Chapter 2: Cells Flashcards
membrane proteins
- peripheral =loosely attached to one side surface (generally hydrophilic, held in place by H-bonding and electrostatic interaction, disrupt/detach by chaning cxn and pH)
- integral=embeds inside membrane (hydrophobic; use detergent to destroy membrane and expose proteins)
- transmembrane = all the way through, both sides (type of integral)
phospholipid membrane permeability
- small, uncharged, nonpolar molecules (polar can only if small and uncharged) and hydrophobic molecules can freely pass across the membrane
- everything else (ions and large polar molecules) requires a protein transporter (large, polar and charged molecules)
- impermeable=”resistant to”
channel proteins
provide passageway through membrane for hydrophilic (water-soluble) substances (polar and charged)
recognition proteins
such as major-histocompatibility complex in macrophage to distinguish between self and foreign; they are glycoproteins due to oligosaccharides attached
ion channels
- passage of ions across membrane.
2. gated channels in nerve and muscle cells respond to stimuli (can be voltage gated, ligand-gated, mechanically gated)
porins
- allow passage of certain ions and small polar molecules
- aquaporins increase rate of H2O passing (kidneys and plant root cells.
- these tend not to be specific, they are just large, if you can fit you’d go through
carrier proteins
- bind to specific molecules, changes shape, molecule is passed through
- for example, glucose into cell (type of transport protein)
- seem to be specific to movement across membrane
transport proteins
- can use ATP (not all transport use ATP)=active transport
- Na+/K+ pump to maintain gradients
- facilitated diffusion
adhesion proteins
attach to neighboring cells, provide anchors for internal filaments and tubules (stability)
receptor proteins
binding site for hormones and other trigger molecules
cholesterol
- adds rigidity to membrane of animal cells under normal conditions (at low temps it maintains fluidity)
- sterols provide similar function in plant cells
glycocalyx
- a carb coat that covers that outer face of cell wall of some bacteria and some animal cells.
- consists of glycolipids (attached to plasma membrane) and glycoproteins (such as recognition proteins)
- may provide adhesive capabilities, barrier to infection, or markers for cell-cell recognition.
nucleus
- chromatin=general packaging structure of DNA around proteins in eukaryotes, the tightness of the packaging varies depending on cell stage
- chromosomes=tightly condensed chromatin when the cell is ready to divide
- histones= serve to organize DNA which coil around in into a bundled nucleosome (8 histones)
- nucleolus=inside the nucleus, the maker of ribsomes (rRNA) ***[rRNA is synthesize in nucleolus + ribosomal proteins imported from cytoplasm= ribosomal subunits form; these subunits are exported to the cytoplasm for final assembly into complete ribosome.
- Nucleus bound by double layer nuclear envelope w/ nuclear pores for transport (mRNA, ribosome subunits, dNTPS, proteins) in /out.
- no cytoplasm in nucleus, instead nucleoplasm.
nuclear lamina
dense fibrillar network inside nucleus of eukaryotic cells (intermediate filament and membrane associated proteins). Provides mechanical support; also helps regulate DNA replication, cell division, and chromatin organization.
nucleoid
irregular shaped region within the cell of prokaryote that contains all/most generic material
cytoplasm
- THIS IS AN AREA, NOT A STRUCTURE!
- metabolic activity and transport occur here.
- cyclosis is streaming movement within cell
- doesn’t include nucleus, but does include cytosol, organelles, everything suspended w/n cytosol but nucleus
cytosol
cytosol doesn’t include the stuff suspended within the gel-like substance, it is JUST the gel-like stuff. THINK JELLO vs VEGGIE STEW
ribosome
- 60S + 40S =80S, eukaryotes
- prokaryote (50S+30S=70S); 3.the two subunits produced inside the nucleolus moved into the cytoplasm where they assembled into a single 80S ribsome (larger S value = heavier molecule) …. made of rRNA+protein,
- function to make proteins
Endoplasmic Reticulum
- Rough ER: creates glycoproteins by attaching polysaccharides to polypeptides as they are assembled by ribosomes [in eukaryotes RER is continuous with the outer nuclear membrane]
- Smooth ER: synthesizes lipids and hormones for export … in liver cells, SER functions to breakdown toxins, drugs, and toxic by-products from cellular rxn
- Smooth and striated muscle have SER called sarcoplasmic reticulums that store and release ions such as Ca2+
lysosomes
- vesicles produced from golgi contain digestive enzymes (low pH for fxn)
- break down nutrients/bacteria/cell debris
- any enzyme that escape from lysosomes remains inactive in the neutral pH of cytosol
- functions in apoptosis (releases contents into cell)
golgi apparatus
- transport of various substances in vesicles
- cis face for incoming vesicles
- trans face for secretory vesicles
- flattened sacs called cisternae
peroxisome
- break down substances (H2O2=H2O+O2), fatty acids, amino acids
- common in liver and kidney where they break toxic substances
- In plant cell, peroxisomes modify by-products of photorespiration
- in germinating seeds, it is called glyoxysomes breakdown stored fatty acids to help generate energy for growth
microtubules
- made up of protein tubulin
- provide support and motility for cellular activities; spindle appartus which guide chromosomes during division
- flagella and cilia (9+2 array–9pairs+2singlets in center) in all animal cells and lower plants (mosses, ferns)
intermediate filaments
provide support for cell shape e.g. keratin
microfilament
- made up of actin
2. for cell motility (skeletal muscle, cleavage furrow)
microtubule organizing centers (MTOC)
- include centrioles and basal bodies (are the base of each flagellum and cilium and organize their development)
- 9x3 array
- plant cells lack centrioles and its division is by cell plate instead of cleavage furrow- PLANTS DO NOT HAVE MTOCS’s
transport vacuoles
move materials between organelles, or between organelles and the plasma membrane
food vacuoles
temporary receptacles of nutrients; merge with lysosomes which break down food
storage vacuoles
plants store starch, pigments, and toxic substances (nicotine)
central vacuoles
large bodies in interior of plant cell. Fully filled and exert turgor pressure on cell walls to maintain rigidity. Store nutrients and lysosomes function (not found in plants)
contractile vacuoles
- in single-celled organisms, collect and pump excess water out of cell (prevent bursting).
