Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 4 Image Slides Chap 4 Cell Structure And Function

The Development of the Cell Theory Robert Hooke coined the term “cell” 細胞. –Look at cork cells under a simple microscope. Anton van Leeuwenhoek –Made better microscopes –Used them to look at a variety of substances and identified animalcules. Mathias Jakob Schleiden –Concluded that all plants were made of cells Theodor Schwann –Concluded that all animals were made of cells

Different cells Prokaryotic 原核細胞 –Structurally simple cells –Lack a nucleus –Lack most other organelles –Bacteria Eukaryotic cells 真核細胞 –More complex –Have a nucleus –Have a variety of organelles –Plants, animals, fungi, protozoa and algae

Cell size Prokaryotic cells –1-2 micrometers in diameter Eukaryotic cells – micrometers in diameter

Initial observations of cells Cell wall 細胞壁 –Outer non-living part of plant cells Protoplasm –Interior living portion of the cell –Nucleus 細胞核 Contains the genetic information of the cell –Cytoplasm 細胞質 Fluid part of the protoplasm –Organelles 胞器 “ Little organs ” within the protoplasm

The Structure of Cell Membranes Cell membranes 細胞膜 –Thin sheets composed of phospholipids 磷脂質 and proteins 蛋白質 Fluid-mosaic model –Two layers of phospholipids Fluid –Has an oily consistency –Things can move laterally within the bilayer. Mosaic –Proteins embedded within the phospholipid bilayer

Organelles composed of membranes Plasma membrane (cell membrane) Endoplasmic reticulum 內質網 Golgi apparatus 高基氏體 Lysosomes 溶小體 Peroxisomes 過氧化體 Vacuoles 液泡 and vesicles 囊泡 Nuclear membrane 核膜

The plasma membrane 細胞膜 Composed of a single phospholipid bilayer Separates the contents of the cell from the external environment Important features –Metabolic activities –Moving molecules across the membrane –Structurally different inside and outside –Identification: Self vs. nonself –Attachment sites –Signal transduction

The endoplasmic reticulum A set of folded membranes and tubes throughout the cell. Provides a large surface area for important chemical reactions. –Because it is folded, it fits into a small space. Two types of ER –Rough Has ribosomes on its surface –Sites of protein synthesis –Smooth Lacks ribosomes Metabolizes fats Detoxifies damaging chemicals

The Golgi apparatus Stacks of flattened membrane sacs. Functions –Modifies molecules that were made in other places. –Manufactures some polysaccharides and lipids. –Packages and ships molecules.

Lysosomes Vesicles containing enzymes that digest macromolecules. –Carbohydrates –Proteins –Lipids –Nucleic acids Digestion –of food taken into the cell Destruction –Disease-causing organisms –Old organelles

Peroxisomes Contain the enzyme catalase –Breaks down hydrogen peroxide –Breaks down long-chain fatty acids –Synthesizes cholesterol and bile salts –Synthesizes some lipids

Vacuoles and Vesicles Membrane-enclosed sacs Vacuoles –Larger sacs –Contractile vacuoles Forcefully expel excess water from the cytoplasm Vesicles –Smaller vesicles

The nuclear membrane Separates the genetic material from the rest of the cell Filled with nucleoplasm Composed of two bilayers Contains holes called nuclear pore 核孔 complexes –Allow large molecules like RNA to pass through the membrane into the cytoplasm

Energy converting organelles Mitochondrion –A small bag with a large bag stuffed inside. –Larger internal bag is folded into cristae 摺襞. Cristae contain proteins for cellular respiration. –Releases the energy from food –Requires oxygen –Uses the energy to make ATP

Chloroplasts –Sac-like organelle –Contain chlorophyll 葉綠素 –Perform photosynthesis Uses the energy in light to make sugar –Contain folded membranes called thylakoids 類囊體 Thylakoids stacked into grana 葉綠餅 Thylakoids contain chlorophyll and other photosynthetic proteins. –Thylakoids surrounded by stroma 基質

Nonmembranous organelles Ribosomes 核糖體 Cytoskeleton 細胞骨架 Centrioles 中心體 Cilia 纖毛 and flagella 鞭毛 Inclusions

Ribosomes Made of RNA and proteins Composed of two subunits –Large –Small Are the sites of protein production Found in two places –Free floating in the cytoplasm –Attached to endoplasmic reticulum

Cytoskeleton Provides shape, support and movement Made up of –Microtubules 微管 –Microfilaments 微絲 –Intermediate filaments 中間絲

Centrioles Two sets of microtubules arranged at right angles to each other. Located in a region called the centrosome 中心體. –Microtubule-organizing center near nucleus. Organize microtubules into spindles used in cell division.

Cilia and Flagella Hair-like projections extending from the cell. Flagella –Long and few in number –Move the cell through its environment Cilia –Small and numerous –Move the environment past the cell arrangement of microtubules

Nuclear components Contains chromatin –DNA + proteins –Becomes condensed during cell division into chromosomes. Surrounded by nuclear membrane Contains one or more nucleoli –Site of ribosome synthesis Contains nucleoplasm –Water, nucleic acids, etc.

Exchange through membranes Diffusion 擴散 Facilitated diffusion 便捷式擴散 Osmosis 滲透

Exchange through membranes Active transport 主動運輸 Endocytosis 胞飲 Exocytosis 胞泌