Eukaryotic Cell

Nucleus: contains most of the genes that control entire cell

1. Nuclear envelope: double membrane, encloses nucleus, regulates molecular traffic by pores.

2. Chromosomes: composed of chromatin (DNA & histone protein)

3. Nucleolus: active in the synthesis of ribosomal parts.

Parts of the Cell

Cytoplasm: area between nucleus & cell membrane.◦ Cytosol: semifluid portion of the cell membrane◦ Cellular organelles: bodies with specialized

functions suspended in cytosol

Parts of the Cell

Ribosomes: non-membrane bound organelles made of rRNA and protein, site of protein synthesis.◦ Free ribosomes: suspended in cytosol; make

proteins that function in cytosol◦ Bound ribosomes: make proteins for membrane

inclusion or export.

Parts of the Cell

Endomembrane System: is a collection of membranes inside & around the cell, related either through direct physical contact or by transfer of membranous vesicles. Many organelles are related through this system.

Parts of the Cell

Vesicles: membrane enclosed sacs that are pinched off portions of membranes moving from the site of one membrane to another.

Parts of the Cell

Endoplasmic Reticulum: extensive membranous network continuous with the outer nuclear membrane, composed of rough (ribosome-studded) and smooth (ribosome free) regions

Parts of the Cell

Smooth ER: lacks attached ribosomes, functions are◦Synthesizes lipids,

phospholipids, and steroids

◦Detoxifies drugs & poisons, participates in carbohydrate metabolism; liver cells

◦Stores calcium ions necessary for muscle contraction

Parts of the Cell

Rough ER: ribosomes attached to the surface◦ Folds polypeptide chain into

proper conformation, adds oligosaccharide if needed, protein departs in vesicle

◦ Attaches phospholipids to protein produced by attached ribosomes, ER membrane transported to other parts of the cell in vesicles

Parts of the Cell

Golgi Apparatus: organelle made of stacked, flattened membranous sacs that store, modify, and route the products of the endoplasmic reticulum.◦ Cis face: receive products contained in transport

vesicles from ER, fuse together, and empty contents into Golgi apparatus

◦ Trans face: pinches off vesicles from the Golgi apparatus and transports to other sites

Parts of the Cell

Lysosome: membrane-enclosed bag of hydrolytic enzymes that digest all major classes of macromolecules.◦ Functions: intercellular digestion where lysosomes

fuse with food vacuoles, recycles cell’s own wastes, and programmed destruction.

Parts of the Cell

Vacuoles: membrane enclosed sacs larger than vesicles; food vacuoles, contractile vacuoles, and central vacuoles which store inorganic ions, dangerous wastes, or water.

Parts of the Cell

Peroxisomes: membrane organelles that contain specialized enzymes (peroxide-producing oxidases) for specific metabolic pathways; used to breakdown fatty acids into acetyl-CoA, detoxify alcohol and hydrogen peroxide

Parts of the Cell

Mitochondria: site of cellular respiration (produces ATP). Smooth outer membrane, inner membrane with folds (cristae) to increase surface area; own DNA due to constant need for enzymes

Parts of the Cell

Cytoskeleton: a network of microtubules, microfilaments, and intermediate fibers that branch throughout the cytoplasm serving a variety of mechanical and support functions

Parts of the Cell

Microtubules: hollow cylinder tubes; function as◦ Cellular support; reinforce cell shape◦ Tracks for organelle movement; move vesicles

from ER to Golgi apparatus◦ Separate & guide chromosomes during cell

division◦ Make up centrioles in animal cells. Cilia and

flagella are examples of microtubules

Parts of the Cell

Microfilaments: (Actin filaments) solid cylinder rods◦ Participate in muscle contraction◦ Provide cellular support; ex. Microfilaments in the core

of intestinal microvilli◦ Responsible for the local contraction of cell; ex.

Pseudopods in amoeba, cytoplasmic streaming in plant cells, and cleavage furrows in animal cells

Parts of the Cell

Tight junctions: hold cells tightly together, no space, common in epithelial cells; water proof tissue.

Desmosomes: rivet cells together at certain points but still allow movement between cells

Gap Junctions: cell membranes connected at certain points to allow direct transport of materials

Intercellular Junctions