Topic 3 Cell Structure Flashcards
What are all living organisms made up of?
Cells which share some come features.
What is the organisation of cells in multicellular organisms?
Cells are organised into tissues.
Tissues into organs.
Organs into organ systems.
Organ systems into the whole organism.
List the organelles of eukaryotic cells.
- Nucleus which contains a nucleolus
- Ribosomes
- Rough and smooth endoplasmic reticulum
- Mitochondria
- Centrioles
- Lysosomes
- Golgi apparatus
List the organelles of prokaryotic cells.
- Cell wall
- Capsule
- Plasmid
- Flagellum
- Pilli
- Ribosomes
- Circular DNA called a nucleoid.
Describe the structure and function of the nucleus.
It’s is bound by the nuclear envelope and stores the genetic material of the cell in the form of chromosomes.
The nuclear envelope contains pores called nucleopores.
These allow mRNA which has been synthesised to enter the cytoplasm.
Describe the structure and function of the nucleolus.
There is at least one inside each nucleus and it is an extra-dense area of almost pure DNA and protein.
It is involved in the production of ribosomes.
Research also suggests it plays a part in the control of cell growth and division.
Describe the structure and function of ribosomes.
The cytoplasm contains 80s ribosomes which consist of a 40S subunit and a 60S subunit.
The ratio of RNA:protein in them is 1:1
The mitochondria contains 70s ribosomes which consist of a sub 30S unit and a 50S sub unit.
The ratio of RNA:protein in them is 2:1
Their function is translation during protein synthesis.
Describe the structures and functions of the rough and smooth endoplasmic reticula.
They are both a 3-D network of membrane bound space extending from the nuclear envelope.
The rough endoplasmic reticulum has ribosomes on its surface.
Its function is the synthesis, storage, and transport of proteins.
The smooth endoplasmic reticulum has no ribosomes on its surface.
Its function is the synthesis, storage, and transport of steroids and lipids.
Both reticula secrete their products in vacuoles by exocytosis to other parts of the cell.
Describe the structure and function of the mitochondria.
They have an outer and an inner membrane.
The outer membrane is smooth while the inner membrane has foldings cristea.
Cristea increase the surface area for aerobic respiration.
Bounded by the inner membrane, there is a fluid called the matrix.
In the matrix, plasmids and 70S ribosomes can be found.
The mitochondria provide energy by aerobic respiration which produces ATP.
Describe the structure and function of centrioles.
Three microtubules joined together is called a triplet.
Centrioles consist of nine sets of triplets.
When a cell divides, the centrioles pull apart to produce a spindle of microtubules that are involved in the movement of chromosomes.
Describe the structure and functions of lysosomes.
These are membrane bound organelles which contain a powerful mix of digestive enzymes.
They confuse with each or other membrane-bound vacuums to break down its contents.
They can also fuse with the outer cell membrane to release their enzymes as extracellular enzymes.
They can also burst to kill a cell if it has become too old or has a mutation.
This programmed cell death is known as apoptosis.
Describe the structure and function of the Golgi apparatus.
It is a stack of parallel, flattened, and separate membrane bound spaces formed by vesicles from the endoplasmic reticulum using together.
The stacks curve to one side and the inside of the curve is called the cis face while the outside of the curve is called the trans face.
Their function is the modification of proteins by adding lipids, carbohydrates, or changing their 3D shape.
After this the proteins are secreted by exocytosis in vacuoles which can fuse with the cell membrane to release extracellular enzymes.
Describe the structure and function of the prokaryotic cell wall
It contains a layer of peptidoglycan that is made of many parallel layers of polysaccharides with peptide cross-links.
Its function is to prevent the cell from swelling and bursting from watering entering it by osmosis.
It also maintains the structure of the cell and gives it support and protection to its contents.
Describe the structure and function of the prokaryotic capsule.
It may be produce from starch, gelatin, protein or glycolipid.
It protects the cell from phagocytosis by white blood cells.
It also covers the cell markers on the cell membrane that identify the cell thus making it easier for the bacterium to be pathogenic as it is less easily identified by the immune system .
Describe the structure and function of the pilli.
They are thread-like protein projections from the cell surface membrane.
They are used for attachment to a host cell, sexual reproduction, and to exchange plasmids with other bacteria.
Describe the structure and function of the flagellum.
These are made of a many stranded-helix of the protein flagellin.
Its function is to move the bacterium by rapid rotations.
Describe the structure and functions of the prokaryotic cell surface membrane.
It is similar both structure and function to the membrane of eukaryotic cells.
However, since there is no mitochondria, it is also the site of some of the respiratory enzymes.
Describe the structure and function of the nucleoid.
It is an area in the bacterial cell where a circular molecule of DNA is folded and coiled to fit into the bacterium.
Describe the structure and function of plasmids.
They are small circular pieces of DNA.
They code for a particular aspect of the bacterial phenotype in addition to the genetic information in nucleoid.
They can be transferred between bacteria using pilli.
