Cells & Tissues Overview

Cells & Tissues

• Cells are the basic unit of life, responsible for protection, support, movement, communication, cell metabolism, energy release, and inheritance.
• Cells are organized into three main regions: nucleus, cytoplasm, and plasma membrane.
• Cell processes include nutrition, digestion, absorption, biosynthesis, respiration, secretion, excretion, response, and reproduction.

Cell Processes - Factors

• Key factors impacting cell processes include matter, energy, organization, and information.

Nucleus

• The nucleus is the control center of the cell, containing genetic material (DNA).
• Three regions within the nucleus include the nuclear membrane (barrier), nucleolus (ribosome production), and chromatin (DNA and protein that condenses to form chromosomes during cell division).

Plasma Membrane

• The plasma membrane, also known as the cell membrane, is a barrier for cell contents, giving strength, shape and protection to the cell.
• It regulates material flow between the cell's interior and its environment, using a double phospholipid layer (hydrophilic heads and hydrophobic tails).
• Other key components include proteins, cholesterol, and glycoproteins.

Plasma Membrane Specializations

• Microvilli are finger-like projections that increase surface area for absorption.
• Membrane junctions include tight junctions, desmosomes, and gap junctions.

Cytoplasm

• Cytoplasm is the material outside the nucleus and inside the plasma membrane.
• Cytosol is the fluid that suspends other elements and is the site of many metabolic pathways.
• Organelles are metabolic machinery of the cell, membrane-bound with unique structures and functions.
• Inclusions are non-functioning units within the cytoplasm.

Cytoplasmic Organelles

• Various organelles, such as the smooth and rough endoplasmic reticulum, lysosomes, mitochondria, peroxisomes, and cytoskeleton (microfilaments, intermediate filaments, microtubules), play specific roles in cellular functions.
• Examples include ribosomes, which are crucial for protein production.
• The Golgi apparatus collects, modifies, packages, and distributes proteins and lipids.

Ribosomes

• Ribosomes are responsible for protein production.
• Free ribosomes are not attached to any organelles, while others are attached to the endoplasmic reticulum (ER).

Endoplasmic Reticulum

• The endoplasmic reticulum (ER) is a series of membranes forming sacs and tubules extending from the outer nuclear membrane into the cytoplasm.
• It includes rough ER (with ribosomes) and smooth ER.

Golgi Apparatus

• The Golgi apparatus collects, modifies, packages, and distributes proteins and lipids.

Lysosomes

• Lysosomes are membrane-bound vesicles containing enzymes that function as intracellular digestive systems.

Peroxisomes

• Peroxisomes are small, membrane-bound vesicles containing enzymes that break down fatty acids, amino acids, and hydrogen peroxide.

Mitochondria

• Mitochondria are the "powerhouses" of the cell, providing ATP for cellular energy.
• They carry out aerobic respiration.

Cytoskeleton

• The cytoskeleton consists of proteins supporting the cell, holding organelles in place, and enabling cell shape changes.
• It consists of microfilaments, intermediate filaments, and microtubules.

Centrioles

• Centrioles are rod-shaped bodies made of microtubules directing mitotic spindle formation during cell division.

Cellular Projections

• Cellular projections, such as cilia and flagella, are used for movement.
• Cilia moves materials across the cell surface, while flagella propel the cell.

Diversity of Cell Types

• Various cell types like epithelial, muscle, nerve, fat, and macrophage, specialize in specific functions (connecting body parts, covering organs, moving parts, storing nutrients, fighting disease).

Membrane Transport

• Membrane transport involves the movement of substances into and out of the cell.
• Methods include passive transport (no energy needed) and active transport (metabolic energy required).
• Solutions, comprised of a solvent (dissolving medium) and solutes (components), regulate this transport.
• The plasma membrane selectively allows materials—allowing some and blocking others—through in both directions.

