Introduction to Cells and Organelles
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Questions and Answers

What is the primary function of the Golgi complex?

  • Modify, sort, and package proteins (correct)
  • Store calcium ions
  • Synthesize lipids
  • Translate mRNA into proteins

    • Cilia and flagella are both made of the same type of molecular structure.

    True

    What are the small holes in the nuclear envelope called?

    nuclear pores

    The _________ are membrane-bound organelles that contain enzymes to digest cellular molecules.

    <p>lysosomes</p> Signup and view all the answers

    Match the following organelles with their primary function:

    <p>Centrosome = Organizes microtubules Rough ER = Synthesizes proteins Smooth ER = Synthesizes lipids Peroxisomes = Detoxifies harmful substances</p> Signup and view all the answers

    Which of the following statements about organelles is true?

    <p>Eukaryotic cells possess membranous organelles.</p> Signup and view all the answers

    What is the primary function of mitochondria?

    <p>Energy processing</p> Signup and view all the answers

    The cytoplasm only contains the cell nucleus.

    <p>False</p> Signup and view all the answers

    Somatic cells divide only through meiosis.

    <p>False</p> Signup and view all the answers

    What is the function of the plasma membrane?

    <p>To separate the external environment from the internal environment and regulate exchange of materials.</p> Signup and view all the answers

    The cytoskeleton is composed of __________, __________, and __________.

    <p>microfilaments, intermediate filaments, microtubules</p> Signup and view all the answers

    What term describes the process where homologous chromosomes exchange genetic information?

    <p>crossing over</p> Signup and view all the answers

    Match the following structures with their primary functions:

    <p>Microfilaments = Cell movement and support Intermediate filaments = Anchor organelles Microtubules = Segregate chromosomes during cell division Centrosome = Organizes microtubules</p> Signup and view all the answers

    The ______ is the region where two sister chromatids are joined together.

    <p>centromere</p> Signup and view all the answers

    Match the phases of mitosis with their correct descriptions:

    <p>Prophase = Condensation of chromatin into chromosomes Metaphase = Alignment of chromosomes at the equatorial plate Anaphase = Separation of sister chromatids to opposite poles Telophase = Formation of two new nuclear envelopes</p> Signup and view all the answers

    Which of the following is NOT a characteristic of living things?

    <p>Photosynthesize</p> Signup and view all the answers

    Anatomy and physiology are unrelated fields of study.

    <p>False</p> Signup and view all the answers

    What is the term for the study of structures in living organisms?

    <p>anatomy</p> Signup and view all the answers

    The _______ system is responsible for exchanging gases between the body and the environment.

    <p>respiratory</p> Signup and view all the answers

    Match the following organ systems with their primary function:

    <p>Integumentary system = Covers and protects the body. Muscular system = Moves and heats the body. Cardiovascular system = Transports blood, nutrients, and gases. Digestive system = Acquires and extracts nutrients.</p> Signup and view all the answers

    What is the primary role of the urinary system?

    <p>Removing wastes and maintaining pH</p> Signup and view all the answers

    Homeostasis refers to the maintenance of varying internal conditions within the body.

    <p>False</p> Signup and view all the answers

    What is the fluid component of blood called?

    <p>plasma</p> Signup and view all the answers

    An example of positive feedback in the human body is __________ during childbirth.

    <p>oxytocin release</p> Signup and view all the answers

    Match the following body regions with their corresponding terms:

    <p>Knee = Popliteal region Neck = Cervical region Wrist = Carpal region Back of the head = Occipital region</p> Signup and view all the answers

    Which type of feedback loop is most common in maintaining homeostasis?

    <p>Negative feedback</p> Signup and view all the answers

    Blood pressure is an example of a dynamic internal condition that the body maintains.

    <p>True</p> Signup and view all the answers

    What type of sensor detects changes in blood pressure in the body?

    <p>baroreceptors</p> Signup and view all the answers

    The __________ plane separates the body into superior and inferior parts.

    <p>transverse</p> Signup and view all the answers

    What happens when homeostasis is not maintained for a prolonged period?

    <p>Development of disorders</p> Signup and view all the answers

    What is the deepest layer of the epidermis called?

    <p>Stratum basale</p> Signup and view all the answers

    The stratum lucidum is present in both thin and thick skin.

    <p>False</p> Signup and view all the answers

    What is the role of melanocytes in skin color?

    <p>To produce melanin, which gives skin its color.</p> Signup and view all the answers

    The outermost layer of skin that consists of dead cells is known as the _________.

    <p>stratum corneum</p> Signup and view all the answers

    Match the layers of the epidermis with their characteristics:

    <p>Stratum basale = Contains stem cells capable of division Stratum spinosum = Provides strength with flat keratinocytes Stratum granulosum = Seals the epidermis with dying cells Stratum corneum = Most superficial layer with dead cells</p> Signup and view all the answers

    What is the outermost layer of the skin called?

    <p>Epidermis</p> Signup and view all the answers

    The dermis is avascular and does not contain blood vessels.

    <p>False</p> Signup and view all the answers

    Name the pigment produced by melanocytes that protects against UV light.

    <p>Melanin</p> Signup and view all the answers

    The __________ layer of skin anchors all structures to the fascia and contains pressure receptors.

