Cell Biology Chapter Quiz

Histology - Basic for PT1 2024-25

• Histology is the science that deals with the microscopic structure of cells and tissues.
• The cell is the basic unit of life and the structural and functional unit of all living tissues.
• The cell is the basic unit of life.
• The science of histology is concerned with the microscopic structure of cells and tissues.
• This course is a basic introduction to cell biology, using objectives to guide the learning process.

Learning Objectives (Lecture 1)

• Distinguish between prokaryotic and eukaryotic cells.
• Identify the structure of a living cell's plasma membrane, cytoplasm, and nucleus, and their functions.
• Understand the structure and function of membranous organelles (endoplasmic reticulum, Golgi apparatus, lysosomes, and mitochondria).

Types of Microscopes

• Light Microscope (LM)
• Transmission Electron Microscope (TEM)

Cell Diversity

• Cells in the same organism show enormous diversity in size, shape, and internal organization.
• Examples of this diversity are seen in the vast differences between a nerve cell and a red blood cell in the human body.

Cell Size

• The female egg is the largest cell in the human body.
• Most other cells are only visible under a microscope.

Cell Shape

• Cell shape reflects a diversity of function.
• The shape of a cell depends on its function.

Internal Cell Organization

• Prokaryotic cells lack a nucleus and membrane-bound organelles.
• Eukaryotic cells have a nucleus and membrane-bound organelles.

Types of Cells

• Prokaryotes
• Eukaryotes (Plant and Animal Cells)

Prokaryotic Examples

• Only Bacteria
• Capsule
• Cell Wall
• Cytoplasmic Membrane
• Ribosomes
• Pili
• Cytoplasm
• Nucleoid
• Flagella

Eukaryotic Cells

• Plant Cells and Animal Cells

Anatomy of an Animal Cell

• Mitochondria
• Microfilaments
• Lysosome
• Rough Endoplasmic Reticulum
• Peroxisome
• Centrioles
• Micro Tubules
• Golgi Apparatus
• Cilia
• Smooth Endoplasmic Reticulum
• Nucleus
• Nuclear pores
• Plasma Membrane
• Nucleolus
• Nuclear Envelope
• Chromatin
• Rough Endoplasmic Reticulum

Anatomy of a Plant Cell

• Vacuole
• Chloroplast
• Cell Membrane
• Cell Wall
• Golgi apparatus
• Mitochondrion

Cytosol and Cytoplasm

• The cytosol is the "soup" within which all the other cell organelles reside and where most of the cellular metabolism occurs.
• The cytoplasm is a collective term for the cytosol plus the organelles suspended within the cytosol.

Organelles

• Both membranous and non-membranous organelles
• Membranous Organelles
  • Cell membrane (plasma membrane)
  • Mitochondria
  • Endoplasmic reticulum (rough and smooth)
  • Golgi apparatus
  • Lysosomes
• Non-membranous Organelles
  • Ribosomes
  • Cytoskeleton

Plasma Membrane (Cell Membrane)

• The boundary of the cell, composed of three distinct layers.
• Two layers of fat and one layer of protein.
• Difficult to see with H&E stains.
• Visible with silver (Ag) stain.
• Appears as 2 electron-dense lines separated by an electron-lucent one (trilamellar) in electron micrographs.

Molecular Structure of Cell Membrane

• 1-Lipid Component

• Phospholipid molecules comprise the lipid bilayer, each having a head and two tails.

• Hydrophilic heads face outward.

• Hydrophobic tails face inwards.

• Cholesterol molecules stabilize the membrane and modulate fluidity.

• 2- Protein Component

• Extrinsic (peripheral) proteins are loosely attached to the membrane surface.

• Intrinsic (integral) proteins extend across the bilayer and act as pathways for ions and molecules.

• Channel proteins & carrier proteins

• 3- Carbohydrate Component

• Glycoproteins and glycolipids form the cell coat (glycocalyx)

• Functions as cell adhesion and immune defense.

Functions of Cell Membrane (Bulk Transport)

• Endocytosis -Phagocytosis (engulfing solid particles) and -Pinocytosis (engulfing fluid droplets)
  • Receptor-mediated endocytosis (selective transport of specific molecules)
• Exocytosis (moving substances from inside the cell to the outside)

The Nucleus

• Brain of the cell.
• Border by a porous membrane (nuclear envelope).
• Contains thin fibers if DNA & protein called chromatin.
• Contains a small round nucleolus, which produces ribosome RNA to make ribosomes
• Rod-shaped chromosomes

Endoplasmic Reticulum

• Complex network of transport channels.
• Smooth ER (no ribosomes): functions in lipid and steroid hormone synthesis.
• Rough ER (with ribosomes): functions in protein synthesis and packaging.

Golgi Apparatus

• Modifies, packages, stores and transports proteins to be secreted (hormones, enzymes, antibodies).
• Works with the endoplasmic reticulum and ribosomes to synthesize proteins.

Lysosomes

• Recycling Center
• Contain a variety of enzymes to recycle cellular debris, digest food particles, nutrients, foreign and dead materials
• Three types :
  • Phagolysosome: digests material phagocytosed by the cell
  • Multivesicular body: formed from the fusion between a primary lysosome with vesicles from endocytosis
  • Autolysosome: contains old organelles

Mitochondria

• Double membranous organelle.
• Size of a bacterium.
• Contains its own DNA (mDNA)
• Responsible for respiration and energy production (ATP).

