Cellular Organization (chapter 3) Flashcards
Cell
smallest living unit
Cytology
study of cells, requires microscope
Two categories of cells
1.sex cells: sperm and oocyte(egg)
2.somatic cells: everything else
Plasma Membrane/Cell Membrane
-mostly phospholipid bilayer: dynami
-6 to 10mm thick
-interface between cell and enviornment
Plasma membrane functions
-physical barrier to maintain homeostasis: separates intracellular contents (cytoplasm) from extracellular fluid
-regulates exchange with environment
-provides sensitivity via receptors: cell communication and signaling, sense change in extracellular environment
-provides structural support: attachment site to hold tissues together
Plasma membrane components
A. phospholipids: self assemble into bilayer
B. cholesterol: resist osmotic lysis: stiffens
C. carbohydrates: linked to other molecules as proteoglycans, glycoproteins, and glycolipids
-carb part protrudes from extracellular side creating outer carb layer called glycocalyx
D. proteins:
-1/2 mass of membrane
-integral proteins: (most common) span width of membrane
-peripheral proteins adhere to inner or outer surface
Functions of glycocalyx
-lubrication and protection
-anchoring and locomotion
-binding specificity (receptor binds ligands)
-self recognition by immune system
Functions of membrane proteins
-anchoring proteins: attachment (both inside and outside)
-recognition proteins: self identification by immune system (glycoproteins)
-enzymes: catalyze rxns in cytosol or extra cellular fluid
-receptors: bind ligands for signaling or import/export (e.g ions, nutrient molecules, hormones, etc)
-carrier proteins: transport solutes in/out
-channels: move ions and H2O in/out
Facilitated diffusion
movement of materials across a membrane by a carrier protein
-substances involved simple sugars and amino acids
Osmosis
diffusion of water molecules across a selectively permeable membrane. Movement occurs toward higher solute concentration because that is where the concentration of water is lower.
-substances involved water only
Diffusion
is the movement of molecules from an area of higher concentration to an area of lower concentration.
-substances involved gasses, small inorganic ions and molecules, lipid soluble materials
Transcription
-making an RNA copy of a DNA gene
-occurs in the nucleus
Translation
making a protein using the mRNA blueprint
-occurs in the cytoplasm on free ribosomes or on fixed ribosomes on the RER
Active Transport
requires proteins that move specific substances across a membrane against their concentration
Endocytosis
packaging of extracellular materials into a vesicle for transport into the cell
Exocytosis
intracellular vesicles fuse with the plasma membrane to release fluids and or solids from the cells
Cytoskeleton
-internal framework
-organizes cell contents and functions
-4 possible types of filaments:
A. Microfilaments
B. Intermediate filaments
C. Microtubules
D. Thick filaments
Centrosome
-located near nucleus
-consists of dense cytoplasm and two centrioles arranged at right angels
-functions as microtubule organizing center
-responsible for assembling spindle apparatus during mitosis
Cilia
-cellular appendages
-contain a microtubule core with cytoplasm covered in plasma membrane
-beating or waving motions
-short, numerous, functio to sweep substances over cell surface
Flagellum
-Very long, singular function to propel cell through environment
Ribosomes
-site of protein synthesis: enzymes to peptide bond amino acids
-2 subunits: large and small both composed of 60% rNA and 40% protein
A. Free ribosomes: in cytoplasm, manufacture proteins for use in cytoplasm
B. Fixed ribosomes: attached to ER, manufacture proteins for export or for in the membrane
Endoplasmic Reticulum
-network of membranes made up of tubes sacs and chambers called cisternae
-attached to the nuclear envelope
-2 forms: RER and SER
Rough ER
-studded with fixed ribosomes
-ribosomes synthesize proteins and feed them into RER cisternae to be modified
-modified proteins put into transport vesicles to go to golgi
-these proteins for exocytosis or use in membrane
Smooth ER
-tubular membranes
-no ribosomes
functions of SER
1. synthesis of phospholipids and cholesterol for membrane
2. synthesis of steroid hormones
3 synthesis and storage of triglycerides
4. synthesis and storage of glycogen
5. storage of Ca2+ ions in muscle cells
6. detoxification/inactivation of drugs in kidney and liver cells
Golgi
-stack of cisternae with an associated transport vesicles
-near nucleus but not attached
-functions:
A.modifies and packages secreations
B. renews or modifies the cell membrane
C. packages enzymes within vesicles to create a temporary digestive organelle called the lysosome
-transport vesicles from RER dock on cisternae face or forming face of golgi
-proteins (and glycoproteins) are modified (phosphate, carbohydrates, or lipids attached, polypeptides, refolded)
-modified proteins transit between cisternae via vesicles from cis face (forming) to trans face (maturing) and are concentrated and sorted by final function and destination
-at trans face proteins are packaged into one of three types of vesicles for transport
Three types of Vesicles for transport
A. secretory vesicles: carry products to be exocytosed for use outside the cell
