Ch 3: Cells Flashcards
What is a cell?
The structural and functional unit of life
List the three major regions of a generalized cell and their functions.
- Plasma membrane
- Cytoplasm
- Nucleus
Describe the chemical composition of the plasma membrane
- Consists of a lipid bilayer
2. 75% phospholipids, 5% glycolipids, 20% cholesterol
What is the interstitial fluid that surrounds the cell called?
Extracellular fluid
What are the 6 functions of membrane proteins?
- Transport
- Receptors for signal transduction
- Attachment to cytoskeleton and extracellular matrix
- Enzymatic activity
- Intercellular joining
- Cell-cell recognition
What are the 2 types of membrane proteins?
- Integral
2. Peripheral
What is an integral protein?
Inserted into the membrane and functions as a transport protein
What is a peripheral protein?
Loosely attached to integral proteins and functions as an enzyme, provides cell-to-cell communications and muscle contractions
What are lipid rafts?
Provides my stabilization to membrane
Phospholipids, sphingolipids, and cholesterol
What are the sugars covering the cells surface?
Glycocalyx
What are the 3 different cell junctions?
- Tight junctions
- Desmosomes
- Gap junctions
What are tight junctions?
The fusion of integral proteins preventing fluids and molecules from moving between the cell
What are desmosomes?
Rivets that anchor cells together consisting of linker proteins and keratin filaments. Assists by reducing tears
What are gap junctions?
Connexons that allow small molecules to pass from cell to cell
What happens when K+ diffuses out of the cell?
Inside of cell membrane becomes more negative
What is the resting membrane potential of a cell?
-70mV
What state is a cell in at RMP?
Polarized
What is the voltage range of the cell membrane?
-50 to -100mV
Explain the key role of K+ in generating resting membrane potential
- K+ diffuse down the gradient via leaky channels. Loss of K+ cause negative charge inside plasma membrane
- K+ moves into cell because they are attracted to negativity
- Negative membrane potential is -90mV happens when K+ in and out cell are equal. The concentration gradient promotes K+ exit opposing electrical gradient
How does Na+ affect RMP?
- Attracted into cell due to negative charge
- Membrane more permeable to K+ than Na+
What is the difference between active and passive transport?
Active transport requires ATP, while passive requires substances to move down its concentration gradient
Define diffusion
When molecules move down or with their concentration gradient typically from a higher concentration to lower
Speed is dependent of molecular size and temperature
How can molecules pass through the membrane?
- Lipid is soluable
- Small enough to go through channels
- Assisted by carrier molecules
What is simple diffusion?
Nonpolar lipid-soluable (hydrophobic) substances diffuse directly through phospholipid bilayer
Ex: O, CO2, Fat soluable vitamins
What is channel mediated facilitated diffusion?
Aqueous channels formed by transmembrane proteins that selectively transport ions and water
What are examples of channel mediated facilitated diffusion?
Leakage channels (always open) and Gated (always regulated) channels
What is osmosis?
Movement of solvent across selectively permeable membrane
What are water channels called?
Aquaporins
What is osmolarity?
The total concentration of solute particles
When solutions of different osmolarity are combined how can they be separated?
- Membrane permeable to all molecules
Solute and water move down their concentration in opposite directions - Membrane impermeable to solutes
Solute molecules are prevented from moving by water moves by osmosis. Volume increases in the compartment with higher osmolarity
What is the ability for a solution to alter a cell’s water volume?
Tonicity
Describe the 3 tonicity scenarios
- Isotonic: cell retains normal size
- Hypertonic: cell shrinks
- Hypotonic: cell bloats or bursts
What is active transport?
- Requires carrier proteins that bind specifically with substance
- Requires energy to move against the concentration gradient
What is primary transport
Takes energy from hydrolysis of ATP to pump ions across the membrane.
How do sodium potassium pumps work?
Works as an antiporter pumpings Na and K gradients to maintain high intracellular K+ and high extracellular Na+ concentrations
What is the ratio of K+ to Na+
2:3
How is secondary transport different than primary?
Secondary depends on ion gradient created by primary active transport
What is cotransport?
Always transports more than one substance at a time
What is the difference between symport and antiport?
Symport: same direction
Antiport: opposite direction
What is vesicular transport?
Requires ATP to transport large particles, macromolecules, fluids in vesicles
What are the different types of vesicular transport?
- Endocytosis
- Exocytosis
- Transcytosis
- Vesicular trafficking
What is the term for moving substance into a cell?
Endocytosis
When a pseudopods engulf solids and bring them into cell’s interior forming phagosomes?
Phagocytosis
When the plasma membrane infolds, bringing extracellular fluid and dissolved solutes inside cell?
Pinocytosis
How is receptor-mediated different from other endocytosis mechanisms?
Contains clathrin-coated pits that stimulate movement
What is the movement of substance out of the cell?
Exocytosis
What is the purpose for exocytosis?
- Functions are hormone secretion
- Neurotransmitter release
- Mucus secretion
- Ejection of wastes
Describe the process of exocytosis regarding SNARES
- Vesicle migrate to membrane
- v-SNARE binds to t-SNARE
- The vesicle fuses and a pore opens up
- Waste is released
What are the roles of Cell adhesion molecules (CAMs)?
- Assist in movement of cells
- Attract WBCs to injured or injected areas
- Stimulate synthesis or degradation of adhesive membrane junctions
- Transmit intracellular signals
What are the roles of Plasma membrane receptors?
