Chapter 3 Cellular Level Flashcards
3 main parts of the cell
Plasma membrane
Cytoplasm
Nucleus
Plasma membrane
Flexible but sturdy barrier that surrounds and contains the cytoplasm of the cell
Structure of the plasma membrane
Lipid bilayer
Integral proteins
Transmembrane proteins
Peripheral proteins
Glycoproteins
Lipid bilayer components
2 back-to-back layers made up of phospholipids (75%), cholesterol (20%), and glycolipids (5%)
Lipid bilayer arrangement
Polar phosphate containing head towards ICF and ECF due to being hydrophilic.
2 non-polar fatty acid “tails” arranged together due to being hydrophobic.
Integral proteins
Extend into or through the lipid bilayer.
Peripheral proteins
Not firmly embedded in the membrane.
Glycoproteins
Proteins with carbohydrate groups attached to the ends which protrude into the ECF.
Ion channels
Integral proteins. Form pores that allow specific ions into or out of the cell.
Carriers
Integral proteins. Selectively move polar substance or ion from one side of the membrane to the other. Also known as transporters.
Receptors
Integral proteins. Serve as cellular recognition sites. Bind a specific molecule known as a ligand.
Integral proteins (enzymes)
Some integral proteins are enzymes that catalyze specific reactions inside or outside of the cell
Linkers
Integral proteins. Anchor proteins in the plasma membrane to neighbouring cells or to protein filaments inside and outside the cell.
Cell-identity markers
Membrane glycoproteins and glycolipids.
Membrane fluidity
Allows mobility, structural and mechanical support. enables cell movement, growth, division, secretion. Allows interactions to occur inside the cell.
Membrane permeability
Selectively permeable. Highly permeable to nonpolar molecules. Moderately permeable to small, uncharged polar molecules. Impermeable to large, uncharged polar molecules.
Concentration gradient
Difference in the concentration of a chemical from one place to another.
Electrical gradient
Difference in electrical charges between two regions. Contributes to membrane potential
Electrochemical gradient
Combined influence of concentration gradient and electrical gradient.
Diffusion
Passive. Random mixing of particles in a solution because of the particles kinetic energy.
Factors that affect diffusion
Steepness of concentration gradient
Temperature
Mass of diffusing substance
Surface area
Diffusion distance
Simple diffusion
Passive process in which substances move freely through the lipid bilayer without the help of membrane transport proteins.
Facilitated diffusion
Passive process in which solutes move down their concentration gradient by the assistance of integral membrane proteins (IE ion channel or carrier)
Channel-mediated diffusion
Solute moves down its concentration gradient through a membrane channel
Carrier mediated facilitated diffusion
Solute moves down its concentration gradient via a transporter
Osmosis
Passive. A type of diffusion in which there is net movement of a solvent through a selectively permeable membrane.
Hydrostatic pressure
Pressure exerted by the solvent outward.
Osmotic pressure
Amount of pressure required to to stop osmosis from occurring. (IE applied pressure)
Tonicity
Measure of the solutions ability to change the volume of cells by altering their water content.
Isotonic solution
Any solution in which the cell maintains its normal shape.
Hypotonic solution
Has a lower concentration of solutes than the cytosol. Causes water to enter the cell, resulting in swelling and lysis.
Hypertonic solution
Higher concentration of solutes than the cytosol. Results in water leaving the cell, causing shrinkage, and crenation.
Active transport
Uses energy to move some polar or charged solutes across the membrane against their concentration gradient.
Primary active transport
Uses ATP to cause a change in the shape of the carrier protein, moving polar or uncharged solute against their concentration gradient (IE sodium-potassium pump)
Secondary active transport
Uses the energy stored in the sodium or hydrogen concentration gradient to drive other substances across the membrane against their concentration gradient. Indirectly uses energy obtained from ATP (IE sodium-glucose symporter)
Symporter
Secondary active transporter that moves two substances in the same direction
Antiporter
Secondary active transport. Moves two substances in opposite directions.
Endocytosis
Receptor mediated, endocytosis, or bulk-phase. Active transport. Involves bringing materials into the cell via formation of a vesicle.
Exocytosis
Releases materials from the cell. Active process. Uses secretory vesicles fusing with the cell membrane to release substance.
Cytosol
Fluid portion that surrounds organelles. 55% of total volume. 75-90% water.
Cytoskeleton
Network of protein filaments that extends through the cytosol.
3 types of filaments that contribute to the cytoskeleton
Microfilaments (smallest diameter)
Intermediate filament (medium)
Microtubule (largest diameter)
Microfilaments
Composed of actin and myosin. Prevalent at edge of cell. Generate movement (muscle contraction, etc) and provide mechanical support (strength and shape) for cell
Intermediate filaments
Found in parts of cell subject to mechanical stress. Help stabilize organelles and help attach cells together.
Microtubules
Long, unbranched hollow tubes comprised of tubulin. Grow outward from centrosome to periphery of cell. Help determine cell shape, and movement of vesicles, chromosomes, and cilia/flagella
Centrosome
Microtubule organizing structure. Consists of a pair of centrioles and the pericentriolar matrix. Plays critical role in cell division.
Centriole
Cylindrical structure composed of 9 clusters of microtubular triplets arranged in a circular pattern.
Pericentriolar matrix
Contains hundreds of ring shaped complexes composed of tubulin.
Cilia
Microtubules are dominant component in cilia. Numerous short, hair-like projections that extend from the surface of the cell.
Ribosomes
Site of protein synthesis. Consists of 2 subunits (small and large subunits). Some attach to the rough ER, others remain as free ribosomes.
