Chapter Three Flashcards
1
Q
Fluid mosaic model
A
- A continually moving “sea” of fluid lipids that contain a mosaic of many different proteins.
- Some proteins float freely like icebergs.
- Others are anchored at specific locations.
2
Q
Plasma membrane function
A
- Surrounds and protects the cell
- Controls the flow of substances in and out of the cell (semi-permeable)
- Participates in cell signaling
- Provides attachment to other cells
3
Q
Plasma Membrane Structure
A
- Lipid bilayer arrangement - 2 back-to-back layers made up of 3 types of lipids:
-
Phospholipids have polar and non-polar parts
- Polar heads face outward and are hydrophilic
- Non-polar tails face inward (towards each other) and are hydrophobic
- Cholesterol is a structural component that helps hold the phospholipids together.
-
Glycolipids are only found in the layer that faces the extracellular fluid.
- Act in cell signaling
4
Q
What are the two types of membrane proteins?
A
- Integral (transmembrane) proteins
- Peripheral proteins
5
Q
Ion channel
A
Allow certain ions to pass in and out of the cell
integral
6
Q
Carrier Proteins
A
Transport specific substances across the membrane
integral
7
Q
Receptor proteins
A
Bind to specific substance to cause change in cell
integral
8
Q
Enzyme
A
act as catalysts to speed up cellular processes
Integral and peripheral
9
Q
Linker protein
A
helps cells attach to other cells
integral and peripheral
10
Q
Cell identity marker
A
distinguishes your cells from anyone else’s
glycoprotein
11
Q
Membrane fluidity and permeability
A
- The cell membrane is a fluid structure
- Most membrane lipids and proteins can move easily in the bilayer
- Cholesterol is embedded within the membrane.
• Serves to stabilize the membrane and reduce fluidity.
• Makes the membrane less permeable to very small water-soluble molecules - Cell membranes are selectively permeable
• Allows small non-polar, uncharged molecules to pass through
• The proteins help polar, charged molecules to pass through
• Macromolecules (too large) can only pass through by endocytosis and exocytosis.
12
Q
Concentration and electrical gradients
A
- Concentration (chemical) gradient
• Difference in the concentration of a chemical between one side of the membrane and the other. - Electrical gradient
• Difference in the concentration of ions between one side of the membrane and the other.
• Responsible for the “Membrane Potential”
• Inside of the cell is more negative - Together the 2 gradients make up the electrochemical gradient.
• Most chemicals and ions will move down their gradient.
• From an area of high concentration to an area of lower concentration until equilibrium (balance) is achieved.
13
Q
Passive processes
A
- no energy required
- simple diffusion
- facilitated diffusion
- osmosis
14
Q
Active processes
A
- requires energy
- vesicular transport
15
Q
Simple Diffusion
A
- Caused by the random motion of molecules.
- Involves the movement of molecules from an area of greater concentration to an area of lower concentration:
- Until equilibrium is reached and molecules are more evenly distributed (diffuse).
- Diffusion of a substance across a membrane can happen only if:
1. The membrane is permeable to that substance.
2. A concentration gradient exists (concentration of the substance is higher on one side of the membrane than the other).
16
Q
Facilitated diffusion
A
- Used to transport solutes that are too polar or charged to move through the membrane by simple diffusion.
- Similar to simple diffusion in that molecules move from areas of higher concentration to lower concentration.
- Uses membrane proteins that function as channels or as carriers.
• Allow molecules to move across cell membrane.
• The number of carrier or channel proteins in the cell membrane limits the rate of this process.
• Examples:
• K+ channels
• Glucose transporters - The number of carrier proteins available on the plasma membrane determines the rate of facilitated diffusion.
• More carrier proteins = increase rate
• Once all of the carriers are occupied, transport maximum is reached.
• Similar to a completely saturated sponge.
17
Q
Facilitated diffusion of glucose
A
• Glucose is the body’s preferred energy source for making ATP.
• Enters the body’s cells through facilitated diffusion.
• The hormone insulin causes the cell to insert more glucose
carrier proteins into the cell membrane.
• Allows the cell to pick up glucose more rapidly from the blood.
• What happens if the body can no longer utilize or produce
insulin?
• Diabetes Mellitus
18
Q
Osmosis
A
- Osmosis = diffusion of water across a selectively permeable membrane.
• From an area of higher water concentration to an area of lower water concentration
• Membrane is permeable only to water – not solutes - Osmotic pressure
• Pressure created by the concentration of solutes (lack of water) on one side of a membrane.
• Higher osmotic pressure = more impermeable solutes, less water
• Lower osmotic pressure = less impermeable solutes, more water - Remember: water will move down its concentration gradient
• Moves from area of low osmotic pressure (more water) to high osmotic pressure (less water).
