Chapter 3- Cellular level of Organization pt.2 Flashcards
Plasma membrane is SELECTIVELY PERMEABLE meaning
it allows some materials to move freely, and restricts other materials
Active transport
requires energy & ATP
Passive transport
no energy required
Diffusion (Passive)
-can be simple/channel-mediated
Always follows concentration gradient, moves “down” concent. from high to low concentration gradient which allows movement
Carrier-mediated transport (passive/active)
-of ions and organic substances
movement of molecules across cell membrane via special transport proteins that are embedded
Vesicular transport (active)
movement within a vesicle
5 factors that influence rate of diffusion in cells
- Distance particle has to move
- effective across short distances - Molecule size
- smaller is faster - Temperature
- more heat, faster motion - Concentration Gradient
- larger gradient, faster diffusion - Electrical Forces
- opposites attract, likes forces repel
Intracellular
Potassium
Extracellular
Sodium & Calcium, Chloride
Why is there a bigger concentration of amino acids inside the cell than outside?
Because amino acids are the building blocks of all cells
Simple Diffusion
Materials diffuse directly through plasma membrane w/o use of protein channel.
EX: triglycerides, lipids, steroids, testosterone, estrogen, cholesterol
Lipid soluble molecules pass into a cell by what method?
Simple diffusion
Channel-mediated diffusion
A concentration gradient drives movement of solute through a transmembrane channel protein
EX: Leak channels for Na, K, or Cl
Channel-mediated diffusion (polar & ionic molecules)
A concentration gradient drives movement of solute through a transmembrane channel protein
EX: Leak channels for Na, K, or Cl
Osmolarity
measure of solute concentration
Isotonic
A solution that does not cause osmotic flow of water in/out of cell
Hypotonic
Has less solutes and loses water through osmosis –>water flows into cell
-Ruptures (LYSING/HEMOLYSIS of red blood cells)
Hypertonic
Has more solutes and gains water by osmosis –> water moves out of cell
-Shrinks (CRENATION of red blood cells)
3 Characteristics common in carrier-mediated transport
- Specificity
- one transport protein, one set of substrates - Saturation limits
- Rate depends on the speed and number of transport proteins, not substrate - Regulation
- cofactors such as hormones play an important role in coordinating carrier protein activity
Carrier-Mediated Transport: FACILITATED DIFFUSION
Passive.
-Carrier proteins transport molecules too large to fit through channel proteins
EX: glucose, amino acids
*molecule binds to receptor site on carrier protein
*protein changes shape, molecules pass through
*receptor site is specific to certain molecules
Carrier-Mediated Transport: ACTIVE TRANSPORT **Pump (primary or secondary)
- moves substrates against concentration gradient, from an area of low concentration to high concentration
- requires energy, such as ATP
Carrier-Mediated Transport: ACTIVE TRANSPORT **Pump (primary or secondary)
-moves substrates against concentration gradient, from an area of low concentration to high concentration
*requires energy, such as ATP
ION PUMPS: move ions against concentration gradient
EXCHANGE PUMPS: exchange of molecules
Primary Active Transport
Sodium-Potassium exchange pump:
*Sodium ions out, Potassium ions in
Secondary Active Transport (another kind of facilitated diffusion)
Glucose and Sodium enter cell through facilitated diffusion. Another channel will pump Sodium out of cell.
Vesicular transport (Bulk transport)
Materials move in and out of cell in vesicles
*Endo (inside) cytosis: active transport using ATP, enter the cell
Endocytosis
-Pinocytosis:
Endocytosis *requires ATP
-Pinocytosis: cells “drink” extracellular fluid
Phagocytosis *requires ATP
Used by specialized cells such as macrophages to surround & engulf an object using pseudopods “cell eating”
Exocytosis *requires ATP
Granules/droplets released from cell
EX: mucus, hormones, proteins
The interior of a cell has a slightly _______ charge w/ respect to the outside. What causes this?
NEGATIVE
Resting potential –> negatively charged protein molecules inside cannot cross membrane
Neurons can conduct electrical signals and muscles can contract, because they have a membrane potential. What is meant by the term RESTING MEMBRANE?
When a neuron is not sending a signal, it is “at rest”
New cells are created in the body by a process of _____.
Mitosis
5 steps in DNA REPLICATION
1.
5 steps in DNA REPLICATION (S phase of Interphase)
- Enzymes called helicases unwind the strands & disrupt the weak hydrogen bonds btwn bases. Molecules of DNA polymerase bind to the exposed nitrogenous bases
- As the 2 original strands separate, DNA polymerase binds to them. DNA polymerase, bound to upper leading strand template adds nucleotides to make a single continuous complementary copy called the leading strand that grows toward “zipper”
- In the lower lagging strand template, the 1st DNA polymerase to bind to it must work from left to right, adding nucleotides in sequence 12345
- DNA ligases splice together the 2 DNA segments into a lagging strand
- Unzipping completely separates the original strands. 2 identical DNA molecules are formed. leaves interphase and proceeds to mitosis
Phases of Interphase
Interphase: Non-diving period
G0- specialized cell functions only
G1- cell growth, organelle duplication, protein synthesis
S phase- DNA replication, and histone synthesis
G2- finishes protein synthesis & centriole replication
5 steps of Mitosis
- Prophase
- DNA condenses to chromosomes
- centrioles move to the poles of the cell
- nuclear envelope disintegrates - Metaphase
- Centrioles, using spindle fibers, pull chromosomes to the middle of the cell - Anaphase
- Centrioles pull chromosomes apart to opposite poles of the cell - Telophase
- Nuclear envelope reforms around chromosomes
Cytokinesis
Divides cytoplasm and organelles into 2 daughter cells
Stem Cell
Undifferentiated biological cells that can differentiate into specialized cell and can divide to produce more
