Chapter 3 Review (13 questions) Flashcards
What are the 4 basic concepts of the cell theory
Cells are the building blocks of all plants and animals
All cells come from the division of preexisting cells
Cells are the smallest units that perform all vital physiological functions
Each cell maintains homeostasis at the cellular level
What are the 4 general functions of the cell membrane
- Physical isolation barrier between cell interior and surrounding extracellular fluid (a.k.a. interstitial fluid)
- Regulation of exchange with the environment
¥ Ions and nutrients enter
¥ Waste and cellular products released - Sensitivity to the environment facilitates communication, receives information about the cell’s surroundings
¥ Extracellular fluid composition, chemical signals - Structural support anchors cells and tissues
What are the 6 general functions performed by membrane proteins
- Anchoring Proteins (stabilizers) attach to other structures, can attach inside or outside of cell
- Recognition Proteins (identifiers) label cells as normal or abnormal
- Enzymes catalyze reactions
- Receptors bind and respond to ligands (ions, hormones)
- Carriers transport specific substances across membrane
- Channels create a pore for water and solute transport
What are the 4 general functions of the glycocalyx
¥ Lubrication and Protection
¥ Anchoring and Locomotion
¥ Specificity in Binding (receptors)
¥ Recognition (immune response)
Be able to identify phospholipids, glycolipids, integral proteins, peripheral proteins, glycoproteins, and cholesterol in a figure of the plasma membrane.
¥ Phospholipid bilayer creates a barrier to ions, water, and large or polar molecules
¥ Hydrophilic heads exposed to the aqueous environment on both sides (extracellular fluid, cytosol)
¥ Hydrophobic fatty-acid tails buried inside membrane
¥ Integral proteins embedded within the membrane
Peripheral proteins bound to inner or outer surface of the membrane
• What are the major nonmembranous organelles? membranous organelles?
¥ Nonmembranous organelles no membrane
¥ Include the cytoskeleton, microvilli, centrioles, cilia, ribosomes, and proteasomes
¥ Membranous organelles enclosed by membrane
¥ Include the endoplasmic reticulum (ER), the Golgi apparatus, lysosomes, peroxisomes, and mitochondria
• Describe the general structure and function of the cytoskeletal filaments (microfilaments, intermediate filaments, microtubules)
¥ Microfilaments smallest filaments built from the protein actin, generally peripherally located
¥ Intermediate filaments mid-sized, stabilize the positions of organelles, anchor to surrounding cells
¥ Microtubules large hollow tubes built from the protein tubulin, cell strength, vesicle transport, cell division (spindle)
• Describe the structure and function of microvilli, centrioles, and cilia.
¥ Microvilli finger-like projections of the cell membrane
¥ Increase surface area for absorption
¥ Centrioles built from 9 microtubule triplets
¥ Centrioles form spindle apparatus during cell division
Cilia long thin extensions from the cell membrane built from microtubule triplets
• Describe the structure and function of ribosomes. Where in a cell are ribosomes located?
Ribosomes build polypeptides
- Free ribosomes in cytoplasm manufacture proteins for cell
- Fixed ribosomes attached to ER manufacture proteins for secretion
• What is the function of a proteasome?
Proteasomes degradative function
¥ Disassemble damaged proteins for recycling
• Describe the structure, location, and the 4 major functions of the endoplasmic reticulum.
¥ Connected to nuclear membrane
Functions
1. Synthesis of proteins, carbohydrates, and lipids
2. Storage of synthesized molecules and materials
3. Transport of materials within the ER
4. Detoxification of drugs or toxins
o What functions are performed by the smooth ER?
¥ No ribosomes attached
¥ Synthesizes lipids and carbohydrates
¥ Phospholipids and cholesterol (membranes)
¥ Steroid hormones (reproductive system)
¥ Glycerides (storage in liver and fat cells)
¥ Glycogen (storage in muscles)
o What functions are performed by the rough ER?
¥ Surface covered with ribosomes
¥ Active in protein and glycoprotein synthesis
¥ Facilitates polypeptide folding into correct protein structures
¥ Encloses products in transport vesicles
• Describe the structure and function of the Golgi apparatus, lysosomes, and peroxisomes.
