Download CELLS- STRUCTURE AND FUNCTION

CELLS
STRUCTURE & FUNCTION
Reading: Chapter 3
Including movement through cell membranes:
p. 58-65 (8th edition)
p. 59-66 (9th edition)
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 H2O
-From an area of high H2O to low H2O 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
End of mechanisms used to transport
molecules across the cell membrane.
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
1ary Lysosome
Enzymes
+
Food/organelle
2ary Lysosome
Wastes
Residual Body
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