1. Cell Structure

2. 7.2 Cell Structure Two major parts: nucleus and cytoplasm
Cytoplasm: portion of cell outside of nucleus
Prokaryotes have a cytoplasm, but no nucleus
There are many parts to the cell
The structures are called organelles because they act like specialized organs

3. Cell as a factory
Different organelles can be compared to the machines and assembly lines of a factory

4. The Nucleus
The nucleus serves as the main office/ control center of factory
The nucleus contains nearly all the cell’s DNA and, with it, the coded instructions for making proteins and other important molecules
Prokaryotes have DNA with same type of instructions

5. The Nucleus structure
Surrounded by a nuclear envelope made of 2 membranes
Nuclear pores
Chromosomes
Chromatin: a complex of DNA
Nucleolus

6. Organelles that store, clean up and support
Many organelles have specific functions
Some functions include storage, clean up and support
Vacuoles, lysosomes and cytoskeleton

7. Storage space: Vacuoles
Many cells contain large, saclike, membrane enclosed structures called vacuoles
Vacuoles store materials like water, salts, proteins and carbohydrates
Plants usually have a large central vacuole
Also found in some unicellular organisms and animals

8. Storage space: Vesicles
Almost all eukaryotic cells contain smaller membrane enclosed structures called vesicles
These store and transport materials between organelles and to and from the cell surface

9. Clean up crew: Lysosomes
Lysosomes are small organelles filled with enzymes.
They break down lipids, carbs and proteins into smaller pieces that the rest of the cell can use
Also break down old organelles
Malfunctioning can cause diseases
Found in animal cells and in some specialized plant cells

10. Support structures: Cytoskeleton
The cytoskeleton is a network of protein filaments that helps the cell maintain its shape and is involved in movement
Acts like conveyor belts to transport materials
Microfilaments and microtubules

11. Microfilaments
Microfilaments are threadlike structures made up of actin protein
Form extensive networks for support
Help cell move
Assembly and disassembly of microfilaments allow cell movement

12. Microtubules
Microtubules are hollow structures made up of tubulin proteins
Maintain cell shape
Form mitotic spindle
Help build projections of cell surface called cilia and flagella
Arranged in “9+2” pattern
Cross-bridges use chemical energy
Centrioles are also made of tubulin and are located near the nucleus to help organize cell division (in animal cells only)

13. Organelles that build proteins
Proteins are important molecules essential for cell function
Catalyze chemical reactions
Make up important structures
Together, ribosomes, the endoplasmic reticulum and the Golgi apparatus synthesize, modify, package, and ship proteins

14. Ribosomes Proteins are assembled on ribosomes
Ribosomes are small particles of RNA and protein found throughout the cytoplasm in all cells
Follow coded instructions that come from DNA

15. Endoplasmic Reticulum
The endoplasmic reticulum (ER) is an internal membrane system found in eukaryotic cells
Where lipid components of membrane are made
Also makes proteins and other materials that are exported from cell

16. Types of Endoplasmic Reticulum
The rough ER is the portion involved in the synthesis of proteins
Called rough because of ribosomes on outside
Proteins made on the rough ER may be targeted for export to the cell membrane, or to specialized locations within the cell

17. Types of Endoplasmic Reticulum
The other portion of the ER is the smooth ER
For many cells the smooth ER contains enzymes that perform specialized tasks
Such as synthesis of membranes and detoxification of drugs

18. Golgi Apparatus
The Golgi apparatus is an organelle that modifies, sorts, and package proteins and other materials from the ER for storage in the cell or release outside the cell
Acts like the post office

19. Building Proteins

20. Organelles that capture and release energy
All living things require a source of energy
How do cells get energy?

21. Chloroplasts
Chloroplasts are present in plants and some other organisms
Chloroplasts capture the energy from the sunlight and convert it into food that contains chemical energy via photosynthesis
Two membranes
Pigment chlorophyll contained inside

22. Mitochondria: The cell power plant
Mitochondria are present in most eukaryotic cells
Mitochondria convert the chemical energy stored in food into compounds that are more convenient for the cell to use
Two membranes
Inherited maternally
Both chloroplasts and mitochondria contain their own genetic information in small DNA molecules

23. Cellular Boundaries All cells are surrounded by a cell membrane.
Many cells also produce a strong supporting layer around the membrane known as a cell wall

24. Cell walls
The main function of the cell wall is to support, shape and protect the cell
Animal cells do not have cell walls
Many cell walls are porous which allows water, gases and certain substances pass through easily
Provides the strength needed by plants

25. Cell membranes
Most cell membranes are made up of a double-layer sheet called a lipid bilayer
The cell membrane regulates what enters and leaves the cell and also protects and supports the cell

26. Properties of Lipids
Lipids have oily fatty acid chains attached to chemical groups that interact strongly with water
Fatty acid is hydrophobic
Opposite end is hydrophilic
Hydrophilic head are exposed to outside of cell while fatty acids form an oily layer in the membrane

27. The Fluid Mosaic Model
Protein molecules are embedded in the lipid bilayer in most cell membranes
Carbohydrates are attached to many of these proteins
Called a “mosaic” because proteins float around the bilayer with many kinds of molecules
Some are channels and pumps
Some act as identification cards

28. Selective permeability
Some substances are too large or charged to cross the lipid bilayer
If a substance can cross a membrane is it permeable to it
It is called impermeable it if cannot cross
Most biological membranes are selectively permeable
Some cross, some don’t

29. Questions?