Chapter 6 – Cells I – 2 Major types of Cells A. Prokaryotic Cells – Belong to domains Bacteria and Archaea. 1. No true nucleus; lacks a nuclear envelope 2. Genetic material found in nucleoid region 3. No membrane bound organelles; ribosomes are found, but they are not membrane-bound B. Eukaryotic Cells – Belong to the domain Eukarya 1. True nucleus; bounded by nuclear envelope 2. Genetic material within the nucleus 3. Membrane bound organelles

II Cell Size – The surface area of the plasma membrane must be large enough for the cell volume, in order to provide an adequate exchange surface for oxygen, nutrients and wastes. III Nucleus and Ribosomes A. Nucleus – membrane bound organelle that contains the genetic material. 1. nuclear envelope – phospholipid bilayer which encloses the nucleus

2. chromatin – complex of DNA and histone proteins, which make up chromosomes 3. chromosomes – long threadlike association of genes, composed of chromatin 4. nucleolus – location for the synthesis of rRNA B. ribosomes – cytoplasmic organelle which is the site for protein synthesis 1. free ribosomes – ribosomes in the cytoplasm 2. bound ribosomes – ribosomes attached to the ER -cells specializing in protein secretions have many bound ribosomes(pancreatic cells

IV Endomembrane System – membranes may be interrelated directly through physical contact or indirectly through vesicles(membrane enclosed sacs that are pinched off portions of membranes moving from one membrane site to another). The endomembrane includes: nuclear envelope, endoplasmic reticulum(ER), Golgi apparatus, lysosomes and vacuoles.

A. Endoplasmic reticulum 1. Smooth ER – synthesizes lipids, phospholipids, and steroids(testes, ovaries, and skin oil glands); participates in CHO metabolism; detoxifies drugs and poisons; Stores Ca used for muscle contraction. 2. Rough ER – is continuous with outer membrane of the nuclear envelope; produces secretory proteins and membranes.

B. Golgi apparatus - modifies, stores, and routes products of the ER; 2 faces of the Golgi apparatus 1. Cis face – receives transport vesicle from ER 2. Trans face – pinches of vesicles from the Golgi and transports molecules to other sites.

C. Lysosomes – membrane enclosed bag of hydrolytic enzymes that digest all major classes of macromolecules. 1. intracellular digestion – phagocytosis 2. recycles cell’s own organic material – may engulf other cellular organelles 3. programmed cell distruction.

D. Vacuoles – diverse functions in cell maintenance. 1. Types and functions a. food vacuole – formed by phagocytosis which is the site of intracellular digestion in some protists and macrophages. b. contractile vacuole – found in some fresh water protozoa that pumps excess water from the cell. c. central vacuole – large vacuole found in most mature plant cells; plays a role in plant growth by absorbing water and elongating the cell.

V. Peroxisomes – contains catalase, an enzyme that converts toxic hydrogen peroxide to water. Functions – breakdown of fatty acids and detoxifies alcohol and other harmful compounds. VI. Mitochondria and Chloroplast – transforms energy transformed from the surroundings into forms useable for cellular work. A. Mitochondria – sites of cellular respiration; number or mitochondria correlates with the cell’s metabolic activity.

B. Plastids – group of plant and algal organelles 1. Amyloplast – colorless plastids that stores starch; found in roots and tubers. 2. Chromoplast – plastids containing pigments other than chlorophyll, responsible for the color of fruits and autumn leaves. 3. Chloroplast – chlorophyll containing plastids which are the sites of photosynthesis.

VII. Cytoskeleton –a network of fibers throughout the cytoplasm that forms the framework for support and movement. A. Microtubules – function in cellular support, tracks for organelle movement, separation of chromosomes, and make up centrioles in animal cells; cilia and flagella – locomotor organelles found in eukaryotes.

B. Microfilaments – participate in muscle contraction, provide cellular support, and responsible for localized contraction of cells. C. Intermediate filaments – specialized for bearing tension; make function as the framework for cytoskeleton, reinforce cell shape.

VIII. Plant cell wall – function to protect plant cells, maintain their shape, and prevent excess water uptake IX. Extracellular matrix – meshwork of macro- molecules outside the plasma membrane that function in support, adhesion, move- ment and development

X. Intercellular Junctions – integrates cells into higher levels of structure and function A. Plants Intercellular Junction 1. Plasmodesmata – channels that perforate plant cell walls, through which cytoplasmic strands communicate between adjacent cells; allows free pass- age of water and small solutes B. Animal Intercellular Junction 1. Tight Junctions – hold cells together tightly enough to block transport of substances through intercellular space.

2. Desmosomes – junctions that rivet cells together into strong sheets, but still permit substances to pass freely through intracellular space. 3. Gap Junctions – junctions that are specialized for material transport be- tween the cytoplasm of adjacent cells.