Biology Chapter on Cell Organelles

CELL STRUCTURE AND ORGANIZATION

• A cell is the simplest unit of a living organism
• It is the basic unit of structure and function of all life
• Cell biology is the study of cell structure, function, molecular organization, growth, reproduction and genetics
• Cytology is another term for cell biology
• Cytology focuses on the study of structures and functions of specialized cells
• Cell biology can be studied through, classical cytology, Cell physiology and Cell biology

HISTORY OF CELL BIOLOGY

• Aristotle (384-322 B.C.) and Paracelsus concluded that all animals and plants are composed of a few basic elements repeated throughout them
• Magnifying lenses lead to the study of microscopic dimensions
• Da Vinci (1485) recommended the use of lenses in viewing small objects
• Gesner (1516-1565) conducted studies on the structure of foraminifera using a magnifying lens

CELL THEORY

• Schleiden (1804-1881) proposed that cells are units of structure in plants
• Schwann (1810-1882) applied the theory of cells being the unit of structure to animals
• All living things are composed of one or more cells 
• All metabolic reactions occur within cells
• All cells come from pre-existing cells
• The cell is the basic unit of structure and function of all life

EXCEPTIONS TO CELL THEORY

• Some organisms do not have cells, but all true cells have three basic characteristics:
• Genes that make blueprints for cellular activities and new cells
• A plasma membrane that regulates the passage of matter and energy
• Metabolic machinery for sustaining cell activities (growth, reproduction and repair)
• Viruses do not fit the parameters of a true cell

ANIMAL CELL

• Contains organelles, including a nucleus which directs cell activities, mitochondria which generates energy, ribosomes which manufacture proteins, Golgi apparatus that modifies, packages, and distributes proteins, and lysosomes that store enzymes for digesting food.
• The cell is enclosed by a lipid membrane that regulates what enters and exits, selectively permeable

PLANT CELL

• Contains a nucleus, mitochondria, ribosomes, smooth endoplasmic reticulum (responsible for lipid production), vacuoles and chloroplasts that capture energy from sunlight.
• The rigid cell wall protects the cell and maintains the shape.

DIFFERENCES BETWEEN PROKARYOTIC AND EUKARYOTIC CELLS

TYPES OF CELLULAR ORGANELLES

• Plasma membrane and cell wall
• Endoplasmic Reticulum (ER)
• Golgi apparatus
• Lysosomes
• Mitochondria
• Plastids (chloroplasts and vacuoles)
• Nucleus
• Chromosomes
• Ribosomes
• Centrioles & Basal bodies
• Cilia & Flagella
• Vacuoles
• Peroxisomes & Glycoxysomes

FUNCTIONS OF CELLULAR ORGANELLES

• Many functions like separating cytoplasm from its environment, controlling movement of material, facilitating transportation etc.

ENDOPLASMIC RETICULUM (ER)

• Network of sheets and tubules throughout a cell
• Transports chemicals within & between cells
• Provides a large surface area for the organization of chemical reactions and synthesis.

GOLGI APPARATUS/COMPLEX

• Stacks of flattened sacs of unit membrane
• Modifies, packages, and dispatches materials within animals and plants.

LYSOSOMES

• Membrane-bound bag containing hydrolytic enzymes
• Break down large molecules inside a cell
• Involved in intracellular digestion
• Mostly found in animal cells

MITOCHONDRIA

• Filled with inner membrane infoldings called cristae
• Site of cellular respiration, release of chemical energy from food.

PLASTIDS

• Two membrane-bound compartments
• Found in plant cells
• Involved in photosynthesis and storage
• Examples: chloroplasts

NUCLEUS

• Contains nuclear material, nucleolus and nucleoplasm
• Controls metabolic and hereditary activities in a cell

CHROMOSOMES

• Components of special organization found in the nucleus
• Involved in heredity, mutation, variation, and evolutionary development of species

RIBOSOMES

• Dense, round, granular particles of ribonucleo protein
• Involved in protein synthesis in cells.

CENTRIOLES AND BASAL BODIES

• Cytoplasmic structures near the nucleus
• Have roles in mitosis, and flagella or cilia formation.

CILIA & FLAGELLA

• Microscopic, contractile, filamentous processes of the cytoplasm
• Functions such as food currents, sensory organs, and cell movement.

VACUOLES

• Single layer of unit membrane
• Plays a role in maintaining turgor pressure and storing water and chemicals.

MICROBODIES

• Spherical membrane-bound bodies found within close association with other organelles
• Contain enzymes for various metabolic reactions.

