Eukaryotic cells
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Eukaryotic Cells. Animals & Plants. The Cell. Building block of the all organisms, from single-celled to human. 200 Types of cells in the human body, categorized by cell shape. Cell size limited by the volume and surface area ratio.

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Eukaryotic Cells

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Eukaryotic cells

Eukaryotic Cells

Animals & Plants


The cell

The Cell

  • Building block of the all organisms, from single-celled to human.

  • 200 Types of cells in the human body, categorized by cell shape.

  • Cell size limited by the volume and surface area ratio.

    • If the cell is too big, it cannot support itself or absorb nutrients/excrete wastes effeciently.


Classes of cell shapes

Classes of Cell Shapes

  • Squamous: Thin & flat cells covering surfaces or lining “tubes”

    • Example: Skin, lining of the esophagus

  • Cuboidal: Square or cube shaped; approximately as wide as they are tall.

    • Example: Liver cells

  • Columnar: Much taller than they are wide.

    • Example: Lining of the intestines

  • Spheroid: Egg cells and fat cells; round or oval.

  • Fusiform: Thick in the middle and tapered towards the ends.

    • Example: Smooth muscle cells

  • Stellate: Star-shaped cells.

    • Example: Some nerve cells


Cell theory

Cell Theory

  • Based on Robert Hook, Theordore Schwann, & Louis Pasteur

  • Modern Cell Theories’ Generalizations:

    • All organisms are composed of cells and cell products.

    • The cell is the simplest structural and functional unit of life.

    • All functions and structures are ultimately due to the activities of cells.

    • Cells come only from pre-existing cells.

    • The cells of all species have many fundamental similarities.


General cell structure

General Cell Structure

  • Eukaryotic cells all have the following general structures:

    • Cell Membrane

    • Cytoplasm

    • Nucleus

    • Intracellular Organelles


Cell membrane

Cell Membrane

  • All cells are surrounded by a plasma membrane made up of proteins and lipids

  • Bilayer of lipids with diverse proteins embedded in it

  • 98% of membrane molecules are lipids

    • 75% of these are phospholipids


Cell membrane1

Cell Membrane

  • Phospholipid Bilayer:

    • Two phospholipid layers thick

    • Hydrophilic heads facing the water on each side of the cell membrane.

    • Hydrophobic tails directed toward the center of the membrane (avoiding the water)

    • Membrane is dynamic and “fluid”


Cell membrane2

Cell Membrane

  • Cell Membrane is the target site of many pharmaceutical agents

  • Proteins only make up 2% of the molecules in a plasma membrane, but are larger then lipids and make up around 50% of the membrane weight.


Cell membranes

Cell Membranes

  • Integral or Transmembrane Proteins: Pass across the plasma membrane and are responsible for many functions. Integral proteins function as…

    • Receptors: Specific for one messenger

    • Second-messenger Systems: Triggered by messengers that bind with surface receptors

    • Enzymes: Produce second messengers and help with digestion in the small intestine

    • Channel Proteins: These molecules have “pores” & allow passage of water & other solutes through the membrane

    • Carriers: Also called “PUMPS” they actively transport molecules into the cell utilizing ATP in the process


Glycocalyx

Glycocalyx

  • The “fuzzy” coat external to the plasma membrane on all animal cells, including humans

  • Acts as an “identification” tag that enables the body to distinguish its own healthy cells from transplanted tissue, invading organism, and diseased cells.


Surface extensions

Surface Extensions

  • Surface extensions aid in absorption, movement, and sensory processes.

  • Microvilli: Extensions of the plasma membrane; serve primarily to increase a cell’s surface area; best developed in cells that specialized in absorption (e.g. the cells lining the small intestine)


Surface extensions1

Surface Extensions

  • Cilia: Multiple hair-like processes that project from the surface of the cell

    • Nonmotile Primary Cilium: Nearly every human cell has a single nonmotile primary cilium.

    • Motile Cilia: Less widespread but occur widely in respiratory tract and fallopian tubes; “wave” to help move materials through internal tubes


Surface extensions2

Surface Extensions

  • Flagella: A single whip-like structure much longer than cilia.

    • The only functional flagellum in humans is the tail of the sperm cell.


Cytoplasm

Cytoplasm

  • Cytoplasm: The fluid that is contained inside the plasma membrane.

    • Crowded with fibers, tubules, passageways, and compartments.

    • Contains cytoskeleton (supportive framework) and intracellular organelles embedded in the cytosol or Intracellular fluid (ICF).


Extracellular fluid

Extracellular Fluid

  • Extracellular fluid (ECF) is the fluid outside the cell.


Nucleus

Nucleus

  • Nucleus: The structure at the center of the cell containing the genetic information for the organism.


Nucleus1

Nucleus

  • Nucleic Acid: DNA or RNA.

    • DNA is the principle type of nucleic acid contained in the cell nucleus.

      • DNA contains the genetic code for organisms and is involved in protein synthesis, cell division (mitosis), and reproduction of the organism.


