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
- nucleolus (contains RNA), inside nucleus, where chromosomes unwind & involved in making ribosomes
- cytoplasm where organelles suspended
- cytoskeleton
- plasma membrane
- membrane-bound organelles
- small vesicles
- ribosomes which assemble proteins
what’s a cytoskeleton
network of protein filaments (actin/microtubules) 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
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
(summary) nucleus:
- control centre of cell
- stores organism’s genome
- transmits genetic info
- provides instructions for protein synthesis
nuclear envelope:
- separates contents of nucleus from cell
- outer/inner membrane fuse in some regions = 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
structure of rough endoplasmic reticulum (RER)
- system of membranes
–> contain fluid-filled cavities (cisternae) that are continuous with nuclear membrane - coated with ribosomes
function of rough endoplasmic reticulum (RER)
- intracellular transport system
- cisternae form channels for transporting substances around cell
- large surface area for ribosomes to 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 (SER)
- system of membranes
- contain fluid-filled cavities (cisternae) continuous with nuclear membrane
- no ribosomes on surface
function of smooth endoplasmic reticulum (SER)
- contains enzymes that catalyse reactions involved with lipid metabolism
- involved with absorption, synthesis & transport of lipids (from gut)
examples of reactions the enzymes in the SER catalyse
- 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
- 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 (exocytosis)
structure of mitochondria (single = mitochondrion)
- spherical, rod-shaped or branched
- surrounded by 2 membranes with fluid-filled space between
- inner membrane folded into cristae
- inner part of mitochondrion is fluid-filled matrix
function of mitochondria
- site of ATP production (aerobic respiration)
- self-replicating so more made if energy demand increases
- abundant in cells where much metabolic activity occurs
structure of chloroplasts
- large
- only in plant cells/some protoctists
- surrounded by double membrane/envelope
- inner membrane continuous with stacks of flatted membrane sacs (thylakoids) which contain chlorophyll
- each stack/pile of thylakoids is called a granum
- fluid-filled matrix = stroma
- contain loops of DNA & starch grains
plural of granum
grana
function of chloroplasts
- site of photosynthesis
- 1st stage of photosynthesis occurs in grana & water split to supply H ions
- 2nd stage occurs in stroma
- abundant in leaf cells
what part of the leaf are chloroplasts abundant in
palisade mesophyll layer
structure of vacuole
- surrounded by membrane = tonoplast
- contains fluid
function of vacuole (plant cells)
- large & permanent vacuole
- filled with water/solutes
- maintains cell stability: full = pushes against cell wall, making cell turgid
- turgid = support plant (especially non-woody plants)
structure of lysosomes
- small bags formed from golgi apparatus
- surrounded by single membrane
- contain powerful hydrolytic enzymes
- abundant in phagocytic cells which ingest/digest invading pathogens
another word for hydrolytic
digestive
function of lysosomes
- keep powerful hydrolytic enzymes separate from rest of cell
- can engulf old cell organelles/foreign matter, digest & return digested components to cell for reuse
structure of cilia/undulipodia
- protrusions from cell
- surrounded by cell surface membrane
- contain microtubules
- formed from centrioles
function of cilia/undulipodia
- epithelial cells lining airways beat/move band of mucus via cilia
- nearly all cell types in body have 1 cilium acting as an antenna which contains receptors & allows cells to detect signals about immediate environment
- only type of human cell with undulipodium = spermatozoon –> enables it to move