B. membrane renewal vesicles: carry products to be incorporated into the plasma membrane
C. lysosomes: temporary organelles membrane bound sacs of digestive enzymes
Lysosomes
-digestion center for large molecules or structures, cell can have many
-functions:
A. cellular cleanup: remove and recycle damaged organelles and extra molecules
B. break down material and objects that have been endocytosed
-endosomes or phagosomes containing endocytosed things and organelles and molecules targeted for destruction are fused with the lysosome and enzymatically broken down
-some solutes diifuse into cytoplasm for use remaining debris are exocytosed
-failure of lysosomes causes build up of cells that eventually prevents cell functions e.g Tay Sach’s disease
Peroxisomes
-membrane sac containing oxidases and catalases to neutralize free radicals
-free radicals (e.g H2O) form during catabolism of organic molecules
-peroxisomes not made by golgi enzymes produced by free ribosomes, cell can have many
Proteasomes
-cylindrical structure composed of protein digesting enzymes called proteases
-functions to degrade and recycle damaged, denatured or abnormal proteins
-hydrolyzes peptide bonds of proteins tagged with ubiquitin to recycle amino acids, cell can have many
Mitochondria
-sausage shaped with double membrane
-outer membrane: smooth
-inner membrane: folded folds called cristae
-center= matrix (fluid)
-aerobic cellular respirations occurs on surface of cristae where glucose is catabolized creating CO2 and H2O waster to convert ADP into ATP
-mitochondria supply most of cell’s energy (~95%: 2ATP per glucose w/o mitochondria 36 ATP per glucose with)
-have their own DNA
-can replicate independent of the cell
-mitochondrial DNA is maternal
Nucleus
-control center of cell: directs proteins synthesis (proteins are responsible for structure and function of cell)
-contains DNA: genetic material
-most cells have one, exceptions skeletal muscle (many), RBCs (none)
-surrounded by nuclear envelope: double membrane, outer layer connected to ER
-has nuclear pores with regulator proteins that control exchange of molecules between cytoplasm and nucleus
-inside is DNA floating in nucleoplasm with nucleotides, RNA and protein enzymes
-in non dividing cells DNA is loose called chromatin
-open form of DNA allows access to information to direct protein synthesis
DNA
-inside a nucleus is DNA floating in nucleoplasm with nucleotides, RNA and protein enzymes
-in non dividing cells DNA is loose called chromatin
-open form of DNA allows access to information to direct protein synthesis
=DNA in chromatin is organized into nucleosomes:DNA wound around histone proteins
nucleosomes
prevent tangling and breakage and reduce amount of space DNA takes up
nuclear division
chromatin is tightly wound into individual visible bundles of DNA called chromosomes (23 pairs in humans)
Genetic Informations
-DNA contains genes
Genes = functional units of heredity
-encode for a product: RNA or protein Humans have ~30 thousand potential genes (most encode enzymes for metabolism)
-this is only 1.5% of total DNA
-remainder is involved with control of genes, some appears to be junk (25%)
-noncoding parts of DNA (non-genes) is highly variable one person to next
-variability allows for identification of an individual by DNA fingerprinting
-in order for a gene to be expressed (used to make a product) it must be unwound from the histone proteins so it can be read
-disassembly of the nucleosomes and
unwinding of the DNA to copy the
information is called gene activation
Genetic Code
-language of the DNA that is read off a gene in order to assemble a protein
-3 bases of DNA = 1 codon
-each codon gives the instructions for one amino acid
-a gene= all the codons for all the amino acids in one protein in the correct order with control regions
Transcription
-making an RNA copy of a DNA gene
-occurs in nucleus
Translation
=making a protein using the mRNA blueprint
-occurs in the cytoplasm on free ribosomes or on fixed ribosomes
Components that assemble in cytoplasm
-two ribosomal subunits
-mRNA
-tRNAs carrying amino acids
The life cycle of a cell
-life span cell depends on type of cell
-all cells eventually die
-some cells must divide to make cells to replace dying cells: function of stem cells -to divide, DNA must be replicated and equally distributed between the stem cell and new daughter
-most cells spend very little time dividing in an adult instead are performing cellular functions
Mitosis
=nuclear division
-Once G1 phase S phase and G2 phase of interphase are complete mitosis begins
apoptosis
controlled to cell death, lysosomes are defused to prevent damage to other cells
The cell cycle
- Interphase: period of time that a cell performs its normal functions
-if a cell never divides, it remains in G0 phase of interphase
-if the cell is preparing to divide, it will go through 3 stages in interphase:
A. G1 phase: cell doubles organelles and synthesizes enough cytoplasm for two cells
B. S phase: cell duplicates DNA
C. G2 phase: copious protein synthesis: cell generates enough enzymes for two cells, centrioles are replicated
DNA Replication
-S phase of interphase
-only performed by cells preparing for division
-will be followed by mitosis
