Animal Cell Biology

Animal Cell Overview

• A cell is the most basic unit that makes up life
• Eukaryotic cells contain a true nucleus and membrane-bound organelles
• Prokaryotic cells do not have a true nucleus or membrane-bound organelles
• Diploid cells contain homologous pairs of chromosomes
• Meiosis is the cell division to produce haploid gametes
• A zygote is a diploid cell that forms from the fusion of two gametes
• The extracellular matrix, composed mostly of collagen, binds animal cells together

Types of Cells

• Simple internal structures of prokaryotic cells are found in Monera (bacteria)
• Complex structures of eukaryotic cells are found in Protista, Fungi, Plantae, and Animalia

Cell Theory

• Robert Hooke (1665) discovered and named cells
• Theodor Schwann (1839) proposed the classical theory where all organisms are made of cells, and cells are the basic units of life which arise from other pre-existing cells (Rudolf Virchow, 1858)
• Modern cell theory states DNA is passed during cell division; cells of similar species look alike chemically; and energy flows within cells
• Anton von Leeuwenhoek was the first to observe red blood cells and microorganisms.

Cell Structure

• The plasma membrane protects cells and regulates the passage of materials
• The nucleus stores DNA and controls the activities of the cell
• Cytoplasm is the fluid that contains the organelles

Organelles

• Centrioles help organize cell division
• The smooth Endoplasmic Reticulum (ER) synthesizes lipids and detoxifies harmful substances
• Ribosome-studded Rough ER is responsible for protein synthesis
• Ribosomes are sites of protein synthesis
• The Golgi apparatus modifies/packages proteins and lipids
• Mitochondria generates ATP and is the powerhouse of cells
• Lysosomes contain digestive enzymes that break down waste
• Peroxisomes break down fatty acids and produce hydrogen peroxide
• Endosomes are formed via endocytosis and involved in cellular transport
• The cytoskeleton provides cells with their shape, movement, and structure
• Microtubules provide transportation and structural support
• Microfilaments are actin-based and offer structural support
• Intermediate filaments provide cell rigidity
• Cilia and flagella help with movement and fluid transport
• Vacuoles are storage sacs within a cell

Key Scientists and Discoveries

• Felix Dujardin (1835) discovered living cell contents, calling it sarcode/protoplasm
• Johannes Purkinje (1839) coined the term protoplasm
• Hugo von Mohl (1846) defined protoplasm as the living cell substance
• Robert Altmann (1886) discovered mitochondria
• Camillo Golgi (1898) discovered the Golgi apparatus
• Keith Porter (1945) discovered the endoplasmic reticulum
• Christian De Duve (1952) discovered lysosomes
• George Emil Palade (1955) discovered ribosomes

Introduction to Zoology

• Zoology is the scientific study of animal life
• Animal structure refers to the physical composition of animals
• Evolution is changes in animal species over time
• Reprodution is the process of producing offspring
• Inheritance is the transmission of genetic material

Subdivisions of Zoology

• Taxonomy focuses on classifying animals
• Ecology is the relationship of animals with the environment
• Zoogeography is the geographic distribution of animals
• Animal evolution studies the origin and adaptation of animals
• Anatomy is the study of the animal structure
• Comparative anatomy is the comparison of different animal structures
• Histology is the study of tissues
• Cytology is the study of cells
• Embryology is the study of early animal development
• Paleontology is the study of fossils
• Genetics is the study of heredity
• Experimental morphology looks at the study of change in body structure
• Biochemistry studies chemical composition of living organisms
• Macromolecular chemistry is the study of biological molecules
• Entomology is the study of insects
• Helminthology is the study of worms
• Herpetology is the study of reptiles
• Ornithology is the study of birds
• Parasitology is the study of parasites
• Ichthyology is the study of fish
• Mammology is the study of mammals

