Topic 2: Cell membranes Flashcards
What is active transport?
Active transport can transport all types of molecules through carrier proteins from an area of low concentration to an area of high concentration.
- requires ATP
- transports sodium ions
What is osmosis?
Osmosis is the net diffusion of water molecules from an area of higher water potential to an area of lower water potential, through a partially permeable membrane
- ATP is not required
- Transports water by osmosis
State what is meant by the term genotype.
the combination of alleles
Explain what is meant by the term phenotype.
the characteristics of an organism determined by the genotype and the environment
what is meant by the term heterozygous?
having two different alleles for a particular gene.
For example one allele for red hair and one allele or brown hair
State what is meant by the term semi-conservative replication
an increase in the number of DNA molecules. Each new molecules consists of one parent and a one new strand
Name one enzyme involved in semi-conservative replication
DNA polymerase
Explain the importance of semi-conservative replication in the production of new cells. (2)
because it results in genetically identical (daughter) cells.
that will have the same structure as the parent cell
Compare and contrast the structure of messenger RNA (mRNA) with the structure of transfer RNA (tRNA).
both contain RNA nucleotides
both are single stranded
mRNA is a straight chain and tRNA is folded
size of mRNA is variable and the size of tRNA is constant.
Describe how the lungs of an elephant are adapted for gas exchange
- attachment of lungs to diaphragm increases volume
- alveoli provides a large surface area for faster diffusion.
Explain why only five amino acids are coded by this sequence of bases.
- three bases form one code of amino acids
- there is no stop codon for this sequence.
(b) Explain why some amino acids, such as alanine, have more than one genetic code.
because it’s a degenerate code which means there are more codes than needed.
Explain the role of the other three genetic codes. (2)
remaining codes are stop codons on RNA therefore no more amino acids can be added to the polypeptide chain.
what is a fluid mosaic?