- Contact signaling: Touching and recognition of cells
2. Chemical signaling: Interaction between receptors and ligands alter cell activity
Explain the process for chemical signaling
Ligand binding → receptor structural change → Protein alteration and G proteins activation
List the components of the cytosol
- Cytosol
- Organelles
- Inclusions
Discuss the structure and function of mitochondria
- Contains cristae that increase surface area for metabolic pathways
- Provide most of cell’s ATP
- Contain their own DNA, RNA, ribosomes
What are ribosomes?
Granules containing protein and rRNA
The site for protein synthesis
What are the functions for RER?
- Manufactures all secreted proteins
- Synthesizes integral proteins and phospholipids
What are the functions for SER?
- Lipid metabolism
- Absorption, synthesis, and transport of fats
- Detoxification
- Converts glycogen to glucose
- Storage and release calcium
What is the purpose for the golgi apparatus?
Modifies, sorts, concentrates, and packages proteins and lipids from the RER
What are the 3 pathways for proteins in the golgi?
- Exocytosis: secretory vesicles
- Incorporation into plasma membrane: vesicles of lipids and transmembrane proteins
- Degradation: lysosomes
What are peroxisomes?
Membranous sacs of oxidases and catalases that detox the cell from harmful substances neutralizing free radicals and catalysis and synthesis of fatty acids
What are lysosomes?
Sacs of acid hydrolases that digest toxins, degrading nonfunctioning organelles
What are the 3 components of the cytoskeleton?
- Microfilament
- Intermediate filament
- Microtubules
What are microfilaments?
They are the thinnest components of the cytoskeleton comprised of actin and provides a retinal web that gives strength and compression resistance
It also provides cell motility, shape change, endocytosis, and exocytosis
What are intermediate filaments?
It is a tough, insoluble rope like protein fibers composed of tetra ear fibrils
It also allows the cell to be resist to pulling forces and attach to desmosomes
What are microtubules?
Radiating from centrosomes, microtubules are composed of tubulins. They determine the overall shape of cell and distribution of organelles
Mitochondria, lysosomes, and secretory vesicles are moved by motor proteins attached to these.
What is the role for motor proteins?
Powered by ATP, protein complexes function in motility in moving organelles and contraction
What do centrioles do?
Generate microtubules and organize mitotic spindle
What is the difference between cilia and microvilli
Cilia: moves substances across the cell
Microvilli: increase surface area for absorption
What does a flagella do?
Propels the whole cell
What are the functions of the nucleus?
Considered to be the genetic library of the cell responding to signals and regulating protein synthesis
What is the use for nuclear envelope?
Protects the nucleus for the outside environment
What does a nucleolus do?
Facilitates the production of ribosomes using rRNA
What is a chromatin?
Threadlike strands of DNA (30%), histone proteins (60%), and RNA (10%) arranged in nucleosomes
List the four stages of cell division
- Prophase
- Metaphase
- Anaphase
- Telophase and Cytokinesis
What is purpose of interphase?
Interphase replicates, synthesizes, and grows cell in preparation for cell division
Explain the difference between meiosis and mitotic cell division
Meiosis is the cell division producing gametes. Mitosis produces clones
What does it mean to be semiconservative replication?
One strand of DNA is from the parent DNA and another on is a new strand
What is the purpose of RNA in regards to protein synthesis?
Decoding DNA and messaging mRNA, rRNA, tRNA
What is a gene?
Segment of DNA with blueprint for one polypeptide
What is the difference between exons and introns?
Exon codes for amino acids while introns are the noncoding segments
Differentiate mRNA, tRNA, and rRNA
- mRNA carries instructions for building a polypeptide from gene in DNA to ribosomes in cytoplasm
- tRNA bind to aa and pair with bases of codons of nRNA at ribosome to begin process of protein synthesis
- rRNA helps translate message from mRNA
Describe the 2 steps of protein synthesis
- Transcription is when DNA information is coded into mRNA
- Transfers DNA gene base sequence to complementary base sequence of mRNA
- mRNA edited and processed, and introns removed by splicesomes
- Translation is mRNA decoded to assemble polypeptides
- Converts base sequence of nucleic acids into aa sequence of proteins
What is a triplet?
3 base sequences of DNA
What is the difference between codon and anticodon?
Codon is complementary 3-base sequence on mRNA. ANticodon binds mRNA codon at ribosomes by hydrogen bonds
What is the purpose of autophagy and ubiquitins?
Protein degradation
What is autophagy?
Cytoplasmic bits and nonfunctional organelles put into autophagosomes; degraded by lysosomes
Describe the importance of ubiquitin-dependent degradation of soluble proteins.
- To tag damaged or unneeded soluble proteins in cytosol
- Digested by soluble enzymes or proteasomes
Theory where aging causes mitochondria to be leaky or less efficient?
Mitochondrial theory of aging
Theory where the body just gets old
Wear and tear theory
The theory where the body could attack itself.
Immune system disorders
The theory where damage of telomeres, cessation of mitosis and cell aging programmed into genes
Gene theory
What is cell differentiation?
Development of specific features in cells
What is the difference between hyperplasia and atrophy?
Hyperplasia is an increase is cell number. Atrophy is the decrease in cell size.
What is the value of apoptosis in the body?
Hyperplasia is an increase is cell number. Atrophy is the decrease in cell size.
