2.1.4 ultrastructure of eukaryotic cells: membrane-bound organelles Flashcards
what do all eukaryotic cells have
- nucleus surrounded by nuclear envelope & contains DNA organised/wound into linear chromosomes
- area inside nucleus called nucleolus (contains RNA) where chromosomes unwind & involved in making ribosomes
- cytoplasm where organelles suspended
- cytoskeleton
- plasma membrane
- membrane-bound organelles
- small vesicles
- ribosomes -> assemble proteins
what’s a cytoskeleton
network of protein filaments within cytoplasm that moves organelles from place to place in cell, allow some cells to move & allow contraction of muscle cells
types of protein filaments (eukaryotic)
actin or microtubules
structure of nucleus, nuclear envelope & nucleolus
nucleus:
- surrounded by double membrane = nuclear envelope
- nuclear envelope has pores in
nucleolus:
- no membrane
- contains RNA
chromatin:
- genetic material -> consists of DNA wound around histone proteins
- (not dividing) chromatin = extended/spread out
- (dividing) chromatin = condense/coils tightly into chromosomes
function of nucleus, nuclear envelope & nucleolus
nuclear envelope:
- separates contents from cell
- some regions = outer/inner membrane fuse = allow dissolved substances/ribosomes to pass through
- pores enable larger substances (eg. mRNA) to leave nucleus & enable substances (eg. steroid hormones) to enter nucleus
nucleolus:
- ribosomes are made
chromosomes:
- contain organisms gene
nucleus:
- control centre of cell
- stores organism’s genome
- transmits genetic info
- provides instructions for protein synthesis
structure of rough endoplasmic reticulum
- system of membranes
–> contain fluid-filled cavities (cisternae) that are continuous with nuclear membrane - coated with ribosomes
function of rough endoplasmic reticulum
- intracellular transport system
- cisternae form channels for transporting substances around cell
- large surface area for ribosomes = assemble amino acids to proteins
- proteins then actively pass through membrane into cisternae & are transported to golgi apparatus for modification/packaging
structure of smooth endoplasmic reticulum
- system of membranes
- contain fluid-filled cavities = cisternae - continuous with nuclear membrane
- no ribosomes on surface
function of smooth endoplasmic reticulum
- contains enzymes that catalyse reactions involved with lipid metabolism
- involved with absorption, synthesis & transport of lipids (from gut)
give examples of the reactions the enzymes contained within the SER catalyse (involved w/ lipid metabolism)
- synthesis of cholesterol
- synthesis of lipids/phospholipids (needed by cell)
- synthesis of steroid hormones
structure of golgi apparatus
- consists of stack of membrane-bound flattened sacs
- secretory vesicles bring materials to/from
function of golgi apparatus
- proteins are modified
- then, proteins packaged into vesicles that are pinched off
examples of proteins modified by the golgi apparatus
- adding sugar molecules to glycoproteins
- adding lipid molecules to glycolipids
- folded into 3D shape
what happens to the proteins (in vesicles) which are pinched off the golgi apparatus
- stored in cell
OR - move to plasma membrane to be incorporated into membrane or exported outside cell
structure of mitochondria (single = mitochondrion)
- spherical, rod-shaped or branched
- 2-5 micrometres long
- surrounded by 2 membranes with fluid-filled space between
- inner membrane folded into cristae
- inner part of mitochondrion is fluid-filled matrix