Cell Organelles and Transport

• Cytology is the study of cells, including their structure, function, anatomy, and shared characteristics.
• Cells perform various functions and display diverse anatomy.
• Metabolism refers to the "working" processes within a cell.
• Cells must dispose of waste or they will die.
• The shape of a cell influences both internal (microscopic) and external factors, although some internal components can be observed without magnification.
• Blood cells and neurons do not undergo cell division.

Cellular Functions

• Covering: Keratinocytes provide a protective barrier, such as the skin
• Lining: Goblet cells, found inside hollowed organs like the small intestine
• Storage: Adipocytes store energy as fat cells within adipose tissue.
• Movement: Muscle fibers shorten to move bone, food, and fluids, as well as lowering collagen fiber.
• Connection: Fibroblasts create collagen, while ligaments connect bone to bone.
• Defense: White blood cells (WBCs) attack pathogens.
• Communication: Neurons control body function as part of the nervous system.
• Reproduction: Gametes and stem cells create babies, involving growth and repair of cells.

Basic Cell Components

• Plasma (cell) membrane
• Cytoplasm
• Nucleus

Plasma Membrane

• Functions as a physical barrier that is flexible and fluid.
• Separates extracellular and intracellular environments.
• Selectively permeable to control the movement of substances in and out of the cell.
• The amount of cytoplasm that can travel through is dictated by its greater surface area
• Primarily composed of lipids forming the main structure of membrane.
• Proteins determine the function of the membrane.
• Glycocalyx is an external carbohydrate coat creates a fuzzy layer.

Membrane Lipids

• Three types of lipids are found in the cell membrane:
  • Phospholipids: Arranged in two layers with heads facing outwards and tails facing inwards
    • Head: Polar-hydrophilic region containing phosphate groups
    • Tail: Nonpolar-hydrophobic region composed of lipids
  • Cholesterol: Helps strengthen the membrane at high temperatures and prevents it from falling apart at lower temperatures
  • Glycolipids: Allow for recognition of foreign pathogens and made of carb+phospholipid
    • Involved in cell-cell recognition and intracellular adhesion.

Membrane Proteins

• Proteins are made of amino acid chains that determine cell function.
• Integral Proteins: Embedded inside through the membrane, transport solutes, and act as transport proteins and enzymes.
• Peripheral Proteins: Line the outside of the membrane and help with intercellular connection -Can anchor the cytoskeleton. -Involved in signal transduction.

Membrane Anatomy

• Arranged with lipids, proteins, and glycocalyx.
• The outside region is hydrophillic, allowing for glycoproteins and glycolipids to attach
• Inside the membrane there are non polar proteins with cholesterol adding more tensile strength.

Passive vs. Active Transport

• Passive transport does not require ATP energy and Solutes move from high to low concentration to reach equilibrium.
• Active transport requires ATP energy and Solutes move from low to high concentration to maintain concentration gradient

Transport Factors

• The number of transport proteins: Affects the rate of transport
• Plasma membrane structure: Affects what can move, what can't
• Lipid solubility: Determines ease of passage through the membrane.
• Concentration gradient: Refers to the difference in solute concentration on either side of the membrane and Higher concentration leads to higher transport.
• Molecular size: Smaller molecules can transfer easily.

Passive Transport

• Does not require ATP energy.
  • Simple Diffusion: Nonpolar, small solutes, moves from high to low concentration and gasses exchange this way in the lungs
    • The movement of these molecules are not repelled by lipids as they made of the cell membranes.
  • Osmosis: Water moves from high to low concentration through integral proteins called aquaporins. _ Aquaporins prevent water from interacting with lipids.
  • Facilitated Diffusion: Large and/or polar solutes requires integral for movement from H-L concentration.
    • These molecules are also repelled by being too large to fit between membranes
  • Bulk Filtration: Passive transport of water and solutes across a membrane using hydrostatic pressure or pressure generated from osmosis.
    • Results in cell growth.

Tonicity

• Hypertonic Solution: Higher solute concentration outside the cell, causing water to move out and the cell to shrink.
• Hypotonic Solution: Higher solute concentration inside the cell, causing water to move in and the cell to grow.
• This can lead to bulk filtration.
• Isotonic Solution: Equal solute concentration inside and outside the cell, maintaining cell stability.