    <p>subcutaneous</p> Signup and view all the answers

    Match each cell type with its function in the epidermis:

    <p>Keratinocytes = Produce keratin Melanocytes = Provide pigmentation Langerhans cells = Engulf invaders Basal cells = Regenerate the epidermis</p> Signup and view all the answers

    Which type of bond links monosaccharides to form disaccharides and polysaccharides?

    <p>Glycosidic bond</p> Signup and view all the answers

    Humans can digest cellulose because they possess the necessary enzymes.

    <p>False</p> Signup and view all the answers

    What are the monomers that make up proteins?

    <p>Amino acids</p> Signup and view all the answers

    A __________ is formed when two amino acids undergo dehydration synthesis.

    <p>peptide bond</p> Signup and view all the answers

    Match the following types of lipids with their descriptions:

    <p>Fatty acids = Building blocks of triglycerides Triglycerides = Main form of energy storage in the body Phospholipids = Key component of biological membranes Steroids = Lipids with a fused-ring structure</p> Signup and view all the answers

    What property of water allows it to absorb a significant amount of energy without a large increase in temperature?

    <p>Specific heat capacity</p> Signup and view all the answers

    Ice sinks in water due to its lower density compared to liquid water.

    <p>False</p> Signup and view all the answers

    What term describes substances that do not dissolve in water?

    <p>Hydrophobic</p> Signup and view all the answers

    Water is a _______ molecule, allowing it to dissolve polar and charged substances easily.

    <p>polar</p> Signup and view all the answers

    Match the following properties of water with their definitions:

    <p>Cohesion = Molecules sticking to one another Specific heat capacity = Ability to absorb energy without a large temperature change Ice formation = Lattice structure that is less dense than liquid water Solvent = Dissolves polar and charged substances</p> Signup and view all the answers

    Study Notes

    Introduction to Cells

    • Cells are the fundamental unit of life.
    • Humans have over 200 distinct cell types.
    • Each cell type has a unique structure that reflects its function.
    • Eukaryotic cells have membranous organelles, while prokaryotic cells do not.

    Organelles

    • Organelles are small, specialized subunits within a cell responsible for specific functions.
    • The plasma membrane is a flexible barrier separating the internal and external environments of the cell.
    • It regulates the exchange of materials between the cell and its surroundings.
    • The cytoplasm fills the space between the plasma membrane and the nucleus, providing an aqueous environment for cellular reactions.
    • The cytoskeleton provides structure, support, and movement for cells and their internal components.

    Components of the Cytoskeleton

    • Microfilaments are composed of actin and myosin.
    • They aid in cell movement and support cell structure.
    • Intermediate filaments are made of diverse protein subunits, providing tensile strength.
    • They anchor organelles such as the nucleus.
    • Microtubules are made of tubulin proteins.
    • They are dynamic structures that rapidly assemble and disassemble.
    • They are crucial for chromosome segregation during cell division.
    • Microtubules also form cilia and flagella for cell movement.

    The Centrosome

    • The centrosome is the microtubule-organizing center of animal cells.
    • It contains centrioles, short microtubules involved in mitotic spindle formation.

    Cilia and Flagella

    • Cilia are short bundles of microtubules that beat like oars to propel cells.
    • They are found in the upper respiratory tract and the oviduct.
    • Flagella are long bundles of microtubules that whip through fluid to move cells.
    • They are found in human sperm.

    The Nucleus

    • The nucleus is a membrane-bound organelle containing DNA.
    • The nuclear envelope, composed of two membranes, has pores that permit the exit of mRNA and ribosomal subunits.
    • The nucleolus within the nucleus is responsible for ribosomal subunit synthesis.

    DNA Packaging

    • DNA is packaged within the nucleus, allowing it to fit within the cell and move during division.
    • In its loose form, DNA is called chromatin and is accessible for transcription.
    • When tightly wound, DNA forms chromosomes, making it inaccessible for transcription.
    • The genome encompasses all the DNA in an organism.

    Ribosomes

    • Ribosomes are responsible for translating mRNA into proteins.
    • They are composed of rRNA and protein.
    • Subunits assemble into ribosomes within the cytoplasm.
    • Some ribosomes attach to the rough endoplasmic reticulum membrane.

    Central Dogma of Biology

    • The flow of information in cells follows the central dogma: DNA is transcribed into mRNA, and mRNA is translated by ribosomes into proteins.
    • Transcription occurs within the nucleus, while translation takes place at the ribosomes.
    • Ribosomes translate mRNA into proteins by reading mRNA triplets called codons.
    • Each codon specifies a specific amino acid.

    Endoplasmic Reticulum (ER)

    • The ER is a network of membranes involved in protein synthesis, modification, and lipid manufacture.
    • The rough ER (rER) is studded with ribosomes and synthesizes proteins destined for organelles.
    • The smooth ER (sER) synthesizes lipids, inactivates drugs, participates in carbohydrate metabolism, and stores calcium ions.

    Golgi Complex

    • The Golgi complex modifies, sorts, finishes, and packages proteins for export.
    • Its membranous folds are called cisternae.
    • Proteins enter from the rER at the entry face and are modified and packaged at the exit face.
    • Proteins are exported in vesicles to their destinations.

    Lysosomes

    • Lysosomes are spherical, membrane-bound sacs containing digestive enzymes.
    • They break down cellular molecules and maintain a pH of 5.
    • Tay-Sachs disease is a lysosomal storage disorder due to defective lysosomes.

