Chapter 6 Cells
Cell consists of nucleus and cytoplasm. • In cytoplasm - organelles (“little organs”)
Cell membrane – boundary of cell. • Membrane thin but selectively permeable (allows certain materials to pass through but not others).
Membrane has receptors that help receive messages (i.e. hormones) • Called phospholipid bilayer (composed of phospholipids); also various proteins in membrane.
1Endoplasmic Reticulum – increased surface area for reactions to take place. • ARough ER – Makes proteins (holds ribosomes) • BSmooth ER – Makes lipids.
2Ribosomes – some attached to rough ER (bound); some scattered throughout cytoplasm (free). • Function - protein synthesis.
3Golgi apparatus – proteins modified and packaged, then sent into cytoplasm.
Modified protein http://web.mit.edu/esgbio/www/cb/org/golgi.gif
4Mitochondria – cellular respiration. • Transform glucose into form of energy cell can use.
5Lysosomes – contain enzymes that break down molecules of foreign particles (“garbage cans” of cell)
6Centrosome – consists of 2 hollow cylinders (centrioles) - function in reproduction by separating chromosomes to new cells.
7Cilia and 8flagella – extensions of cells; used for cell movement. • Flagella - longer and fewer. • Cilia - smaller and more numerous.
http://pediatrics.med.unc.edu/div/infectdi/pcd/images/cilia.jpghttp://pediatrics.med.unc.edu/div/infectdi/pcd/images/cilia.jpg Respiratory cilia
9Vacuoles – vesicles found in cell that have various functions. • AFood vacuole – breakdown of food. • BCentral vacuole – storage of waste. • CContractile vacuole – removal of water (osmoregulation).
10Microfilaments and microtubules – responsible for movement within cell (also responsible for structure)
11Nucleus – center of cell. • Covered by nuclear envelope with pores to allow substances to pass through. • Contains 12nucleolus (ribosome production) and chromatin (loose DNA).
Movement through cells • Passive does not require energy. • 4 passive movements (diffusion, facilitated diffusion, osmosis, filtration). • 1Diffusion – molecules or ions spread randomly from area of high concentration to area of low.
Particles will move until equilibrium reached (both sides equal). • Happens in lungs; O2, CO2 move by diffusion to be exchanged with air.
2Facilitated diffusion - substance too large to cross cell membrane. • Special protein carrier allows substance to pass through membrane.
Cells in Solutions with Water • Hypertonic- Greater concentration of dissolved particles than water. Cell will shrink as water moves into solution • Isotonic- Equal concentration of dissolved particles and water. Cell remains the same size. • Hypotonic- Lower concentration of dissolved particles than water. Cell will swell as water moves into the cell from the solution.
Filtration –molecules forced through membranes (result of blood pressure)
Active movement – requires energy. • Active transport – movement from area of low [ ] to high [ ]. • Requires pumps (a.k.a carrier molecules) to cross membrane.
2 processes – no crossing membrane. • 1Endocytosis – substances fuse with membrane, brought into cell. • 2Exocytosis – substances move out of cell (2 types).
APinocytosis – cell lets out small droplets of liquid. • BPhagocytosis – cell lets out solids.
Cell Cycle • Life cycle of cell - cell cycle. • Interphase is the first part of the cell cycle. • It is the period of preparing for cell division. • Mitosis is the division of the nucleus and is divided into four phases.
Prophase - The chromosomes appear in nucleus from chromatin. Centrioles move to opposite sides of the nucleus. • Metaphase - The newly formed chromosomes line up midway between the centrioles and attach spindle fibers to the centrioles.