Cell Structure Chapter 3

Looking at Cells 1st microscope invented in the 1600s Robert Hooke (Cork Cells) Scientists use the Metric System or International Systems of Measurements SI units are based on powers of 10 μ = micro μm = micrometer

Characteristics of Microscopes Light Microscope Light passes through one or more lenses to produce an enlarged image Electron Microscope Forms an image of a specimens using a beam of electrons rather than light

Characteristics of Microscopes MAGNIFICATION – is the quality of making an image appear larger than its actual size RESOLUTION – is the measure of the clarity of an image

Types of Microscopes Compound Light Microscopes 2 lenses Objective Lens (40 X) Ocular Lens (10 x) Magnification up to 2000 X View images from 0.5 μm to 0.5 cm Used to view images such as living cells Lower magnification than electron microscopes

Types of Microscopes Electron Microscope Magnification up to 200,000 X Object & electron beam are placed in a vacuum chamber Object is stained with metal ions Electron beam is absorbed by the ions Electrons produce a fluorescent image called the TEM

Types of Microscopes Scanning Electron Microscope Electrons bounce off the specimen Creating a 3-D image Scanning Tunneling Microscope Uses needle-like probe to measure differences in voltage caused by electrons that leak from the surface 3-D images Living organisms can be viewed with this scope

Section 1 Review 1. How many cm are in a m? 2. What is the difference between resolution and magnification? 3. What measurement system do scientists use? 4. Why can living cells not be viewed under an electron microscope? 5. The English scientist Robert Hooke used a crude microscope to examine these….

Section 2: Cell Features Schleiden, Schwann, Virchow CELL THEORY 1) All living things are made of one or more cells 2) Cells are the basic units of structure and function in organisms 3) All cells arise from existing cells

Cell Size Small cells are more efficient than large cells All substances that enter or leave a cells have to cross the cell’s surface Surface area- to- Volume LOW – substances can not enter or leave Small cells have a higher surface area- to – volume ratio Shorter distance to travel

Common Features of Cells CELL MEMBRANE – encloses the cell Regulates what enters & leaves the cell CYTOPLASM – cell’s interior CYTOSKELETON – fibers suspended in the cytoplasm RIBOSOMES – cellular structures on which proteins are made DNA – instructions for the cell

Prokaryotes The smallest and simplest cells Are single-celled organisms Lack a NUCLEUS Examples: Bacteria Reproduce Rapidly Do not need oxygen to survive Some can make their own food

Characteristics of Prokaryotes CYTOPLASM – semi-solid material that surrounds everything inside the cell DNA, Ribosomes & enzymes CELL WALL – surrounds the cell membrane Function: Provides support & structure Found in plants, fungi & some bacteria Made of polysaccharides

Characteristics of Prokaryotes Capsule – surrounds the cell Cling to lots of things Flagella – long, threadlike structures that extend from the cell surface Function: helps the cell move

Eukaryotic Cells Have a Nucleus NUCLEUS – houses the DNA Organelles - internal compartments Carry out specific activities in the cell Vesicles – move proteins & other molecules from cell to cell CILLIA – short hair-like projections Functions: Movement & transport of materials across the cell membrane

Eukaryotic Cells CYTOSOL – fluid material that makes up the cytoplasm CYTOSKELETON Made of protein fibers Function: Holds the cell together All connected to one another 3 kinds of fibers – Actin Fibers, Microtubules & Intermediate Fibers

Cytoskeleton Actin Fibers – determine the shape Microtubules – act as a highway system Transport info from the nucleus to the rest of the cell Intermediate Fibers – are an anchor for ribosomes & enzymes

The Cell Membrane Selective Permeability Only let certain things enter or exit Phospholipid = 1 lipid + 2 fatty acids Head  Polar Phosphate Group Attracted to water 2 Tails  NonPolar Repel water

The Cell Membrane LIPID BILAYER – double layer of phospholipids Marker Proteins -- “Name Tags” Direct cells to the proper location Receptor Proteins -- “Antenna” Receive and transmit info Transport Proteins -- “Locked Door” Allow only certain ions and molecules to cross the cell membrane Enzymes – assist in biochemical reactions

Section 2 Review 1. Describe the importance of surface-area-to volume ratio of a cell. 2. How are Prokaryotic & Eukaryotic Cells similar? Different? 3. Describe the function of 2 cell membrane proteins. 4. What does the cell theory state? 5. What does the term “selectively permeable” mean in regards to a cell membrane?

Section 3: Cell Organelles Cell functions are controlled by the NUCLEUS Surrounded by the NUCLEAR ENVELOPE Made up of 2 lipid bilayers NUCLEAR PORES Ribosomal RNA pass through the pores into the cytoplasm Ribosomes are partially assembled in the NUCLEOLUS

The Nucleus DNA stored inside the nucleus Eukaryotic DNA is wound around proteins CHORMOSOMES – DNA strands Humans = 46 Garden Peas = 14

Ribosomes & the ER RIBOSOMES make protein & RNA ENDOPLASMIC RETICULUM Mobile in the cytoplasm Stationary on the Rough ER ENDOPLASMIC RETICULUM Move proteins & other substances throughout the cell Has a membrane that is made up of a lipid bilayer

Ribosomes & the ER VESICLE – is a small membrane bound sac that transports substances inside the cell Separates proteins made on the Rough ER from proteins made in the cytoplasm SMOOTH ENDOPLASMIC RETICULUM Lacks ribosomes Function: Makes lipids & breaks down toxic substances

Packaging & Distribution of Proteins GOLGI APPARATUS Is a set of flattened, membrane-bound sacs that package & distribute Proteins are modified in the GA & enter new vesicles Vesicles take the proteins outside the cell OR Vesicles remain in the cell & become LYSOMES Contain digestive enzymes

Mitochondria Function: Harvest energy to make ATP Muscle cells can have 100s – 1000s 2 Membranes (Inner & Outer) Here chemical reactions produce ATP Also has DNA Circular – similar to prokaryotic DNA

Structures of Plant Cells 3 Organelles NOT found in Animal Cells 1) CELL WALL Adds additional support, give shape, protects from damage & connects with adjacent cells 2) Chloroplasts Use light to make carbohydrates from carbon dioxide and water Surrounded by 2 layered membrane & contains DNA

Structures of Plant Cells 3) Central Vacuole Takes up most of volume Contains Water Ions Nutrients Waste When full it makes the cell rigid Allows the plant to stand upright

Section 3: Review 1. Describe the role of the nucleus in cell activities. 2. Sequence the course of newly made proteins from the rough ER to the outside of the cell. 3. Name 2 organelles a plant has that an animal cells does not. 4. The mitochondria has the nickname “The Powerhouse”. Why is this a good nickname?