Eukaryotic and Prokaryotic cells Flashcards
Nucleus, nuclear envelope and nucleolus structure
The nucleus surrounded by double membrane (nuclear envelope) containing pores
Nucleolus contains RNA (no pores)
Chromatin
Genetic material consisting of DNA wound around histone proteins
When cell is not dividing, chromatin is spread out/extended
When cell is about to divide, chromatin condenses and coils tightly into chromosome
Nucleus, nuclear envelope and nucleolus functions
Nuclear envelope separates contents of nucleus from rest of the cell
outer and inner nuclear membranes fuse together- dissolved substances and ribosomes can pass through
pores enable large structures eg. mRNA to leave nucleus
substances can enter the nucleus from the cytoplasm via pores
nucleus controls centre of the cell, stores organisms genome, transmits genetic info, provides instructions for protein synthesis
vesicles
a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer
form naturally during the processes of secretion, uptake, and the transport of materials within the plasma membrane.
Rough endoplasmic reticulum structure
System of membranes containing fluid filled cavities (cisternae) that are continous with the nuclear membrane
Coated with ribosomes (hence its roughness)
RER functions
transport system: cisternae form channels transporting substances from one area of cell to another
large SA for ribosomes which assemble amino acids into proteins
proteins actively pass through membrane into cisternae and are transported to golgi apparatus for modification and packaging
Smooth endoplasmic reticulum structure
system of mmebranes containing cisternae that are continuous with the nuclear membrane
no ribosomes on surface
SER functions
contains enzymes that catalyse reactions such as:
synthesis of cholesterol, synthesis of lipids/phospholipids, synthesis of steroid hormones
involved with absorption, synthesis, and transport of lipids (from gut)
Golgi apparatus structure
stack of membrane-bound flattened sacs
secretory vesicles bring materials to and from the golgi apparatus
Golgi apparatus function
Proteins are modified by:
adding sugar molecules to make glycoproteins
adding lipid molecules to make lipoproteins
being folded into their 3D shape
The proteins are packaged into vesicles that are pinched off and then:
stored in the cell
moved to plasma membrane
Mitochondria structure
Spherical, rod-shaped or branched, and are 2-5µm
surrounded by two membranes with a fluid-filled space between them
inner membrane is highly folded into cristae
inner part of the mitochondrion is fluid-filled matrix
Mitochondria function
site of ATP (energy currency) production during aerobic respiration
self-replicating, so more can be made if the cell’s energy needs to increase
abundant in cells where metabolic activity takes place
Chloroplasts structure
large organelles, 4-10µm
surrounded by double membrane/envelope
inner membrane is continuous with stacks of flattened membrane sacs (thylakoids) containing chlorophyll
contains loops of DNA and starch grains
chloroplasts function
site of photosynthesis
abundant in leaf cells- particuarly the palisade mesophyll layer
Vacuole structure
surrounded by a membrane (tonoplast) containing fluid
vacuole function
filled with water and solutes and maintains cell stability
only plant cells have permanent vacuoles
Lysosomes structure
small bags formed from the golgi apparatus
surrounded by a single cell membrane
contains powerful hydrolytic (digestive) enzymes
Lysosome function
Keeps hydrolytic enzymes separate from rest of cell
engulfs old organelles and foreign matter, and digests them, returning digested components to the cell for reuse
Cilia and undulipodia structure
protrusions from cell surrounded by cell surface membrane
contains microtubules
formed from centrioles
Cilia and undulipodia function
cilia beats and moves band of mucus in epithelial cells
cilium contains receptors that allows the cell to detect signals in its immediate environment
ribosome structure
non-membrane bound
small spherical organelles, 20nm in diameter
made of ribosomal RNA
made in nucleolus, passes through nuclear envelope into cell cytoplasm
ribosome function
bound to exterior of RER to synthesise proteins
ribosomes free in cytoplasm are the site of assembly of proteins used inside cell
Centriole structure
non-membrane bound
does not contain DNA
two bundles of microtubules at right angles to eachother
microtubules made of tubulin an protein subunits, arranged to form a cylinder
Centriole function
involved in formation of cilia and undulipodia
organises microtubules that serve as the cell’s skeletal system
help determine the locations of the nucleus and other organelles within the cell.
cytoskeleton structure
non-membrane bound
network of protein filaments (actin or microtubules) within cytoplasm
rod-like microfilaments made of subunits of protein actin (7nm in diameter)
intermediate filaments 10nm in diameter
straight, cylindrical microtubules made of protein subunits (tubulin) 18-30nm in diameter
cytoskeleton function 1
move organelles within the cell, allow some cells to move, and allow contraction of muscle cells
keeps cell shape stable
microtubules provide shape and support to cells and help substances and organelles move through cytoplasm
form the spindle before a cell divides, enabling chromosomes to be moved within the cell
cytoskeleton function 2
microtubules make up cilia, undulipodia and centrioles
enables cell to cell signalling, allowing cells to adhere to a basement membrane and stabilises tissues
intermediate filaments are made of a variety of proteins which anchor the nucleus within the cytoplasm, extend between cells in tissues and special junctions
cellulose cell wall structure
non-membrane bound
on the outisde of plasma membrane
made from bundles of cellulose fibres
cellulose cell wall function
prevents plant cells from bursting when turgid
provides plant cells with strength and support, maintenance of cell shape, strength and support of plant, permeable and allows solutions to pass through
prokaryotic cell wall structure
made of peptidogylcan instead of cellulose
How are proteins made and secreted (using example of how insulin is made in beta cells)
mRNA copy of instructions (gene) for insulin is made in the nucleus
mRNA leaves nucleus though nuclesr pore
mRNA attaches to ribosome (eg on RER)
ribosome reads instructions to assemble protein
insulin molecules are ‘pinched off’ in vesicles and travel to golgi apparatus
vesicles fuse with golgi apparatus
golgi apparatus processes and packages insulin molecules for release
packaged insulin molecules are pinched off in vesicles from golgi apparatus and move towards plasma membrane
vesicles fuse with plasma membrane
plasma membrane opens to release insulin molecules outside
comparing prokaryotic and eukaryotic cells (similarities)
both have:
plasma membrane
cytoplasm
ribosomes for assembling amino acids into proteins
DNA and RNA
comparing prokaryotic and eukaryotic cells (differences)
prokaryotic cells are much smaller
P cells have a less well-developed cytoskeleton with no centrioles
P cells have no nucleus
P cells have no membrane-bound organelles, eg. mitochrondria, endoplasmic reticulum, chloroplasts or golgi apparatus
P cells have a wall made of peptidoglycan (not cellulose)
have smaller ribosomes
naked DNA not wound around histone proteins
Prokaryotic cells (extra structures)
waxy capsule surrounding cell wall
small loops of DNA (plasmids) and a main large loop of DNA
flagella- allows bacteria to move (structure differs from eukaryotic undulipodia)
pili- smaller hair-like projections that enable bacteria to adhere to host cells or to eachother, and allow passage of plasmid DNA from one cell to another
By what process do prokaryotic cells divide
Binary fission