- active transport
- found in Protista like amoeba and paramecia, organisms live in hypotonic environment
cell walls
- found in plants, protists, and bacterial (cellulose in plants; chitin in fungi, peptidoglycans in bacteria, polysaccharides in archea)
- provides support
- sometimes a secondary cell wall develops beneath the primary one
extracellular matrix
found in animals, in area between adjacent cells (beyond plasma membrane and glycocalyx); occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by cells
2. provide mechanical support and helps adjacent cells (collagen is most common here, also see integrin + fibronectin; network of collagen and proteoglycans connected to integrins in the cell membrane via fibronectin)
3. laminin can be seen as well (acts similar to fibronectin)
NOTE: cells adhere to the ECM in two ways
a) focal adhesions (connection of ECM to actin filaments in the cell)
b) hemidesmosomes (connection of ECM to intermediate filaments e.g. keratin)
plastids
- found in plants cells
- chloroplasts (site of photosynthesis), leucoplasts (can specialize to store starch/lipid/protein as amyloplasts/elaioplasts/proteinoplasts respectively, or serve general biosynthetic fxns)
- chromoplasts (store carotenoids)
mitochondria
- make ATP
- make fatty acid catabolism (Beta-oxidation)… fatty acids made in cytosol
- have their own circular DNA and ribosomes (endosymbiotic theory)
- have double membrane
cytoskeleton
- mictotubules (flagella and cilia), microfilaments, intermediate filaments
- in eukaryotes=aids in cell division, cell crawling, movement of cytoplasm and organelles
plant cells (hypertonic, iso, and hypo)
- hypotonic solution (less concentration of solute, more water)= normal state of plant cells, vacuole swells
- isotonic= plant cell is flaccid
- hypertonic=cell plasmolyzed (shrinks) and cytoplasm pulls away from the cell wall
- fungal cells remain turgid to due to cell wall, but animal cells will burst (cytolysis)
endomembrane system
- network of organelles and structures, either directly or indirectly connected, that function in the transport of proteins and other macro-molecules into or out of the cell
- includes plasma membrane, ER, GA, nuclear envelope, lysosomes, vacuoles, vesicles, endosomes
- NOT MITOCHONDRIA OR CHLOROPLASTS
anchoring junctions (desmosomes)
- desmosomes=kertain filaments inside attach to adhesion plaques which bind to adjacent cells together via connecting adhesion proteins, providing mechanical stability, hold cellular structures together)
- in animal cells, present in tissues with mechanical strength-skin epithelium, cervix, uterus
tight junctions
- completely encircles each cell, producing a seal that prevents the passage of materials between cell
- characteristic of cells lining the digestive tract where materials are required to pass through cells into blood
- they prevent the passage of molecules and ions through the space between cells.. so materials enter the cells by diffusion or active transport in order to pass through the tissue
- ANIMAL CELLS
gap junctions
- narrow tunnels between animal cells (connexins)
- prevent cytoplasms of each cell from mixing, but allow passage of ions and small molecules
- essentially channel proteins of two adjacent cells that are closely aligned (smooth muscle signal of spreading action potential)
- ANIMAL CELLS … tissues like the heart have these to pass electrical impulses
plasmodesmata
- narrow tunnels between plant cells (narrow tube of ER called desmotubules)
- exchange material through cytoplasm surrounding the desmotubules
eukaryotes
include all organisms except for bacteria, cyanobacteria, and archaebateria
prokaryotes
plasma membrane, DNA molecule, ribosomes, cytoplasm, and cell wall
- no nucleus
- single (circular DNA) with no proteins so no chormatin
- prokaryote ribosomes (50S+30S=70S)
- cell walls (peptidoglycan); archea (polysaccharides)-many have sticky capsules on wall
- flagella are constructed from flagellin NOT microtubules in prokaryotes
substance movement
- hypertonic=higher solute conc
- hypotonic=lower solute conc
- iso=equal solute concentration
bulk flow
collective movement of substances in the same direction in response to a force or pressure (blood pressure)
passive transport
- high to low conc without energy … simple diffusion.. molecules move randomly back and forth to establish equilibrium (so can move against gradient, but net diffusion is what we talk about)
a) osmosis
b) dialysis=diffusion of different solutes across selective permeable membrane
C) plasmolysis= movement of water out of the cell results in collapse . shrinking
d) facilitate diffusion= using channel protein .. water can move through plasma membrane but faster through aquaporins
d) countercurrent exchange= diffusion by bulk flow in opposite directions- blood and water in fish gills
active transport
- movement of transports against their concentration gradient requiring energy
- usually solutes like small ions, amino acids, monosaccharides
vesicular transport
use vesicles in cytoplasm to move macromolecues or large particles across the membrane such as…..
exocytosis
vesicles fusing with the plasma membrane and releasing their contents to the outside of cell
endocytosis
capture of substance outside of cell when plasma membrane merges to engulf it …. 3 kinds
- phagocytosis=”cellular eating”… undissolved material (solid) enter cell; white blood cell engulfs.. plasma membrane wraps around it
- pinocytosis=”cellular drinking”.. dissolved material (liquid).. plasma membrane invaginates
- receptor-mediated: form of pinocytosis; specific molecules (ligands) bind to receptors; proteins that transport cholesterol in blood (LDL) and hormones target to specific cells by this.