Theories of the Origin of Life

• The theory of special creation says that life was created by a divine power
• Abiogenesis claims life originated from non-living matter
• Biogenesis requires life to come from pre-xisting life
• The Cosmozoic theory claims life came from outer space
• Modern chemical theory says life originated through chemical evolution
• The theory of Catastrophism claims life was repeatedly created and destroyed

Characteristics of Living things

• Living things possess order in their structure
• Irritability/sensitivity is the ability to respond to stimuli
• Reproduction is the production of offspring
• Growth & Development is the increase in the size and complexity
• Metabolism are chemical reactions for energy
• Homeostasis is the maintenance of internal balance
• Evolution is the changes over generations through natural selection

Levels of Organization in Living Things

• Atoms are the smallest unit of matter
• Molecules are a chemical structure of atoms
• Macromolecules include large biological molecules like DNA and proteins
• Organelles are specialized cell structures
• Cells are the basic unit of life
• Tissues are groups of similar cells performing a function
• Organs are structures composed of tissues
• Organ systems are groups of organs working together
• Organisms are individual living beings
• Populations are groups of organisms of the same species
• A community is made of multiple populations in an area
• An ecosystem is the interaction of living and non-living components
• The biosphere includes all the ecosystems on Earth

Cell Cycle

• The cell cycle is an ordered sequence of events for cell division
• During G1 phase (Gap 1), the cell grows and prepares for DNA synthesis
• During S Phase, DNA replication occurs
• During G2 Phase (Gap 2), the cell prepares for mitosis
• The M phase (mitosis) is where the nucleus and cytoplasm divide
• Interphase includes the G1, S, and G2phases, and is the longest part of the cycle
• Checkpoints are regulatory mechanisms ensuring DNA integrity
• Apoptosis is programmed cell death to prevent damage

Cell Division in Prokaryotes

• Asexual reproduction occurs via binary fission in prokaryotic cells
• Chromosome duplication occurs with DNA copied before division
• Daughter cells are two genetically identical cells

Mitosis

• Cell division occurs in somatic (body) cells producing diploids in mitosis
• Diploid (2n) cells contain two sets of chromosomes
• During prophase, chromatin condenses and spindle fibers form
• During metaphase, chromosomes align at the metaphase plate
• During anaphase, sister chromatids break apart and move toward opposite poles
• In telophase, the nuclear envelopes reform around chromosomes
• Cytokinesis is division of cytoplasm, completing cell division

Meiosis

• Cell division occurs in germ cells which produce haploid cells
• Haploid (n) cells have half the chromosome number
• Genetic variation is introduced by crossing over and independent assortment

Meiosis I

• Homologous chromosomes pair up during prophase I and exchange genetic material (crossing over)
• Homologous chromosome pairs align at the metaphase plate during metaphase I
• Homologous chromosomes separate during anaphase I
• Two haploid cells form during telophase I

Meiosis II

• Chromosomes condense during prophase II
• Chromosomes align at the metaphase plate during metaphase II
• Sister chromatids separate during anaphase II
• Four genetically unique haploid cells form during telophase II

Comparing Mitosis and Meiosis

• Somatic cells are body cells that undergo mitosis
• Germ cells are sperm and egg cells which undergo meiosis
• Mitosis involves 1 division, and meiosis involves 2
• Mitosis produces 2 identical daughter cells; meiosis produces 4 genetically unique cells
• Ploidy is diploid (2n) in mitosis and haploid (n) in meiosis
• There is no genetic variation in mitosis; there is high genetic variation in meiosis

Conclusion

• The cell cycle ensures organism growth and development
• Mitosis creates identical cells, while meiosis produces diverse gametes for reproduction
• Cancer prevention requires proper cell cycle regulation, preventing uncontrolled cell division

Animal Tissues

• Unicellular organisms perform all life functions within one cell
• Multicellular organisms have specialized cells for different functions
• Levels of organization progresses from protoplasm to cells to tissues to organs and then to organ systems
• Tissues are a group of similar cells performing a function
• Histology is the study of tissues
• Organs are structures composed of multiple tissues
• An Organ system is a group of organs working together