Golgi Apparatus protein modification and sorting
Functions
1. Modifies and packages secretions
¥ Hormones or enzymes
¥ Released through exocytosis
2. Renews or modifies the plasma membrane
3. Packages special enzymes within vesicles for use in the cytoplasm
Lysosomes powerful enzyme-containing vesicles degrade old organelles, extracellular materials, damaged cells
Peroxisomes enzyme-containing vesicles
¥ Break down fatty acids, organic compounds
¥ Produce hydrogen peroxide (H2O2)
• What process connects many membranous organelles to one another?
Membrane Flow is a continuous exchange of membrane parts by vesicles
¥ All membranous organelles (except mitochondria)
¥ Nuclear envelope, RER, SEM, transport vesicles, Golgi, secretory vesicles, cell membrane, endosomes, lysosomes, peroxisomes are all interconnected
¥ Allows adaptation and change
• Describe the structure and function of the mitochondrion.
¥ Structure outer membrane, inner membrane, cristae, matrix
¥ Function transform energy stored in “food” molecules into energy stored in ATP
¥ Glycolysis, citric acid cycle, electron transport chain, aerobic metabolism
• Describe the structure and function of the nucleus.
Nucleus information storage and retrieval
¥ Largest organelle
¥ Structure nuclear envelope, nuclear pores, nucleoli
¥ Function the DNA within the nucleus has all the information to build and “run” the organism
o How is DNA organized within the nucleus?
Contents of the Nucleus
¥ Chromatin Loosely coiled DNA and structuring proteins (cells not dividing)
¥ Chromosomes tightly coiled DNA (cells dividing)
• The synthesis of a protein requires gene activation, transcription, and translation. What happens during each of these steps?
Protein Synthesis requires
- Gene activation uncoiling DNA to access information
- Transcription copying information from DNA to mRNA
- Translation interpreting information in mRNA to build polypeptide
• What signals RNA polymerase to start and end transcription?
¥ Promoter base sequence reads “start here”
¥ Terminator base sequence reads “stop here”
¥ RNA polymerase produces messenger RNA (mRNA)
¥ Pre-mRNA is “edited” during RNA processing
• What signals the ribosome to start and end translation?
¥ Ribosome reads code from mRNA (in cytoplasm)
¥ tRNA delivers amino acids to the ribosome according to mRNA codons
¥ Assembles amino acids into polypeptide chain
• What 4 factors influence the permeability of a molecule?
¥ Size
¥ Electrical charge
¥ Molecular shape
¥ Lipid solubility
• How can membrane transport be characterized?
¥ By energy requirements: ¥ Active (requiring energy and ATP) ¥ Passive (no energy required) ¥ By mechanism: ¥ Diffusion (passive) ¥ Carrier-mediated transport (passive or active) ¥ Vesicular transport (active)
• What is diffusion?
Diffusion is the movement of a substance from an area of higher concentration to an area of lower concentration
o When does diffusion occur?
¥ Occurs spontaneously
o When does diffusion not occur?
When energy is required
o What factors influence the rate of diffusion?
¥ Distance shorter is faster
¥ Molecule Size smaller is faster
¥ Temperature hotter is faster
¥ Concentration Gradient larger difference is faster
¥ The difference between high and low concentrations
¥ Electrical Forces
¥ Opposites attract, like charges repel
o What kinds of molecules can diffuse directly across the cell membrane?
¥ Simple = hydrophobic
¥ alcohols, fatty acids, steroids, O2, CO2
¥ Channel = hydrophilic
¥ Simple sugars, ions
¥ Size, charge, interaction with channel protein
o What is the difference between simple diffusion and channel-mediated diffusion?
¥ Simple diffusion move directly across phospholipid bilayer
¥ Channel mediated (facilitated diffusion) move through a protein to cross the membrane
• What is osmosis?
¥ Osmosis is the diffusion of water across the cell membrane
o What is the relationship between the # of solute molecules and the # of water molecules?
More solute molecules lower concentration of water molecules
o What is the membrane permeability for water?
Membrane must be freely permeable to H2O
o What is the membrane permeability for solutes?