Plasma membrane

Plasma Membrane

  • Plasma Membrane: Acts as a barrier and gateway between the cytoplasm and the extracellular fluid.

  • Selectively Semi-Permeable: The plasma membrane lets some things through and blocks other things; this is tremendously important in clinical practice!


Plasma membrane1

Plasma Membrane

  • Methods of Transporting Substances: Passive and Active transport.

  • Passive Transport includes…

    • Filtration

    • Diffusion

    • Osmosis

  • Active Transport requires ATP and includes…

    • Active transport

    • Vesicular transport


Filtration

Filtration

  • Filtration: The process by which particles are driven through a filter, or selectively permeable membrane, via hydrostatic pressure exerted on a membrane by water.

    • Example: Coffee Filter

      • Weight of water forces water through the grounds and coffee filter.

      • Filter holds back the larger particles (coffee grounds)

    • Most important filtration in the human body occurs in the capillary wall – transfer of water, salts, nutrients, etc. from blood stream to tissue and extracellular fluid & wastes to kidneys


Simple diffusion

Simple Diffusion

  • Simple Diffusion: The net movement of particles from an area of higher concentration to an area of lower concentration.

    • The result of constant, spontaneous movement of molecules known as Brownian Movement.

  • Concentration Gradient: When the concentration of a substance differs from one point to another.

  • Movement occurring down or with the concentration gradient is movement from the higher concentration area to the lower.


Simple diffusion1

Simple Diffusion

  • IF the membrane is semi-permeable and permeable to that substance, than diffusion will occur.

  • IF the membrane is not permeable to the substance, it will not diffuse across the membrane.


Diffusion rates

Diffusion Rates

  • Diffusion Rates: Important to cell survival because they determine how quickly a cell can acquire nutrients or rid itself of wastes.

  • Factors affecting diffusion rate:

    • Temperature: The higher the temp, the faster the diffusion rate.

    • Molecular Weight: Heavy molecules diffuse more slowly.

    • Membrane Surface Area: The more surface area the faster the diffusion rate.

    • “Steepness” Of Concentration Gradient: The greater the concentration difference, the faster the diffusion.

    • Membrane Permeability: The permeability of the membrane.

    • Diffusion Distance: Distance diffusion occurs across.

    • Facilitated Diffusion: Whether a solute binds to a specific transporter (changes the shape and releases the solute on the other side of the membrane).


Osmosis

Osmosis

  • Osmosis: The diffusion of water through a selectively permeable membrane from the area of higher concentration to the area of lower concentration.

    • The higher solvent (water) concentration area has a low solute concentration.

    • The higher solute concentration has a low solvent concentration.


Tonicity

Tonicity

  • Tonicity: The ability of a solution to affect the fluid volume and the pressure in a cell.

    • If a solute cannot pass through a plasma membrane, but remains more concentrated on one side of the membrane than on the other, it triggers osmosis.


Tonicity1

Tonicity

  • Hypotonic Solution: Area surrounding a cell has a lower concentration of nonpermeating solutes than the intracellular fluid.

    • Cells absorb water, swell, and lyse (burst).

  • Hypertonic Solution: Area surrounding cell has a higher concentration of nonpermeating solutes than the intracellular fluid.

    • Cells will lose water and crenate (shrivel).

  • Isotonic Solution: The area surrounding the cell has the same total concentration of nonpermeating solutes as the intracellular fluid.

    • Cells will neither loose nor gain water molecules & do not change size or shape.


Active transport

Active Transport

  • Active Transport: The carrier-mediated transport of a solute through a plasma membrane but against a concentration gradient.

    • Utilizes ATP and energy to move against the normal concentration gradient from an area of low concentration to high concentration.

  • Example: The sodium-potassium pump.


Sodium potassium pump

Sodium-Potassium Pump

  • Used to regulate the balance of sodium and potassium within the cell.

  • 1 ATP molecule exchanges 3 sodium atoms (Na+) for 2 potassium (K+) atoms.

    • Keeps the potassium higher and sodium lower within the cell.

    • Plasma membrane continuously leaks Na+ and K+, so the pump keeps the balance corrected.

    • Na+ and K+ play a critical part in nerve impulses and cardiac function.


Vesicular transport

Vesicular Transport

  • Vesicular transport moves large particles and droplets of fluid or numerous molecules through the plasma membrane all at once.

  • Endocytosis: Vesicular processes that bring matter into the cell. Two types:

    • Phagocytosis: “Cell eating” where foreign particles are engulfed (e.g. monocytes)

    • Pinocytosis: “Cell drinking” where droplets of extracellular fluid containing molecules used by cells are taken in.

  • Exocytosis: Vesicular processes that release matter from the cell.


Organelles

Organelles

  • Organelles: The internal structures within a cell that carry out specific functions.

    • Some are surrounded by one or two layers of a unit membrane and are therefore referred to as “membranous organelles.”

