Biology - 2.1.1 - structure of eukaryotic cells
what are the key features of eukaryotic cells
genetic material held in a membrane bound nucleus
dna tightly wrapped around histones, forming chromosomes
dna is a linear molecule, not looped
most organelles are membrane bound
which organelles are membrane bound?
golgi apparatus, endoplasmic reticulum, mitochondria, nucleus, vacuole, chloroplasts
which organelles arent membrane bound
80s ribosomes
what are the key features of prokaryotic cells
much smaller than eukaryotes
no membrane bound organelles so dna is found in cytoplasm
dna is arranged as a loop or as a plasmid
70s ribosomes
slime capsule to prevent phagocytosis
what is the role of the nucleus in protein synthesis
contains the genes needed for protein synthesis to transcript to mRNA, which is translated by a ribosome and synthesised.
what is nucleoplasm
substance containing nucleotides and enzymes needed for DNA and RNA synthesis
what is the nuclear envelope
the double membrane surrounding the nucleus. consists of 2 phospohipid bilayers
what are nuclear pores
small gaps which allow molecules to enter and leave the nucleus, such as RNA nucleotides entering from cytoplasm
what is chromatin
consists of dna coiled around proteins called histones, forming chromosomes.
what is the nucleolus
ribosomal RNA is produced here, which forms part of ribosome structure and is where ribosome subunits are assembled
what are cisternae
flattened saces of membranes which contain a range of different enzymes
what is the function of the rough ER
cisternae studded with ribosomes that synthesise proteins, which are then modified in the RER by addition of carbohydrates to form glycoproteins or changing of polypeptide chain, to be exported by golgi apparatus
what is the function of the smooth ER
cisternae not studded with proteins, processes lipids and carbohydrates
what is the function of the golgi apparatus
allows for further modification of polypeptides, transports functional proteins from RER to cell membrane in vesicles, which fuse with and secrete from the cell membrane
what is the structure of the golgi apparatus
series of flattened stacks of membranes as an extension of the ER
what do lysosomes contain and what do they do
contains powerful digestive enzymes that digest larger molecules into smaller ones
why do lysosomes have a low pH
lysosomal enzymes have an acidic optimum pH
what role do lysosomes have in phagocytosis
lysosomal enzyms digest bacterium that has been engulfed by a white blood cell
what is the function of a lysosome
can destroy damaged or not functional organelles. they fuse with the vacuole membrane and digest the organelle. they transfer their enzymes vie exocytosis outside the cell to digest unwanted proteins/dead cells
what is the function of mitochondria
site of aerobic respiration in all eukaryotes, releasing energy as ATP from carbohydrates and lipids.
what is the structure of mitochondria
double membrane, outer and inner mitochondrial membrane
matrix is a liquid in the centre with enzymes found for the Krebs cycle
enzymes for oxidative phosphorylation on the inner mitochondrial membrane
why is the inner membrane folded
called cristae, increases surface area for enzymes needed for oxidative phosphorylation
where is DNA found in mitochondria
found as a loop in the matrix, contains genes required for enzymes involved in aerobic respiration
when are mitochondria more frequent
in cells which require a lot of energy, such as muscle cells
what is a thylakoid
membrane bound flattened discs where light dependent reactions are performed. they contain chlorophyll and enzymes needed.
what are stacked thylakoids
granum/grana - light is absorbed more efficiently
what are lamellae
flattened membranes connects different grana, allowing chemicals to pass between and play a role in light dependent reactions
what is stroma
a fluid material where light dependent reactions take place. enzymes for them are found here
how are products of photosynthesis stored
glucose is converted into insoluble starch and stored as starch granules
does chloroplasts contain DNA
yes - a loop, contains genes which encode for some of the proteins needed for photosynthesis
do chloroplasts contain ribosomes
yes - they synthesise proteins encoded by chloroplast DNA
what are the functions of the cell wall
strengthens the plant cell to prevent bursting from movement of water inwards
how does water affect a plant cell
water movement inwards for photosynthesis causes hydrostatic pressure inside the cell, pushing outwards and making the cell rigid
is a cell wall permeable
yes - partially permeable for water molecules
what is the structure of the cell wall
made of cellulose, a polymer of beta glucose. they form hydrogen bonds with eachother, creating microfibrils which make a strong mesh in the plant wall
what is the middle lamella
material between cell walls of neighbouring cells made of calcium and magnesium ions, and polysaccharides. it acts as a glue between cells
what is the cell wall made of in algae
cellulose and glycoproteins
what is the cell wall made of in fungi
chitin, polysaccharides, and glycoproteins
what is the structure of a permanent vacuole
surrounded by a membrane called the tonoplast which controls movement in and out, contains cell sap comrpised of dissolved sugars, mineral salts and amino acids
what is the function of a permanent vacuole
allows water to enter via osmosis due to low water potential of the cell sap, creating hydrostatic pressure acting outwards, allowing the cell to have mechanical strength and remain turgid
what is the structure of the cell membrane
consists of a phospholipid bilayer
what is the function of a cell surface membrane
impermeable to water, must be transferred across through channel proteins etc., proteins regulate movement in and out