Structure of Cells Flashcards
surface-area-to-volume-ratio
requires that cells be small
large cells- decreases the efficiency of transporting material in and out of cells
Small cells-large surface area to volume ratio is beneficial for exchanging molecules
compound light microscope
-maximum magnification of 1000x
-light passes through and is focused by glass lenses
transmission electron microscope (TEM)
- electrons are passed through and focused by a set of magnetic lenses
-100,000x
scanning electron microscope (SEM)
-sprayed within a thin coat of metal
- electron beam is scanned across the surface, the surface metal emits secondary electrons
-electrons are detected and focused by magnetic lenses
Prokaryotic cells
-lack membrane-bound nucleolus
-structurally smaller and simpler
-bacteria and archaea
bacteria vs archaea
bacteria: causes diseases and acts as decomposers.
archaea: live in extreme habitats.
structure of prokaryotes
1.spherical coccus
2. rod-shaped bacillus
3. spiral spirillum (if rigid) or spirochete (if flexible)
cell envelopes of prokaryotes include
plasma membrane- lipid bilayer with embedded and peripheral proteins
cytoplasm
-semifluid solution
-contains water, inorganic and organics molecules and enzymes
nucleoid
a region that contains the single, circular DNA molecule
plasmids
small accessory (extrachromosomal) rings of DNA
Ribosomes
tiny structures in the cytoplasm that synthesize proteins
flagella
provides motility
fimbriae
small, bristle-like fibers that sprout from the cell surface
conjugation pili
rigid tubular structures used to pass dna from cell to cell
Eukaryotic cells
contains a plasma membrane that separates cell content and regulates passage of materials in and out
-membrane bound nucleus that houses DNA
-contains organelles that isolate reactions from other reactions
Eukaryotic cell organelles are divided into 4 categories…
- nucleus and ribosomes
-endomembrane system
-energy related organelles
-cytoskeleton
Chromatin
network of fine strands that are composed of DNA, proteins, and some rna
types of RNA
Messenger (mRNA)- carries the information for the amino acid sequence of a protein
Ribosomal (rRNA)- combines with specific proteins to form the subunits of ribosomes
what separates the contents of the nucleus from the cytoplasm?
nuclear membrane
what do nuclear pores do?
permits the passage of ribosomal subunits and mRNA out of the nucleus and proteins into the nucleus
ribosome subunits
one large and one small are assembled in the cytoplasm and used to make proteins
where are ribosomes found?
-prokaryotes and eukaryotes
-eukaryotic cells: single ribosomes in the cytoplasm. Attached to the endoplasmic reticulum (ER)
ribosomes proteins
-used in different parts of the cells
-proteins from free ribosomes are used in the cytoplasm
-proteins from ribosomes attached to the ER are deposited in the ER
endomembrane system components
- nuclear membrane
- endoplasmic reticulum
- Golgi apparatus
- vesicles
what are Saccules?
membranous channels and flattened vesicles found in the ER
what does the golgi apparatus consist of and do?
consist of numerous flattened saccules
receives protein transport vesicles from the er and packages them in new vesicles
-directs the new vesicles to the location intended for the protien
what are lysosomes
Golgi vesicles which contain proteins that digest molecules or structures within the cell
what are vacuoles?
membranous sacs that are larger than vesicles
-vacuoles can store nutrients, ions, or other molecules
two types of membranous organelles that specialize in energy conversion are…?
chloroplast: uses solar energy to synthesize carbohydrates via photosynthesis
mitochondria: breaks down carbohydrates to produce ATP
what does the stroma contain?
-enzymes for photosynthesis
-a third set of membranes, organized as a series of disk like sacs called thylakoids
How are thylakoids organized?
stacks or grana
what is the matrix?
where chemical reactions products end up
how is cristae formed and what does it do?
the convolutions of the inner membrane in the mitochondria form cristae
-increases surface area
cellular respiration
the breakdown of molecules in the presence of oxygen to produce ATP
what are microtubules?
proteins arranged to form hollow cylinders
-assembled by the centrosome
what are intermediate filaments and what do they do?
intermediate in size between actin filaments and microtubules -ropelike polypeptides support the nucleolus and plasma membrane
what are centrioles and what do they do?
short cylinders with a 9+0 pattern of microtubules triplets
-involved in cell division
cilia and flagella
hairlike projections that allow organisms to move
-both are membrane-bound cylinders
-both have a basal body in the cytoplasm
