Cell Structures and Functions

1. Cell Membrane or Plasma Membrane – thin covering on outer surface a. phospholipid bilayer embedded with proteins b. selectively permeable c. first line of defense d. regulates what enters and leaves the cell

2. Nucleus – main control of cell activities through genetic code a. nucleoplasm – thick colloid of protein containing chromatin material (RNA) b. nuclear membrane – double membrane, similar to plasma membrane. Connects to RER c. nucleolus – enlarges in time of reproduction, made of RNA, DNA and protein, makes ribosomes d. chromosomes – contain chromatin, contains genetic info. for organism e. chromatin – DNA with protein wrapped around it. Bundles to form chromosomes before cell division

3. Cytoplasm – made of cytosol and organelles a. cytosol – gel like colloid containing water, salts, organic compounds, etc. Functions to surround and support organelles – many chemical reactions occur here.

4. Rough Endoplasmic Reticulum – connected to nuclear membrane, contains ribosomes a. produces and packages proteins for cell use and new membranes

5. Smooth Endoplasmic Reticulum – doesn’t have ribosomes, appears more tube-like than RER and is connected to RER. a. Manufactures and packages lipids, phospholipids and steroids

6. Golgi Apparatus – series of stacked pancakes or pita bread with small vesicles at end of stacks a. Modifies, packages and transports materials from RER and SER. Vesicles attach to entry face, are transferred thru Golgi and exit thru the exit face. Vesicles may be membrane vesicles (products used in membranes), secretory vesicles (products exported from cell) or storage vesicles (products used in chemical reactions within the cell)

7. Mitochondria – powerhouse of cell, site of cell respiration for the production of ATP molecule a. Cristae – double folded inner membrane. Enzymes occur on membranes to run aerobic portion of respiration b. Matrix – gel like fluid in center of mitochondria containing enzymes which run anaerobic portion of respiration

8. Lysosome – contain enzymes which dissolve protein. Breakdown and recycle cell parts as well as destroy foreign materials/invaders. Lots of these in white blood cells

9. Peroxisome – membrane contained enzymes which breakdown toxic substances such as hydrogen peroxide 10. Cytoskeleton – scaffolding that supports the cell a. Microfilament – smallest filament – known as cell muscle. Made of actin and used to move cell during cell division and to help cell parts move b. Intermediate Filament – medium size – used to support points of stress and tension and to hold organelles such as the nucleus in place c. Microtubule – large hollow tubes used in cell movement (cilia and flagella) as well as tracks for cell parts and vesicles to move along

11. Cell Junctions – connect cells together and allow for communication within cell a. Plasmodesmata – only in plant cells. Allows for movement of molecules between adjacent plant cells to chemically communicate b. Tight Junction – between animal cells. Plasma membranes of cells fuse together forming a leakproof sheet of cells. Found in intestines and skin c. Anchoring Junction – between animal cells. Allows passage of some molecules between the cytoskeleton fibers filling the space between cells d. Communicating Junction – between animal cells – similar in function to plasmodesmata in plants – allows for passage of molecules, esp. ions, between cells for communication.

12. Vacuole – a. in animals: small storage sacs b. in plants: large central vacuole stores water leucoplasts – store starch (remember potato in lab) – food storehouse chromoplasts – store red pigment (remember tomato in lab)

13. Chloroplasts – In plants only – the site of photosynthesis a. contain grana and stroma. It is a double membrane enclosed sac. Inside the inner membrane is a thick fluid called stroma – this is where the dark reaction or Calvin cycle of photosynthesis occurs. In the stroma are the grana – stacks of discs that capture light energy for the light cycle of photosynthesis to occur (it occurs here)

14. Cell Wall – in plants only – occurs outside the cell membrane a. made of three layers b. protects and supports the cell c. is permeable to water, oxygen, carbon dioxide and other substances

15. Centriole – in animals only a. pair of tubular structures containing microtubules b. area around the centrioles creates the spindle fibers for cell division c. the centrioles organize the microtubules for cilia and flagella

16. Cilia – primarily in animals a. numerous, short, hair-like projections containing microtubules b. move small protists, move materials in fluid across the cell membrane (i.e. respiratory tract)

17. Flagella – primarily in animals, but also in plant reproductive cells and protists a. long projection of microtubules – may be single or double b. move cell