    Peroxisomes

    • Peroxisomes are spherical, membrane-bound sacs containing oxidases.
    • They metabolize fatty acids, detoxify alcohols, and oxidize hydrogen peroxide.
    • They are found in various human cells.

    Proteasomes

    • Proteasomes are large, protein-degrading machines in the cytoplasm.
    • They break down large polypeptides into smaller peptides.
    • Defective proteasomal function is linked to diseases like Parkinson's and Alzheimer's.

    Mitochondria

    • Mitochondria are involved in energy-processing reactions.
    • They have two membranes: an outer membrane and an inner membrane.
    • The inner membrane folds into cristae, which enclose the mitochondrial matrix.
    • Aerobic cellular respiration occurs in the cytoplasm and at the inner mitochondrial membrane, generating ATP for cellular energy.
    • Mitochondria are maternally inherited and contain their own DNA.
    • Damaged mitochondria can trigger cell death.

    Cell Division

    • Somatic cells divide by mitosis and cytokinesis.
    • The cell cycle consists of interphase and M phase.
    • Interphase is the non-dividing phase, including G1, S, and G2 phases.

    DNA Replication

    • During S phase, DNA replication proceeds semi-conservatively.
    • Each daughter molecule is composed of one original strand and one newly synthesized strand.

    Mitosis

    • Mitosis is nuclear division, divided into four phases: prophase, metaphase, anaphase, and telophase.
    • During prophase, the nuclear envelope dissolves, and chromatin condenses into chromosomes.
    • Metaphase involves the alignment of chromosomes at the equatorial plate and attachment of the mitotic spindle.
    • Anaphase is characterized by the pulling of chromosomes to opposite poles of the cell.
    • Telophase involves the partitioning of the two components into two forming daughter cells.

    Cytokinesis

    • Cytokinesis completes cell division, dividing the cytoplasm and organelles.

    Chromosome Anatomy

    • An unreplicated chromosome is called a chromosome.
    • A replicated chromosome is also called a chromosome, composed of two sister chromatids joined at the centromere.
    • The kinetochore protein complex at the centromere serves as an attachment site for the mitotic spindle.

    Telomeres

    • Telomeres are DNA sequences at chromosome ends that protect against shortening.
    • They are added by telomerase, an enzyme that helps maintain chromosome integrity.
    • Shortening telomeres are linked to aging and cell death.
    • Cancer cells have overactive telomerase, leading to rapid cell division and tumor formation.

    Meiosis

    • Meiosis is the division of reproductive cells into gametes.
    • Gametes are haploid cells with half the number of chromosomes.
    • Meiosis I divides replicated chromosomes into daughter cells, and crossing over occurs between homologous chromosomes.
    • Meiosis II separates sister chromatids, resulting in four nonidentical haploid daughter cells called gametes.

    Cell Membrane Structure

    • The plasma membrane is a fluid mosaic, meaning its lipids and proteins can move freely.
    • The membrane is primarily composed of a phospholipid bilayer, with the polar heads facing the solvent and the nonpolar tails forming the core.
    • Cholesterol, glycolipids, and proteins contribute to the mosaic nature of the membrane.

    Membrane Fluidity

    • Membrane fluidity is essential for biological function.
    • The saturation of fatty acid tails affects fluidity; unsaturated fatty acids increase fluidity.
    • Cholesterol acts as a fluidity buffer.
    • Temperature also influences membrane fluidity.

    Selective Permeability

    • Membranes are selectively permeable, allowing only specific solutes to pass through.
    • Nonpolar molecules can diffuse through the membrane readily.
    • Polar molecules typically require transport proteins to cross the membrane.

    Membrane Proteins

    • Integral membrane proteins are embedded within the hydrophobic core of the lipid bilayer.
    • Peripheral membrane proteins are attached to the membrane's surface by electrostatic interactions.
    • Glycoproteins are membrane proteins with bound saccharides, found on the extracellular side.
    • Membrane proteins serve various functions, including acting as receptors, enzymes, linkers, and cell identity markers.

    Simple Diffusion

    • Simple diffusion is the passive movement of solutes down their concentration gradients.
    • It does not require energy and is driven by entropy.
    • The rate of diffusion is affected by solute size, temperature, and concentration gradient.

    Facilitated Diffusion

    • Facilitated diffusion involves the movement of solutes down their concentration gradients with the assistance of transport proteins.
    • Ion channels provide pores for diffusion of charged substances.
    • Carrier proteins change shape to transport specific solutes.
    • Both ion channels and carrier proteins create a hydrophilic path through the membrane for polar molecules.

    Active Transport

    • Active transport moves substances against their concentration gradients, requiring metabolic energy (ATP).
    • It helps maintain specific concentrations of solutes within the cell.
    • Examples include the establishment of the negative membrane potential in most cells.

    Active Transport

    • Active transport moves solutes against their concentration gradients across membranes.
    • The sodium-potassium (Na+-K+) pump keeps Na+ at a higher concentration outside the cell and K+ at a higher concentration inside the cell.
    • The Na+-K+ pump is a carrier protein that changes shape using energy derived from ATP hydrolysis.
    • Primary active transporters use energy derived from ATP hydrolysis to move solutes up their concentration gradients.
    • Secondary active transporters use the electrochemical gradients set up by primary active transporters to power solute movement.
    • Secondary active transporters move two solutes simultaneously, one down its concentration gradient while the other moves up its concentration gradient.
    • When both solutes flow in the same direction, it's called symporters.
    • When solutes flow in opposite directions, it's called antiporters.
    • Cyanide inhibits ATP production in the mitochondrion, negatively affecting all active transport processes.