  • Membranous Organelles: Nucleus, mitochondria, lysosomes, endoplasmic reticulum, golgi complex.

  • Non-Membranous Organelles: Ribosomes, centrosome, centrioles, basal bodies.


Membranous organelles nucleus

Membranous Organelles: Nucleus

  • Nucleus: The largest organelle, spheroid in shape.

    • Most cells have a single nucleus

    • Nucleus surrounded by nuclear envelope or membrane

  • Nucleoplasm: The material contained within the nucleus.

    • Includes…

      • Chromatin (DNA and protein)

      • Nucleoli (produces ribosomes)


Membranous organelles endoplasmic reticulum er

Membranous Organelles: Endoplasmic Reticulum (ER)

  • Endoplasmic Reticulum: “Little network within the cytoplasm”

  • A system of interconnected channels that extend through the cytoplasm and reach the nuclear membrane.

    • Channels called Cisternae


Membranous organelles endoplasmic reticulum er1

Membranous Organelles: Endoplasmic Reticulum (ER)

  • Two Types:

    • Rough Endoplasmic Reticulum: Channels are covered with ribosomes (synthesize proteins).

    • Smooth Endoplasmic Reticulum: Extends from the Rough ER to form membranous tubules network.

  • Smooth ER synthesizes steroids & lipids

  • Rough ER is responsible for detoxifying alcohol and other drugs

  • Rough ER most abundant in cells that produce large amounts of proteins – such as those in the digestive glands


Membranous organelles golgi complex

Membranous Organelles: Golgi Complex

  • Golgi Complex: The small system of cisternae which synthesize carbohydrates and put the finishing touches on protein and glycoprotein synthesis.


Membranous organelles golgi complex1

Membranous Organelles: Golgi Complex

  • Primary function is to package protein into membrane-bound golgi vesicles

  • Some become secretory vesicles and store cell products such as breast milk & digestive enzymes

    • Some of these can become lysosomes


Membranous organelles lysosomes

Membranous Organelles: Lysosomes

  • Lysosomes: A package of enzymes which are bounded by a single unit membrane – usually produced by the Golgi complex

    • Primary function is to hydrolyze or digest proteins, nucleic acids, complex carbohydrates, and phospholipids

    • Autophagy: The digestion of surplus cells by their own lysosomal enzymes (as in the liver).


Membranous organelles peroxisomes

Membranous Organelles: Peroxisomes

  • Peroxisomes: Resemble lysosomes but are smaller and contain different enzymes (oxidase) and are not produced by the Golgi Complex\


Membranous organelles mitochondria

Membranous Organelles: Mitochondria

  • Mitochondria: Organelles specialized for synthesizing ATP

    • Power-house of cells

    • Bean shaped

    • Outer and inner membranes

    • Generate most of the cell’s ATP

    • Cristae contain enzymes for aerobic respiration

    • Matrix enclosed in the inner membrane; site of oxidation of organic molecules; contains DNA and ribosomes.


Non membranous organelles ribosomes

Non-Membranous Organelles: Ribosomes

  • Ribosomes: Small granules of protein and ribosomal RNA found in several places in the cytoplasm:

    • On Rough ER

    • In the Nuclear Envelope

    • Floating freely in cytoplasm

  • Primary function is protein synthesis.


Non membranous organelles ribosomes1

Non-Membranous Organelles: Ribosomes

  • Responsible for assembling amino acids based on messenger RNA codes.


Non membranous organelles centrioles

Non-Membranous Organelles: Centrioles

  • Centrioles: A short cylindrical assembly of microtubules.

    • 2 centrioles lie at right angles to each other within a small clear area of cytoplasm called the centrosome

      • Play a role in cell division – Mitosis


Cytoskeleton

Cytoskeleton

  • Cytoskeleton: A collection of protein filaments and cylinders that determine the shape of a cell.

    • Lend structural support

    • Organize cellular contents

    • Help move stuff through the cell

    • Contribute to movements of the cell

    • Connected to integral proteins of the plasma membrane

    • Made up of microfilaments and microtubules


Inclusions

Inclusions

  • Inclusions: 2 Kinds

    • Stored cellular products such as glycogen granules or fat droplets OR foreign bodies such as dust particles

    • NO unit membrane

    • Not essential to cell survival

    • Not organelles

    • Temporary structures; not permanent


Mitosis

Mitosis

  • Mitosis: The process by which cells divide to grow or to repair damage. 4 Stages:

    • Prophase

    • Metaphase

    • Anaphase

    • Telophase


Mitosis1

Mitosis

  • Prophase: Condensing of chromatin fibers into chromatid pairs


Mitosis2

Mitosis

  • Metaphase: The chromatid pairs line up along the metaphase plate


Mitosis3

Mitosis

  • Anaphase: The centromeres joining the chromatids split, identical sets move to opposite sides of the cell


Mitosis4

Mitosis

  • Telophase: Nucleoli reappear around two new sets of chromosomes and cell begins to split for cytokinesis – the division of the cell material.


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