The Cell Membrane

A membrane is a device that selectively permits the separation of one or more materials from a liquid or gas. What is a membrane? ?

Passive Transport The transport of substances through the cell membrane without using energy.

Now there are two different ways to transport material through the cell membrane WITHOUT using energy: 1-Diffusion/Osmosis 2-Facilitated Diffusion

Diffusion The process of moving from areas of high concentration to areas of low concentration

Add: Homeostasis is the maintenance of a stable internal environment.

Osmosis The diffusion of water from areas of high concentration to areas of low concentration through a semi- permeable membrane.

Osmosis Cont. The concentration (amount) of all substances affects the movement of materials in and out of the cell.

Osmosis

Water can cross the cell membrane through the lipid bi- layer and with special proteins. If enough water enters the cell by osmosis, the cell can swell enough to burst open and die. This is demonstrated in the picture.

Hypotonic Solute concentration: contains a low concentration of solute Water concentration: contains a high concentration of water Water movement: water diffuses into the cell Effect on the cell: causing the cell to swell and possible explode

Cells in hypotonic solution

Draw a picture

Isotonic   Solute concentration: is equal to the water concentration   Water concentration: is equal to the solute concentration   Water movement: equal diffusion (water diffuses into and out of the cell at equal rate)   Effect on cell: none

Normal cells in isotonic solution

Draw a picture of an isotonic solution next to the definition

Hypertonic Solute concentration: contains a high concentration of solute Water concentration: contains a low concentration of water Water movement: water diffuses out of the cell Effect on the cell: causing the cell to shrivel

Cells in hypertonic solution

Draw a picture next to the definition

Quiz yourself Write this down on the bottom of page

Active transport

  The transport of molecules from areas of high to low concentration with the use of energy.   The cell energy is the ATP made in the mitochondria.

Bulk movement of substances across the membrane Endocytosis:   Phagocytosis   Pinocytosis Exocytosis

Endocytosis   A process by which a cell surrounds and takes in materials from its environment by engulfing them.

Phagocytosis   Process in which phagocytes engulf and digest microorganisms and cellular debris   "phagocyte" or eating cell (phago = "eating", cyte = "cell").   An important defense against infection

Pinocytosis   process by which certain cells can engulf and incorporate droplets of fluid

Exocytosis   when transport. is out of the cell.

Cell Division & Mitosis

Cell division varies between Prokaryotic and Eukaryotic Cells   Prokaryotic cells are single celled organisms. Before the bacterium can divide there must be two copies of its DNA. This occurs by the DNA molecule unzipping itself into two different strands, which will form two separate interdependent strands.

 Once the DNA has replicated itself and the cell has grown to an appropriate size, the bacterium splits into two equal halves through a process called binary fission.

 Draw a picture of Binary Fission Asexual Reproduction

 Eukaryotic cells undergo nuclear division ( asexual reproduction). The life of a eukaryotic cell is traditionally diagrammed as a cell cycle.

1. G1 Phase: rapid growth and metabolic activity, protein synthesis, cell spends most time in this phase.

2. S phase: DNA synthesis and replication (copies), chromosomes duplicate and other cellular organelles.

3. G2 Phase: centrioles replicate; cell prepares for division

4. M phase: MITOSIS-period of nuclear division in which two daughter nuclei are formed, each containing a complete set of chromosomes.

5. C Phase: Cytokinesis- process following mitosis or meiosis in which the cells cytoplasm divides and separates into new cells. Division of the Cytoplasm

Mitosis

The Cell CYCLE consists of Interphase and MITOSIS (division of the nucleus). Most of the time the cell is in INTERPHASE as the cell prepares for division.

G1 S G2 M C

INTERPHASE 1. The cell’s chemical machine operates and the cell grows (G 1 phase). 2. The SYNTHESIS of DNA (S phase). 3. PREPARE for cell division

MITOSIS 1. The chromatin CONDENSES (shortens) into chromosomes. Chromatin vs. Chromosomes Long/thin Invisible Active Working cell Short/thick Visible Inactive Dividing cell

2. The nuclear membrane and nucleolus DISAPPEAR. 3. Centrioles move apart to opposite ends of the cell. 4. SPINDLE fibers from the centrioles attach to centromeres.

Chromosomes

Metaphase 1. Chromosomes line up on the EQUATOR of the cell.

Anaphase 1. Centromere SPLITS. 2. Chromosomes are PULLED to the ends of the cell.

Telophase 1. Chromosomes ARE AT the ends of the cell. 2. Chromosomes DECONDENSE (lengthen) to form chromatin. 3. The nuclear membrane and nucleolus REAPPEAR. 4. The centrioles SEPARATE. 5. The CYTOPLASM is divided. (Cytokinesis)