Chapter 4 - general features of the cell Flashcards
which monomers of macromolecules were produces prior to the existence of cells?
nucleotides and amino acids
four overlapping stages @ origin of life
- nucleotide and amino acids produces prior to the existence of cells
- nucleotides and amino acids polymerized into DNA, RNA, and proteins
- likely formed on clay surfaces (not aqueous solution) - aggregate of prebiotic molecules became enclosed in membranes
- Polymers enclosed in membranes acquired cellular properties
which macromolecule were the first of protobionts (non-living organic molecules in a membrane)
RNA
Advantages of a DNA, RNA, and protein world
- evolution of DNA relieves RNA of informational role and allowed RNA to perform other functions
- DNA less likely to undergo mutations
- Protein have a greater catalytic potential and efficiency (better for metabolic functions)
- proteins also useful for structure and transport
cell theory
- all living organisms are composed of one or more cells
- cells are the smallest units of life
- new cells come only from pre-exiting cell by cells division
3 visual adjustments in microscopy
- resolution
- the ability to observe two adjacent objects as distinct from one another - contrast
- how different structures look from one another
- can be enhanced by special dyes (most cells are transparent, many dyes have an affinity to the nucleus) - magnification
- ratio between the size of an image produced by a microscope and its actual size
two kinds of microscopes
- light microscope
- 0.2 micrometer resolution (200nm)
- election microscope
- 2nm resolution (100x better than light)
two methods of fluorescent microscopy
- standard - used to specifically label a particular type of protein or organelle
- confocal - computer takes image in slices so its less blurry
two types of electron microscopes
- Transmission electron microscopy (TEM)
- bean of electrons transmitted through sample
- thin slices stained with heavy metals
- some electrons are scattered while others pass through to form an image - scanning electron microscopy (SEM)
- sample coated with heavy metal and beam scans surface to make 3D image
prokaryotes
- simple cell structure with DNA but no nucleus (nucleoid)
- aren’t very complicated but can still be interesting (extremophiles)
- 1-10 micrometers in diameter
- about 10x smaller than eukaryotes
eukaryotes
- DNA enclosed within membrane-bound nucleus (double membrane)
- internal membranes form organelles
how polar vs non polar molecules get through the membrane
- polar molecules use transmembrane proteins
- non polar molecules can diffuse through the membrane
two types of prokaryotes
- bacteria
- very abundant in the environment and our body
- vast majority is not harmful to humans but some can cause disease - archaea
- less common
- often found in extreme environments
parts of bacterial cell
inside plasma membrane
- cytoplasm
- nucleoid region
- ribosomes
outside plasma membrane
- cell wall
- glycocalyx
- pili and flagella
cytoplasm
all substance between the plasma membrane and the nucleus
cytosol
fluid part of the cytoplasm
nucleoid region
part of prokaryotic cells where DNA congregates
ribosomes
site of protein synthesis
cell wall
provides support to plant cells
glycocalyx
- gel-like material that is sticky and allows cells to adhere to surfaces to live on
- helps protect the cell, especially from pathogens
cell appendages
- pilli (attachment)
- flagella (movement)
characteristics of eukaryotic cells
- DNA housed inside membrane-bound nucleus
- organelles
- variety in shape, size, and function
- compartmentalization - allows for more specialization
oganelles
membrane-bounds compartments found in eukaryotic cells that have a unique structure and function
how does cell morphology vary?
- eukaryotic cells have lots of variation and shape
- even cells with the same genome can have different morphologies
- ex: brain cells are designed so they can have lots of contact with other cells
what do plant cells have that animal cells don’t?
- Central Vacuole - provides storage for waste and regulation of cell volume (prevents lysing)
- cell wall - provides support to the cell
- chloroplast - makes sugar that the cell breaks down for energy
Centrosome
site where microtubules grow and centrioles are found
nuclear pore
passage way for molecules into and out of the nucleus
nucleus
area where most of the genetic material is organized and expressed
nuclear envelope
- double membrane that encloses the nucleus
- nuclear pores provide passageways
nucleolus
- part of nucleus
- site for ribosome subunit assembly
chromatin
- part of nucleus surrounding the nucleolus
- chromatin - a complex of protein and DNA
nuclear envelope
double membrane that encloses the nucleus
lysosome
- site where macromolecules are degraded
- contains acid hydrolase that perform hydrolysis (varies depending on what you are breaking down)
- autophagy - breakdown of dead organelles via endocytosis
ribosome
site of polypeptide synthesis
plasma membrane
- membrane that controls movement of substances into and out of the cell
- site of cell signaling using receptors
- boundary between the cell and extracellular env.