    Vesicular Transport

    • Vesicular transport is an active transport process using membrane sacs called vesicles.
    • Endocytosis is the movement of substances into cells via vesicles.
    • Exocytosis is the movement of substances out of cells.
    • Transcytosis is the movement of substances through cells by endocytosis followed by exocytosis.
    • Receptor-mediated endocytosis imports specific molecules into cells.
    • Phagocytosis is the "eating" of molecules or invaders by phagocytic cells, where substances are engulfed and internalized into a vesicle that fuses with a lysosome for digestion.
    • Pinocytosis, also known as bulk-phase endocytosis, is the cell "drinking" of dissolved solutes.
    • Both endocytosis and exocytosis require ATP hydrolysis.

    Osmosis

    • Most bodily solutions use water as a solvent.
    • Water moves from low solute concentration to high solute concentration.
    • Osmosis is the movement of water across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.
    • Water can move across the lipid bilayer but very inefficiently.
    • The diffusion of water across biological membranes occurs efficiently through channel proteins called aquaporins.

    Tonicity

    • Cells behave differently in different solutions with varying solute concentrations compared to the cell's interior.
    • Hypertonic solutions have a higher solute concentration than inside the cell, causing water to move out of the cell.
    • Hypotonic solutions have a lower solute concentration than inside the cell, causing water to move into the cell.
    • Isotonic solutions have the same solute concentration as inside the cell, resulting in no net water movement.
    • The total concentration of a solution is known as its osmolarity.
    • Osmolarity determines tonicity, which influences how a cell behaves when placed in that solution.

    Cell Division

    • Somatic cells divide by mitosis, producing two identical daughter cells.
    • Reproductive cells divide by meiosis, producing four nonidentical gametes.
    • Before cell division, DNA must be replicated.

    Characteristics of Living Things

    • Living things metabolize complex chemical substances, respond to stimuli, move, grow and develop, and reproduce.

    Anatomy and Physiology

    • Anatomy is the study of structures and their relationships.
    • Physiology is the study of function.
    • Structures are specialized for a particular function, and functions are limited or enhanced by structure.

    Levels of Structural Organization

    • There are six levels of structural organization in the human body: chemical, cellular, tissue, organ, system, and organismal.

    Organ Systems

    • An organ system is a group of related organs with interdependent functions that work together to perform a coordinated function.
    • The 11 organ systems in humans are:
      • Integumentary: skin, nails, and hair; covers and protects the body.
      • Skeletal: bones, joints, and cartilage; protects and supports the body.
      • Muscular: skeletal muscles; moves and heats the body.
      • Nervous: brain, spinal cord, nerves, and sensory organs; senses signals and coordinates electrical responses.
      • Endocrine: cells and glands that secrete hormones; senses signals and coordinates chemical responses.
      • Cardiovascular: heart, blood, and vessels that carry blood; transports blood, nutrients, and gases.
      • Lymphatic/Immune: lymph nodes, thoracic duct, red bone marrow, lymphatic vessels, spleen, thymus, and tonsils; defends the body from invaders.
      • Respiratory: pharynx, larynx, trachea, bronchial tubes, lungs, and diaphragm; exchanges gases and disposes of carbon dioxide waste.
      • Digestive: liver, oral cavity, pharynx, esophagus, stomach, small and large intestines; acquires and extracts nutrients and eliminates wastes.
      • Urinary: urinary bladder, urethra, kidney, and ureter; removes wastes and maintains pH of the body, disposes of nitrogenous wastes.
      • Reproductive: gonads, testes, ovary, vagina, prostate, penis, uterus; produces gametes, enables copulation, and houses and nourishes young (females).

    Body Fluids

    • Extracellular fluid is the fluid outside of cells.
      • Interstitial fluid is between tissue cells.
      • Blood plasma is the fluid component of blood in blood vessels and organs of the cardiovascular system.
    • Lymph is the fluid inside of lymph vessels.
    • Organisms must maintain the volume and composition of body fluids for survival.

    Homeostasis

    • Homeostasis is the dynamic upkeep of a set of internal conditions within set parameters.
    • Homeostasis depends on:
      • A receptor to detect the change.
      • A control center to coordinate a response.
      • An effector to carry out the response according to the control center.

    Negative Feedback Loops

    • Negative feedback loops reverse changes to maintain homeostasis.
    • Example: an increase in blood pressure.
      • Receptor: baroreceptors in the walls of blood vessels.
      • Control center: brain --> nerve impulses.
      • Effectors: heart --> decreases blood volume leaving the heart (slows contractions) and blood vessels --> dilation to increase flow.
      • Net response = decrease in blood pressure.

    Positive Feedback Loops

    • Positive feedback loops move the body away from homeostasis.
    • Positive feedback loops enhance the initial change.
    • Example: childbirth in human females.
      • Receptor: nerves in the cervix sense dilation.
      • Control center: brain --> pituitary gland --> release of oxytocin into circulation.
      • Effectors: myometrium of the uterus contracts --> cervix continues to stretch.