Active Transport

• Requires ATP Energy
• Ion Pump: integral proteins to pump ions from Low to High Concentrations
• Bulk Transport: active transport of big molecules/substances across membranes using vesicles and ATP
  • Exocytosis: moves solute out of the cell
  • Endocytosis: moves solute into cell
  • Phagocytosis: Generalized eating with pseudipodia
  • Pinocytosis: Cellular drinking using membranes
  • Receptor-Mediated Endocytosis: Via glycocalyx

Components of Cytoplasm

• Cytoplasm: all materials (solid & liquid) between membrane and nucleus.
• Cytosol: thick fluid that fills cells
• Cytoplasmic Inclusions: large collection of a specific solute, i.e. melanin, glycogen
• Organelles: specialized structures that perform various functions.

Organelles

• Specialized structures within the cell performing various functions.
• Can be membrane-bound or non-membrane-bound
• Non-Membrane bound organelles include ribosomes, centrioles, and cytoskeleton
• Membrane Bound Organelles Include:
  • Nucleus
  • Lysosome
  • Rough & Smooth ER
  • Peroxisome
  • Golgi Apparatus
  • Mitochondria

Membrane Protein Functions

• Transport: Movement of substances across the membrane
• Intercellular connection
• Anchorage for the cytoskeleton: Allows for cell shape
• Enzyme activity: Controls Ion pump activities
• Cell-cell recognition: Uses glycoproteins.
• Signal transduction: Where the outside molecule interacts with cell and changes its function.

Factors Affecting Membrane Transport

• Concentration gradient:
• A larger gradient leads to more transport.
• Higher transport will occur as molecules try to reach equalibrium.
• Lipid solubility
• Hydrophobic molecules can pass through the membrane.
• Molecular size
  • Small molecules can easily transfer across the membrane.
• Number of Transport Proteins:
  • A higher number of transport proteins means more molecules can exit/enter.

3 Components of Cytoplasm

• Cytosol: Fluid material
• Inclusions: collection of a specific solute
• Organelles: Specialized structures that perform various functions.

Organelle Functions

• Smooth Endoplasmic Reticulum: Synthesizes lipids, metabolizes carbohydrates, and detoxifies drugs and alcohol.
• Rough Endoplasmic Reticulum: Synthesizes proteins for secretion, cell membrane, and lysomal enzymes
• Golgi Apparatus: Modifies, Packages, and sorts the synthesize of proteins for secretion
• Lysosome: Digests material brought into the cell and worn out organelles, causing autolysis.
• Peroxisome: Converts hydrogen peroxide (H2O2).
• Mitochondria: Produces ATP by cellular respiration.
• Nucleus: Contains DNA and acts as control center.
• Nucleolus: Synthesizes rRNA and assembles ribosomes.
• Fixed Ribosomes: Assembles proteins for cell mmbrn or for secretion outside of cell.
• Free Ribosomes: Assembles proteins that stay within the cell.
• Microvilli: Increases membrane surface area for absorption or secretion.
• Cilia: Moves fluid, mucus, and materials over the cell's surface.
• Centrosome: Directs formation of mitotic spindle in cells.
• Cytoskeleton: provides structural support for cell and helps organelles.
• Flagellum: propels sperm cells in males

Scenario: Transport Types and Cell Anatomy

• Cell anatomy: the inner region should be small enough to fit between membranes.
• Red Solute: Active/Facilitated diffusion and moves from high concentration to low concentration.
• Blue Solute: Active/Facilitated Diffusion of small solutes move from H-L concentration but is too big to squeeze by itself needing integral proteins.

Working Together

• Organelles required to work together to create a protein inside of the cell
• The nucleus contains the cellular DNA/instructions for a protein located in the cytoplasm.
• The nucleolus produces the ribosomes needed for cellular synethesis.
• The proteins will then be synthesized in the free ribosomes.
• Organelles required to work together to create a protein that would leave the cell
• The nucleus, DNA, nucleolous, fixed ribosomes, rough ER, goli apparatus all work together.
• Organelles required to work together to create a lipid that would leave the cell
• The nucleus, smooth ER, goli apparatus all work together
• Organelles required to work together to breakdown material brought into the cell
• The cell membrane, vesicles, lysosomes, peroxisomes and cytoskeleton all work together.

Test your knowledge of cell organelles and their functions, including the endoplasmic reticulum, Golgi apparatus, ribosomes, and peroxisomes. Explore the processes of protein synthesis, detoxification, and ATP generation. Review the principles of passive transport across cell membranes.