B2.2 Organelles and compartmentalisation Flashcards
what are organelles
separate subunits of cells
what are the only organelles common to eukaryotes and prokaryotes
cell membranes and ribosomes
what is the advantage of separating the nucleus and the cytoplasm
keeps DNA separate, protecting it from many cellular reactions that occur in the cytoplasm
allows gene transcription and translation to be kept separate
what are exons
the sections of the gene that carries important data ( coding for amino acids)
what are introns
the non coding sequences in the gene
what is post transcriptional modification
since introns are useless, the introns are removed as soon the mRNA has been formed through an enzyme catalysed reaction
also known as RNA splicing
what is the result of RNA splicing
the shortened lengths of mRNA are described as mature and can be passed on for protein synthesis
what is the advantage of RNA splicing
for eukaryotic cells, variants of protein can be produced from a single gene
why is RNA splicing not possible in prokaryotes
there is no nuclear membrane, meaning mRNA instantly meets ribosomes
So prokaryote genes do not have introns
what is the nuclear membrane made of
a phospholipid bilayer, permeable only to small, non polar molecules
what is the role of the nuclear pores
the nuclear pores in the nuclear envelope control the exit of mRNA and movement of proteins
what are the nuclear pores made of
specific proteins forming a specific structure that is quite tiny ( 100 nm)
what is the estimate of nuclear pores present in the nuclear membrane
quite numerous, around 1/3rd of the nuclear membrane
what does the presence of nuclear pores suggest to us
suggests that communication between nucleus and cytoplasm is quite important
the selective movement of proteins and RNA through the nuclear pores plays ___?
an essential role in regulating eukaryotic gene expression
how does nuclear pores differ in transport mechanisms of other organelles
they are able to transport proteins in their folded conformation and ribosomal components in assembled particles
does export of RNA through nuclear pores require energy
yes, its an active process
where is Ribosomal RNA assembled
assembled with ribosomal proteins in the nucleolus and ribosomal subunits are then transported into the cytoplasm
what does compartmentalization in cells allow
allow for the correct concentration of metabolites to be present for specific metabolic process and the appropriate enzymes to be present
incompatible biochemical processes can be separated
why is compartmentalisation useful in lysosomes
they contain digestive enzymes in an acidic environment
the pH of the cell is slightly alkaline in case of leakages
it allows functions to occur that would not be possible in the rest of the cell
explain compartmentalization in phagocytic vacuoles
the formation of phagolysosome ( phagocytic vacuole and lysosome) is required and creates a contained space where digestion can take place at a low pH.
explain the process of respiration in the cell
in the cytoplasm, through a process called glycolysis, which is anaerobic produces pyruvate, which then diffused into the mitochondria, where aerobic respiration takes place
what happens when pyruvate goes inside the mitochondria
carbon is removed along with hydrogen which is split into protons and electrons
electrons pass down a sequence of proteins in the inner membrane, releasing energy that pumps into protons, which create an electrochemical gradient
this passes through ATP synthase, generating ATP
how do cristae help in the generation of ATP
assists by increasing the surface area of ATP synthase, leading to more ATP production
what is the process of producing ATP in the mitochondria called
the Krebs cycle, which occurs in the matrix of the mitochondria
what is the structure of the membranes in the chloroplasts
double membrane, along with a third inner membrane that folds extensively at various points known as thylakoids
what is the structure of the thylakoids
organized into flat compact circular piles called grana/granum
between the grana, loosely arranged membranes are suspended into a watery stroma
separate grama are connected by lamella
where are chlorophyll molecules found
grouped together in structures called photosystems, held in the thylakoid membrane by proteins. Large surface area of thylakoid membrane optimised the ability to harvest light energy
what is the Calvin cycle
light energy causes electrons to pass down a chain, causing protons to be pumped into the thylakoids, leading to a build up of proteins
protons flow down electrochemical gradient through ATP synthase proteins, generating ATP, leading to the production of glucose
why is compartmentalisation an advantage in chloroplasts
allows the separation of light harvesting activity of the chloroplasts in the thylakoids from the enzymes and the substrates of the Calvin cycle in the stroma
what is the inner nuclear membrane lined with
nuclear lamina , which is a meshwork of filaments that extend into the interor of the nucleus and provide structural support
composed of lamins, a fibrous protein
what happens to the nuclear envelope when the cell divides through mitosis and meiosis
nuclear envelope dissociates into small vesicles enabling the chromosomes to encounter the cytoplasm and spindle apparatus , central to manipulating chromsomes
what is a polysome
when ribosomes move along the mRNA, allowing many copies of a particular protein to be produced simultanously
what is the structure of the golgi apparatus
consists of stack like collection of flattenned membranous sacs called cisternae
which way do proteins enter the golgi apparatus
they enter the golgi on the side facing the RER and exit on the opposite side facing the opposite side
how are proteins moved through the golgi apparatus
they are transferred from one cisterna to the next. Each cisterna contains enzymes, catalysing different types of proteins modification
what can the enzymes in the golgi apparatus caus
glycosylation
sulfation
phosphorylation
explain the process of endocytosis
a protein binds to a receptor on the cell surface. specialised protein then acts to cause the membrane in the region to invaginate( tuck in)
which protein helps with the formation of vesicles
clathrin which polymerizes into a lattice network around the growing membrane bud to form a clathrin coated pit, eventually breaking off the membrane to form a vesicle
what happens to the clathrin on the vesicle after the vesicle is formed
it breaks off and attaches back to the membrane