Epithelial tissue

• Epithelial tissue covers body surfaces, lines cavities, and forms glands
• Characteristics are cells tightly packed with little intercellular space
• There are simple (single layered) epithelium which includes squamous, cuboidal, columnar, ciliated, and glandular epitheliums
• Squamous epithelium are thin and flat
• Cuboidal epithelium are cube shaped and facilitate secretion and absorption
• Columnar epithelium are tall can have microvilli
• Ciliated epithelium have cilia for movement
• Glandular epithelium secrete substances, containing exocrine (ducts) and endocrine glands (ductless)
• Compound epithelium are multi-layered with a protective function
• Tight junctions prevents leakage
• Adhering junctions hold cells together
• Gap junctions allow cells to communicate

Connective tissue

• Connective tissue supports, binds, and protects organs
• They contain cells, fibers (collagen/elastin), and a matrix
• Loose connective tissues includes areolar and adipose
• Areolar tissue supports epithelium
• Adipose tissue stores fat and insulates
• Regular dense connective tissue contains parallel fibers
• Irregular dense connective tissue contains random fibers
• Specialized connective tissues include cartilage, bone, and blood
• Cartilage provides flexible support
• Bone provides rigid framework and facilitates blood cell production
• Blood is fluid and facilitates transport

Muscle tissue

• Muscle tissues function to enable movement and contraction
• Skeletal muscle is striated, voluntary, attached to bones
• Smooth muscle is non-striated and involuntary
• Cardiac muscle is striated, involuntary and contains intercalated discs

Nervous tissue

• Nervous tissue controls the bodies functions and responsiveness
• Neurons are functional units transmitting electrical impulses
• Dendrites receive signals
• Axons send signals
• Neuroglial cells support and protect neurons
• Synapse are junctions between neurons for communication
• Epithelial tissue serves for protection, secretion, absorption
• Connective tissue supports, binds, and transports
• Muscle tissue enables movement
• Nervous tissue controls and coordinates body functions

Organs

• Organs are a group of tissues forming a functional unit
• Organology is the study of organ arrangement
• Parenchyma is the chief functional cell of an organ
• Stroma is the supporting tissue of an organ
• Organ systems are groups of organs that work together

10 organ systems in higher animals

• The integumentary system contains components like skin, hair, feathers, claws, nails, hooves, and glands and functions in protection, temperature regulation, sensation, and biochemical production
• The skeletal system contains bones, ligaments and cartilages and functions in structural support, organ potection and muscle attachment
• The muscular system contains skeletal, smooth and cardiac muscles and functions in movement, locomotion and ivoluntary actions
• The digestive system contains a mouth, pharynx, esophagus, stomach, intestines, liver, pancreas and anus and functions in ingestion, digestion, absoprtion and elimination
• The respiratory system component includes lungs, trachea, and breathing tubes and functions in oxygen intake and carbon dioxide disposal
• The circulatory system contains a heart, blood vessels and blood and functions in oxygen and nutrient distribution
• The excretory system contains kidneys, ureters, urinary bladder, and urethra and functions in waste disposal osmotic balance
• The endocrine system components include the pituitary, thyroid, pancreas and hormone-secreting glands and functions in regulation of metabolism, growth, and reproduction
• The nervous system contains a brain, spinal cord, nerves and sensory organs and functions in coordination of activities and response to stimuli
• The reproductive system components include ovaries, testes, and associated organs, and functions in production of offspring
• The immune and lymphatic system contains bone marrow, lymph nodes, spleen and white blood cells for defese against infection and diseases

Integumentary system

• The integumentary system components include skin, hair, feathers, claws, nails, scales and glands for protection, temperature regulation, waste excretion and sensory perception

