Chapter7 Looking at cells

Where does cork come from? The bark of an oak tree that grows in Spain and Portugal The bark is dead All that is left are the cell walls enclosing air

Microscopes reveal cell structure Robert Hooke , an English scientist, invented the microscope in the 1600’s to view cork He named the “little boxes” he saw, “cells”

Anton van Leeuwenhoek 10 years after Hooke’s findings Used a microscope to view pond water He named the single-celled organisms he discovered “animalcules”

The Cell Theory All living things are made of cells Cells are the basic units of structure and function in organisms All cells arise from existing cells

Measuring the size of cell structures Measurements are in metric units International System of Measurements (SI) Based on powers of 10 Micrometers are one-millionth of a meter ( the size of a bacterial cell)

Cells must be small Small is good! Big is bad! Lower surface area to volume ratio = inability to move substances across the membrane in large enough numbers Higher surface area to volume ratio = greater ability to exchange substances Small is good! Big is bad!

Common features of all cells Cell membrane Cytoplasm Cytoskeleton Ribosomes Genetic material

Prokaryotes do not contain internal compartments No nucleus Smaller Ex: bacteria

Characteristics of bacteria Prokaryotes All have a cell wall surrounding the cell membrane Some have flagella for movement DNA is circular instead of linear Some have a capsule for clinging

Eukaryotic cells are organized Have a nucleus Have other membrane enclosed organelles Some have flagella or cilia for movement

Eukaryotes Larger More complex Many are highly specialized Plants, animals, fungi, and many protists

Cell Organization Two divisions: Nucleus- eukaryotes only Cytoplasm- fluid portion of the cell outside the nucleus Eukaryotes and prokaryotes

Organelles Specialized structures “Little organs”

Nucleus Controls cell functions Surrounded by a double membrane with nuclear pores Contains DNA wound around proteins Wind up into chromosomes before division takes place

Nucleus Nucleolus- where ribosomes are made Nuclear pores- allow materials in and out

Vacuoles Large, saclike, membrane-enclosed structures that store materials such as water, salts, proteins, and carbohydrates

Vacuoles Plants- large central vacuole, helps keep leaves and flowers rigid Found in some unicellular organisms and animals Contractile vacuole in paramecium

Vesicles In almost all eukaryotic cells Used for storage and movement

Lysosomes Small organelle filled with enzymes Digest old organelles, cellular “junk,” lipids, proteins, and carbohydrates Type of vesicle, found in animal and some plant cells

Ribosomes Made of RNA and protein Produce proteins Found in the cytoplasm (free) and rough ER (attached)

Endoplasmic Reticulum (ER) A system of internal membranes that moves proteins and other substances through the cell Rough ER- has ribosomes on the surface that create exported proteins Smooth ER- no ribosomes, makes lipids for the cell membrane Detoxifies drugs

Golgi Apparatus Stack of flattened sacs Modifies, sorts, and packages proteins made from the rough ER Sent into or out of the cell

Sources of Energy Mitochondria- animal and plant cells Chloroplasts- plant cells

Chloroplasts Converts sunlight into food energy in a process called photosynthesis Double membrane Contains a green pigment called chlorophyll

Mitochondria In eukaryotic cells Power plant of the cells Converts food energy into smaller units the cell can more easily use Double membrane

Mitochondria Inherited only from your mother A way to trace the maternal lines of animals

Endosymbiotic Theory Chloroplasts and mitochondria have their own DNA and double membranes Theory states: These may have been independent organisms at one time Create their own energy May have been beneficial once absorbed and found to be beneficial

Unique features of plant cells Cell wall -surrounds the cell membrane, supports and protects the cell Chloroplasts- green structures that absorb sunlight and produce glucose Central vacuole- stores water and other substances, when full makes a cell rigid

Cytoskeleton Network of protein filaments Gives cells their shape and internal organization Helps to transport materials inside the cell Protein filaments Microtubules Microfilaments

Microfilaments Threadlike structures made of protein called actin Make up a tough flexible framework that helps support the cell Help cells move Amoebas- assemble and disassemble to help them move

Microtubules Hollow structures Made of protein tubulin Maintains cell shape Centrioles Makes spindle during mitosis to separate chromosomes

Microtubules Make up cilia and flagella Arranged in a 9+2 pattern Used for swimming Arranged in a 9+2 pattern Small bridges between aid in movement

Cell Boundries Cell wall Cell membrane

Cell Wall Prokaryotes, plants, algae, fungi Outside the cell membrane Animal cells do not Outside the cell membrane Strong supporting layer Porous- allows water, carbon dioxide and oxygen to pass through

Cell Membrane Protects and supports cell Regulates what enters and leaves Phospholipid bilayer- to layers of lipids