Cells Chapter 7

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.

1 Endoplasmic Reticulum – increased surface area for reactions to take place. A Rough ER – Makes proteins (holds ribosomes) B Smooth ER – Makes lipids.

2 Ribosomes – some attached to rough ER (bound); some scattered throughout cytoplasm (free). Function - protein synthesis.

3 Golgi apparatus – proteins modified and packaged, then sent into cytoplasm.

Modified protein

4 Mitochondria – cellular respiration. Transform glucose into form of energy cell can use.

5 Lysosomes – contain enzymes that break down molecules of foreign particles (“garbage cans” of cell)

6 Centrosome – consists of 2 hollow cylinders (centrioles) - function in reproduction by separating chromosomes to new cells.

7 Cilia and 8 flagella – extensions of cells; used for cell movement. Flagella - longer and fewer. Cilia - smaller and more numerous.

Respiratory cilia

9 Vacuoles – vesicles found in cell that have various functions. A Food vacuole – breakdown of food. B Central vacuole – storage of waste. C Contractile vacuole – removal of water (osmoregulation).

10 Microfilaments and microtubules – responsible for movement within cell (also responsible for structure)

11 Nucleus – center of cell. Covered by nuclear envelope with pores to allow substances to pass through. Contains 12 nucleolus (ribosome production) and chromatin (loose DNA).

Movement through cells Passive does not require energy. 4 passive movements (diffusion, facilitated diffusion, osmosis, filtration). 1 Diffusion – 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; O 2, CO 2 move by diffusion to be exchanged with air.

2 Facilitated diffusion - substance too large to cross cell membrane. Special protein carrier allows substance to pass through membrane.

3 Osmosis - movement of water only from area of high to low. If substance has higher [ ] of solute - hypertonic. If lower [ ] - hypotonic. Isotonic means they are even.

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. 1 Endocytosis – substances fuse with membrane, brought into cell. 2 Exocytosis – substances move out of cell (2 types).

A Pinocytosis – cell lets out small droplets of liquid. B Phagocytosis – 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.

Prophase

Anaphase - The chromosomes begin to separate into chromatids. Telophase - The chromatids are now separate in their new cells.

Anaphase

Telophase

After the nucleus has divided, cytokinesis (division of the cytoplasm) occurs. This is the last phase of the cell cycle. The two cells are now completely separated.

This will break and the cells will be separated.

Cell differentiation occurs to allow cells to become specialized.