eukaryotic cell ultrastructure Flashcards
what does the cell theory state
- cells are the basic unit of life
- all organisms are made up of cells
- cells arise from pre-existing cells by division
- cells contain information (DNA) used as instructions for growth, development and functioning
- chemical reaction to mantain life takes place inside cells
size comparison of cells + organelles
plant cell > animal cell > nucleus > chloroplast > mitochondria > lysozome > ribosome
major structural features of eukaryotic cells
- cell surface membrane
- nucleus
-
cytoplasm contains:
* cytosol (fluid)
* organelles
* cytoskeleton (support and mantain shape of cell)
structure of the nucleus
- double membrane
- has nuclear pores
- contains DNA
- contains one or more nucleolus
functions of the nucleus
- controls cell activity by regulating protein and enzyme synthesis
- nuclear division is the basis of cell replication
- nucleolus synthesises and partially assembles ribosomes
- synthesises DNA
structure of cell surface membrane
- phospholipid bilayer with hydrophobic tails on interior and hydrophillic heads on exterior
- phospholipid consists of a phosphate group attached to two fatty acid chains
function of cell surface membrane
- partially permeable membrane
- barrier between cytoplasm and environment
- prevents most water soluble subtances from entering or leaving cell
structures of centrioles
- cylindrical structures composed of microtubules
- two centrioles make a centrosome
- found in pairs in only animal cells or single structures
functions of centriole
- produces spindle fibers which attach to and seperate chromosomes during cell division
- forms cillia and flagella
structure of ribosomes
- no membranes
- made out of protein and RNA
- 2 subunits - large and small
- found attached to the RER or freely in cytosol
function of ribosome
site of protein synthesis
structure of endoplasmic reticulum
- found on outer nuclear envelope membrane
- consists of a network of membranous sacs called cisternae
- smooth ER has no ribosomes, rough ER has ribosomes on its surface
functions of ER (smooth and rough)
SMOOTH ER:
synthethises lipids and steroid hormones
ROUGH ER:
site of protein synthesis and transport through cisternae
structure of golgi apparatus
- consists of FLATTENED membranous sacs called cisternae
- continually being formed at cis face and continually budded off at trans face where vesicles are pinched off
function of golgi apparatus
- chemically modifies, sorts and transports molecules
- forms lysozomes
structure of lysozome
- small spherical vesicles containing hydrolytic digestive enzymes
- single membrane
function of a lysozome
- digestion of materials taken in by cell
- autophagy - digestion of worn out or improperly functioning organelles
- autolysis - self digestion of cell by releasing lysozome contents
structure of mitochondria
- double membrane
- outer membrane : smooth and continuous
- inner membrane : extesively folded to form cristae that project into the interior (matrix)
- contains circular DNA, RNA, ribosomes
function of mitochondria
releases energy via cellular respiration
structure of chloroplast
- double membrane
- outer membrane : smooth and continuous
- inner membrane : gives rise to membranes named thykaloids which extends throughout the interior
- interior has a gel like matrix called stroma
- within the stroma, thykaloids are stacked into grana and joined by the intergranal lamellae
- green, contains photosynthetic pigments
- contains DNA
function of chloroplast
site of photosynthesis
structure of a vacuole
- fluid filled bound by a single membrane
- known as vesicles in animal cells
-
large central vacuole for plant cells,
surrounded by a membrane (tonoplast) containing cell sap
functions of vacuole
- entry of water is important in cell expansion and normal water relations of plants
- hydrolytic enzymes sometimes present, can act as a lysozome
- waste products accumulate within vacuole
- some dissolved substances act as food reserves
structure of cell wall
- plant cells - made out of cellulose
- strong yet permeable to let free passage of substances in and out of cell
for PROKARYOTES :
fungi – chitin cell wall
bacteria – peptidoglycan cell wall
function of cell wall
- mechanical support
- protective layer
organelle(s) with no membrane
ribosome
organelle(s) with single membrane
- lysozome
- vacuole
organelle(s) with double membrane
- nucleus
- mitochondria
- chloroplast
organelle(s) containing DNA
- nucleus
- mitochondria
- chloroplast
organelle(s) containing RNA
- mitochondria
- ribosome
differences between animal and plant cells
-
cell wall
animal : absent
plant : present, cellulose -
lysozome
animal : present
plant : absent -
vacuole
animal : small and scattered (vesicles)
plant : large and central -
centrioles
animal : present
plant : absent -
choroplasts
animal : absent
plant : present
describe the protein secretary pathway
- ribosome bound to RER synthesises polypeptide chains into the RER
- protein is enclosed in an ER vesicle. ER vesicle containing the protein buds off from the RER
- travels and fuses with cis face of GA
- GA chemically modifies, sorts and transports the proteins. The proteins move through the GA by Golgi vesicles budding off from one cisterna and fusing with another.
- secretory vesicle containing protein buds off trans face of the GA , travels and fuses with cell membrane, hence releasing protein out of the cell.
