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Transcript
Cell Structure Dr. Stafford 2015 1 KEY CONCEPT Cells are the Basic unit of life. Scientists Robert Hooke – 1665 –Looked at cork –Looked like monastery rooms (cells) –Named the structures in the cork – “CELLS” Scientists Anton van Leeuwenhoek – 1674 –Father of microbiology –Observed “living cells – “animalcules” Scientists Simple light microscope vs. compound light microscope –Simple – one lens –Compound – 2 or more lens Scientists Matthius Schleiden – 1838 – German –Plants are made of cells Theodor Schwann – 1839 – German –All animals are made of cells –“all living things are made of cells” Scientists Rudolp Virchow – 1855 – German –“all cells come from preexisting cells” Scientists Cell Basics • Cell Theory – All living organisms are made of cells – The cell is the basic unit of all living organisms – All cells come from preexisting cells 9 • Early studies led to the development of the cell theory. – The Cell theory has three principles. • All organisms are made of cells. • Early studies led to the development of the cell theory. – The Cell theory has three principles. • All organisms are made of cells. • All existing cells are produced by other living cells. • Early studies led to the development of the cell theory. – The Cell theory has three principles. • All organisms are made of cells. • All existing cells are produced by other living cells. • The cell is the most basic unit of life. Cell Basics • Things found in all cells – DNA – genetic code – different for cells from different organisms – Plasma membrane – boundary of all cells – maintains homeostasis inside the cell – Cytoplasm – jelly-like fluid that fills the cell – Ribosomes – nonmembrane-bound organelle that assembles proteins 13 Cell Basics • Types of cells – all living organisms fall into two categories – Prokaryotes – bacteria • • • • • No nucleus No membrane bound organelles Smaller First living organisms Most have a cell wall Bacterium 14 (colored SEM; magnification 8800x) Cell Basics • Types of cells (cont.) – Eukaryotes – all except bacteria • • • • • Has a membrane-bound nucleus Has membrane bound organelles Larger than prokaryotes More complicated – came later in history Some have cell wall….some don’t 15 s nucleus •s organelles cell membrane cytoplasm Eukaryotic Cell Structures • Cell Boundaries –Plasma membrane – selectively permeable membrane • Maintains homeostasis – controls what goes into or leaves a cell • Phospholipid bilayer with proteins, cholesterol, and carbohydrate chains added in or on it • Found around the outside of all cells 17 Eukaryotic Cell Structures • Cell Boundaries (cont.) –Cell wall – fairly rigid structure found outside the plasma membrane • Provides additional support and protection • Found in plants, fungi, and some protist cells • Not selectively permeable – allows most everything to flow through it • Made of cellulose in plants • Gives the cell its more rigid shape 18 • Plant cells have cell walls and chloroplasts. – A cell wall provides rigid support. Eukaryotic Cell Structures • Nucleus – control center of the cell – contains two main structures –1. DNA - holds the code for making proteins which is what controls all the activities of the cell – comes in two forms • Chromatin – loosely arranged DNA – the form usually found in an active cell doing its daily work • Chromosomes – densely packed DNA – found during cell division (mitosis) 20 Eukaryotic Cell Structures •Nucleus – contains two main structures (cont.) – 2. Nucleolus – seen as a smaller dark structure inside the nucleus •Makes ribosomes 21 Eukaryotic Cell Structures • Nucleus – control center of the cell (cont.) –Nuclear envelope – a double membrane that surrounds the nucleus • 2 phospholipid bilayers • Nuclear pores – holes in nuclear envelope for substances like mRNA and ribosomes to pass out of the nucleus into the cytoplasm where proteins are made 22 • Several organelles are involved in making and processing proteins. • The nucleus stores genetic information. Eukaryotic Cell Structures • Cytoplasm – jelly-like fluid that fills the cell from the outside of the nucleus to the plasma membrane –Suspends the organelles –Contains many substances the organelles need to work with • Building blocks for structures and macromolecules • Ions • Water 24 Eukaryotic Cell Structures •Assembly. transport, and storage – the organelles that make and complete proteins and transports them around the cell and out of the cell (secretion) • Home of CELLS alive! 25 Eukaryotic Cell Structures • Assembly, transport, and storage (cont.) –Ribosomes – found in all cells – organelle that makes proteins • Made by nucleolus – combination of proteins and rRNA • Found in cytoplasm • 2 part organelle • Can be attached to endoplasmic reticulum • Can be unattached to endoplasmic reticulum – free-floating 26 • Several organelles are involved in making and processing proteins. (continued) • Ribosomes link amino acids to form proteins. Eukaryotic Cell Structures • Assembly, transport, and storage (cont.) –Endoplasmic reticulum (ER) – site of cellular chemical reactions – Highway of the cell • Highly folded membranes – increase surface area • Found in cytoplasm – close to the nucleus • Rough ER – has ribosomes attached to it – makes proteins for membranes, proteins to leave the cell (secreted), or proteins that are transported to other organelles within the cell 28 Eukaryotic Cell Structures • Assembly, transport, and storage -ER (cont.) Smooth ER – used to produce other substances besides proteins such as lipids 29 • Several organelles are involved in making and processing proteins. • The nucleus stores genetic information. • Many processes occur in the endoplasmic reticulum. • There are two types of endoplasmic reticulum. • rough endoplasmic • smooth endoplasmic reticulum reticulum Eukaryotic Cell Structures • Assembly, transport, and storage (cont.) –Golgi apparatus (GA) – post office of the cell • Found in the cytoplasm – closer to the plasma membrane • Flattened system of tubular membranes • Modifies the proteins • Packages and sorts proteins in transport vesicles to be sent to their appropriate destination inside or out of the cell 31 Eukaryotic Cell Structures • Assembly, transport, and storage (cont.) –Transport vesicles – bud off the GA to carry the packages of completed proteins to their appropriate destination inside the cell or out of the cell (secretion) 32 • Several organelles are involved in making and processing proteins. (continued) • Ribosomes link amino acids to form proteins. • Vesicles are membrane-bound sacs that hold materials. Eukaryotic Cell Structures • Assembly, transport, and storage –Vacuoles – membrane-bound spaces in the cytoplasm for temporary storage of: • Food • Waste • Enzymes • Water in some organisms Plants have a large central vacuole for storage of starch or water. Animals have several small vacuoles 34 • Other organelles have various functions. • Mitochondria supply energy to the cell. • Vacuoles are fluid-filled sacs that hold materials. Eukaryotic Cell Structures • Assembly, transport, and storage (cont.) –Lysosomes – membrane-bound organelle in cytoplasm that contains digestive enzymes to digest worn out organelles, food particles, and viruses and bacteria. • An intact membrane is important to contain the digestive enzymes • Can combine with a vacuole to digest the contents of the vacuole 36 Eukaryotic Cell Structures • Assembly, transport, and storage (cont.) – Lysosomes (cont.) • Sometimes the lysosomes release their digestive enzymes into the cytoplasm of a cell if the organism wants to destroy a cell – this is how a tadpole gets rid of its tail – this is also how human fetuses get rid of their tail 37 • Other organelles have various functions. • Mitochondria supply energy to the cell. • Vacuoles are fluid-filled sacs that hold materials. • Lysosomes contain enzymes to digest material. Eukaryotic Cell Structures • Energy Transformers – energy cannot be made – it can only be transformed into another form –The form of energy a cell uses is ATP – just the same as a gas car can only use gasoline to do its work; a cell can only use energy in the form of ATP to do its work –2 different organelles can transform energy from a source outside the cell into ATP 39 Eukaryotic Cell Structures • Energy transformers (cont.) –Chloroplasts – capture light energy from the sun and transform it into ATP or store the light energy in the form of sugars for later energy use • Found in the cytoplasm of plants and some protists • Double membraned organelle – inner membrane is highly folded • Contains a green pigment called chlorophyll that captures the energy from sunlight 40 • Plant cells have cell walls and chloroplasts. • A cell wall provides rigid support. • Chloroplasts convert solar energy to chemical energy. Eukaryotic Cell Structures • Energy transformers (cont.) –Mitochondria – takes the sugar produced by chloroplasts and breaks it down to release the energy stored in the sugar molecule and transforms that energy into ATP – a form of energy the cell can use 42 Eukaryotic Cell Structures • Energy transformers (cont.) –Mitochondria (cont.) • Found in the cytoplasm of all eukaryotic cells – including plants cells • Double membrane with inner membrane highly folded • Vary in number found in cells depending on the cells need for energy – found in high numbers in muscle cells 43 • Other organelles have various functions. • Mitochondria supply energy to the cell. Eukaryotic Cell Structures • Cytoskeleton – structure for support of the cell and movement of organelles within the cell. Made up of: 1. Microtubule – thin, hollow cylinders made of protein 2. Microfilaments –thin, solid protein fibers –Forms the framework of the cell – constantly changing 45 • Cells have an internal structure. • The cytoskeleton has many functions. • • • • • supports and shapes cell helps position and transport organelles provides strength assists in cell division aids in cell movement Eukaryotic Cell Structures • Structures for locomotion – located on the outside of cells – Cilia – short, numerous , hair-like projections that move in wave-like motion – found in our airways – Flagella – longer projections that move in a whip-like motion – usually only one or very few – Both are used for movement of many unicellular organisms 47 Eukaryotic Cell Structures • Plant and animal cell comparisons –Plant cells have three structures not found in animal cells and are usually larger and have a more fixed shape • Cell wall – for extra structure and protection • Chloroplast – to convert sunlight into ATP • Large central vacuole – to store sugar as starch and water 48 Eukaryotic Cell Structures • Plant and animal cell comparisons –Animal cells – usually smaller than plant cells • Centriole is the only organelle found in animal cells and not plant cells • Usually have many small vacuoles • Could have flagella or cilia while a plant cell will not 49 • Other organelles have various functions. • • • • Mitochondria supply energy to the cell. Vacuoles are fluid-filled sacs that hold materials. Lysosomes contain enzymes to digest material. Centrioles are tubes found in the centrosomes. Eukaryotic Cell Structures • The eukaryotic cell has many different organelles that each have their own function that contributes the work of the whole cell. • The fact that all these organelles have evolved and can work together for the good of the whole cell gives eukaryotic cells the ability to do a lot more than prokaryotic cells 51 Eukaryotic Cell Structures • The nucleus and more precisely, the DNA within the nucleus is what controls all the organelles along with the plasma membrane. • It does this by directing which proteins are produced and when. These proteins, many of which are enzymes, control all the chemical reactions (metabolism) of a cell. 52