cytoskeleton supports the cell framework and contains protein rods and tubules

Ribosomes

• Ribosomes are composed of protein and RNA
• Ribosomes either exist freely in the Cytoplasm or attached to ER
• Ribosomes Provide structural support and enzyme activity to link amino acids in protein synthesis

Endoplasmic Reticulum (ER)

• ER which is a tubular transport system consists of membrane-bound sacs, canals and vesicles
• Rough ER contains ribosomes and conducts protein synthesis
• Smooth ER lacks ribosomes and conducts lipid synthesis

Vesicles

• Vesicles are membranous sacs that store or transport substances

Golgi Apparatus

• The Golgi Apparatus consists of flattened membranous sacs
• Golgi Apparatus Refines, packages, and delivers proteins made on the RER

Organelle Interaction Example

• Milk secretion involves interaction among roughs and smooths ER, the Golgi apparatus, and transport vesicles

Mitochondria

• Mitochondria are membrane-bound, fluid-filled sacs
• Mitochondria house chemical reactions to extract energy from nutrients (cellular respiration) producing ATP
• Mitochondria are referred to as the "powerhouse of the cell"

Lysosomes and Peroxisomes

• Lysosomes are small, membranous sacs containing digestive enzymes
• Lysosomes digest proteins, carbohydrates, nucleic acids, bacteria, debris, and worn-out cell parts
• Lysosomes act as "garbage disposals" of the cell
• Peroxisomes are membranous sacs similar to lysosomes
• Peroxisomes contain enzymes that digest lipids, alcohol, and hydrogen peroxide

Microfilaments and Microtubules

• Microfilaments, microtubules, and intermediate filaments create the cytoskeleton
• Microfilaments are tiny rods of actin that provide cellular movement, like muscle contraction
• Microtubules are larger tubes of tubulin that maintain cell shape through rigidity
• Microtubules make up cilia, flagella, and centrioles, and they help move organelles

Intermediate Filaments

• Intermediate filaments Provide cytoskeletal structure and support the nuclear envelope, they are composed of several proteins

Centrosome Structures

• The centrosome consists of 2 centrioles
• The centrosome Located in the cytoplasm, near the nucleus
• Centrioles produce spindle fibers during cell division, distributing chromosomes to forming daughter cells
• Centrioles Are cylindrical and composed of Microtubules

Cilia and Flagella

• Cilia are motile extensions of cell membrane consisting of microtubules in a cylindrical pattern
• They form a "fringe" on the surface of certain epithelial cells
• Cilia are Shorter and very abundant compared to Flagella
• Cilia beat back and forth in a coordinated manner
• Cilia propel mucus in the respiratory tract and propel an egg toward the uterus
• Flagella are another type of motile extension from the cell membrane
• Flagella are similar in structure to cilia but longer
• Flagella Causes the entire cell to move
• The Tail of the Sperm cell is the only flagellum in a human cell

Microvilli

• Microvilli are composed of Actin, they're tiny extensions of the cell membrane which increase the surface area for Absorption

Inclusions

• Inclusions Present only in some types of cells
• They're chemicals not necessary for survival, one example is Melanin Granules

Clinical Applications Relating to Organelles (Melas, Krabbe disease and Adrenoleukodystrophy)

• Melas is a Mutant gene in the DNA of the Mitochondria
• Patients With Melas cannot extract maximum energy from nutrients
• Krabbe disease Caused by inability to produce one lysosomal Enzyme
• Patients suffering from Krabbe Disease cannot produce Myelin for nerve cells
• Adrenoleukodystrophy ADL Caused by lack of a protein in membrane of peroxisomes
• Patients Are unable to transmit nerve impulses fast enough
• Resulting from Fatty acid buildup, destroying myelin Sheaths of Nerve cells

Cell Nucleus Components

• The nucleus contains genetic material and controls cell activities
• It also separates nucleoplasm from cytoplasm and contains the Nucleolus and Chromatin
• The dense body of RNA and protein is the Nucleolus
• The Nuclear envelope around the nucleus has Nuclear pores allows passage of certain substances
• Chromatin consists of a cells chromosomes, the site of Ribosome Production and Stores information for protein synthesis

Physical and passive transport

• Physical and passive transport do not require ATP
• Diffusion, osmosis, facilitated diffusion, filtration

Diffusion

• Diffusion is the Movement of atoms, molecules, or ions, from region of higher concentration to region of lower concentration
• Diffusion Occurs due to constant motion of atoms, molecules, and ions

Substance Permeability

• Diffusion Occurs only with substances that the cell membrane is permeable to, like oxygen, carbon dioxide, and other lipid-soluble substances
• Diffusion Solutes and water can diffuse across a membrane that is permeable to both of them until they reach equilibrium

Facilitated diffusion and ATP

• Facilitated Diffusion Across the cell membrane through Ion channels or transporters
• Facilitated Diffusion uses Water-soluble substances (Na+, K+, Cl , glucose, amino acids)
• The Facilitated Diffusion process is passive which means No ATP is required

Osmosis

• Movement of water across a selectively permeable membrane from region of higher water concentration to region of lower water concentration
• Commonly referred to as "diffusion of water"
• Water moves into a region containing higher impermeant solute concentration
• Water moves through aquaporins in the cell membrane’s phospholipids
• Osmosis is a passive process which means no ATP is required

