Transcript cell theory
Cell Structure & Function The Cell • The cell is the smallest unit of life that can carry out life processes. Chapter 4 Section 2 Introduction to Cells Cellular Organization Discoveries Leading to The Cell Theory • Robert Hooke – 1665 -observed cork through a light microscope. • Anton Van Leewenhoek – 1675 observed LIVING cells. • Theodor Schwann – 1839 –animals are made of cells • Rudolf Virchow – 1855 – all cells come from other cells. • Matthias Schleiden – 1883 –plants are made of cells. The Cell Theory The cell theory states that: • all living organisms are made of one or more cells • cells are the basic units of structure and function • cells come only from pre-existing cells Prokaryotic Cell • Prokaryotic• Do not have a nucleus • Do not have internal membranebound structures – Most unicellular organisms are prokaryotes. – Bacteria Eukaryotic Cell • Eukaryotic• Has a nucleus • Has internal membrane-bound structures – Most multicellular organisms are eukaryotes. – Yeast and algae (unicellular, eukaryotes) – Plant and animal Cilia and Flagella • Aid in movement and feeding • Composed of microtubules • Cilia-short, numerous hair-like projections that move in a wavelike motion • Flagella-long, whip-like projections Organelles • “little organs” • Specialized parts within a cell that has a specific function Features Common to Cells: • Cytoplasm – • Gel like material that protects, supports and suspends organelles. Features Common to Cells: • Cell membrane – Semi-permeable • Controls what enters and leaves the cell. This helps to maintain cellular homeostasis. Structure of the Plasma Membrane • Phospholipid Bilayer -2 layers ofphospholipids. • Phospholipid- phosphate head attached to two lipids (fattyacid tails). • Polar phosphate group allows membrane to interact with its environment. • Fatty acid tails create a water-insoluble layer in the middle which is non-polar. • Fluid mosaic modelmembrane is flexible • Cholesterol-keeps fatty acid tails from sticking together • Transport proteins-allow needed substances to move through the membrane Chapter 4 Parts of the Cell Nucleus • “Command center” • Contains genetic material: – Chromosomes – DNA • Nucleolus-makes ribosomes – Ribosomes-site where proteins are made • Can be found floating in the cytoplasm or attached to endoplasmic reticulum Endoplasmic Reticulum (ER) • Series of folded membranes allow a large amount of work to be done in a small amount of space • Transportation unit for the cell • Rough Endoplasmic Reticulum (RER) – Ribosomes attached – Protein synthesis • Smooth Endoplasmic Reticulum (SER) – No ribosomes – Produce and store lipids Golgi Apparatus Vesicles • Flattened tubular membranes • Packaging plant • Modify, sort, package, and transport proteins throughout the cell VACUOLES • Storage areas Temporary storage of materials – Store food, enzymes, waste, water • Plant cells have one large vacuole. • Animal cells have many small vesicles. LYSOSOMES • Contain digestive enzymes • Digest excess or worn organelles, food particles, viruses, and bacteria • Surrounded by membrane that prevents it from destroying the cell • Can burst causing cell death Chapter 4 Mitochondria • converts food into energy • Cell “Powerhouse” • Number of mitochondria depends upon the function of the cell – Ex: muscles cells have more mitochondria than fat cells Centriole • Help with cell reproduction • Only found in animal cells Chloroplast Located in plant cells, some bacteria, and protists. • Capture light energy to produce and store food • Contain chlorophyll-green pigment that traps light energy Features Common to Cells: • Cytoskeleton – tiny fibers that give structure and support to the cell. Cell wall • Rigid outer covering PLANT CELLS • Located outside the cell membrane • Provides support and protection • Helps produce turgor pressure • Animal Cell Plant Cell Plant cell vs. Animal Cell Plant vs. Animal Cells • • • • Plant Has chloroplasts Large central vacuole Has cell wall No centrioles Animal • No chloroplasts or cell wall • Small vacuoles • Has centrioles