Passive Transport

• Different mechanisms of passive transport include diffusion (particles move from higher to lower concentration), osmosis (water movement), and filtration (pressure-driven movement).
• Diffusion types include simple and facilitated diffusion. (simple if substance can pass through membrane pores.)

Active Transport

• Active transport moves substances against the concentration gradient—requiring energy (ATP).
• Examples include solute pumping (amino acids, sugars, and ions) and bulk transport (moving substances in vesicles, such as exocytosis, endocytosis—phagocytosis and pinocytosis).

Cell Division

• Cell division, via mitosis or meiosis, leads to the formation of two daughter cells from a single parent cell, distributing identical DNA to the daughter cells except for sex cells.

Mitosis

• Mitosis, a cell division process, has distinct phases (interphase, prophase, metaphase, anaphase, telophase, and cytokinesis) in which genetic material duplicates and distributes.

Protein Synthesis

• Protein synthesis happens within cells using proteins as building blocks, with genes encoding instructions and DNA specifying RNA structures.
• Protein synthesis uses transcription and translation process.

Role of RNA

• mRNA carries instructions from the nucleus to ribosomes.
• tRNA transfers amino acids to the ribosome for protein building.
• rRNA forms the ribosomes where proteins are built.

Transcription and Translation

• Transcription—transferring DNA base sequence information to mRNA complementary base sequence—occurs in the nucleus.
• Translation translates the nucleic acid sequence to amino acid sequence, taking place in the cytoplasm.

Body Tissues

• Tissues are groups of cells with similar structures and functions.
• The four primary tissue types are epithelial, connective, muscle, and nervous tissues.

Epithelial Tissue

• Epithelial tissue covers and protects surfaces, and its cells fit closely together, with tissues having a free surface and a basement membrane.
• This tissue is avascular yet regenerates when it’s well-nourished.
• Epithelial tissue functions include protection, absorption, filtration, secretion.

Epithelial Tissue Classifications

• Characterized by cell layers (simple or stratified) and cell shapes (squamous, cuboidal, columnar).
• Major types of epithelial tissues include simple (one-layer) and stratified (multiple-layer) squamous, cuboidal, columnar, pseudostratified.

Glandular Epithelium

• Endocrine glands (ductless) secrete hormones directly into the bloodstream.
• Exocrine glands (duct-bearing) secrete products into ducts, such as sweat and oil glands.

Connective Tissue

• Connective tissue binds, supports, protects, and transports substances in the body.
• Extracellular matrix composed of ground substance (mostly water) and protein fibers (collagen, elastic, reticular) surrounds living cells.
• Different connective tissue types include bone, cartilage (hyaline, elastic, fibrocartilage), dense fibrous, areolar, blood.

Muscle Tissue

• Muscle tissue produces movement, classified into skeletal, cardiac, and smooth muscles.

Skeletal Muscle

• Skeletal muscle is voluntary, with striated cells each containing multiple nuclei.

Cardiac Muscle

• Cardiac muscle is involuntary, found in the heart, and has striated cells with intercalated disks and one nucleus per cell.

Smooth Muscle

• Smooth muscle is involuntary, surrounds hollow organs, lacks striations and contains one nucleus per cell.

Nervous Tissue

• Nervous tissue is responsible for sensing and communicating information, containing neurons and nerve support cells called glial cells.

Nerve Cells

• Nerve cells (neurons) carry impulses between the brain and other areas of the body.

Tissue Repair

• Tissue repair in the body uses regeneration (same cells replacing) or fibrosis (scar tissue forming).
• Repair steps include inflammation, formation of granulation tissue, regeneration of surface epithelium.

Tissue Regeneration

• Epithelial tissue and fibrous connective tissue/bone regenerate easily, while nervous and cardiac muscle regenerate with scar tissue.

This quiz explores the fundamental concepts of cells and tissues, focusing on their structure and essential processes. Participants will learn about the nucleus, plasma membrane, and various cellular functions. Perfect for students keen to understand the building blocks of life.