Chemistry, Cells, and Tissues

Principle parts of a cell

Cytoplasm, nucleus, and cell (plasma) membrane

Nucleus

Contains DNA of cells

Cell Membrane (Plasma Membrane)

Outer covering that defines and encloses each cell. Like the “security guard” of a cell - regulates what substances enter and leave cell

Cytoplasm

Cellular contents between the cell/plasma membrane and the nucleus

2 primary components of cytoplasm

1. Cytosol - gel-like medium with organic compounds

2. Organelles - miniature organs that carry out physiological processes that sustain life for the cell (the “organ system” of a cell)

Types of Organelles

1. Mitochondria

2. Endoplasmic Reticulum (ER)

3. Golgi Apparatus

4. Lysosomes

5. Centrosome

6. Cytoskeleton

Mitochondria

The powerhouse of the cell - contains enzymes that break down glucose to produce ATP (adenosine triphosphate) which releases energy

Intracellular fluid

Fluid found INSIDE cells make up 2/3 of the total water in a human body

Extracellular fluid

Fluid found OUTSIDE cells - remaining 1/3 makes up the liquid component of blood, lymph, interstitial fluid (fluid that fills the interstitium - small spaces between cells)

Interstitial Fluid

a type of extracellular fluid that fills the Interstitium (small spaces between cells). Constantly circulates around cells providing a medium from which nutrients are extracted and waste is released

Interstitium

The area between cells where the interstitial fluid is located

Transport Mechanisms: 2 categories in which substances move across the cell membrane

Passive transport & Active transport

Passive Transport

A transport mechanism that occurs when the cell does not have to expand energy (no need for ATP) to move a substance through the cell membrane 2 methods:

1. Diffusion

2. Filtration

Diffusion

Passive transport mechanism in which atoms/molecules move across the cell membrane from an area of higher concentration to an area of lower concentration (looking for an “open” area to spread out more evenly)

Osmosis - the diffusion of water (not dissolved particles/solutes because they can be too large to cross the cell membrane) from an area of higher concentration to lower concentration

Facilitated diffusion - when a carrier molecule is involved in the diffusion process

Filtration

A passive transport mechanism driven by differences in pressure. When fluid presses against a barrier, they create HYDROSTATIC PRESSURE (fluid pressure) which pushes fluid and small solutes through any opening from an area of high pressure to an area of low pressure

ex) audience at back of rock concert pushes people closer to the front to get a better view, no energy is expended from the people at the front when they are pushed forward

Active Transport

A transport mechanism that requires the cell to use energy (break down ATP molecules) to move substances across the cell membrane. Moving against the concentration gradient (from an area of low to high)

three examples of active transport:

1. Ion pumps

2. Phagocytosis

3. Exocytosis

Phagocytosis

An example of active transport. Literally means “cell eating”. Process is carried out by specialized cells called Phagocytes found in blood, lymph, and connective tissue. Cell membrane of Phagocyte engulfs/“eats” a particle by folding around it and pinching off a portion to form a sac (called a Vesicle) within the Phagocyte. The vesicle is then delivered to a Lysosome for digestion and destruction.

Phagocytes

specialized cells found in blood, lymph, and connective tissue.

Vesicle

A particle-filled sac formed by phagocytes

Pinocytosis

“Cell drinking” - process similar to phagocytosis, but the substance being engulfed by the cell is a liquid instead of a particle