Chapter 3 - Cellular Form & Function Flashcards
What are the different cell sizes?
1) Most human cells are about 10-15um wide.
2) Nerve cells can be over a 1 m long and muscle cells can be up to 30 cm.
What are the different cell shapes?
1) Squamous - thin, flat, scaly shape.
2) Cuboidal - squarish looking
3) Columnar - taller than wide
4) Polygonal - having irregular angular shape
5) Stellate - having multiple pointed processes projecting from the cell body
6) Spheroidal to ovoid - round to oval
7) Discoid - disc-shaped
8) Fusiform - elongated with a thick middle and tapered ends
9) Fibrous - long, slender, and threadlike
What is the plasma membrane?
The membrane at the cell surface that prevents escape of cell contents, regulates exchange of materials between cytoplasm and ECF, and is involved in intercellular communication
What percentage of the molecules in the membrane are lipids?
98%
What percentage of the lipids are phospholipids?
78%
How are phospholipids arranged?
Phospholipids arrange into a bilayer, with the hydrophilic heads facing out and the hydrophobic tails directed toward the center
What are the two classes of membrane proteins?
a) Integral proteins penetrate into or through the membrane.
b) Peripheral proteins adhere to one surface of the membrane.
What are the functions of membrane proteins?
Receptors Second-messenger system Enzymes Channel proteins Carriers Cell-identity markers Cell-adhesion molecules
What are Receptors?
Surface proteins where chemical signals from other cells bind
What does the Second-Messenger System do?
A chemical messenger binds to an EC receptor triggering an IC peripheral protein to relay the message to an enzyme which converts a molecule to a second messenger
What do Enzymes do?
Digest nutrients, help produce second messengers, and breakdown signaling molecules
What are Channel Proteins?
Passageways that allow water and hydrophilic solutes to move through the membrane
What are Carriers?
Transmembrane proteins that transfer solutes to the other side of the membrane
What are Cell-Identity Markers?
Glycoprotein acting as “identification tags”
What are Cell-Adhesion Molecules?
Membrane proteins that bind one cell to another or to extra cellular material
What are microvilli?
Extensions of the plasma membrane that serve to increase absorptive surface area and play some sensory roles
How are microvilli best developed?
In cells specialized for absorption
What is brush border?
Dense microvilli at the apical cell surface
What are cilia?
Hair-like processes on the surface of a cell
What are flagellum?
Tail of sperm for motility
The membrane is..?
Selectively permeable - it allows some things through but prevents other things from entering or leaving the cell
What are the methods of moving substances through the membrane?
a) Passive mechanisms require no energy.
b) Active mechanisms consume ATP.
c) Carrier-mediated mechanisms use a membrane protein to transport the substance.
What is filtration?
A process in which pressure forces fluid through a membrane
What is simple diffusion?
The movement of particles from a place of high concentration to a place of lower concentration
What is concentration gradient?
The concentration of a substance differs from one point to another
What are the different types of concentration gradients?
a) Down or with the gradient - particles move from a region of high concentration to a region of lower.
b) Up or against the gradient - particles move from a region of low concentration to a region of higher.
What are factors that affect the rate of diffusion?
a) Temperature - the warmer a substance is, the more rapidly its particles diffuse.
b) Molecular weight - heavy molecules diffuse more slowly than light.
c) Steepness of concentration gradient.
d) Membrane surface area - more surface area means more diffusion.
e) Membrane permeability - nonpolar, hydrophobic, lipid-soluble substances diffuse through phospholipids.
What is osmosis?
The flow of water through a selectively permeable membrane
How does movement occur in osmosis?
a) Movement is from the side with the higher concentration of water molecules to the side with the lower water concentration.
b) Solute particles on one side draw water away from the other side.
What is tonicity?
The ability of a solution to affect the fluid volume and pressure in a cell
What is hypotonic solution?
a) Solution has a higher concentration of solutes than the ICF.
b) Cells in the hypotonic solution absorb water, swell, and may burst.
What is hypertonic solution?
a) Solution has a higher concentration of solutes than the ICF.
b) Cells in the hypertonic solution lose water and shrivel.
What is carrier-mediated transport?
