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Transcript
Chapter 3 Cells Cells- the basic units of living things • Cells were not discovered until microscopes were invented in the 1600’s • Robert Hooke first discovered cells in 1665 when he observed cork cells • Anton van Leeuwenhoek first observed living cells from pond water in 1675 Measuring Cell Size: • Most cells are too small to see with the naked eye • Cells are usually measured in micrometers because they are so small – Ex: Red Blood Cells The Cell Theory • The cell theory was created based on observations made by 3 scientists: Mattias Schleiden, Theodor Schwann, & Rudolph Virchow • The Cell Theory Has 3 Parts: 1) All living things are made of one or more cells 2) Cells are the basic units of structure and function in all living things 3) Cells come from other cells Cell Size • There are about 100 trillion cells in the human body • It is better to have many tiny cells than only a few large ones, why? • Cells need a large surface area in comparison to their internal size(volume) Common Features of Cells • Cell Membrane- encloses the cell and separates it from the outside environment • Cytoplasm- the material inside the cell membrane • Cytoskeleton- a system of microscopic fibers that support cell structures • Ribosomes- make proteins for the cell Prokaryote Cells • Prokaryotes are the smallest & simplest type of single celled organisms • Prokaryotes are single celled and have NO NUCLEUS • Prokaryotes are believed to be the 1st living things on earth – Ex: Bacteria Characteristics of Prokaryotes • Prokaryotes live in a wide range of conditions Ex: in the soil, water, animals • Cytoplasm- everything on the inside of the cell membrane • DNA- prokaryotes have a single circular loop of DNA • Cell Wall- protective outer layer that provides structure and support • Cell Membrane- thin, flexible layer just beneath the cell wall • Flagella- long threadlike tails that allow movement Prokaryotes Eukaryote Cells • Eukaryotes are more complex single and multicellular organisms • Eukaryotes have internal cell structures and have a nucleus • Eukaryotes are thought to have evolved from prokaryotes Characteristics of Eukaryotes • Eukaryotes contain many specialized structures called organelles • Cytoplasm- the fluid & organelles inside the cell membrane • Nucleus- contains the DNA in the cell, controls cell functions • Cell Membrane- surrounds the cell and controls movement of things into and out of the cell • Flagella- tail-like structure used for movement • Cilia- short hair-like structures used for movement Eukaryotes Cell Structures • The Cytoskeleton- provides an interior framework for an animal cell – Has a similar function to the skeleton in the human body – The Cytoskeleton is made of 3 types of fibers: • Actin Fibers- long slender strands of protein • Microtubules- hollow tubes made of tubulin, that transmit information from the nucleus to different parts of the cell • Intermediate Filaments- thick ropes of protein that provide structural support inside the cell and hold cell parts in place The Cytoskeleton The Cell Membrane • The cell membrane surrounds the cell and acts as a barrier between the inside and outside of a cell • Selectively Permeable- only certain substances are allowed to enter and leave the cell through the cell membrane Membrane Structure • The cell membrane is a phospholipid bilayer • Phospholipids: molecules made form phosphate molecules and lipids Polar “head” Non-Polar “tails” • Bilayer: the cell membrane is 2 layers thick, a double layer of phospholipids Cell Membrane Diagram Membrane Proteins • • The cell membrane has various proteins stuck in it that have specific jobs Types of Membrane Proteins: 1) Cell Surface Marker- identifies cell type 2) Receptor Proteins- recognizes & binds substances outside the cell 3) Transport Proteins- help substances move into and out of the cell 4) Enzymes- perform chemical reactions inside the cell Membrane Proteins Cell Parts • Organelles- structures inside the cell that perform specific functions The Nucleus • Control center of the cell • Instructs all other cell parts what to do • Contains chromosomes made of DNA • Nuclear Envelope- membrane that surrounds the nucleus – Contains pores“holes” that allow substances into and out of the nucleus • Nucleolus- central core of the nucleus that makes ribosomes The Nucleus Ribosomes • Ribosomes make proteins for the cell – Free Ribosomes: are scattered throughout the cytoplasm – Attached Ribosomes: are located on the surface of the rough endoplasmic reticulum Endoplasmic Reticulum(ER) • The ER is a system of folded membranes found near the nucleus • The ER transports proteins throughout the cell • Smooth ER- has no ribosomes on it’s surface • Rough ER- has ribosomes on it’s surface Endoplasmic Reticulum Golgi Apparatus • The Golgi is a flattened membrane of sacs found in the cytoplasm • The Golgi packages & distributes materials inside the cell using vesicles • Vesicles- small sacs that hold and carry substances in the cell Golgi Apparatus Processing Proteins Lysosomes • Lysosomes are small, spherical organelles containing digestive enzymes • Lysosomes break down food molecules & toxins inside the cell Mitochondria • The mitochondria is a bean shaped organelle found throughout the cytoplasm • The mitochondria produces energy(ATP) • The “Powerhouse” of the cell * Mitochondria have their own DNA inside Plant Organelles • Cell Wall- protective outer membrane – Supports and maintains cell shape – Made of a material called cellulose • Chloroplasts- use light(solar) energy to make food for plants – Contain a green pigment called chlorophyll • Vacuole- a large water, mineral, and waste storage chamber in plant cells – The vacuole takes up a very large area in a plant cell Plant Organelles END OF CHAPTER 3 NOTES!!!