A Tour of the Cell Chapter 6

Objectives Be familiar with the regions of the cell and the overall role of each region Be familiar with the basic organelles and their function Be familiar with the way neighboring cells can communicate

Cell Types All living organisms are made of cells Two kinds of cells –Prokaryotic: lacks membrane bound structures other than plasma membrane Bacteria –Eukaryotic: contains membrane bound organelles enabling compartmentalization leading to specialization animals, plants, protists, fungi

Cell Size Limits on cell size determined by ability to perform metabolic processes –Lower: can all necessary components fit –Upper: can we regulate supplies adequately (surface to volume ratio)

Regions of a Eukaryotic Cell Nucleus: contains genetic material (DNA) necessary for cell regulation. Reference library Cytoplasm: consists of cytosol (cell fluid) and organelles (specialized structures that carry out metabolic activities of cell) Plasma Membrane: contains the cell and regulates movement of materials into/out of the cell

Cell Overview

Nucleus Control center of cell Dual membrane system that fuse to form nuclear pores DNA and Protein complexes called Chromatin Nucleolus: region of RNA within the Nucleus

Nuclear Pore Structure To get materials into the nucleus there is a 27 Amino Acid tag (zip code) added onto molecules and are assisted by proteins called importins To leave the nucleus exportin proteins, a specific zip code, GTP and Ran are required

Import Summary

Ribosomes Sites of Protein synthesis May be free or bound –Free make proteins typically used in the cell –Bound are attached to membrane (ER) and make proteins typically for export

Endoplasmic Reticulum (ER) Part of the endomembrane system Smooth ER: site of lipid synthesis, detox, carbohydrate metabolism Rough ER: site of protein synthesis (contains bound ribosomes)

Golgi Apparatus “When it absolutely, positively, has to leave the cell” Finishes, sorts, and packages manufactured products of the cell cis: receives products from “ER” trans: ships materials to other parts of cell (often the plasma membrane)

Lysosomes Membrane bound structures responsible for the degradation of “spent” organelles and “food” items Contain hydrolytic enzymes

Vacuoles Membrane bound storage areas for resources Named after the resource they contain

Mitochondria, Chloroplast Mitochondria: site of most ATP synthesis Chloroplast: site of carbohydrate synthesis

Peroxisomes Modify molecules through redox reactions (fatty acid) Produce peroxide as a result (H 2 O 2 ) Split into two as they grow

Cytoskeletal elements Provide structural framework for the cell Movement of materials inside and on the surface of the cell Microtubules –grow from centrosome –load bearing Microfilaments –pulling forces Intermediate filaments –pulling forces

Organelles of Motility Flagellum: moves the entire cell Cilium (cilia): moves things along the surface of the cell

Extracellular Surfaces Most cells have a combination of proteins, lipids and sugars that form an extracellular matrix Plants have a cell wall

What distinguishes one cell’s function from another? The quantity and type of organelles determine how the cell can function.

Communication is Critical Connections between cells are called junctions –Tight junctions: leak- proof connections between cells –Desmosomes: fasten cells together strengthening the tissue –Gap junctions: provide cytoplasmic channels between cells –Plasmodesmata: plant cell channels In order for many cells to function as a unit (as in multicellular organisms) there must be a minimal level of communication