Chapter 7 Section 2: Eukaryotic Cell Structure

Objectives  Describe the function of the cell nucleus.  Describe the functions of the major cell organelles.  Identify the main roles of the cytoskeleton.

Eukaryotic Cells  Divided into two major parts: Nucleus Cytoplasm: organelles and cytosol

Organelles  Membrane-bound structures  Perform a specific function

Nucleus  Contains nearly all cell DNA  Surrounded by nuclear envelope Nuclear Envelope  lined with pores  RNA, proteins, and other molecules can move into cell

 Chromatin: DNA bound to protein  Chromosomes: condensed chromatin  Nucleolus: assembly of ribosomes begins here.

Ribosomes  Small particles of RNA and protein  Proteins are assembled here

Endoplasmic Reticulum  Site where lipid components of the cell membrane are assembled.  Proteins and other materials are assembled.

Rough ER  Portion involved in protein synthesis  Newly synthesized proteins leave ribosomes and are inserted into Rough ER  A lot of ER = a lot of protein being produced in that particular type of cell.

Smooth ER  No ribosomes  Synthesize membrane lipids

Golgi Apparatus  Proteins move from ER to Golgi  Stack of closely apposed membranes  Modifies, sorts, and packages proteins and other materials from ER for Storage in cell Secretion outside of cell *Customizes and ships proteins to final destinations.

Lysosomes  Filled with enzymes  Digestion of lipids, proteins, & carbs for use in the cell  Digests old, useless organelles

Vacuoles  Store water, salts, proteins, and carbs  Plants: single, large, central vacuole used for support  Single-celled organisms: pumps excess water out of cell  Helps control water content = maintain homeostasis

Mitochondria  Convert chemical energy stored in food  compounds that cell can use  Enclosed by two membranes  Nearly all mitochondria come from MOM

Chloroplasts  Capture energy from sunlight  Convert energy into chemical energy via photosynthesis  Two membranes  Contain chlorophyll

ORGANELLE DNA  Lynn Margulis: “Prokaryotes that carried their own DNA evolved into Mitochondria and Chloroplasts that took residence in Eukaryotic cells.” ENDOSYMBIOTIC THEORY

Cytoskeleton  Support  Network of protein filaments: help maintain cell shape

MICROFILAMENTS  Made of actin  Produce a framework that supports the cell  Help cells move

MICROTUBULES  Made of tubulins (proteins)  Maintain cell shape  Important in cell division: form spindle fibers  Form centrioles  Form cilia and flagella