Chapter 3 - Cells: The Living Units Flashcards
Regardless of type, all cells are composed of?
carbon, hydrogen, nitrogen, oxygen and trace amounts of several other elements.
What 3 main parts do human cells have?
Plasma membrane (outer boundary of cell), Cytoplasm (intracellular fluid packed with organelles, small structures that perform specific cell functions) and the Nucleus (an organelle that is the control center for cellular activity).
What separates two of the body’s major fluid compartments, the intracellular fluid with cells and the extracellular fluids outside cells?
The plasma membrane. Synonym used is “cell membrane”.
What forms the “fabric” of the plasma membrane?
A lipid bilayer constructed largely of phospholipids with smaller amounts of glycolipids, cholesterol and areas called lipid rafts.
What has a charged, hydrophilic head and an uncharged, hydrophobic tail?
phospholipids
What is found only on the outer plasma membrane surface, is a lipid with an attached sugar group and accounts for about 5% of total membrane lipids?
Glycolipids. (Head is polar and tails are non polar)
What makes of 20% of membrane lipid, has a polar and non polar region, and wedges it’s platelike hydrocarbon rings between the phospholipid tails to stabilize the membrane?
Cholesterol. This also decreases the mobility of the phospholipids therefore decreasing the fluidity of the membrane.
What makes up about half of the plasma membrane by mass and are responsible for specialized membrane functions?
Proteins. 2 distinct types of membrane proteins: integral and peripheral.
Where can you find integral proteins?
Firmly inserted into the lipid bilayer. Some protrude from one membrane face only, but some are transmembrane that span the entire membrane and protrude on both sides.
What do transmembrane proteins do?
some are involved in transport and form channels through which ions can move. Some are carriers that bind to a substance then move it through the membrane. Some are enzymes and some receptors for hormones and chemical messengers and relay messages to the cell interior. (process called signal transduction)
These proteins do not embed themselves into the lipid bilayer but instead attach themselves loosely to integral proteins. What are they?
Peripheral proteins. They are easily removed without disrupting the membrane.
What purpose do peripheral proteins serve?
they support the membrane from its cytoplasm side. They are a network of filaments. Some are enzymes. Some are involved in motor function such as changing cell shape during cell division and muscle cell contraction.
About 20% of the outer membrane surface contains dynamic assemblies of saturated phospholipids called?
Lipid rafts.
What is the “sugar coating” on the outer surface of cells?
The Glycocalyx. Every cell has a different pattern of sugars in its glycocalyx therefore it acts as a biological marker for approaching cells to recognize one another. Ex. How a sperm recognizes an ovum and how cells of the immune system recognize bacterium.
What 3 factors act to bind cells together?
- Glycoprotiens in the glycocalyx act as an adhesive. 2. Wavy contours of the membranes of adjacent cells fit together in a tongue and groove fashion. 3. Special cell junctions form (this most important)
