1. Cell Structure
Chapter 3

2. 3.1 Looking at Cells 1600’s the microscope was invented
Robert Hooke 1665 looked at cork and saw little boxes he called “cells”

3. Anton Van Leeuwenhoek later looked at pond water and saw tiny animals he called “animalcules”

4. Measuring Cell Structures
Based on metric system
giga- mega kilo- hecto- deka- BASE deci- centi- milli- micro- nano-
Giga = G
Mega = M
Micro = µ
Nano = n

5. Characteristics of Microscopes
Light Microscope – light passes through 1 or more lenses
Electron Microscope – image made by beams of electrons
Micrograph – image from a microscope
Labeled with what kind of microscope and magnification value
Magnification – how many times larger it appears
Resolution – measure of clarity
Electron Micrograph Ebola Virus
160,000 x magnification

6. Types of Microscopes Compound Light Microscope
2 lenses with light bulb shining through slide
Objective lens in close to slide
Ocular lens is near eye
40x x 10x = 400x magnification
Third lens hurts resolution
Most powerful = 2,000x
See something 0.5 µm in diameter
40 x
400 x

7. Electron Microscope Up to 200,000x
Beam and specimen must be in vacuum so e- don’t bounce off gas (no living things)
Transmission Electron Microscope
Stained with metal ions
Very thin slices of specimen
Internal structures
Black and white but computers add color
Scanning Electron Microscope
Specimen coated with thin layer of metal
3-D cell surface
Artificial color

8. Scanning Tunneling Microscope
Needlelike probe measures differences in voltage caused by e- that tunnel from surface of object
3-D image
Used on living things

9. 3.2 Cell Features 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

10. Cell Size Smaller is more efficient
Everything must cross cells surface
Surface area to volume ratio
Too low - substances cannot enter and leave in large enough numbers
Small cells have a high ratio

11. Common Features of Cells
Cell Membrane
Outer boundary enclosing cell that separates interior
Controls flow in and out
Cytoplasm
Cell interior

12. Cytoskeleton
System of microscopic fibers
Act as support structures

13. Ribosomes DNA Where proteins are made All cells have it
Protein instructions
Regulate cellular activities
Allows for reproduction

14. Prokaryotes Smallest, simplest, single-celled organism
No nucleus (and other parts missing)
Cannot carry out many special functions due to missing parts
Around at least 3.5 billion years ago (bya)
Nearly 2 bya were only organisms on earth
Very small from 1 – 15 µm
Bacteria
Subset that causes infection and food spoiling

15. Characteristics Large range of environments
Many grow and divide rapidly
Some don’t need oxygen, others can’t have it
Some make own food

16. Everything inside cell membrane is in cytoplasm
Enzymes and ribosomes free to move around
Singular, circular DNA located in center
Cell Wall – surround membrane
Provides structure and support
No cytoskeleton so cell wall gives shape
Cell wall made of polysaccharides connected by short amino acid chains
Some cell walls surrounded by capsule = polysaccharides (allows them to cling to many things)

17. Flagella – long, threadlike structures that provide movement

18. Eukaryotic Cells Internal compartments Evolved about 2.5 bya
Have an internal compartment for DNA = nucleus
Have structures that carry out specific activities = organelles
Cytoplasm = everything inside membrane but outside nucleus
Membranes connect organelles and provide channels
Form envelopes called vesicles that move proteins between organelles

19. Flagella Cilia Cytoskeleton
– short, hair-like structures
Used for cell movement or movement of materials over cell
Cytoskeleton
Protein fibers
Holds cell together, keeps it from collapsing
Cytosol – fluid surrounding organelles, internal membranes and cytoskeleton

20. The Cytoskeleton Interior framework of animal cell
Protein fibers anchored to inside of plasma membrane
3 kinds of fibers
Actin Fibers
Long, slender microfilaments
Made of the protein actin
Determine shape of animal cells
Microtubules
Hollow tubes
Made of protein tubulin
Highway for transport from nucleus to parts of cell
Intermediate fibers
Thick ropes of protein
Frame for ribosomes and enzymes keeping them in certain locations

21. The Cell Membrane Fluid, like a soap bubble
Lipids form a barrier allowing only certain things through - selective permeability
Phospholipid = 2 fatty acids and a phosphate group
Polar head – phosphate group; attracted to H20
2 nonpolar fatty acid tails; repelled by H20
Phospholipids are in a double layer so called the lipid bilayer
Allows lipids and nonpolar substances to pass through

22. Membrane Proteins Proteins are made of amino acids
Some are polar and some are nonpolar
Some move around
Marker proteins attached to carbohydrate tell what kind of cell it is (liver, heart)
Receptor proteins bind specific substances (signal molecules)
Enzymes in cell membrane important in biochemical reactions
Transport Proteins help move things in and out

23. 3.3 Cell Organelles Nucleus Controls most cell functions
Surrounded by nuclear envelope
Double membrane (two lipid bilayers)
Nuclear pores = small channels allow passage through
Nucleolus – ribosomes partially assembled here
Most DNA stored here
Wound around proteins but in elongated thin strands
When about to divide they become more compact into chromosomes and form dense rod shaped structures
Number of chromosomes depends on species
Humans = 46
Peas = 14

24. Ribosomes and Endoplasmic Reticulum
Ribososmes
Where proteins are made
Made of dozens of different proteins and RNA
May be free in cytosol but proteins made there stay in cell

25. Production of Proteins
Endoplasmic Reticulum is a system of internal membranes that move proteins and other structures through the cell
It is a lipid bilayer with embedded proteins
Rough ER
Attached ribosomes
Proteins made enter ER
Pinched off and form vesicles
Keep separate
Smooth ER
No ribosomes
Make lipids
Break down toxic substances

26. Packaging and Distribution of Proteins
Vesicles go from ER to Golgi Apparatus
Golgi Apparatus
Flattened membrane-bound sacs
Enzymes inside modify proteins
Modified proteins repackaged by GA and bud off
Lysosomes – vesicle that contains digestive enzymes

27. Steps of Protein packaging and distribution
Ribosomes on Rough ER make proteins and they are packaged
Go from ER to GA
In the GA proteins are modified and repackaged
Many vesicles move to cell membrane and release cargo
Other vesicles remain in cell and go a job

28. Mitochondria
Harvests energy from organic compounds to make ATP which is used as energy by cell
Most ATP is made here
Cells that use ATP have lots of mitochondria
2 membranes
Outer = smooth
Inner = folded; large surface area
Forms 2 compartments

29. Mitochondrial DNA
DNA and ribosomes make their own proteins though most come from cytosol
Mitochondrial DNA (mDNA) is independent from nuclear DNA, similar to circular DNA of prokaryotic cell
Believe prokaryotes were ancestors to mitochondria

30. Structure of Plant Cells
Cell Wall
Surrounds cell membrane
Made of proteins and carbohydrates (cellulose)
Helps support and maintain shape
Protection
Connects to other cells

31. Chloroplasts Use light to make carbohydrates from CO2 and H20
Along with mitochondria supplies much of energy needed to power cell
2 membranes
Contain their own DNA (ancient prokaryotes)

32. Central Vacuole Stores water May contain ions, nutrients, or wastes
When full, cell is rigid