    Homeostatic Imbalances

    • Prolonged or chronic homeostatic imbalances lead to disorder, disease, and/or death.
      • Disorders result from abnormal body function.
      • Diseases are disorders with characteristic signs and symptoms linked to specific cause.
      • Symptoms are changes in body functions that are felt or reported (subjective).
      • Signs are changes in body functions that can be measured and observed (objective).

    Anatomical Position

    • Anatomical position is a reference point for describing the human body.
    • The body is standing erect, with feet slightly apart, palms facing forward, and thumbs pointing away from the body.
    • Supine position is lying face up.
    • Prone position is lying face down.

    Body Regions

    • A body region is a generalized area of the body, such as the neck (cervical region).

    Directional Terms

    • Directional terms tell you how structures are related to each other.
    • The midline is an imaginary line that divides the body into right and left sides.
    • Medial/lateral: nearer to the middle of the body/further away from the middle of the body.
    • Proximal/distal: closer to the place of attachment/further away from the place of attachment.
    • Superior/inferior: closer to the head of the body/closer to the feet.

    Planes and Sections

    • A plane is an imaginary flat surface that divides the body.
    • Sections are cuts along a plane.

    Body Cavities

    • Body cavities protect, hold, and support internal structures.

    Dorsal Body Cavities

    • Cranial cavity: formed by cranial bones and contains the brain.
    • Vertebral canal: formed by vertebrae and contains the spinal cord.

    Ventral Body Cavities

    • Thoracic cavity and abdominopelvic cavities.
    • The diaphragm is a muscle that divides the ventral cavities into the thoracic and abdominopelvic cavities.
    • Organs inside ventral cavities are called viscera.

    Serous Membranes

    • Serous membranes surround the viscera.
    • Serous membranes are thin, slippery, and do not open to the exterior of the body.
      • Pleura: encases the lungs in the pleural cavity.
      • Pericardium: encases the heart in the pericardial cavity.
      • Peritoneum: encases the abdominal cavity and its organs.
        • Visceral peritoneum lines the viscera.
        • Parietal peritoneum lines the abdominal cavity wall, including the inferior surface of the diaphragm.

    Thoracic Cavity

    • Formed by the ribs, intercostal muscles, sternum, and thoracic vertebrae.
    • Pericardial cavity contains the heart.
    • Pleural cavities contain the lungs.
    • Mediastinum is the space between the lungs.

    Abdominopelvic Cavity

    • Two cavities that extend from the diaphragm to the groin.
      • Abdominal cavity contains organs of the digestive system and accessory glands.
      • Pelvic cavity contains the urinary bladder and organs and glands of the reproductive system.

    Peritoneum Subdivision

    • The peritoneum can be further subdivided.
      • Peritoneal viscera: stomach, spleen, liver, gallbladder, small intestine, most of the large intestine.
      • Retroperitoneal viscera: kidneys, adrenal glands, pancreas, duodenum, ascending and descending colon, parts of the abdominal aorta, inferior vena cava.

    Abdominopelvic Cavity Terminology

    • The midclavicular lines divide the cavity into three columns.
    • The subcostal and transtubercular lines divide the cavity into three rows.
    • Resulting regions: right and left hypochondriac regions, right and left lumbar regions, right and left inguinal regions, epigastric region, umbilical region, and hypogastric region.

    Quadrants

    • Quadrants are a simpler way to divide the abdominopelvic cavity.
    • Formed by a midsagittal line and transverse line drawn at the umbilicus (belly button).
    • Resulting quadrants are: right upper quadrant, right lower quadrant, left upper quadrant, left lower quadrant.

    Summary

    • Anatomy is the study of structure, physiology is the study of function.
    • The human body can be organized into ascending levels of complexity, from atoms to an organism.
    • There are 11 organ systems, each with a specialized function.
    • Organ systems are interdependent and cooperate.
    • The volume and composition of body fluids must be maintained for survival.
    • Homeostasis is the constant maintenance of conditions within a particular range, mostly maintained through negative feedback loops.
    • Human anatomy can be described using positional, directional, and regional terms.

    The Integumentary System

    • The integumentary system is the largest organ system in the body, contributing 7% of body weight.
    • It is comprised of skin, hair, nails, associated oil and sweat glands, and sensory receptors.
    • The skin, or cutaneous membrane, consists of two primary layers: the epidermis and the dermis.
    • The epidermis is the outermost layer of the skin and is avascular, meaning it lacks blood vessels.
    • The dermis, situated beneath the epidermis, is made up of connective tissue which is vascularized (has blood vessels).
    • Anchoring the dermis to the underlying fascia is the subcutaneous layer, also known as the hypodermis.

    Functions of the Integumentary System

    • Regulates body temperature.
    • Protects the body from external insults like abrasion, dehydration, radiation, and invasion.
    • Senses external stimuli such as touch, pressure, temperature, and pain.
    • Excretes waste products like sweat and sebum.
    • Absorbs certain substances, including medications.
    • Stores blood and energy.
    • Synthesizes Vitamin D, crucial for calcium absorption.

    The Epidermis

    • Composed of keratinized stratified squamous epithelium.
    • Contains several cell types, each playing a distinct role.

    Keratinocytes

    • Layered cells that produce keratin, a tough protein that provides structural integrity to the skin.
    • Form lamellar granules, which release lipids that waterproof and seal the skin, preventing water loss.

