CELL STRUCTURE & FUNCTION CHAPTER 4

CELLS ALL LIVING THINGS ARE MADE UP OF ONE OR MORE CELLS A CELL IS THE SMALLEST UNIT THAT CAN CARRY ON ALL OF THE PROCESSES OF LIFE.

DISCOVERY OF CELLS *Robert Hooke (mid-1600s) – Observed sliver of cork from the bark of a cork oak tree. – Saw “row of empty boxes” – Coined the term cell (reminded him of the cubicles or “cells” where monks live.) Anton van Leewenhoek (1673) – First person to observe living cells. – Able to observe cells with green stripes from an alga of the genus spirogyra and bell shaped cells on stalks of a protist of the genus vorticella

CELL THEORY (1839)Theodor Schwann & Matthias Schleiden “ all plants are made up of cells” “ all animals are made up of cells” (50 yrs. later) Rudolf Virchow “all cells come from cells” These three observations Were combined to form a basic Theory about the cellular nature of Life. CELL THEORY: All living things are made of cells Smallest living unit of structure and function of all organisms is the cell All cells arise from preexisting cells

CELL DIVERSITY Cell Shape: The diversity in cell shapes reflects the different functions of cells. Each cell has a shape designed to allow the cell to perform its function effectively. Cell Size: The size of a cell is limited by the relationship of the cell’s outer surface area to its volume..

Characteristics of All Cells ALL CELLS HAVE THREE BASIC FEATURES IN COMMON: Plasma membrane (cell membrane) – cell’s outer boundary, acts as a barrier between the inside and the outside of a cell Cytoplasm- region of the cell within plasma membrane that includes fluid, cytoskeleton, and all organelles except nucleus. Control center (nucleus)- contains DNA

TWO BASIC TYPES OF CELLS Prokaryotic First cell type on earth Cell type of Bacteria and Archaea No membrane bound nucleus Nucleoid = region of DNA concentration Organelles not bound by membranes Eukaryotic Nucleus bound by membrane Include fungi, protists, plant, and animal cells Possess many organelles that perform specific functions in the cell Usually much larger than prokaryotic cells

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ORGANELLES & THEIR FUNCTION

Plasma Membrane Functions: 1) allows only certain molecules in or out of a cell 2) separates internal metabolic reactions from external environment 3) allows cell to excrete wastes and interact with its environment. Made primarily of phospholipids : Phospholipid B-Layer

Membrane Proteins: Plasma membranes contain specific proteins embedded within the lipid bi- layer called integral proteins. Integral proteins play important roles in actively transporting molecules into the cell.

Nucleus Most of the functions of a eukaryotic cell are controlled by the nucleus, and houses/protects the cells genetic information. Nucleoplasm- jellylike liquid which holds the contents of the nucleus. Nuclear envelope – double membrane that surrounds nucleus. Made up of two phospholipid b-layers. Nucleolus – Dense area where DNA is concentrated.

Mitochondria Tiny organelles that transfer energy from organic molecules to adenosine triphosphate (ATP), which powers the cell. Mitochondrial DNA –mitochondria have their own DNA and can reproduce only by the division of preexisting mitochondria.

Ribosomes Small roughly spherical organelles that are responsible for building protein. Ribosomes do not have a membrane, they are made of protein and RNA molecules.

Endoplasmic Reticulum System of membranous tubes and sacs, called cisternae. Functions: intracellular highway, a path along which molecules move from one part of the cell to another. Two types of ER: -Rough endoplasmic reticulum – system of interconnected flattened sacs covered with ribosomes, which produces proteins. -Smooth endoplasmic reticulum- lacks ribosomes which has a smooth appearance and builds lipids.

Golgi Apparatus system of flattened sacs that receive vesicles from the ER containing newly made proteins or lipids. The Golgi apparatus labels and packs cellular products and prepares them for export. The “mail man” of the cell

Vesicles Lysosomes- vesicles that bud from the Golgi apparatus and contain digestive enzymes that break down large molecules. Lysosomes also digest worn-out organelles (autophagy), and break down cells (autolysis). Peroxisomes- abundant in liver and kidney cells where they detoxify alcohol and other drugs.

Cytoskeleton Network of thin tubes and filaments that crisscross the cytosol, which give shape to the cell.

CILIA & FLAGELLA CILIA & FLAGELLA: hair like structures that extend from the surface of the cell, where they assist in movement. Cilia are short and a re present in large numbers on certain cells whereas flagella are longer and far less numerous.

PLANT CELLS Cell wall – rigid layer that lies outside the cell’s plasma membrane, which contain a carbohydrate called cellulose. Central vacuole – A large, fluid-filled organelle that stores water, enzymes, metabolic wastes, and other materials. Chloroplasts – use light energy to make carbohydrates from carbon dioxide and water. Contains chlorophyll ( molecules that absorbs light and captures light energy for the cell)