Chapter 8 Part 4

• Cells are the basic functional units of the body
• Differentiation is the process by which cells become specialized
• Tissues are groups of cells with a common job grouped closely together
• Organs are groups of tissues that perform interrelated jobs
• Cells perform seven general functions: movement, conductivity, metabolic absorption, secretion, excretion, respiration, and reproduction
• There are two general classes of cells: sex cells and somatic cells
• Sex cells are also known as germ cells or reproductive cells
• Somatic cells are all other cells in the body
• Cells are highly organized structures surrounded by a cell membrane
• Parts of the cell include the cell membrane, the nucleus, and the cytoplasm

Cell Membrane

• Gives form to the cell and is where cellular activity takes place
• Provides physical isolation between the intra- and extracellular compartments
• Controls the movement of substances in and out of the cell
• Selectively permeable or semi-permeable, allowing certain substances to pass while restricting others
• Contains several embedded membrane proteins
• Channel proteins act as a core to allow substances to passively enter the intracellular compartment
• Enzyme receptors are sites enzymes combine
• Other proteins act as receptor sites with binding sites on the outside and are specific to certain molecules
• Identifier proteins are used to determine self from non-self
• Carrier proteins bind to substances and transport them across the cell membrane; an example is the sodium-potassium pump
• Some membrane proteins attach to the cytoskeleton to help determine its shape
• Some membrane proteins permit tissues to form

Cytoplasm

• Fluid-like material where organelles are suspended between the cell membrane and the nucleus
• Contains membranous networks, protein frameworks, and a cytoskeleton
• Cytosol is the fluid portion, the site of many chemical reactions
• Organelles perform specific functions related to cell structure, growth, maintenance, and metabolism

Organelles

• Centrioles are cylindrical structures composed of short microtubules that form spindle-shaped structures for DNA movement during cell division
• Cilia and flagella are structures that extend from certain cell surfaces
• Ribosomes are involved in protein formation, either floating freely or attached to the endoplasmic reticulum (ER)
• Endoplasmic Reticulum (ER) is a network of canals and sacs connecting the nuclear membrane to the cell membrane
• Smooth ER lacks ribosomes and synthesizes phospholipids and cholesterol
• Rough ER has ribosomes and is found in cells that produce proteins to be excreted
• Golgi apparatus consists of a stack of flattened sacs and concentrates/packages secretions that are released outside the cell
• Golgi Apparatus packages special enzymes inside vesicles for use in the cytosol
• Golgi Apparatus renews or modifies the cell membrane
• Lysosomes are tiny sacs that perform housekeeping tasks within the cell; its enzymes digest nucleic acids, fats, proteins, polysaccharides, lipids, and nonfunctional organelles
• Certain white blood cells have lysosomes containing enzymes to digest bacteria
• Microfilaments are composed of actin and myosin proteins, found in muscle cells, and enable cell movement and contraction
• Mitochondria are the power plants of the cells, the location of aerobic respiration, and play a central role in energy production via ATP
• The outer mitochondrial membrane gives the organelle its shape
• The inner mitochondrial membrane creates folds called cristae important for cellular respiration
• Peroxisomes contain enzymes that speed up reactions and are abundant in liver and kidney cells
• Thick filaments are massive bundles of subunits composed of myosin, appearing in muscle cells to interact with actin filaments and produce powerful contractions
• Vesicles/Vacuoles are bubble-like structures that transport a wide variety of substances inside and outside the cell

Nucleus

• Large structure located near the center of a cell that encases the nucleoplasm
• The nucleoplasm contains DNA
• Nucleoplasm is a fluid within the nucleus that suspends the nucleolus and chromatin