41 WJEC Biology AS Level - Marianne Izen - 2nd Edition Flashcards
How are viruses described and why?
Viruses are not made of cells and so they are described as ‘acellular’.
Do viruses have organelles, chromosomes and cytoplasm?
There are no organelles, no chromosomes and no cytoplasm.
How does the virus exist outside a living cell?
Outside a living cell, a virus exists as an inert ‘virion’.
What happens when viruses invade a cell?
When viruses invade a cell, they are able to take over the cell’s metabolism and multiply inside the host cell.
What is each virus particle made up of?
Each virus particle is made up of a core of nucleic acid, either DNA or RNA, surrounded by a protein coat, the capsid.
What surrounds the capsid in some viruses?
In some viruses, a membrane derived from the host cell surrounds the capsid.
What groups of organisms can be infected with viruses?
Cells of all groups of organisms can be infected with viruses.
What are bacteriophages?
The viruses that attack bacteria are called bacteriophages.
What bacteriophage attacks Escherichia coli (E.coli) ?
T2
What property do viruses have that cannot be seen in living organisms?
Viruses can be crystallised, not a property associated with living organisms.
What is the only characteristic of life that viruses show?
The only characteristic of life that viruses show is their ability to reproduce, which contributes to the long debate as to whether they can be regarded as being alive.
What is paleovirology?
The new field of paleovirology examines the evolution of viruses. They probably emerged several different times very early in the history of life.
What diseases do viruses cause?
Viruses cause a variety of infectious diseases.
Summarise in a table, the various hosts and the viruses that infect them?
Single-celled organism carry out ———– within——
Single-celled organisms carry out all life functions within a single cell.
Multicellular organisms have ——– forming———– which have ————
Multicellular organisms have specialised cells, forming tissues and organs, which have various structures and roles.
What potential do stem cells have?
Stem cells have the potential to become any cell type in the body.
What is differentiation?
The development of a cell into a specific type is called differentiation.
What happens as cells differentiate?
As they differentiate, cells become specialised in structure and in the chemical reactions that they perform.
Differentiation (Key Term)
The development of a cell into a specific type.
Draw a labelled diagram of a T2-bacteriophage.
What does this picture show?