Endoplasmic reticulum
Extends from the nuclear membrane. Constitutes more than half the membranous surface of most cells. Contains 2 different types (rough and smooth ER)
Rough ER
Continuous with the nuclear membrane. Outer surface is studded with ribosomes. Proteins are made and sorted into vesicles here.
Smooth ER
Extends from rough ER. Does not have ribosomes on the outer surface. Has unique enzymes to synthesize fatty acids and steroids. In the liver, enzymes here release glucose, and detoxify substances.
Golgi complex
Consists of 3-20 saccules which are often curved. Has entry (cis) face and exit (trans) face. Permits each of these areas to modify, sort, and transport vesicles to different destinations.
Lysosome
Membrane enclosed vesicle formed from golgi complex. Contains acidic environment. Removes final products of digestion. Helps recycle worn out organelles with autophagy. Can help destroy cell during autolysis.
Peroxisome
Contain oxidases. Oxidize substances from metabolism as well as toxic substances.
Proteasomes
Break down and recycle proteins into amino acids. Play a role in negative feedback regarding protein metabolism.
Mitochondria
Consists of external membrane and internal membrane with mitochondrial cristae. Generates ATP for energy. Plays a role in apoptosis. Self replicate. Has own DNA (37 genes) and some ribosomes.
Nucleus
Contains nuclear envelope that separates nucleus from the cytoplasm. Contains nucleoli, DNA, and RNA.
Nuclear pore
Controls movement of substances between nucleus and cytoplasm. Allows movement of ions. RNA and proteins move across membrane via active transport.
Nucleoli
Produces ribosomes. Site of synthesis of rRNA.
Genes
Arranged chromosomes. Human cells contain 46 chromosomes (23 from each parent)
Chromosome
Long molecule of DNA that is cooked together with some proteins.
Chromatin
Complex of DNA, RNA, and proteins.
Nucleosome
Double stranded DNA wrapped twice around a core of eight proteins called histones. String between linker beads is called linker-DNA
Chromatin fibre
Occurs in non-dividing cell. His tone promotes coiling of nucleosomes into larger diameter chromatin fibre.
Chromatids
DNA replicating condensed loops, forming a pair of chromatids.
Transcription
Copying of a specific code of information from DNA to produce a specific molecule of RNA.
Translation
RNA attaches to a ribosome where the information is translated to make a protein.
Base triplet
Complementary sequence of 3 nucleotides. Codes for 1 amino acid
mRNA
Messenger RNA. Directs synthesis of a protein.
rRNA
Ribosomal RNA. Joins ribosomal proteins to make ribosomes.
tRNA
Binds to amino acid and holds it in place on ribosome to incorporate it into a protein.
RNA polymerase
Catalyzes transcription of DNA.
Promoter
Nucleotide sequence which is located near the beginning of a gene.
Terminator
Nucleotide sequence at the end of a gene. Detaches RNA from the DNA.
Introns
Regions within a gene that do not code for a protein.
Exon
Regions within a gene that do code for a protein.
snRNP
Small nuclear ribonucleoproteins. Enzyme that cut out introns and splice together exons on mRNA.
Binding sites on large ribosomal subunits
Peptidyl (P) site: binds tRNA carrying AA
Aminoacyl (A) site: binds tRNA carrying AA to be transferred to protein.
Exit (E) site: binds tRNA just before it is released from the ribosome
Interphase
Cell replicates DNA. State of high metabolic activity. Produces additional organelles. Consists of G1, S, and G2 phases.
G1 phase
Cell is metabolically active, replicates organelles and DNA, replication of centrosomes begins. Last approx 8-10 hours.
S phase
DNA replication occurs. Lasts approx 8 hours. DNA separates and each old strand is paired with a new strand.
G2 phase
Cell growth continues. Enzymes and other proteins are synthesized. Replication of centrosomes is completed.
Mitotic phase
Results in the formation of 2 identical cells. Consists of prophase, metaphase, anaphase, and telophase.
Prophase
Chromatin fibres condense and shorten into chromosomes. Tubulins start to form the mitotic spindle. Football shaped assembly of microtubules attach to the kinetochore
Metaphase
Microtubules of mitotic spindle align the centromeres of chromatid pairs as the exact centre of mitotic spindle. Formation of metaphase plate.
Anaphase
Centromeres split, separating the 2 members of each chromatid pair to each pole. Separated chromatids are called chromosomes.
Telophase
Begins after chromosomal movement stops. Identical sets of chromosomes uncoil. Nuclear envelope forms around each chromatin mass. Mitotic spindle breaks up.
Cytokinesis
Begins in late anaphase with the cleavage furrow. Actin microfilaments pull plasma membrane progressively inward.
Meiosis
Reproductive cell division of gamete cells. Occurs in ovaries and testes. Occurs in 2 stages: meiosis 1 and 2.
Meiosis 1
Begins once chromosomal replication is complete. Consists of prophase 1, metaphase 1, anaphase 1, and telophase 1.
Meiosis prophase 1
2 sister chromatids pair off, called synapsis. Forms 4 chromatids together called tetrad. Can exchange chromosomes.
Meiosis metaphase 1
Tetrads formed by homologous pairs of chromosomes line up along the metaphase plate.
Meiosis anaphase 1
Members of each homologous pair of chromosomes are pulled to polar opposites of the cell. Paired chromatids, held by a centromere stays together.
Meiosis 2
Consists of prophase 2, metaphase 2, anaphase 2, and telophase 2. Each of the 2 haploid cells from meiosis 1 divides. Net result is 4 haploid gametes genetically different from the original diploid cell.