    Melanocytes

    • Contain melanin granules, which absorb ultraviolet (UV) radiation and protect the DNA of skin cells from damage.
    • Melanin is a brown-black pigment that accumulates on the surface of the nucleus facing UV light.
    • UV light can damage DNA by causing mutations.

    Intraepidermal Macrophages (Langerhans Cells)

    • UV-sensitive phagocytes found in the epidermis.
    • Engulf and destroy invaders like bacteria and viruses through phagocytosis.

    Tactile Epithelial Cells (Merkel Cells)

    • Specialized sensory receptors that detect touch.
    • Directly contact tactile discs, which are nerve endings.

    Strata of the Epidermis

    • The epidermis is composed of multiple layers, or strata, of keratinocytes, each representing a different stage of maturity.
    • The majority of the body is covered in skin with four strata, while high abrasion areas like palms and soles have five strata.

    Stratum Basale

    • The deepest layer of the epidermis.
    • Contains stem cells that constantly divide to replenish the overlying layers.
    • Abundant in keratin intermediate filaments (IFs), providing strength and reinforcing cell junctions (desmosomes and hemidesmosomes).
    • Cells have large nuclei and numerous ribosomes, reflecting their active role in cell division and protein synthesis.

    Stratum Spinosum

    • Provides tensile strength to the skin.
    • Composed of 8-10 layers of flat keratinocytes with thicker, tougher keratin IFs.
    • Reinforced desmosomes further strengthen this layer.
    • Fewer cells in this layer are capable of cell division.

    Stratum Granulosum

    • A layer that seals the epidermis and contains dying cells.
    • 3-5 layers of cells undergoing apoptosis (programmed cell death).
    • Organelles disintegrate, keratin filaments persist, and cells produce:
    • Keratohyalin, a dark-staining substance that aids in keratin filament assembly.
    • Lamellar granules, which release lipids as the cells die, creating a waterproof barrier that prevents invasion and fluid loss.
    • The stratum granulosum represents a boundary between metabolically active and dead cells.

    Stratum Corneum

    • The most superficial layer of the skin.
    • Thin skin has 4 strata, while thick skin has 5.
    • Composed of flat, thin, dead, and overlapping cells that are continuously sloughed off with abrasion.
    • Renewed by division from the stratum basale.

    Stratum Lucidum

    • Only present in thick skin.
    • Found between the stratum granulosum and the stratum corneum.
    • Has a clear (lucid) appearance.
    • Made up of dead, flat keratinocytes with thick keratin filaments and thick plasma membranes, providing additional mechanical support in thick skin.

    Growth of The Epidermis

    • Takes approximately 4-6 weeks for new cells from the stratum basale to migrate to the stratum corneum.
    • Keratinization, the process of keratin buildup in cells, reinforces the skin.
    • As keratinocytes move further from the stratum basale, their access to nutrients decreases, contributing to their eventual death and shedding.

    The Dermis

    • The dermis, located beneath the epidermis, is composed of connective tissue, giving it significant tensile strength.
    • It is further divided into two distinct regions: the papillary region and the reticular region.

    Papillary Region

    • Made up of areolar connective tissue with collagen and elastic fibers.
    • Contains dermal papillae, tissue projections extending from the dermis into the epidermis, which house capillaries.
    • Also contains nervous tissue, responsible for touch and pain sensation.
    • Represents the top 20% of the dermis.

    Reticular Region

    • Composed of dense irregular connective tissue.
    • A mesh-like network of thick collagen fibers, fibroblasts, and other cells.
    • Provides resistance to stretching and shearing forces, maintaining the skin's integrity.
    • Contains glands, nerves, and blood vessels.
    • Anchors the dermis to the subcutaneous layer.
    • The bottom 80% of the dermis.

    Fingerprints

    • Formed by epidermal ridges in thick skin that interlock with the dermal papillae.
    • Fingerprints are unique to each individual, even identical twins.
    • Increase friction for grip and surface area for touch sensation.
    • Sweat pores open on the surface of the skin, leaving behind fingerprints.

    Structural Basis For Human Skin Color

    • Differences in human skin color are primarily due to the amount of melanin produced by melanocytes, not the number of melanocytes.
    • Melanin accumulation can manifest as freckles, age spots, or nevuses (moles).
    • A tan is a temporary increase in melanin production triggered by UV exposure.

    Tanning

    • Melanocytes contain tyrosinase, an enzyme involved in melanin synthesis.
    • UV light exposure stimulates tyrosinase activity, leading to increased melanin production and a tan.
    • A tan eventually fades as the skin cells slough off and are replaced by cells with lower melanin production.

    Depth of Skin Color

    • Dark skin has a higher concentration of melanin, ranging in color from yellow to black.
    • Light skin has lower levels of melanin, resulting in translucent skin, allowing the red/pink color of hemoglobin in blood to be visible.
    • The stratum corneum also stores carotene, a pigment with an orange hue. Excess carotene can accumulate in the skin, giving it an orange tinge.

    Tattoos

    • Made by injecting pigments into the dermis using specialized needles.
    • Tattoo removal involves using laser treatment to destroy pigmented cells, which are then engulfed and removed by phagocytosis.

    Hair

    • Found on the scalp, eyebrows, eyelashes, nasal cavity, axillae (armpits), and external genitalia.
    • Provides protection and insulation, and aids in sensing stimuli.
    • Hair on the scalp protects from UV radiation, and hair on the eyes and nasal cavity provides protection from invasion.
    • Hair traps air close to the skin, minimizing heat loss.
    • Touch receptors associated with hair follicles detect hair movement, indicating potential touch or danger.

