Midterm 1: Lec 3 Slides Flashcards
What is the largest organelle?
Nucleus
What is the nuclear envelope’s structure?
2 membranes perforated by nuclear pores
What is chromatin?
DNA combined with protein; “uncondensed” or uncoiled chromosomes
What does each chromosome contain?
One long molecule of DNA, comprising many genes
What happens at the nucleolus?
Ribosome assembly; cell may have more than one
Nucleoplasm
Fluid material within the nuclear envelope
Nuclear lamina
Network of proteins (lamins) which maintains the nucleus’s shape
When do chromosomes form the X shape?
Just prior to cell division
Where are ribosomes located?
Floating in cytoplasm, attacked to rough ER, or in energy-producing organelles (mitochondrial matrix, chloroplast stroma)
Ribosomal structure
Type of RNA with protein; has small subunit and large subunit
Endomembrane system (what is it and what’s in it)
Series of interrelated membranes and compartments in eukaryotic cells; comprises endoplasmic reticulum and Golgi apparatus (“endogolgi reticulatus”)
Why would cells have more ER?
They synthesizes proteins for export
What takes place in the smooth ER?
Hydrolysis of glycogen and steroid synthesis
Smooth vs. Rough ER - what’s the difference?
No ribosomes vs. yes ribosomes
What takes place in the rough ER?
Manufacture of proteins for export/incorporation into membranes/movement into endomembrane system organelles; also addition of short sugar chains to proteins
Regions of the Golgi apparatus
Cis region: closest to nucleus
Trans region: closer to cell surface
What happens in Golgi?
Modification, packaging, and sorting of proteins; synthesis of some polysaccharides for cell wall
Describe vesicle movement as related to the Golgi
Vesicles from rough ER fuse with cis region, and secretory vesicles are pinched off of trans region
What do signal sequences do in proteins?
Direct them to their cellular destinations
What signal sequence directs polypeptide chain to the ER?
Hydrophobic sequence of ~25 amino acids at the beginning of the polypeptide chain
Mitochondria function (specific, not just powerhouse of the cell)
Convert energy from food into ATP (energy currency of cell)
Mitochondria structure
Inner and outer membrane; inner membrane folds to form cristae
What is in the mitochondrial matrix?
Ribosomes and DNA
What does it mean if a cell has more mitochondria?
It is very active (e.g., heart muscle)
What is the size of mitochondria?
Small, similar in size to many bacteria
What is the function of plastids and where are they found? Give an example of a plastid.
- Present in plants and some protists
- Manufactures or stores food
- Example is chloroplast
Chloroplast structure
Surrounded by 2 unfolded membranes; inner membrane forms thylakoids (stack of flattened disk-like sacs)
What are stacks of thylakoids called?
Grana
Where is chlorophyll found?
Thylakoid membrane
What is in the stroma fluid and where is it?
- Located in inner membrane of chloroplast
- Contains suspended grana, ribosomes and DNA
Endosymbiotic theory
Larger prokaryotes engulfed smaller prokaryotes (aka mitochondria and chloroplasts)
Lysosome function
Participate in phagocytosis and contain hydrolytic digestive enzymes (“suicide bags”)
What replaces lysosomes in plant cells?
Large vacuoles (perform same role)
Peroxisome function (and found where?)
Use oxygen to carry out metabolic reactions like creation of hydrogen peroxide; uses other enzymes to break down molecules like H2O2; also functions in lipid breakdown
-found in plant and animal cells
Glyoxysome function (and found where?)
Break down lipids in plant cells (only found in plant cells)
Vacuole function (and found where?)
Store waste products and provide turgor (keeps plants rigid); only in plant cells
Components of primary lysosome (4) and functions?
Proteases (break down proteins), lipases (break down lipids), nucleases (break down nucleic acids), carbohydrate-digesting enzymes
How does the interior pH of lysosomes compare to the cell?
It’s acidic (pH 5.5) compared to pH 7 of normal cell - why compartmentalization is good
What lysosome problem is central to Tay Sachs disease?
Inability to break down gangliosides, a type of lipid
Autophagy
Breakdown of worn-out cell organelles
Cytoskeleton function
Maintain cell shape, facilitate cell movement, and certain fibers are “motor protein” tracks
Cell wall - which cells have it?
Plants, fungi, bacteria, and some protists
Extracellular matrix location and composition
Surrounds animal cells; composed of proteins (collagen, glycoproteins, proteoglycan)
Cytoskeleton components
Microfilaments, intermediate filaments, microtubules
What are microfilaments and what do they do?
Strands of actin; involved in movement during animal cell division, and muscle contraction
What are intermediate filaments and what do they do?
Tough, fibrous protein molecules twisted into rope-like structures - stabilize cell structure (e.g., keratin)
What are microtubules and what do they do?
Hollow cylinders composed of tubulin; involved in structure and function of cilia and flagella, centrioles, and organelle movement - important in mitotic spindle
What do dynein and kinesin (motor proteins) do?
Use energy from ATP to change their shape and move things
What structures are unique to plant cells?
Cell wall, chloroplasts, vacuoles (animal cells may have small ones)
What structures are unique to animal cells?
Flagella, centrioles, extracellular matrix (plant cells may have it)