Skin Layers

• The epidermis is the outer layer containing keratinocytes with a barrier function, melanocytes with pigment production, Langerhans cells function in immunity and Merkel cells function in sensory perception
• The dermis contains blood vessels, nerves, glands and collagen fibers
• The hypodermis is a fatty layer for insulation and energy storage

Skin Functions

• Melanin production protects against UV rays
• Temperature regulation involves vasodilation (heat loss) and vasoconstriction (heat retention)
• Excretion involves sweat, carbon dioxide, and waste products
• The skin also facilitates Absorption like with medications

Cutaneous Glands

• Sudoriferous glands secrete water and electrolytes
• Eccrine glands secrete sweat and electrolytes
• Apocrine glands secrete oily substances in hair areas
• Apoeccrine glands secrete watery fluid in apocrine regions
• Sebaceous glands secrete sebum (oil) to lubricate skin and hair
• Ceruminous glands produce ear wax (cerumen) to protect the ear canal
• Mammary glands produce milk for nourishment

Skin Pigment Cells

• Melanophores produce melanin resulting in dark coloration
• Xanthophores contain carotenoid pigments which results in a yellow/red coloration
• Iridophores produce silvery/metallic effects from guanine crystals

Special Features in Animals

• Frog's skin functions as a respiratory organ with mucus and poison glands
• Bird's have a preen gland that produce oil near the tail for feather maintenance
• Mammal's have specialized skin glands for thermoregulation, protection, and reproduction

Skeletal System

• The skeleton provides a hardened framework which functions in shape, protection, and movement
• Exoskeletons are external skeletons while endoskeletons are internal

Types of skeletons

• Exoskeletons are made of chitin, calcium carbonate, or silica, and require molting
• Endoskeletons are made of bone and cartilage, and provide internal support
• Hydrostatic skeletons use fluid pressure for support

Divisions of Vertebrae Skeleton

• The axial skeleton lies in the midline of the body and includes the skull, vertebral column, ribs, and sternum
• The appendicular skeleton has limbs and girdles and includes the pectoral girdle, forelimb, pelvic girdle, and the hindlimb

Classification of Bones

• Long bones include the femur and humerus
• Short bones include carpals and tarsals
• Flat bones include the skull, ribs and scapula
• Irregular bones include vertebrae and hip bones
• Sesamoid bones include the patella
• Sutural bones lie between skull bones

Bone Structure

• The epiphysis is the end of the bone and contains spongy bone.
• The diaphysis is the shaft and contains the medullary cavity
• Metaphysis is the flared part near epiphysis
• Articular Cartilage covers the joint surfaces
• The periosteum is an outer covering and contains osteoblasts
• The endosteum is an inner lining and is involved in bone growth and repair
• The Haversian system is a microscopic unit of compact bone with blood vessels

Bone cells

• Osteoprogenitor cells are precursors to bone cells
• Osteoblasts are bone-forming cells and secrete bone matrix
• Osteocytes are mature bone cells and maintain bone
• Osteoclasts are bone-resorbing cells and break down bone

Bone formation

• Bone formation is ossification
• Intramembranous ossification is bone formation by direct deposition
• Endochondral ossification is cartilage replaced by bone
• Epiphyseal Plate are responsible for lengthwise bone growth

Bone remodeling

• Bone remodeling occurs as osteoblasts deposit bone and osteoclasts resorb bone
• Bone growth and repair require calcium, phosphorus, vitamins A, C, D, and hormones like growth hormone, calcitonin, and PTH

Tendons and Ligaments

• Tendons connect muscle to bone
• Ligaments connect bone to bone
• Ossified tendons and ligaments are found in certain species

Joints

• Arthrology is the study of joints
• Arthritis is Inflammation of the joints

Types of Joints

• Diarthrosis joints are freely movable
• Amphiarthrosis joints are slightly movable
• Synarthrosis joints are immovable
• Fibrous joints have no cavity and little to no movement
• Cartilaginous joints are connected by cartilage which allows little movement
• Synovial joints have fluid-filled cavity and allow a range of mobility