    Anatomy of Hair

    • Hair consists of a root embedded in the dermis or subcutaneous layer, and a shaft, the visible portion.
    • The root and shaft are made of three layers:
    • The medulla, the deepest layer, containing pigmented cells.
    • The cortex, the middle layer, making up the bulk of the hair.
    • The cuticle, the outermost layer, composed of flat keratinized epithelial cells arranged like shingles.
    • The hair follicle surrounds the hair root, with an outer layer of epithelial tissue and an inner layer called the hair matrix.
    • The hair matrix continuously divides, allowing for hair growth.

    Associated Hair Structures

    • Hair follicles are associated with smooth muscle, called arrector pili.
    • When contracted, arrector pili muscles pull on the hair shaft, causing it to stand on end, a response often triggered by cold or fear.

    Glands of the Skin

    • Sebaceous glands, associated with hair follicles, produce sebum, an oily substance that lubricates and waterproofs the skin and hair, preventing drying.
    • Sweat glands release sweat to cool the body through evaporation. Two types:
    • Eccrine glands secrete a watery solution containing salts and waste products.
    • Apocrine glands, found in the axillae and groin, produce a thicker, odorless sweat that is broken down by bacteria, resulting in body odor.

    Nails

    • Made of hard keratin and cover finger and toe tips providing protection and aiding in manipulation of small objects.
    • Nails are composed of:
    • A free edge
    • A nail body
    • A nail root, embedded in the skin.
    • Nail matrix, responsible for nail growth.
    • Lunula, pale crescent-shaped region at the nail base.

    Wound Healing

    • An essential process for maintaining integumentary homeostasis.
    • Involves three phases:
    • Inflammatory phase, characterized by blood clotting, inflammation, and phagocytosis of debris by immune cells.
    • Migratory phase, where fibroblasts migrate to the wound site and lay down collagen fibers, forming granulation tissue.
    • Proliferative phase, involving the formation of epithelial cells across the wound, and eventual contraction of the wound by myofibroblasts.

    Burns

    • Damages the skin, classified according to depth and severity, categorized as:
    • First-degree burn, affecting the epidermis.
    • Second-degree burn, affecting the epidermis and dermis.
    • Third-degree burn, affecting the epidermis, dermis, and subcutaneous layer.
    • Burns leading to life-threatening complications include edema, sepsis, and loss of fluids and proteins.

    Skin Cancer

    • The most common type of cancer in the United States.
    • Can arise from excessive UV exposure, leading to uncontrolled proliferation of epithelial cells.
    • Three main types:
      • Basal cell carcinoma, originating in the stratum basale, the most common type (78%) and generally benign.
      • Squamous cell carcinoma, originating in the stratum spinosum, accounting for 20% of skin cancers.
      • Malignant melanoma, involving melanocytes, the deadliest form of skin cancer.

    Summary

    • The integumentary system plays a vital role in protecting the body, regulating temperature, and sensing the environment.
    • Skin color is determined by melanin production, which can be influenced by UV exposure.
    • Wound healing is a vital process to maintain the skin’s integrity.
    • Burns pose a significant threat, requiring immediate and appropriate care.
    • Skin cancer, a common type of cancer, is often linked to excessive UV exposure.

    Water Properties

    • Water molecules exhibit cohesion due to hydrogen bonds, causing them to stick together.
    • Water has a high capacity to absorb heat, moderating temperature changes. This is why water can absorb a lot of energy before its temperature significantly increases.
    • Water releases absorbed heat back into the environment, helping to regulate temperatures.
    • When water freezes, it expands, making ice less dense than liquid water. This property allows freshwater organisms to survive winter by allowing ice to float.
    • Water is an excellent solvent due to its polar nature, allowing polar and charged substances to dissolve. These substances are called hydrophilic. Nonpolar substances like oils and lipids are hydrophobic.
    • Buffers help to minimize changes in pH levels, critical for maintaining the pH of blood between 7.35-7.45.

    Biological Molecules

    • All living things are made of matter, governed by the same chemical and physical laws.
    • Organic molecules contain carbon.
    • Molecules containing only carbon and hydrogen are called hydrocarbons.
    • Functional groups are other atoms or molecules attached to the carbon skeleton, giving molecules unique chemical properties.
    • Four major classes of biological monomers form polymers:
      • Carbohydrates: contain carbon, hydrogen, and oxygen.
      • Lipids: hydrophobic molecules composed of carbon, hydrogen, and a small proportion of oxygen.
      • Proteins: large molecules composed of carbon, hydrogen, oxygen, and nitrogen.
      • Nucleic acids: composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

    Carbohydrates

    • Monosaccharides (simple sugars) are the monomers of carbohydrates.
    • Monosaccharides join through dehydration synthesis to form complex carbohydrates.
    • The bond created between monosaccharides during dehydration synthesis is called a glycosidic linkage.
    • Disaccharides are formed by joining two monosaccharides, examples include lactose and sucrose.
    • Polysaccharides are made of many monosaccharides, including:
      • Glycogen: A branched chain of glucose monomers, the storage polysaccharide in animals.
      • Starches: Linear chains of glucose monomers, the storage polysaccharide in plants.
    • The difference between glycogen and starches lies in the stereochemistry of the glycosidic bond between monomers.
    • Humans lack the enzyme to break down cellulose.