A solute binds to a carrier in the plasma membrane, which then changes shape and releases the solute to the other side
What are the different kinds of carriers?
a) Uniport - carriers that move one type of solute.
b) Symport - carriers that can transport two or more solutes through the membrane in the same direction.
c) Antiport - carriers that transport two or more solutes in opposite directions.
What are the mechanisms of carrier-mediated transport?
a) Facilitated diffusion - transport of a solute through the membrane down its concentration gradient.
b) Primary active transport - transport of a solute through the membrane up its concentration gradient using energy from ATP.
c) Secondary active transport - transport that requires an energy input, but depends only indirectly on ATP.
What does the Na+-K+ pump do?
Binds three Na+ in the cell and releases these to the ECF while it binds two K+ in the ECF and releases them into the cell
What are the types of transport of the Na+-K+ pumps?
a) Secondary active transport - maintains a steep Na+ concentration gradient across the membrane.
b) Regulation of cell volume - the pump reduces IC ion and H2O concentration.
c) Maintenance of a membrane potential - the ICF is negatively charged and the ECF is positively charged because of unequal distribution of ions.
What do vesicles do?
Vesicles move large particles, droplets of fluid or numerous molecules all at once from one side of the membrane to the other
What is endocytosis?
Vesicular processes that bring matter into a cell
What is phagocytosis?
Engulfing particles to keep the tissues free of debris and infectious microbes
What is pinocytosis?
Taking in droplets of ECF containing molecules of use to the cell
What is receptor-mediated endocytosis?
Particles in the ECF bind to the receptors on the cell membrane, the receptors cluster, and the cell membrane sinks inward forming a pit then becoming a vesicle
What is transcytosis?
Transport of material across a cell, endocytosis on one side and exocytosis on the other
What is exocytosis?
The process of releasing material from a cell by means of a vesicle approaching the cell surface, fusing with the membrane and expelling its contents
What is cytoskeleton?
A network of protein filaments and cylinders
What are microfilaments?
Thin filaments made of the protein actin
What do microfilaments do?
a) Provide support for the phospholipids of the plasma membrane and microvilli.
b) Actin is involved in muscle contraction, other cell motility, endocytosis, and cell division.
What are intermediate filaments?
Thicker filaments that give the cell its shape, resist stress and participate in junctions that attach cells to neighbors
What is a microtubule?
A cylinder made of parallel chains of globular proteins called tubulin
What do microtubules do?
a) Hold organelles in place, form bundles that maintain cell shape and rigidity, and act like tracks for motor proteins to “walk” along carrying organelles and macromolecules.
b) Form the core of cilia and flagella and are responsible for beating movements, and form the mitotic spindle that guides chromosome movement during cell division.
What are organelles?
Structures in a cell that carry out specialized metabolic tasks
What is the nucleus?
The largest organelle, it contains the cell’s chromosome and is the genetic control center of the cell
What is the nuclear envelope?
Two membranes surrounding the nucleus
What are nuclear pores?
Proteins that perforate the envelope, regulate traffic through the envelope and hold the membranes together
What is chromatin?
Fine thread-like matter composed of DNA and protein
What is nucleoli?
Masses where ribosomes are produced
What is the Endoplasmic Reticulum (ER)?
Interconnected channels
What is the Rough ER?
Flattened sacs covered with ribosomes, where phospholipids and proteins
What is the Smooth ER?
Tubular channels with no ribosomes, where detoxification occurs, steroid hormones are synthesized, and calcium is stored for muscle contraction
What are the ribosomes?
Small granules of proteins and RNA, they interpret the genetic code and synthesize polypeptides
What is the Golgi complex?
a) System of channels that synthesize carbohydrates and finish up protein and glycoprotein synthesis.
b) Vesicles bud off the Golgi and become lysosomes, add new proteins and phospholipids to the membrane, or become secretary vesicles.
What are lysosomes?
A package of enzymes used for IC digestion and autophagy
What is peroxisomes?
A package of enzymes that use O2 for detoxification and breaking down fatty acid which produces hydrogen peroxide
What is mitochondria?
A double membrane organelle that synthesizes ATP
What is a centriole?
A short assembly of microtubules that play a role in cell division and also from the basal body of a flagellum or cilium