Function of Epithelial Tissue

• Protective barrier
• Absorption
• Filtration
• Secretion

Classification of Epithelium

• Based on thickness ("simple" and "stratified")
• Shape ("squamous," "cuboidal," and "columnar")

Features of Epithelium (Surface)

• Microvilli, cilia, and flagella.

Features of the Basal Surface of Epithelium

• Basal lamina
• Basement membrane

Features of Lateral Surface of Epithelium

• Cell junctions (tight junctions, gap junctions, desmosomes).

Types of Connective Tissue

• Loose Connective Tissue (Areolar, Adipose, Reticular, Mucoid)
• Dense Connective Tissue (Regular, Irregular, Elastic)
• Supportive Connective Tissue (Cartilage: Hyaline, Fibrocartilage, Elastic) (Bone)
• Fluid Connective Tissue (Blood)

Cell Types (Connective Tissue)

• Resident
• Fibroblasts
• Adipose cells
• Pericytes
• Mast cells
• Macrophages
• Transient
• Plasma cells
• Lymphocytes
• Neutrophils
• Eosinophils
• Basophils
• Monocytes
• Macrophages

Matrix Cells (Connective Tissue)

• Fibroblasts: make connective tissue/fibers.
• Chondroblasts: produce cartilage
• Osteoblasts: produce bone
• Hematopoietic stem cells: produce blood.

Matrix Fibers (Connective Tissue)

• Collagen fibers: most abundant; provide flexibility and tensile strength.
• Elastic fibers: intermediate; allow for stretch and recoil.
• Reticular fibers: small and delicate; form a structural framework for some organs.

Types of Muscle Tissue

• Skeletal muscle
• Cardiac muscle
• Smooth muscle

Skeletal Muscle Anatomy

• Epimysium
• Perimysium
• Endomysium

Microscopic and Functional Anatomy of Skeletal Muscle

• Fibers are long and cylindrical.
• Each fiber is formed by fusion of embryonic cells, hence multinucleate.
• Nuclei are peripherally located.
• Myofibrils are made up of myofilaments.
• Myofibrils are long rods with cytoplasm.
• Composed of functional units called sarcomeres.

Sarcomere

• Z discs anchor the myofilaments.
• Thin filaments are composed of actin.
• Thick filaments are composed of myosin.
• A band contains the full length of the thick myosin filament
• I Band contains the thin actin filaments
• H zone is the middle of the A band that contains thick myosin filaments.
• M line holds thick filaments together.

Myofibrils: Proteins of Muscle

• Contractile proteins (myosin, actin)
• Regulatory proteins
• Structural protein

Innervation of Skeletal Muscle

• Each skeletal muscle is supplied by one nerve, artery, and two veins.
• A motor neuron supplies multiple muscle cells at the neuromuscular junction.

Events Occurring After Nerve Signal

• Arrival of nerve impulse at nerve terminal causes the release of ACh.
• ACh binds to receptors on muscle motor end plate opening channels.
• Inside of muscle cell becomes more positive, triggering a muscle action potential.
• Release of Ca+2 from the SR into the sarcoplasm triggers the sliding of actin filaments over myosin.
• Acetylcholinesterase breaks down the ACh so the muscle cells relax.

Relaxation

• Acetylcholinesterase breaks down ACh within the synaptic cleft.
• Muscle action potential ceases
• Ca+2 release channels close
• Active transport pumps Ca+2 back into storage in the sarcoplasmic reticulum.
• Calcium-binding protein (calsequestrin)

T-tubules & Sarcoplasmic Reticulum (SR)

• Special tubular system.

Tendons & Ligaments

• Connective tissues.
• Tendons connect muscle to bone.
• Ligaments connect bone to bone

The Vascular System

• Major components: Arteries,Veins, &Capillaries
• Three Layers of vessel: Intima, Media, &Adventitia
• Function of blood vessels.
• Differences between a medium-sized artery & medium-sized vein

Capillaries

• Formed by a single layer of simple squamous epithelium resting a basal lamina, which curls up into a tube
• Three types (continuous, fenestrated, sinusoid).

Lymphatic System

• Network of vessels throughout body that transport lymph back into the blood.
• Lymph is a fluid similar to plasma
• Pathways
  • Lymphatic capillaries
  • Lymphatic vessels
  • Lymph nodes
  • Lymphatic trunks
  • Collecting ducts
• Lymphatic vessels
• Lymphatic trunks
• Lymphatic ducts (thoracic and right)

Lymphatic Organs

• Primary (bone marrow & thymus).
• Secondary (lymph nodes, spleen, tonsils, and Peyer's patches)

Functions of Lymphatic System

• Drains interstitial fluid and returns it to blood circulation.
• Transports dietary lipids.
• Carries out immune responses

Tissue Fluid & Lymph

• Lymph moves due to skeletal muscles contraction, pressure change in the thoracic cavity.
• Interstitial fluid – High in nutrients, oxygen, and small protein.

The Thymus

• Asymmetric bilobed organ where mature T-cells are formed.
• Located in the superior mediastinum, behind the manubrium

Red Bone Marrow

• Site of blood cell formation.

Test your knowledge on key concepts related to mitochondria, connective tissues, and cellular processes. This quiz covers fundamental questions about cellular structures, their functions, and characteristics. Perfect for students studying cell biology and histology.