    Lipids

    • Represent 18-25% of total body mass in humans.
    • Types of lipids include:
      • Fatty acids: Hydrocarbon chain with a carboxyl group at one end.
      • Triglycerides (fats and oils): Three fatty acids bonded to a glycerol backbone. Fats are solid at room temperature, while oils are liquid.
      • Phospholipids: Glycerol backbone attached to two fatty acids and a phosphate group. They have a polar phosphate head (hydrophilic) and hydrophobic fatty acid tails, making them amphipathic.
      • Steroids: Made from four fused carbon rings; cholesterol is the precursor for other steroids.
      • Eicosanoids: 20-carbon compounds; include prostaglandins and leukotrienes involved in immune signaling.
      • Fat-soluble vitamins: Essential nutrients (vitamins D, E, and K).
    • Triglycerides are stored in fat cells called adipocytes.
    • Saturated fats contain mostly saturated fatty acids, while unsaturated fats are monounsaturated or polyunsaturated.
    • No monomer unit for lipids.

    Proteins

    • Composed of carbon, hydrogen, oxygen, and nitrogen.
    • Account for 12-18% of human body mass.
    • Determine the structure of body tissues.
    • Monomers called amino acids (20 naturally occurring) contain a central carbon atom bonded to:
      • Amino group
      • Carboxyl group
      • R group (side chain), giving each amino acid unique properties.
    • Amino acids undergo dehydration synthesis to form peptide bonds.
    • Several amino acids form peptides, while many form polypeptides.
    • While small proteins may be a single polypeptide chain, large proteins are made up of multiple polypeptide chains folded into complex arrangements.
    • Protein structure dictates function.
      • Primary structure: Amino acid sequence determined by gene sequence.
      • Secondary structure: Repeated folds in proteins, either α-helices or β-sheets stabilized by hydrogen bonds.
      • Tertiary structure: Three-dimensional shape determined by primary and secondary structure, including bonds and atomic forces, such as disulfide bridges, hydrogen bonds, ionic bonds, and hydrophobic interactions.
      • Quaternary structure: Arrangement of multiple polypeptide chains in multi-peptide proteins.
    • Fibrous proteins form long parallel bundles and are water-insoluble, such as keratin (hair) and actin (muscle thin filaments).
    • Globular proteins are round or “blob-like” and water-soluble, including antibodies and most enzymes.
    • Denaturation occurs when proteins lose their structure, becoming biologically inactive.

    Enzymes

    • Biological catalysts that accelerate chemical reactions without being consumed.
    • May require nonprotein molecules, called cofactors, to assist in catalysis. Organic cofactors are called coenzymes.
    • Chemical reactions would be too slow or wouldn’t occur without enzymes.
    • How enzymes work:
      • Step 1: Substrates bind to the active site, forming a substrate-enzyme complex.
      • Step 2: Chemical reactions occur, breaking and making bonds and rearranging atoms.
      • Step 3: Reaction products are released, freeing the enzyme to bind more substrates.
    • Enzyme characteristics:
      • Highly specific: Substrates bind to the active site of the enzyme through a "lock and key" mechanism.
      • Efficient: Enzymes lower activation energy, the amount of energy required to break a bond, increasing the rate of chemical reaction.
      • Regulated: Cells control the synthesis and activity of enzymes. Proenzymes are inactive forms that require processing under the right conditions to become active.

    Nucleic Acids

    • Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.
    • Include deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
      • Genes are segments of DNA that code for specific proteins.
      • DNA is transcribed into RNA.
      • RNA is translated by ribosomes to produce proteins.
    • Monomers called nucleotides:
      • Nitrogenous base (A, G, C, T for DNA, A, G, C, U for RNA)
      • Pentose sugar
      • Phosphate group
      • Purines (A & G) are double-ring bases, while pyrimidines (T & C or U) are single-ring bases.
      • In DNA, the pentose sugar is deoxyribose; in RNA, it is ribose.
      • Phosphate groups and pentose sugars form the backbone of the molecule.
    • DNA forms a double helix due to nucleotide properties:
      • The bases pair up, one purine with one pyrimidine: A with T and G with C for DNA.
      • Watson and Crick proposed the double helix structure in 1953.
    • RNA is a single-stranded molecule with three major types:
      • Messenger RNA (mRNA)
      • Ribosomal RNA (rRNA)
      • Transfer RNA (tRNA)
    • Adenosine triphosphate (ATP) is a biologically important nucleotide:
      • The energy currency of cells.
      • Comprised of three phosphate groups bound to adenosine (adenine + ribose).
      • Produced by exergonic cellular reactions and consumed by endergonic cellular reactions for cellular work.
      • Hydrolysis of the terminal phosphate releases a large amount of energy, which can be regenerated by ATP synthase during aerobic cellular respiration.

    Summary

    • Biological molecules are diverse and essential for life.
    • Four main classes of biological molecules include carbohydrates, lipids, proteins, and nucleic acids.
    • Lipids are the only class not composed of polymers.
    • The structure of biological molecules plays a crucial role in their function.

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    This quiz covers the essential concepts of cell biology, including the fundamental unit of life, the various cell types in humans, and the significance of organelles. It also explores the structure and function of the cytoskeleton and its components. Test your knowledge of these vital biological concepts.

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