Basic Structure of a Cell 1 Introduction to

Basic Structure of a Cell 1

Introduction to Cells are the basic units of organisms Cells can only be observed under microscope Basic types of cells: Animal Cell Plant Cell Bacterial Cell 2

What is used to view cells? • Compound microscopes – Anton van Leeuwenhoek inventor – a microscope which uses multiple lenses to collect light from the sample and then a separate set of lenses to focus the light into the eye.

Electron microscopes – Developed in the 1930’s • Scanning electron microscopes (SEM) – Scan surface of cells

Electron microscopes • Transfer electron microscopes (TEM) – Study structures combined with cells

Scanning Tunneling Microscope – is an instrument for imaging surfaces at the atomic level. Xenon on Nickel (110)

Cell theory • All organisms are comprised of one or more cells • The Cell is the basic unit of life • All cells come from preexisting cells

Number of Cells Organisms may be: • Unicellular – composed of one cell • Multicellularcomposed of many cells that may organize 8

Cells May be Prokaryotic or Eukaryotic § Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles §Eukaryotes include most other cells & have a nucleus and membrane-bound organelles (plants, fungi, & animals) 9

Prokaryotes Nucleoid region contains the DNA • Cell membrane & cell wall • Contain ribosomes (no membrane) to make proteins in their cytoplasm 10

Eukaryotic Cell Contain 3 basic cell structures: • Nucleus • Cell Membrane • Cytoplasm with organelles 11

Two Main Types of Eukaryotic Cells Plant Cell Animal Cell 12

Cell Structures = Organelles Very small size Can only be observed under a microscope Have specific functions Found throughout cytoplasm 13

Organelles Found in Cells Cell membrane Lies immediately against the cell wall in plant cells Made of protein and phospholipids Selectively permeable Living layer Controls the movement of materials into and out of the cell 14

Cytoplasm of a Cell Cytoplasm Jelly-like substance enclosed by cell membrane Provides a medium for chemical reactions to take place 15

More on Cytoplasm Contains organelles to carry out specific jobs Examples: chloroplast & mitochondrion 16

Control Organelle Nucleus Controls the normal activities of the cell Contain the DNA Bound by a nuclear membrane Contains chromosomes 17

More on the Nucleus Each cell has fixed number of chromosomes that carry genes Genes control cell characteristics 18

Smooth & Rough Endoplasmic Reticulum Smooth ER lacks ribosomes & makes proteins USED In the cell. Also makes lipids. Rough ER has ribosomes on its surface & makes proteins to EXPORT Located close to nucleus. 19

Golgi Bodies • Stacks of flattened sacs (pancakes) • Have a shipping side & a receiving side • Receive & modify proteins made by ER • Transport vesicles with modified proteins pinch off the ends Transport vesicle 20

Ribosomes Comprised of protein and RNA molecules Scattered throughout cytoplasm and on the rough ER. Provide structural support for RNA and aid in making proteins 21

Lysosome • Contain digestive enzymes • Break down food and worn out cell parts for cells • Programmed for cell death (lyse & release enzymes to break down & recycle cell parts) • Are found in blood cells- can destroy bacteria. 22

Nucleolus • Cell may have 1 to 3 nucleoli • Inside nucleus • Disappears when cell divides • Makes ribosomes that make proteins 23

Cell Powerhouse Mitochondria Rod shape Site of Cellular respiration Produces ATP 24

Warm UP • What is the function of the cell membrane, mitochondria, ribosome and nucleus?

Plant Cell Organelles Chloroplast Contain the green pigment chlorophyll Traps sunlight to make sugars (food) Process called photosynthesis 26

Plant Cell wall Dead layer Large empty spaces present between cellulose fibers Freely permeable 27

Plant Cell wall Protect and support the enclosed substances (protoplasm) Resist entry of excess water into the cell Give shape to the cell 28

Plant Cell Organelles Vacuole Have a large central vacuole Contains cell sap Sugars, proteins, minerals, wastes, water, and pigments Animal cells have one it is just not as large 29

Animal Cell Organelles • Near the nucleus • Paired structures • Help cell divide 30

Similarities cells and between plant animal cells Both have a cell membrane surrounding the cytoplasm Both have a nucleus Both contain mitochondria 31

Differences between plant cells and animal cells Animal cells Plant cells Relatively smaller in size Relatively larger in size Irregular shape Regular shape No cell wall Cell wall present 32

Differences between Plant Cells and Animal Cells Animal cells Plant cells Vacuole small or absent Large central vacuole Nucleus at the center Nucleus near cell wall 33

The cell is the Basic Unit of Life • Cell is the smallest unit of living organisms • Unicellular organisms are made of one cell only • The cells of multicellular organisms are specialized to perform different functions 34

Levels of Organization ³Atoms ³Molecules ³CELLS (muscle cells, nerve cells) ³TISSUES (muscle, epithelium) ³ORGANS (heart, lungs, stomach) ³SYSTEMS (circulatory system) ³ORGANISM (human) 35

Levels of Organization (con’t) ³Population ³Community ³Ecosystem ³Biome 36

Centriole