CELLS STRUCTURE & FUNCTION Reading: Chapter 3 Including movement through cell membranes:

Introduction to Cells The cell is the structural and functional unit of life. Cells come in MANY sizes and shapes. All cells have these 3 parts: 1)Cell membrane 2)Cytoplasm (with organelles) 3)Nucleus

CELL STRUCTURES 1. Cell membrane/plasma membrane/plasmalemma a) Structure = phospholipids, proteins, cholesterol = fluid mosaic pattern b) Functions: -gives cell integrity -shape -flexibility -gatekeeper -communication

CELL STRUCTURES (con’t) 1. Cell membranes (con’t) c)How molecules move across cell membranes PASSIVE MECHANISMS = NO energy needed 1. Diffusion 2. Osmosis ACTIVE MECHANISMS = you NEED energy 3. Active Transport 4. Endocytosis: Pinocytosis & Phagocytosis 5. Exocytosis

PASSIVE MECHANISMS 1)Diffusion - movement of molecules -from an area of greater to lesser concentration -NO energy needed (molecules keep moving)

PASSIVE MECHANISMS 2)Osmosis -Movement of H 2 O -From an area of high H 2 O to low H 2 O concentration -NO energy needed

2) Osmosis (con’t) Terms to describe osmotic concentration: a) isotonic solution = same salt concentration as the inside of a cell b) hypertonic solution = more salt than a cell c) hypotonic = less salt than a cell What happens to a cell in each of these solutions?

ACTIVE MECHANISMS 3) Active Transport -Carriers move molecules from low to high concentration -~40% of energy used by our cells is used to operate these “pumps” - Uses ATP (energy)

ACTIVE MECHANISMS 4) Pinocytosis (cell drinking) - This is one type of “endocytosis” -Cell membrane surrounds fluid -The sac pinches off and brings liquid inside

ACTIVE MECHANISMS 5)Phagocytosis (cell eating) - This is one type of “endocytosis” - Cell membrane surrounds particles - Sac pinches off and brings particle(s) inside 6) Exocytosis = the reverse

5) Exocytosis: The reverse of endocytosis -a vesicle forms around the liquid or solid particle -the vesicle moves to the _____________ where it is released.

Back to our list of cell structures.

CELL STRUCTURES 2. CYTOPLASM -fluid portion inside cell membrane -organelles are found within this fluid -very structured (microtubules)

3. NUCLEUS -Double membrane separates nucleus from cytoplasm -Contains DNA as chromatin threads -Chromatin clumps up during cell division to form chromosomes (23 pairs) -“Brain” of cell Nucleolus = “little nucleus” -inside nucleus -no membrane -produces ribosomes

4. Ribosomes - “protein factories” - reads genetic code sent from nucleus to build proper protein -free in cytoplasm or -attached to RER * *

5. Endoplasmic Reticulum (2 types) a) rough (RER) = “granular ER” - ribosomes attached - ribosomes produce proteins - RER transports proteins b) smooth (SER) = “agranular ER” - no ribosomes attached - transports proteins & lipids - produces steroids - inactivates toxins - stores Ca ++ (muscle contraction)

CELL STRUCTURES (con’t) 6. Golgi Apparatus - 6 flat sacs - continuous with Endoplasmic Reticulum - separates and packages proteins for export

7. Mitochondria - Oval-shaped - Double membrane - Internal membrane produces energy ATP - Contain DNA (can self-replicate)

8. Lysosomes (lys = split, some = body) - small sacs of enzymes (chemicals) - the enzymes break down molecules - “digestive system” of cell - in apoptosis (programmed cell death) lysosomes are “suicide packets” Enzymes + Food/organelle Wastes 1 ary LysosomeResidual Body2 ary Lysosome

9) Cilia and Flagella - projections from cell membrane a)Cilia:-many & small -sweeping motion Ex: -respiratory tract -fallopian tubes

9) Cilia and Flagella - projections from cell membrane b)Flagella:-single & large -whip like motion Ex: spermatozoa

10)Centriole - collections of small microtubules - found in pairs (1 pair = centrosome) - separate the chromosomes during cell division Pair = centrosome

CELL DIVISION 1)Mitosis - asexual cell division - occurs in most cells - each new cell = identical to original cell - in humans, most cells have 46 chromosomes

CELL DIVISION 2)Meiosis - sexual cell division -only occurs in ovaries & testes -each new cell (sperm or egg) only has 23 chromosomes

End of Cells