cytosol
- fluid part of the cytoplasm
- site of many metabolic pathways, including catabolism and anabolism
cytoplasm
all substance between the plasma membrane and the nucleus, including organelles
Golgi apparatus
- site of modification, sorting, and secretion of lipids and proteinsn from the ER
- stack of flattened, membrane-bounded compartments
- vesicles transport materials between stacks
- cis, medial, and trans sides
peroxisome
- catalyzes reactions that break down molecules by removing hydrogen or adding oxygen
- uses catalase to break down byproduct hydrogen peroxide (H2O2)
cytoskeleton
- protein filaments that provide shape and aid in movement
mitochondrion
- site of ATP synthesis
- highly envaginated inner membrane
- high concentration of protons in inter membrane space
- need active transport to get there
smooth ER
- site of detoxification and lipid synthesis
- performs diverse metabolic processes
- liver cells have lots of smooth ER
rough ER
- ribosomes embedded in membrane
- site of protein sorting and secretion
- overrepresented in neurons
central vacuole
- site that provides storage
- regulation of cell volume
chloroplast
- site of photosynthesis
- use light energy to make glucose
proteomes
- the part of DNA that is expressed
- relevant to disease
determines:
-which proteins and subtypes of proteinsare produced
-the levels of expression
post-translational modifications
catabolism
breakdown of a molecule into smaller components
anabolism
synthesis of cellular molecules and macromolecules
microtubules
- long, hollow cylindrical structures, about 25nm
- dynamic instability (alternating periods of rapid growth and shrinking)
- emerge from centrosome
- can serve as transport lanes
- organization of organelles
intermediate filaments
- 10nm twisted, ropelike structure
- provide mechanical strength
- anchorage of cell and nuclear membranes
actin filaments/microfilaments
- 5/7nm
- long, thin fibers
- distributed more towards the periphery
- give sell shape and strength
- used in muscle contraction
- intracellular movement of cargo
motor proteins
- three domains - head, hinge and tail
- “walk” along cytoskeleton
the kinds of motor protein movement
- motor protein carries cargo along filament
- motor protein remains in place and the filament moves
- protein and filament both restrained - action of motor protein exerts a force that bends the filament
- muscle contraction
flagella
- relatively long cell appendages that help cellular movement or movement of extracellular fluids
- typically found singly or in pairs
cilia
- realatively short extracellular appendages
- facilitate cells movement
- more numerous than flagella
8 parts of the endomembrane system
*not materials within the nucleus
- nucleus
- nuclear envelope
- lysosome (animal)
- peroxisome
- vacuole (plant)
- endoplasmic reticulum
- Golgi apparaturs
- plasma membrane
How is the endomembrane system connected
can be directly connected to each other or pass materials via vesicles
describe the synthesis path of ribosomes
- assembled in the nucleolus
- transported out through nuclear pores
- can either float around int he cytosol or attach to rough ER
three types of vacuoles
- central vacuoles
- in plants for storage and support - contractile vacuoles
- in protists for explain excess water - phagocytic vacuoles
- in protists and white blood cells for degradation
three main functions of transmembrane proteins
- cell signaling
- cell adhesion
- membrane transport
what are the two semiautonomous organelles and what are their features
- mitochondria and chloroplasts
- grow and divide to reproduce on their own
- divide by binary fission
- depend of the cell for synthesis of internal components
- carry their own DNA - used to be fully autonomous
Endosymbiosis in chloroplasts and mitochondria
- in evolutionary history, bacteria took up residence in primordial eukaryotic cells and later became mitochondria and chloroplasts
- mitochondria come from proteobacteria
- chloroplasts come from cyanobacteria
what are the three ways proteins are sorted?
- remain in cytosol
- cotranslational sorting
- post-translational sorting
cotranslational sorting (5 steps
- for ER, Golgi, lysosomes, vacuoles, plasma membrane, and secreted proteins
1. SRP bings to ER signal sequence and pauses translation
2. SRP binds to receptor in ER membrane
3. SRP is released and translation resumes
4. ER signal sequence is cleaved by signal peptidase
5. polypeptide is completely synthesized and released into the ER lumen
SRP
- signal recognition particle
- recognizes and binds to ER signal sequence to in cotranslational sorting
Post-translational sorting (8 steps
- most proteins for nucleus, mitochondria, chloroplasts, and peroxisomes
- synthesized in cytosol and taken up by target organelle
- short amino acid sequence directs the protein to its target where it is taken up from the cytosol
chaperones
- prevent amino acid sequence from folding during post-translational sorting
four interacting parts of the eukaryotic cell
- nucleus
- cytosol
- endomembrane system
- semiautonomous organelles
clathryn
protein coating that surrounds vesicles during nedo and exocytosis to keep it round