Cells And Organelles Flashcards
What are organelles
Organelles are structurally distinct from each other and have specific functions
What is the nucleus surrounded by
A double membrane or an envelope
What is the largest organelle
The nucleus
What is the outer membrane in terms with the rough endoplasmic reticulum
The outer membrane is continuous with the rough endoplasmic reticulum
What are the pores in the nuclear envelope for
They let mRNA and ribosomes out and nutrients and hormones in
In the nucleus what are the chromosomes present as
They are in a loosely coiled state known as chromatin
What is chromatin
DNA coiled around proteins called histones
What is the nucleus’ purpose
It controls the activities of the cell
What is in the centre of the nucleus
The nucleolus
What is the nucleolus’ purpose
It makes rRNA (ribosomal RNA) and packages it with ribosomal protein to make ribosomes.
What are the two types of chromatin and how do they appear under an electron microscope
Heterochromatin is darker and is densely packed DNA
Euchromatin is lighter and is loosely packed DNA
What is the purpose of euchromatin
It acts as a template for mRNA synthesis
What is the Rough Endoplasmic reticulum made out of
Lots of membranous tubes are present in the cytoplasm. Many are studded with ribosomes giving it a rough appearance.
When the ribosomes make proteins what happens
It is transported within the ER’s flattened sac like sheets called cisternae.
What is the difference between the smooth and rough ER
The smooth ER lacks ribosomes
What is the purpose of the smooth ER
Makes lipids and steroids (cholesterol and sex hormones)
It contains enzymes that detoxify (remove toxic substances)
It is a storage site for calcium in skeletal muscle cells.
What is the Golgi apparatus made out of
A series of tightly packed flattened sacs or cisternae.
What does the Golgi apparatus do
it collects and processes protein and lipids
What happens at the maturing face of the Golgi apparatus
Vesicles bud off the maturing face and go to either the surface membrane (secretion) or form lysosomes
Do mitochondria have a double or single membrane
They have a double membrane or envelope
What happens to the inner membrane of the mitochondria
The inner membrane is highly folded to form crystae which project into the internal solution or matrix ( a jelly like substance similar to the cytoplasm.)
What do mitochondria do
They complete the later stages of aerobic respiration and synthesise most of the ATP for the cell.
What does the mitochondria have its own
It has its own DNA which is (mt)DNA so can produce their own enzymes and can reproduce themselves.
Is a chloroplast surrounded by a double or single membrane
It has a double membrane or envelope
What is the internal solution called and what runs through it
The internal solution is called the stroma and flattened sacs or thylakoids run through it.
When the thylakoids are stacked what are they called
Grana
What is the chloroplasts purpose
It’s the site of photosynthesis. Grana trap light energy which is used to fix CO2 in the stroma.
Where does the light dependant and independent stages of photosynthesis occur in the chloroplast
Light independent occurs in the stroma and light dependant in the Grana/thylakoid.
What is a lysosome
A round organelle surrounded by a membrane with no clear internal structure.
What is a lysosome
A round organelle surrounded by a membrane with no clear internal structure.
What do lysosomes contain
They contain digestive enzymes. They digest invading cells or breaks down worn out cell components.
What is the plasma membrane
It is a very thin membrane (7-10nm).
What is the purpose of a plasma membrane
It is selectively permeable controlling entry and exit of materials.
How many layers does a plasma membrane have
It has a trilaminar (3-layered) appearance with 2 dark layers separated by a paler middle layer.
What is the planet cell wall
A rigid structure that surrounds plant cells and it’s made of cellulose.
What is the cytoskeleton
A complex network of protein structures in cells that run through the cytoplasm
What are its three main components in increasing diameter size
Microfilaments, intermediate fibres, microtubules
what do microfilaments contain
they contain the protein actin, allowing the fibres to contract
What are microfilaments involved in and an example
They are involved in cell movement, for example during cell division the cell membrane is pulled inwards dividing the cell into 2.
What do intermediate fibres do and an example
They strengthen the cell, for example skin cells are subjected to mechanical stresses due to movement. So intermediate fibres prevent the stresses from damaging the cell.
How are microtubules are formed
They are formed from subunits of the protein tubulin. Tubulin subunits assemble to form tubular polymers which assemble to form microtubules.
What do microtubules do and an example
they are responsible for the movement of organelles. E.g vesicle movement during secretion. They also form spindly fibres allowing the movement of chromosomes ion mitosis and meiosis.
What is the last thing Microtubules do
They also form complex networks to determine the shape of cells.
What are centrioles and where are they found
A pair of centrioles are present just outside the nucleus set at right angles to each other. Triplets of microtubules form a ring.
Are centrioles found in animal and plant cells
No they are just found in animal cells
What are ribosomes made out of
They are made out of a small subunit and a large subunit. They are made of a protein and some ribosomal RNA.
Where are ribosomes found
They can be attached to a membrane (rough ER) or free in the cytoplasm.
What do ribosomes do
They translate the instructions carried on mRNA into protein
What is the arrangement of cilia
They have a 9 + 2 arrangement
What are cilia
Small hair like projection made of microtubules
What is the difference between cilia and centrioles in terms of arrangement
Centrioles have 9 triplet tubules. They have no tubules in the centre./
What is the difference between cilia and flagella
If they are long and few in number they are flagella, if they are short and numerous in number they are cilia.
How are proteins produced in terms of organelles in eukaryotes (step 1)
The proteins are synthesised on ribosomes on the RER, they then pass into its cisternae and are packaged into vesicles, the vesicles move towards the Golgi via the cytoskeleton, the vesicles fuse with the cis face of the Golgi apparatus and the proteins enter.
How are proteins produced in terms of organelles (step 2)
The proteins are structurally modified before leaving the Golgi from its trans face. Secretory vesicles carry proteins that are released from the cell. They move towards and fuse with the plasma membrane releasing their content by exocytosis. Some vesicles form lysosomes.
What are vacuoles
Membrane lined sacs in the cytoplasm containing sap.
What is the purpose of the permanent vacuole
They are very important in maintaining turgor pressure so that the contents of the cell push against the cell wall and maintains a rigid framework for the cell.
What is the membrane of the vacuole called and what’s it function
It is called the tonoplast, it’s selectively permeable which means that some small molecules can pass through.
What is the plasmodesmata
Microscopic channels that traverse the cell walls of plant cells and allow transport and communication between the adjacent cells.
What are the enzymes inside a lysosome and what is their PH
They are hydrolytic enzymes, and they are acidic.
