Unit 2 part 2 (the cell) Flashcards
All Cells Contain certain features
- bounded by plasma membrane
- contain cytosol
- chromosomes
- ribosomes
Eukaryotic vs. Prokaryotic cells
Eukaryotic:
- most of DNA is contained in the nucleus
-contain organelles
-larger
Prokaryotic:
- DNA concentrated in nucleoid, a non-membrane bound region
-smaller
cytosol
a jellylike substance in which subcellular components are suspended
ration of surface area to volume in cells
- critical
- for each section of membrane, only a limited amount of a particular substance can cross per second
- smaller objects have a greater ratio
- need for surface area large enough for volume explains microscopic size and oval like shapes of some cells
microvilli
long thin projections from the surface of a cell which increase surface area
nucleus
contains most of the genes in a eukaryotic cell
-directs protein synthesis by synthesizing messenger RNA according to DNA instructions
nuclear envelope
a lipid bilayer membrane, perforated by pores that surrounds the nucleus
pore complex
lines each pore in the nuclear envelope, regulates passage of proteins, RNA, and macromolecules
nuclear lamina
lines the nuclear side of the envelope
- net of protein filaments that maintains the shape of the nucleus by mechanically supporting the envelope
- may help organize genetic material
chromosomes
structures that carry genetic info. Each contains one DNA molecule wrapped around associated proteins
chromatin
the complex of DNA and proteins making up chromosomes
-chromosomes cannot be distinguished when cell is not dividing
nucleolus:
mass of densely stained granules and fibers in the nucleus
- location where ribosomal RNA is synthesized
- proteins are assembled with rRNA into large and small subunits of ribosomes
- exit into cytoplasm and combine
Ribosomes
complexes made of rRNA and protein that carry out protein synthesis
free ribosomes
suspended in cytosol, proteins function within cytosol, intended for cells own use
bound ribosomes
attached to ER or nuclear envelope.
-produce proteins bound for insertion into membranes, packaging into organelles, or usually export from the cell
endomembrane system
includes the nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles and vacuoles, and the plasma membrane
-carries out synthesis and transport of proteins, metabolism, movement of lipids, and detoxification of poisons
Endoplasmic Reticulum:
consists of a network of membranous tubules and sacs called cisternae
-ER membrane separates internal compertment(lumen or cisternal space) from cytosol
smooth ER
outer surface lacks ribosomes
- may function in synthesis of lipids, metabolism of carbs, detoxification of poisons, and storage of calcium ions
- produces steroids in animal cells
- detoxification involves adding hydroxyl to a group so it is more soluable
- stored calcium can trigger responses, such as muscle contraction
Rough ER
studded with ribosomes on outer surface
- ribosomes produce secretary proteins
- depart from ER in transport vesicles that bubble out of the transitional ER
- membrane factory for the cell; Adds membrane proteins and phospholipids to its own membrane and portions of it are transferred as transport vesicles to other compartments of the endomembrane system
The Golgi Apparatus
- products of ER are modified and stores and then sent to their destinations
- consists of membranous sacks
- membranes of cisternae on opposite sides of the stack differ in thickness and composition
- proteins modified as the pass from cis to trans face
- sorts products, phosphate groups added to products act as ZIP codes or transport vesicles may have membranes that recognize certain docking points
cis face of Golgi
-near ER, receiving part of Golgi
trans face of Golgi
-shipping, gives rise to vesicles that travel to other sites
cisternal maturation model
says that cisternae of the Golgi progress forward from the cis to trans face, carrying and modifying cargo as they go
Lysosome
a membranous sac of hydrolytic enzymes that an animal cell uses to digest macromolecules
-hydrolytic enzymes and lysosome are made by Rough ER then transferred to Golfi
Phagocytosis
Food vacuoles engulf smaller organisms and then fuse with lysosome whose enzymes digest the food
-digestion products pass into cytosol and are used as nutrients for the cell
autophagy
Lysosomes recycle the cells own organic material
- damaged organelle becomes surrounded by a double membrane
- lysosome fuses with outer membrane of the vesicle, enzymes dismantle enclosed material which are returned to cytosol for reuse
- allows cell to continually renew itself
Vacuoles
large vesicles derived from the ER and the Golgi
- used for storage
- in plants, can hold reserves of organic compounds, poisons, or pigments
Food vacuoles
formed by phagocytosis of microorganisms to be used as food for the cell
contractile vesicles
pump excess water out of the cells, maintaining a suitable concentration of ions and molecules
Central vacuole
found in mature plant cells
- contain cell sap- the plant cells main repository of inorganic ions
- enlarges cell as it absorbs water
mitochondria
the sites of cellular respiration, the metabolic process that uses oxygen to generate ATP by extracting energy from fuels
- cells can contain hundreds, more active the cell, the more mitochondria
- move around, change shape, and divide
Structure of mitochondria
enclosed by two membranes- outer is smooth, inner has infoldings called cristae which give this membrane a large surface area
-intermembrane space; the narrow region between the inner and outer membrane
mitochondrial matrix: contains many different enzymes as well as DNA and ribosomes
Chloroplasts
- contain chlorophyll and function in the photosynthetic production of sugar
- -move around, change shape, and divide
thylakoids
a membrane system within the chloroplast
- in some regions, stacked like poker chips
- each stack is called a granum
Stroma
in the chloroplast, fluid outside the thylakoids which contains the chloroplast DNA and ribosomes and enzymes
plastids
a family of closely related plant organelles
Peroxisome
a specialized metabolic compartment bounded by a single membrane
- contain enzymes that transfer H atoms from various substrates to oxygen creating H2O2
- some use oxygen to break down fatty acids and convert H2O2 to water
glyoxysomes
found in fat-storing tissue of plant seeds.
-convert fatty acids to sugar, which is used for energy by the seedling
Cytoskeleton
a network of fibers that organizes structures and activities in the cell
Roles of the Cytoskeleton
- gives mechanical support to cell and maintains its shape (stabilized by a balance between opposing forces exerted by elements)
- provides anchorage for organelles and molecules
- several types of cell motility involve the cytoskeleton (ex. reacts with motor proteins)
- manipulates plasma membrane- bends it inward to create vesicles
microtubles
hollow rods measuring w=25nm and l=200nm-25um
- made up of tubulin, each tubulin dimer is made up of 2 slightly different polypeptides
- grow by adding tubular dimers
- two ends are slightly different
- shape and support cell, serve as tracks
Centrosomes
a region often located near the nucleus which grows and organizes microtubles
Centrioles
located within the centrosome, composed of nine sets of triplet microtubles arranged in a ring
-replicate before animal cells divide
microfilaments
aka actin filaments
- role is to bear tension
- 3D network formed by microfilaments just inside the plasma membrane supports cell structure and gives cortex( outer cytoplasmic layer) a semisolid consistency
- part of a contractile apparatus in muscle cells
psuedopodia
cellular extensions that help an amoeba to pull itself forwards
cytoplasmic streaming
a circular flow of cytoplasm within cells; speeding the distribution of material within the cell
Intermediate filaments
larger than microfilaments but smaller than microtubules
- diverse and specialized for bearing tension
- more permanent, especially sturdy, play an important role in reinforcing the shape of the cell
actin filaments and muscle cell contraction
- myosin filament projections walk along microfilaments, shortening the cell
- similar process used to pinch dividing animal cell into two and helps amoeba motility
