Chapter 3 Flashcards
Why are cells called the structural and functional units of life?
Because it is the smallest unit of life
Describe the 3 main parts of a cells
- plasma membrane: the outer boundary of the cell, which acts as a selectively permeable membrane
- cytoplasm: the intracellular fluid packed with organelles, small structures that perform specific cell functions
- Nucleus: an organelle that controls cellular activities. typically it lies near the cell’s center.
What is the purpose of the plasma membrane? describe the major components of the plasma membrane
The plasma membrane separates two of the body’s major fluid compartments (ICF and ECF). The major components include:
1. lipid bilayer “studded” with proteins
2. glycocalyxes
3. cell junctions
The lipid bilayer of the plasma membrane is composed of?
- phospholipids-polar hydrophilic heads, so tails close together, heads opposite
- cholesterol- 20% of the membrane is lipid is cholesterol.
Describe each of the functional classifications of membrane proteins
- transport: transports molecules in or out of the cell; ex: glucose, water-soluble molecules, molecules too big to pass through the lipid bilayer.
- receptors: has binding site to fit specific molecules like hormones or other chemicals. When chemical bind, it starts a chain of reactions which occur in the cell
- Anchor- provides attachment points to anchor the membrane to extracellular structures
- Enzymes-a membrane protein may be an enzyme with its active site exposed to substances in the adjacent solution
- intracellular joining-membrane proteins of adjacent ells may be hooked together in various kinds of intracellular junctions
- cell-cell recognition- some glycoproteins (proteins bonded with sugars) serve as identification tags that are specifically recognized by other cells.
Describe each structural classifications of membrane proteins
- Integral proteins- firmly inserted, mainly transmembrane; transport proteins (channels and carriers), enzymes or receptors
- peripheral proteins-loosely attached to integral proteins. Enzymes, motor proteins (shape change during cell division and muscle contraction) and cell to cell connections
What are the glycocalyces?
sugars (carbs) sticking out of cell surface
-can be attached to lipids (glycolipids) or proteins (glycoproteins). different patters of this “sugar coating”. Biological markers to cell to cell recognition; immune system recognize self vs nonself
What is the purpose of cell junctions? describe the 3 types of cell junctions
- tight junctions- impermeable junctions. form continuous seals around the cell. prevent molecules from passing between cells.
- desmosomes- anchoring junctions. Bind adjacent cells together like molecular velcro. Help keep cells from tearing apart
- communicating junctions. Allow ions and small molecules to pass from cell to cell. particularly important in heart cells and embroyonic
What is the purpose of microvilli?
Small, fingerlike extensions of plasma membrane. Increases surfaces area for food absorption in intestines
For each of the ways that substances can cross the cell membrane, know if it passive or active transport, how each works to move substances across.
- Passive transport: crossing the membrane passively (no energy required). Simple diffusion, facilitated diffusion and osmosis.
- Active transport: energy is required in order to cross the plasma membrane.
Define concentration gradient. How is concentration gradient associated with diffusion?
A concentration gradient occurs when the concentration of particles is higher in one area than in another.
The direction of diffusion is said to be with the concentration gradient.
What is the speed of diffusion influenced by?
It is influenced by the difference of concentration of two substances between two areas
What is the difference between carrier-mediates and channel-mediated facilitated diffusion?
Carrier-mediated: substances bind to protein carriers
Channel-mediated: substances move through water-filled channels; leakage channels are always open, some channels are closed
What are aquaporins?
they are an integral membrane proteins that serve as channels in the transfer of water.
Define osmolarity. Know how osmolarity affects osmosis.
osmolarity: the measure of total concentration of solute particles-amount of solute per kg of water.
When there are different osmolarity solutions on the outside versus the inside of the plasma membrane, osmosis will occur until equilibrium is reached.