¥ selectively permeable to solutes
o What is the relationship between osmotic pressure and hydrostatic pressure?
Osmotic pressure the force of a concentration gradient of water
¥ Equals the force (hydrostatic pressure) needed to block osmosis
• What happens to a cell placed in an isotonic solution? hypotonic solution? hypertonic solution?
Isotonic surrounding solution has same solute concentration
¥ Water neither flows into or out of a cell
Hypotonic surrounding solution has less solutes
¥ Water flows into cell
Hypertonic surrounding solution has more solutes
¥ Water flows out of cell
• What are 3 important characteristics of carrier-mediated transport?
¥ Specificity one transport protein, one set of substrates
¥ Saturation Limits rate depends on transport proteins, not substrate
¥ Regulation cofactors such as hormones
• Be able to identify cotransport and countertransport in a figure.
Cotransport two substances move in the same direction at the same time
Countertransport two substances move in opposite directions at the same time
• Compare/contrast facilitated diffusion and active transport.
Passive Transport (aka facilitated diffusion)
¥ From [high] to [low]
¥ With concentration gradient
¥ Carrier proteins transport molecules too large to fit through channel proteins (glucose, amino acids)
Active Transport
¥ From [low] to [high]
¥ Against concentration gradient
¥ Requires energy, such as ATP
¥ Ion pumps move ions (Na+, K+, Ca2+, Mg2+)
• Compare/contrast primary active transport and secondary active transport.
Primary active transport requires a direct input of energy = ATP hydrolysis
¥ Ex: Sodium–potassium exchange pump
¥ 1 ATP moves 3 Na+ and 2 K+
¥ Sodium ions (Na+) out, potassium ions (K+) in
Secondary active transport requires an indirect input of energy = potential energy stored in an ion gradient
¥ Ex: Sodium–glucose cotransporter
¥ Na+ concentration gradient drives glucose transport
¥ ATP energy pumps Na+ back out
o How are these 2 processes connected?
Vesicular Transport (Bulk Transport) ¥ Materials move into or out of the cell in vesicles ¥ All vesicular transport is active = requires input of energy ¥ Exocytosis use vesicles to transport materials out of the cell ¥ Endocytosis use vesicles to transport materials into the cell
• Compare/contrast receptor-mediated endocytosis, pinocytosis, and phagocytosis.
Receptor-mediated endocytosis
¥ Receptors (glycoproteins) bind target molecules (ligands)
¥ Coated vesicle carries ligands and receptors into the cell
¥ The contents of the endosome are processed by the cell
Pinocytosis “drinking” bring in extracellular fluid
Phagocytosis bring in large substances
¥ Use pseudopodia
• What is transmembrane potential?
Transmembrane Potential is the potential energy stored across the membrane due to the separation of charges (ions)
o How is transmembrane potential created/maintained?
¥ Charges are separated by the membrane potential energy
¥ Sodium (Na+) is highly concentrated outside the cell
¥ Potassium (K+) is highly concentrated inside the cell
o What units are used in measuring the transmembrane potential?
¥ The transmembrane potential can be measured
¥ Resting potential ranges from –10 mV to –100 mV, depending on cell type
• When in the cell cycle does the cell grow and perform normal functions?
G1 Phase
• When in the cell cycle does DNA replication occur?
S phase
• What are the phases of mitosis?
interphase prophase metaphase anaphase telophase
• What types of cells divide rarely (are long lived)? What types divide rapidly (are short lived)?
¥ Muscle cells, neurons rarely divide
¥ Exposed cells (skin and digestive tract) live only days or hours – replenished by stem cells
• How is cell division regulated?
¥ Normally, cell division balances cell loss
¥ Growth factors can stimulate cell division
¥ Repressors can inhibit cell division
¥ p53 is an important repressor
¥ About half of all cancers are associated with abnormal forms of p53
• How do cancers develop?
¥ Abnormal cell mutation, replication error
¥ Primary tumor first mass of abnormal cells
¥ Metastasis dispersion of abnormal cells
¥ Secondary tumor new mass of abnormal cells at distant location
• Why does a liver cell have a different structure and perform different functions as compared to a red blood cell?
differentiation
