Cell Membrane

Phospholipids

A molecule that is a part of the inner bilayer of biological membranes, having a polar, hydrophilic head (phosphate group) and a nonpolar, hydrophobic tail.(2 fatty acids instead of 3) _________are the most important membrane building compounds

Receptor-mediated endocytosis

A process triggered by the binding of certain external molecules to specific receptor proteins built into the membrane

Phospholipid Bilayer

A two-layered membrane where the hydrophilic portions are wet and the hydrophobic portions hide from the water

Phagocytosis

A type of endocytosis in which a cell engulfs a particle and packages it within a food vacuole, "cellular eating"

Pinocytosis

A type of endocytosis in which the cell gulps droplets of fluid by forming tiny vesicles causing it to be unspecific to the substances it transports, "cellular drinking"

Passive Transport

Diffusion across a membrane that does not require any energy

Membrane proteins

Embedded proteins that perform specific functions for the cell membrane.

Osmoregulation

The control of water balance

How does the concentration gradient affect the rate of osmosis?

The high the concentration gradient, the higher the rate of osmosis because with more solute moving, the faster the rate of the water moving as well and vice versa

Fluid Mosaic

This is described as the behavior of the membrane, _____ because the molecules can move freely past each other and _____because of the diversity of proteins that float around in the membrane

How do large complex material (bacteria) get in and out of cells?

Through endocytosis (Pinocytosis) and exocytosis

How do large proteins get in and out of cells?

Through endocytosis (Pinocytosis) and exocytosis

How does glucose get in and out of cells?

Through the GluT transporter using facilitated diffusion

How do ions get in and out of cells?

Through the ion channel using diffusion

How does water get in and out of cells?

Through the lipid bilayer or aquaporins using osmosis

How does carbon dioxide get in and out of cells?

Through the lipid bilayer using diffusion

How does oxygen get in and out of cells?

Through the lipid bilayer using diffusion

How do enzymes get in and out of cells?

Through the plasma membrane using exocytosis

Signal Transduction Pathway

When proteins and other molecules relay the signal and convert it to chemical forms that work within the cell

Protein channels

(In Passive Transport) __________allow large molecules to cross the membrane. Amount of protein channels determines speed of diffusion

Concentration gradient

An increase or decrease in the density of a solute in an area

What are the six functions of proteins in the cell membranes?

1. Attachment to the cytoskeletons and extracellular matrix 2. Cell signaling 3. Enzymatic activity 4. Transport 5. Intercellular joining 6. Cell-cell recognition

Cholesterol

A "base steroid" from which your body produces other steroids, a type of fat or lipid found in membranes with phospholipids and excess is removed through receptor-mediated endocytosis It helps to stiffen the membrane, making it less soft. It also helps the membrane to remain relatively fluid (as in "fluid mosaic model"). It also provides (ib lipid rafts) a suitable molecular environment for certain membrane proteins. It makes the nearby portion of a cell membrane less permeable to small molecules that are soluble in water.

Carbohydrates

A biological molecule consisting of simple single-monomer sugars (monosaccharides), two-monomer sugars (dissacharides) and other multi-unit sugars (polysaccharides) ______________often attach to the external surface of integral proteins. These carbohydrates may hold adjoining cells together or act as sites where viruses or chemical messengers such as hormones can attach.

Selectively Permeable

It allows some substances to cross the membrane more easily than others and blocks some altogether

Why do phospholipids spontaneously form membranes when mixed with water?

Phospholipids spontaneously form membranes when mixed with water because their heads which are hydrophilic face towards the water while the hydrophobic tails face away from the water, forming a membrane

Isotonic

Solutions of equal solute concentration Animal: normal Plant: flaccid, wilts

Transport Proteins

Specialized proteins built into the membranes that regulate the passage of materials in and out of the cell

Facilitated diffusion

The passage of a substance across a biological membrane down its concentration gradient, aided by specific transport proteins that act as selective corridors

Osmosis

The passive transport of water across a selectively permeable membrane

Endocytosis

The process in which a cell takes in material within vesicles that bud inward from the plasma membrane

Exocytosis

The process in which secretory proteins exit the cell in transport vesicles that fuse with the plasma membrane, then spilling the contents outside of the cell

Plasmolysis

The process of a plant cell losing water, shriveling and the plasma membrane pulling away from the cell wall

Hypertonic

The solution with a higher concentration of solute (less water) Animal: shriveled Plant: shriveled

Hypotonic

The solution with a lower concentration of solute (more water) Animal: lysing, swelling Plant: turgid, healthy

Diffusion

The tendency for molecules of any substance to spread out into available space (from where there is more to where there is less)

Active transport

The transport of solute that requires a cell expend energy to move molecules across a membrane