Osmotic Pressure and Tonicity

• Osmotic pressure increases as impermeant solute concentration increases
• Isotonic solution same osmotic pressure, results in cells having no net gain or loss of water
• Hypertonic solution, higher osmotic pressure, results in cells losing water
• Hypotonic solution, lower osmotic pressure, cells gain water

Filtration in the Cell

• Filtration is the Process that forces molecules through membranes by exerting pressure
• When Blood Plama leaves capilleries small solutes and water filter out while large Pasma proteins are not
• Filtration is passive and requires No ATP energy

Active mechanisms in the Cell

• Active Mechanisms Require Atp to move substances across the Cell membrane
• Includes Active transport, endocytosis, exocytosis, and transcytosis

Active Transport

• Active transport Involves the movement of substances against the gradient (lower to higher concentration)
• Active transport Requires carrier “pumps” molecules in cell membrane and Requires atp Energy to Work
• Examples of Active transport are Sugars, amino acids, Ca+2, H+, Na+/K+ Pump

Types of Active Transport

• In secondary ative transport uses a carrier, Transporting other substances while not requiring atp energy
• Endocytosis transports substances into a cell inside a vehicle
• Pinocytosis membrane engulfs droplets of liquids
• Phagocytosis membrane engulfs solid particles
• Endocystosis Allows large substances that are too big to enter to pass into the cell through this method

Types of Endocytosis

• Receptor mediated Is when themembrane engulfs substances bound to receptors on the membrane

Cell waste transportation types, Exocytosis and Transcytosis

• Exocytosis Transports celluar waste as Releases the substances or particles From a cell, it does this when the Vesicles containing the cellular waste material fuse with cell membrane
• Transcytosis Involves receptor Mediated endocytosis followed by exocytosis and Quickly transports from one cell to another, It's Used to transport the cellular material substance through formed by connecting cells for example HIV

Cell Cycle Stages

• The cell cycle encompasses changes from formation to division
• The stages of the cell cycle are interphase, mitosis, and cytokinesis

Cell Cycle and Interphase

• A very active period in cell Cycle
• Cell grows and maintains normal functions
• Cell replicates genetic material (DNA) to prepare for mitosis
• Cell synthesizes organelles, membranes, and biochemicals to prepare for cytokinesis (division of cytoplasm)

Phases in Interphase

• The DNA gets replicated during ( S synthesis phase)
• Structues and other Molecules get duplicated during G1 and G2 (growth or gap phases)

Somatic cell

• Somatic Cell has its parts split through two main processes Mitosis is cell part or nucleus division through karyokinesis and Cytokinesis where the Cyptoplasm also Splits

4 Main mitosis stages, Prophase, Metaphase, Anaphase and Telophase

• In prophase Chromatin condenses to form chromosomes, centrioles disperse and move toward opposite pole
• Metaphase (centrioles attach to chromosomes, and align them midway between poles
• Anaphase (chromatids separate and move to opposite poles or directions toward centrioles
• Telophase (chromatids return to Chromatine structure
• Each chromosome set has nucleoli become visible
• Nuclear envelope surrounds it

Cytoplasmic Division

• Cytoplasmic division or Cytokinesis = cytoplasmic division
• Cytokinesis Starts during Anaphase, continues through Telophase
• The cytoplasm Is pinched In half at the site Of actin Filaments forming The site Of a Contractile Division Consteiction

Mitotic Clock

• Cell division Frequency is strictly regulated based on cell division type for example, Skin cells can undergo Intesitial cell division
• Neurons stop dividinf after a certain time
• Cells undergo mitosis from the chromosome tips called telomeres
• Fluctuating of a single cell can influnce an entire cell
• Surface volume also changes
• Contact Inhibition is where the cell decides when there is space

Tumors

• Tumors can also for from the loss of mitosis and cell crowding
• There are 2 forms Benign where it stays in the same space, and Malignant Invasive or cancerous

Types of Genes and Cancer

• Oncogenes abnormal forms of genes can affect the cell
• Abnormal Genes prevent cycle regulation
• Tumors Sppresor Genes limit mitosis

Characteristics of A cancer Cell

• Heritability
• Loss off cell cycle control
• Contact inhibitor lose

Types of cells Stem Pro progenitor Cells

• Dediffrentation
• Cell ability to go anyhwer and transform
• Transblantabitly ( the ability to go to other organs
• Stem Cell Can divide to form 2 new stem cell
• Stem cells can diferentiate to any cell

Differentiation and cell types

• Cell specializes
• Totipoten is the cell that spcializes,
• The egg gets fertizlized turning it to a speclziation cell type Differentitation Is process of speclization of cells

Appoptosis and Cell destruction type and Necrosis is Destruction from outside influences

• Process that is step wide in a controlled fashion.
• Webbed fingers.
• Normal process that can happen. Cell destruction type appoptosis.
• Necrosis - Cell death from outside influence's.
• Sunburn
• Is not a normal process.

Explore cells as the fundamental units of the body, measured in micrometers, with varied sizes and shapes related to their function. Learn about the composite cell, including the nucleus, cytoplasm, and cell membrane. Understand the selectively permeable membrane and its role in signal transduction.