• To make solutes less concentrated
20
Q
Isotonic solution
A
- concentration of water and solutes is same on outside and inside.
• No change - Equal amounts of water move in and out - no change to the cell
21
Q
Hypertonic Solution
A
- solution has higher osmotic pressure
• Greater concentration of solutes outside cell
• Water moves out of cell into surrounding solution = cell shrinks (crenation). - Water moves out of the cell – cell shrinks (crenation)
22
Q
Hypotonic Solution
A
- solution has lower osmotic pressure
• Lower concentration of solutes outside cell
• Water moves into cell = cell swells and can burst (cytolysis) - More water moves into the cell – cell swells and can burst (hemolysis)
23
Q
Active transport
A
- Used to move substances against their concentration or electrical gradient.
• From an area of low concentration to an area of higher concentration. - Requires energy (ATP)
• Often uses proteins as “pumps”.
• Example: The sodium-potassium pump (Na+-K+ATPase - Energy derived from ATP changes the shape of a transporter protein which pumps a substance across a plasma membrane against its concentration gradient
25
Q
Cytoplasm
A
- Consists of all the cellular contents between the plasma membrane and the nucleus
- 2 components:
- Cytosol (intercellular fluid)
- Organelles
- Cytosol is the fluid portion of cytoplasm that makes up about 55% of the total cell volume
- mostly water plus various dissolved and suspended components
- Most cell activities occur in the cytoplasm where nutrients are received, processed, and stored
- Organelles have specific functions
26
Q
Endoplasmic Reticulum (ER)
A
- A network of membranes in the shape of flattened sacs or tubules
- provides tubular transport system inside the cll
- participates in the synthesis of protein and lipid molecules
- 2 types:
- Rough ER: studded with ribosomes, synthesizes glycoproteins and phospholipids
- Smooth ER: no ribosomes, synthesizes fatty acids and steroids
27
Q
Ribosomes
A
- site where protein synthesis occurs
- composed of 2 subunits- protein and rRNA
- Can be attached to the ER or scattered throughout the cytoplasm
28
Q
Golgi Complex
A
- Composed of flattened sacs.
- Refines, packages, modifies, and delivers proteins.
- Proteins from the ER arrive at the Golgi enclosed in vesicles.
- Vesicles fuse with Golgi apparatus, and the contents are modified.
- The modified proteins are released from the Golgi in transport vesicles.
- The transport vesicles can move to and fuse with the cell membrane to release its contents to the outside of the cell (exocytosis).
29
Q
Mitochondria
A
- Energy producer for the cell
- Produce and store ATP through aerobic respiration.
- ATP is what cells use for energy.
- Very active cells such as muscle cells contain many thousands of mitochondria.
- Mitochondria can divide (replicate) and contain their own DNA.
• Mitochondrial DNA (mtDNA) is passed on from mother to offspring.
• Can be used to trace maternal lineage.
30
Q
Lysosomes
A
- “garbage disposals” of the cell
- Tiny membranous sacs that contain enzymes that break down old cell components and bacteria
33
Q
Centrosome
A
- Structure near the Golgi apparatus and nucleus.
- Made up of 2 cylinders called centrioles.
- Help form and organize microtubules.
- Functions in the separation of chromosomes during cell division.
34
Q
Cilia and Flagella
A
- Motile extensions from the cell surface.
- Cilia help move substances across cell surface.
- Flagella help cell to propel the cell (sperm cells).
36
Q
Nucleus
A
- Largest organelle in the cell.
• Surrounded by a nuclear envelope.
• Contains nuclear pores that allow the passage of certain substances. - Nucleus contains the following structures:
• Nucleolus – dense body composed of RNA and protein.
• Chromatin – consists of loosely coiled fibers of protein and DNA. - During cell division chromatin condenses to form structures called chromosomes.
41
Q
Interphase
A
- A period of great metabolic activity.
- Cell grows and synthesizes new molecules and organelles.
- Interphase can be broken into different phases.
- S-phase – DNA is replicated in preparation for cell division (synthesis phase).
- G1 and G2 phases – cell grows and other structures are duplicated (growth phase).
42
Q
Prophase
A
- First stage of mitosis.
- DNA (chromatin) condenses into paired chromosomes.
- Centrioles migrate to poles.
- Microtubules organize into spindle fibers.
- Nucleolus and nuclear envelope disappear.
43
Q
Metaphase
A
- Spindle fibers attach to centromeres on chromosomes.
- Chromosomes align at center of the cell (metaphase plate).
44
Q
Anaphase
A
- Centromeres split.
- Identical sets of chromosomes move to opposite poles of the cell.
- Beginning of cytokinesis*
45
Q
Telophase
A
- Nuclear envelope and nucleolus begin to reappear.
- Chromosomes disperse into chromatin.
