BIOLOGICAL SCIENCES

By:

MARIA KRISIA FAE DELOS REYES DE ASIS, BSN-RN

Please bring out any piece of paper and prepare for a quiz..

GOOD LUCK!

QUESTION:

1. An orderly set of stages that take place between the time a eukaryotic cell divides and its daughter cells divide?

QUESTION:

2-4. What are the three phases of division of cells?

QUESTION:

5. What is the stage wherein cells do not complete the cell cycle and is in permanent arrest?

QUESTION:

6. What is the stage wherein DNA replication or synthesis occur?

QUESTION:

7. What is the process in which a cell’s nucleus replicates and divides in preparation for division of the cell?

QUESTION:

8. What is the PHASE wherein exactly half of the chromatids face one pole, and the other half face the other pole?

QUESTION:

9. What is the PHASE wherein a new nuclear membrane forms around each new group of chromosomes?

QUESTION:

10. What is the stage of cell division wherein the cell’s cytoplasm separates in half, with each half containing one nucleus?

PLASMA MEMBRANE

- thin molecular layer that surrounds all living cells- separates the cell from its surroundings, protects it from changes in the chemical and physical environment, and regulates the traffic of molecules into and out of the cell- is composed primarily of two types of molecules — lipids and proteins

PLASMA MEMBRANE

+ FLUID-MOSAIC MODEL

-Introduced by S. Singer and G. Nicholson-Proposed that the membrane is a fluid phospholipid bilayer in which protein molecules are partially or wholly embedded

PLASMA MEMBRANE

+ FLUID-MOSAIC MODEL

-Introduced by S. Singer and G. Nicholson-Proposed that the membrane is a fluid phospholipid bilayer in which protein molecules are partially or wholly embedded forming a mosaic pattern

PLASMA MEMBRANE

STRUCTURE

-A phospholipid molecule has a head region at one end that is hydrophilic—it can mix with water. At the other end are two long tails that are hydrophobic—they do not mix well with water

PLASMA MEMBRANE

STRUCTURE

-phospholipid molecules are arranged so that their hydrophilic heads point outward on either side of the membrane, and their hydrophobic tails point toward each other in the middle of the membrane

PLASMA MEMBRANE

STRUCTURE

-the plasma membrane stays intact precisely because the phospholipid molecules strongly resist any change in configuration that would expose their hydrophobic tails to the watery environment

PLASMA MEMBRANE

STRUCTURE

-The movement of the phospholipid and protein components through the plasma membrane permits the membrane to change shape

-In animal cells, cholesterol also contributes to the fluidity of the plasma membrane

PLASMA MEMBRANE

CHOLESTEROL

-is a small lipid molecule that nestles among the hydrophobic tails of the phospholipids in the interior of the membrane

-It prevents phospholipid molecules from packing together too tightly and making the membrane rigid

PLASMA MEMBRANE

+ The lipid and protein molecules that make up the plasma membrane are manufactured inside the cell and routed to the cell surface.

PLASMA MEMBRANEFUNCTION

-The plasma membrane forms an extremely effective seal around the cell. Only a very few molecules can pass directly through the lipid bilayer to get from one side of the membrane to the other

-Many substances that a cell needs in order to survive cannot cross the lipid bilayer on their own

PLASMA MEMBRANEFUNCTION

-A cell uses two methods to move such substances from one side of the plasma membrane to another, known as passive transport and active transport. Both of these processes involve proteins in the plasma membrane.

PLASMA MEMBRANEPASSIVE TRANSPORT-accomplished by diffusion, the spontaneous movement of a substance from a region of greater concentration to a region of lesser concentration-does not require the cell to expend energy-Water, oxygen, carbon dioxide, and a few other small molecules diffuse directly across the plasma membrane by passing between phospholipid molecules

PLASMA MEMBRANEPASSIVE TRANSPORT

-Substances that cannot pass directly through the plasma membrane diffuse into or out of cells with the aid of hollow, channel-like proteins in a process known as facilitated diffusion

-This enables a cell to control precisely the molecules that travel in and out of the cell

PLASMA MEMBRANEACTIVE TRANSPORT-In order to move substances from the side of the plasma membrane where the concentration of a substance is lower to the side where it is already higheR, a cell must expend energy in a process known as active transport

-achieved by membrane proteins called pumps, which have a docking site that is shaped to fit a specific substance

PLASMA MEMBRANEACTIVE TRANSPORT

-When the proper molecule or ion attaches to the docking site, the pump changes shape so that the docking site moves its opening to the other side of the plasma membrane, releasing the molecular cargo

PLASMA MEMBRANEFUNCTION

-also plays a critical role in communication between cells

-Proteins embedded in the plasma membrane act as receptors, binding to hormones and other molecules sent as signals from other cells

PLASMA MEMBRANEFUNCTION

-certain membrane proteins also act as markers that help the immune system distinguish the body’s own cells from foreign cells

-These marker proteins help trigger the immune reaction that protects humans and other animals from disease-causing organisms such as bacteria, viruses, and fungi