Unit 2: Cell Structure & Function Flashcards
prokaryotic cells
- include bacteria
- genetic material is a circular chromosome located in the center of the cell in the nucleoid region
- can contain extra genetic material outside of the chromosome, which is held in small circular pieces of DNA called plasmids
eukaryotic cells
- contain membrane-bound organelles; more complex than prokaryotic
- DNA packaged into linear chromosomes that are contained in a membrane-bound nucleus
all cells
contain genetic material, ribosomes, cytosol, and a plasma membrane
ribosomes
- protein synthesis
- made of proteins and ribosomal RNA
- large subunit + small subunit
- ribosomes assemble amino acids into polypeptide chains during translation
- free ribosomes are found in the cytosol; bound ribosomes in eukaryotes are found on the rough ER membrane
endoplasmic reticulum
- series of membrane channels in eukaryotes
- rough ER: ribosomes bound to its membranes; protein synthesis
- smooth ER: lipid synthesis and detoxification of harmful substances
Golgi complex
- stack of flattened membrane stacks
- lumen: interior of each cisterna; contains enzymes
- controls modification and packaging of proteins for transport
- proteins made on rough ER are sent to the complex, then they’re modified at the Golgi and packaged into vesicles for transport
lysosomes
- animal cells
- membrane-bound sacs containing hydrolytic enzymes
- digestion of macromolecules, breakdown of unnecessary parts, apoptosis, destruction of bacteria/viruses
vacuole
- food or water storage, water regulation, waste storage
- occupy majority of cells in well-hydrated cells
- provide plant cell with turgor pressure and support by filling space
mitochondria
- produce energy (ATP) for cell
- double membranes with smooth outer membrane and folded inner membrane
- folds increase surface area available for energy production during cellular respiration
- double-membrane allows for creation of proton gradient necessary for ATP gradient
- center of mitochondria: matrix, where Krebs (citric acid) cycle
- contain their own DNA, called mtDNA
chloroplasts
- found in plants and algae
- carry out photosynthesis
- double membranes with smooth outer membrane and pancake-shaped membranous sacs called thylakoids
- thylakoids stacked into structures called grana, which are surrounded by liquid called stroma
- thylakoids function in light-dependent reactions of photosynthesis, enzymes in stroma function in light-independent reactions of photosynthesis
- contain their own DNA, called cpDNA
centrosome
- found in animal cells
- helps microtubules assemble into spindle fibers needed in cell division
- defects in centrosome can be associated with dysregulation of the cell cycle
amyloplasts
- plant cells
- excess glucose produced by photosynthesis is stored as starch molecules here
- frequently found in root and tubers of starchy vegetables
peroxisome
- plant and animal cells
- oxidize molecules and break down toxins
nucleolus
- plant and animal cells
- NOT membrane-bound
- region in nucleus where ribosomes are assembled
cytoskeleton
- fibers give cells shape and can move things in the cell
endosymbiosis hypothesis
- membrane-bound organelles (like mitochondria and chloroplasts) were once free-living prokaryotes that were absorbed into larger prokaryotes
- these prokaryotes became interdependent on each other; smaller engulfed prokaryotes evolved to become membrane-bound organelles
- EVIDENCE: mitochondria and chloroplasts have their own DNA, which is similar to prokaryotic DNA; mitochondria and chloroplasts have their own ribosomes, which are similar in structure to prokaryotes; mitochondria and chloroplasts reproduce through binary fission like bacteria
advantages of compartmentalization
- different processes in different parts of the cell
- minimizes risk of enzymes and molecules from different processes cross-reacting, which would hurt efficiency
- internal folded membranes in some eukaryotes provides greater surface area for reactions to occur
- folded membranes of prokaryotes create more surface area
surface area to volume ratio (SA:V)
- all materials exchanged between a cell and its environment must pass through the cell’s surface area
- as the size of the cell increases, SA:V decreases; eventually cell’s ability to exchange materials will be limited
- larger cells have lower SA:V ratio and less efficient exchange of materials; smaller cells have higher SA:V ratio and more efficient exchange of materials
- SA:V can be increased by folding membranes
plasma membranes
- help maintain an optimal internal environment
- selectively permeable: some materials can cross and some can’t, which protects the cell
- made of phospholipid bilayer of hydrophilic heads and hydrophobic tails; heads face aqueous environment
- embedded with glycoproteins, glycolipids, and steroids, which can flow throughout the membrane
- proteins in membrane can transport materials, help with cell signaling, anchor cell to surroundings, and catalyze reactions
glycoproteins and glycolipids
found in membrane, function in cell recognition
steroids
found in membrane, adjust membrane fluidity in response to changing environment
fluid mosaic model
- structure of the plasma membrane
- selective permeability: small hydrophobic molecules can pass through, while large polar or ionic molecules cannot unassisted
cell wall
- in plants, fungi, and prokaryotic cells
- surrounds the cell membrane
- provides rigidity to the cell and is an added barrier for substances entering/exiting the cell
passive transport
movement of molecules from areas of higher concentration to lower concentration; moves molecules “down” the gradient; does not require energy
diffusion
movement of molecules down concentration gradient without energy
osmosis
diffusion of water down its concentration gradient
facilitated diffusion
passive transport for polar or charged molecules using a membrane protein; ex. aquaporins allow large quantities of water to move down their gradient; rate of facilitated diffusion is limited by the number of membrane proteins available
channel proteins
can be used for passive transport of ions
active transport
moves molecules from areas of low concentration to high concentration; movement “against” the gradient that requires energy input; ex. sodium potassium pump that pumps Na+ to area of their higher concentration while pumping K+ to area of their lower concentration to maintain cell’s membrane potential
endocytosis
used by cell to take in water and macromolecules by enfolding them into vesicles formed from plasma membrane; requires energy
exocytosis
vesicles containing molecules are fused with plasma membrane, expelling molecules from the cell; requires energy
water potential
- potential energy of water in a solution/the ability of water to do work
- focuses on concentration of water in solution
- the more water, the higher the water potential
- water flows from areas of high water potential to areas of lower water potential
- not relative
hypotonic solution
lower concentration of solute (relative)
hypertonic solution
higher concentration of solute (relative)
isotonic
same concentration of solute as that of another solution (relative)
solute potential
water potential due to solute concentration
pressure potential
water potential due to pressure potential
ionization constant
- i
- how many particles/ions a solute will form in a solution
concentration of solute
- C
- if concentration of solute increases, solute potential decreases
- solutions with higher concentration of solute will have lower water potentials
pressure constant
- R
- 0.0831
osmolarity
total concentration of solutes in a solution; living organisms must closely regulate their internal solute concentration and water potential to avoid death
contractile vacuole
organelle found in some organisms used to store excess water and pump it out of the cell to regulate water potential and solute concentration
