CELL PROCESSES Notes

Four main processes: 1. Photosynthesis

2. Cellular Respiration / Fermentation 3. Transportation

4. Cell Division

1) Photosynthesis: • The process through which plants turn sunlight, water, and carbon dioxide to make

food (glucose) • Occurs only in plants and some protists (ex: algae) • Occurs in the chloroplast • 6CO2 + H20 + Light energy è C6H12O6 + 6O2

2) Cellular Respiration

• The process through which cells take food (created through photosynthesis) and turn it into energy for the cell

• Glucose is broken down to produce carbon dioxide, water and energy • It is the opposite of photosynthesis • Occurs in the mitochondria • C6H12O6 + 6O2 è 6CO2 + H20 + Energy (ATP)

• Fermentation is respiration without oxygen

o Process through which cells obtain energy, when oxygen is NOT available o Two types:

A. Lactic Acid Fermentation: occurs in muscle cells after strenuous activity.

B. Alcoholic Fermentation: occurs in yeast and other unicellular organisms.

3) Transportation All cells require materials (food, water, oxygen, etc) of various sizes and in varying concentrations. As a result, cells have a number of mechanisms to transport materials in or out of the cell…across the cell membrane.

Two types: A) Passive Transport: moves ions or molecules across the cell membrane with NO

expenditure of energy by the cell. Materials move through protein channels. B) Active Transport: requires the cell to expend (use) energy, usually in the form of

ATP. Usually move materials AGAINST the direction of diffusion. PASSIVE TRANSPORT

• Passive transport relies on the physical process of diffusion. • Diffusion is the spreading of particles through a liquid or a gas • Diffusion involves the movement of particles from an area of high

concentration to an area of low concentration. • When molecules are evenly spread out in the liquid or gas, a state of

equilibrium has been reached.

• Types of Passive Transport: - Particles move into/out of the cell by squeezing between the 2 layers of

fat cells in the cell membrane. These particles move from high to low concentration by diffusion.

- Particles moving through the proteins scattered throughout the cell membrane. This is called Facilitated Diffusion. The proteins are called Protien Channels. These particles move from high to low concentration by diffusion.

- Osmosis is when WATER moves into/out of the cell

• Equilibrium: the point at which a roughly equal amount of particles are

entering and leaving the cell at the same rate (speed)

• Influences of the diffusion rate: - Distance: The greater the distance, the longer the time required

Molecules Size: Ions and small organic molecules such as glucose diffuse more rapidly than do large proteins

- Temperature: The higher the temperature, the faster the rate of diffusion

ACTIVE TRANSPORT 1) Endocytosis: The movement of large molecules INTO the cell. The cell

membrane surrounds a particle and encloses it in a vesicle. Large protein molecules and bacteria ENTER the cell this way.

Three types:

A) Pinocytosis: (cell drinking) a type of endocytosis in which fluids move into the cell B) Phagocytosis: (cell eating) a type of endocytosis where cells

ingest large objects such as large chunks of dead organic material. These are sealed off into large vacuoles. Lysosomes then merge with the vacuole, turning it into a digestive chamber. The products of the digestion are then released into the cytosol.

C) Receptor-mediated endocytosis: an endocytotic mechanism in which specific molecules are ingested into the cell. Receptors on the plasma membrane of the target tissue will specifically bind to ligands on the outside of the cell. An endocytotic process occurs and the ligand is ingested.

Check out these two websites, which show the processes of Endocytosis.

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/endocyta.htm 2) Exocytosis: The opposite of endocytosis. Exocytosis is the movement of large

molecules OUT of the cell. Large molecules that are manufactured by the cell are released this way.

4.) Cell Division

Interphase

(Technically not part of mitosis, but it is included in the cell cycle)

Cell is in a resting phase, performing cell functions.

DNA replicates (chromatin threads copy).

Organelles double in number, to prepare for division.

Prophase

Centrioles move to opposite sides of the cell.

Spindle fibers begin to grow out of each centriole.

Chromatin spirals up and chromosomes become visible.

Nuclear membrane begins to disappear.

Metaphase

Chromosomes line up along the center of the cell.

Spindle fibers grow longer and connect to the centromere of each chromosome.

Anaphase

The spindle fibers pull apart the chromosome at the centromere.

The chromatids separate and move to opposite poles

Telophase

Spindle fibers disappear

Nuclear membrane forms around each group of chromosomes

Chromosomes begin to unwind into chromatin

Cell begins to squeeze apart

Cytokinesis

Cell actually splits into two

DNA is now unwound (chromatin)