Eukaryotic cells Flashcards
Advantages of compartmentalization
-efficiency of metabolism
-localized conditions
-toxic/damaging substances can be isolated
-numbers and locations of organelles can be changed, dependent on the cells requirments
Determinants
- Contain a nucleus
- Compartmentalized by membrane-bound structures (organelles) that preform specific roles
4 kingdoms
1) Protista
2) Fungi
3) Plantae
4) Animalia
Protista
unicellular but multicellular without a specialized tissue
Fungi
have cell wall made of chitin and obtain nutrition via heterotrophic absorbtion
Plantae
have cell wall made of cellulose and obtain nutrition autrotrophically (photosynthesis)
Animalia
no cell wall, obtain nutrition via heterotrophic ingestion
Nucleus
-spherical with double membrane
-pores in the membrane
-genetic info in the form of chromosomes (DNA, histone proteins)
-mRNA is transcribed
mRNA leaves the nucleus via the pores (DNA is too large)
-uncoiled
-chromosomes are referred as chromatin
Mitochondrion
-double membrane
-smooth outer membrane and folded inner membrane
-the folds are reserved to as cristae
-variable in shape
site of ATP production by aerobic respiration (if fat is used as a source of energy it is digested here)
Free ribosomes
-80S ribosomes 20nm (larger)
-dark granules in the cytoplasm
-no membrane
-synthesizes the proteins to function in the cytoplasm, for use within the cell. eg; enzymes
Rough endoplasmic reticulum (rER)
-flattened membrane sacs, called cisternae
-often located near the nucleus
-80S ribosomes are attatchted to the outside of the cisternae
-rER synthesizes proteins which are transported, by vesicles, to the golgi apparatus for modification before secretion outside the cell
Smooth rER
-no ribosomes present
Golgi apparatus
-This organelle also consists of flattened membrane sacs called cisternae, like rER.
–Different to rER:
–No attached ribosomes
–Often sited close to the plasma membrane
-The cisternae are shorter and more curved that those of the rER
-The Golgi apparatus processes (modifies) proteins from from the rER. The proteins are then repackaged in vesicles for secretion outside the cell.
Vesicles
-a single membrane with fluid inside
-very small in size
-used to transport materials inside the cell
Lysosomes
-spherical with a single membrane
-formed from golgi vesicles
-contain digestive enzymes for breakdown of: ingested food in vesicles, unwanted/damaged organelles, the cell itself
-high concentration of enzymes cause this organelle to stain heavily and hence appear dark on micrographs
Vacuoles
-single membrane with fluid inside
-in plant cells vacuoles are large and permanent, often occupying the majority of the cell volume
-in animal cells vacuoles are smaller and temporary and used for various reasons, e.g. to absorb food and digest it
Flagellum
-thin protection (often singular) from the cell surface
-contain microtubules
-used to move the cell
Cilia
-Thin projections from the cell surface
-Contain microtubules
-Used to either move the cell or to move the fluids next to the cell
Microtubules
-Small cylindrical fibres called microtubules
-Have a variety of functions, e.g. part of the structure of flagella and they play a role in cell division
Centrioles
-Consist of two groups of nine triple microtubules
-Are mainly found in animal cells, not present in vascular plants or fungi.
Function of the palisade cells in the leaf mesophyll
-Where most of the photosynthesis occurs in the leaf
-contain a lot of chloroplasts to help them perform this photosynthesis
-are closely packed to optimize light absorbtion
Chloroplast
-A double membrane
-Inside are stacks of thylakoids
-Each thylakoid is a disc composed of a flattened membrane
-The shape of chloroplasts is variable but is usually ovoid
-The site of photosynthesis and hence where glucose is produced.
-Starch grains maybe present if photosynthesis is happening quickly
Cell wall
-an extracellular component not an organelle.
-secreted by all plant cells (fungi and some protists also secrete cell walls).
-Plant cell walls consist mainly of cellulose which is:
–Permeable
–Strong
–Hard to digest