PEROXISOMES

• Involved in metabolic reactions, such as breakdown of fatty acids

GLYCOXYSOMES

• Found in plants
• Involved in fatty acid metabolism

CHARACTERISTICS AND CLASSIFICATION OF LIVING THINGS

• Movement
• Reproduction
• Nutrition
• Irritability
• Growth
• Excretion
• Respiration
• Death

CLASSIFICATION OF LIVING THINGS

• Grouping living things to reflect evolutionary relationships and modes of nutrition.

BIOLOGICAL INTERACTIONS

• Types of relationships between organisms in an ecosystem.
• Examples of interactions:
  • Mutualism
  • Commensalism
  • Protocooperation

PARASITISM

• One organism is harmed while the other is benefited
• Can include types of interaction that can potentially result in harm to the host. 

PREDATION

• One organism eats another
• Types of examples would be herbivores, carnivores and or insect parasitism, cannibalism

AMENSALISM

• The interaction that results in the harm of one population/species which has minimal effect on the second species/population

COMPETITION

• The interaction when organisms attempt to utilize the same resource which is limited
• Types of competition: interspecies and intraspecies

ECOSYSTEM

• Includes all the organisms living in a given area, with their physical environment and energy flow.
• Includes diverse types of interactions that lead to a continual exchange of energy and nutrients between biotic and abiotic components. 

KINDS OF ECOSYSTEMS

• Natural ecosystems
• Terrestrial ecosystems: (forests, grasslands, deserts, savannahs etc.)
• Aquatic ecosystems:
  • Freshwater ecosystems (lotic, and lentic)
  • Marine ecosystems
• Artificial ecosystems: (croplands, villages, etc.)

STRUCTURE OF ECOSYSTEMS

• Abiotic components (moisture, inorganic substances like phosphorus, sulfur, carbon, nitrogen, hydrogen, organic substances like proteins, etc)
• Biotic components (nutritional relationships between living organisms- Autotrophs, or Heterotrophs- herbivores, carnivores etc.)

FUNCTION OF ECOSYSTEM

• Rate of biological energy flow, nutrient cycles, and ecological regulation.

FOOD CHAIN IN ECOSYSTEMS

• Transfer of food energy through a group of organisms.
• Example: producers --> primary consumers --> secondary consumers --> tertiary consumers

ECOLOGICAL PYRAMIDS

• Graphical representation of trophic structure and function at successive trophic levels.
• Types: pyramid of numbers, pyramid of biomass, pyramid of energy

ENERGY FLOW IN ECOSYSTEM

• Energy flows from the sun through producers to consumers
• Gradual decrease in energy content at each trophic level

ECOLOGICAL NICHE

• The role or position of a species in a community.

CELL DIVISION

• Process whereby a cell divides to form two or more new cells
• Used for growth, repair, and asexual reproduction

MITOSIS

• Produces two identical daughter cells. 
• Essential for the growth, repair, and asexual reproduction of most eukaryotic organisms.

MEIOSIS

• Forms four daughter cells with half the genetic material as the parent cell
• Necessary for sexual reproduction in eukaryotic organisms

HEREDITY

• Passing of genetic information through generations
• Includes terminologies like alleles, carriers, and genotypes.

EVOLUTION

• The sum total of adaptive changes over long periods of time, in terms of structure and function.
• Fossil records, geographical distribution, comparative anatomy and domesticated organism show that life forms changes over time.

LAMARCK'S THEORY OF EVOLUTION

• Suggested use and disuse of organs, as an important factor in evolution. 
• Theory doesn't explain how species change to adapt to the environment.

DARWIN'S THEORY OF EVOLUTION

• Theory of Natural Selection
• Species with variations better adapted to their environments, are more likely to survive, reproduce, and pass their traits 
• Includes processes such as variation, heredity, struggle, natural selection, and genetic traits.

MODERN EVOLUTIONARY THEORY

• Combination of natural selection and genetics
• Includes that variation exists in populations
• Individuals with favourable variations are more adapted
• The fittest contribute more offspring
• Main cause of variation is mutation 

TISSUES

• Groups of cells performing similar functions.
• Includes:
  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue

EPITHELIAL TISSUE

• Covers body surfaces
• Lines body cavities
• Forms glands

CONNECTIVE TISSUE

• Supports and connects other tissues
• Includes cartilage, bone, blood, and lymph

MUSCLE TISSUES

• Enables movement of the body
• Includes three types:
  • Skeletal muscle
  • Smooth muscle
  • Cardiac muscle

NERVOUS TISSUE

• Enables the transmission of signals
• Found in the brain, spinal cord, and throughout the body 

NEURAL COMMUNICATION

• How neurons/nervous system interact

REFLEXES

• Rapid, predictable, and usually involuntary response to stimuli
• Includes the:
  • Somatic reflexes
  • Autonomic reflexes