Chapter 3 Cell Structure and Function Cell Theory

Chapter 3: Cell Structure and Function

Ø Cell Theory Ø Cell Size Ø Function of Organelles

Cell Theory Ø All organisms are composed of one or more cells Ø Cells are the basic living unit of structure and function in organisms Ø All cells come only from other cells

Cell Size • Surface Area to Volume Ratio Ø Surface area affects the ability of nutrients to get into the cell and wastes to get out Ø Large cells need more nutrients and produce more wastes than small cells Ø Small cells have more surface area per volume than large cells

Eukaryotic Organelles • What defines a eukaryotic cell? ØHas a nucleus • How do plant cells differ from animal cells? Ø Cell wall § Primary cell wall Cellulose = strength § Secondary cell wall Lignin = even stronger Ø Chloroplasts § Chlorophyll Photosynthesis

The Outer Boundaries • Plasma membrane Composition: § Phospholipid bilayer with embedded proteins Function: § Defines cell boundary § Regulates entrance and exit of molecules • Cytoplasm – Semifluid medium that contains organelles – Surrounds the nucleus inside the cell membrane

The Nucleus Composition: Ø Nuclear envelope (Double membrane with pores) Ø Nucleoplasm Ø Chromatin (DNA and proteins) Ø Nucleoli (Nucleolus) o Composition: Concentrated area of chromatin, RNA and proteins o Function: Ribosomal subunit formation Function: Storage of genetic information Ø Synthesis of DNA and RNA Ø

View Fig 3. 4, p. 52 in your textbook

Composition: Ribosomes Ø Protein and r. RNA Ø Two subunits (large and small) Ø Very small organelles Ø Occur in the cytoplasm: - Singly - Groups (polyribosomes) Ø Attached to the Endoplasmic reticulum Function: Ø Protein synthesis

The Endomembrane System Consists of: Ø Nuclear envelope Ø Endoplasmic Reticulum Ø Golgi Apparatus Ø Lysosomes Ø Transport Vesicles

The Endoplasmic Reticulum Composition: Ø Membranous, flattened channels, tubular canals Function: Ø Synthesis and/or modification of proteins + other substances ØDistribution via vesicle formation The Rough ER Composition: studded with ribosomes Function: protein synthesis The Smooth ER Composition: having no ribosomes Function: lipid synthesis and forms vesicles for

The Golgi Apparatus Composition: Ø Stack of membranous saccules Function: Ø Processing Ø Packaging Ø Secretion Ø Distribution of proteins and lipids Ø Formation of lysosomes

Lysosomes Composition: Ø Membranous vesicle produced by Golgi apparatus Ø Contains hydrolytic digestive enzymes Function: Ø Intracellular digestion § Macromolecules § Bacteria § Cell contents

Vacuoles Composition: Ø Large membranous sac (vacuoles are larger than vesicles) Ø Both animals and plant have them, but much bigger in plants (in plants: large, central, filled with water, sugar, salt, pigments, toxins support, color and protection) Function: Ø Store substances

Peroxisomes Composition: Ø Membranous vesicles ØContain specific enzymes Function: Ø Various metabolic tasks Ø Result in the production of hydrogen peroxide molecules ØCatalase breaks into water and oxygen

Energy-Related Organelles ATP CO 2 + H 2 O Useable energy for cells Carbohydrate Mitochondria Cellular Respiration: carbohydrate + oxygen Solar energy + carbon dioxide +water Chloroplast Photosynthesis: Solar energy + carbon dioxide +water carbohydrate + oxygen

Chloroplasts (only in plant cells) Composition: Membranous grana bounded by two membranes Ø Stroma (fluid filled space with DNA, ribosomes, enzymes) Ø Thylakoids (flattened sacs) stacked = grana Ø contains chlorophyll Ø Function: ØPhotosynthesis

Mitochondria Composition: Ø Double membrane ØInner membrane folded= Cristae ØIncreases surface area for ATP production ØInner fluid filled space = Matrix Ø Contains DNA, ribosomes, enzymes to break down carbohydrates Function: Cellular Respiration (produce ATP) Ø

Composition: Ø Microtubules The Cytoskeleton § Help evenly distribute chromosomes during cell division § Maintain shape and help organelles move around Ø Intermediate filaments § Help support nuclear envelope and plasma membrane § Lends mechanical strength Ø Actin filaments § Structural role § Formation of Pseudopods § Movement of cells and organelles (Myosin) Function: Ø Shape of the cell Ø Movement of cell parts

Centrioles (only in animal cells) Composition: Ø 9+0 pattern of microtubule triplets Function: Ø Formation of basal bodies organization of cilia + flagella Ø Microtubule formation

Composition: Cilia and Flagella Ø 9+2 pattern of microtubule doublets, around 2 central microtubules Ø Membrane bounded cylinders enclosing a matrix Ø Cilia are much shorter than flagella Functions: Ø Movement of the cell

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