Topic 1 - Cell biology (3) Flashcards
EXCHANGE SURFACES:
What do cells use diffusion for?
Give 2 examples
to take in substances they need and to get rid of waste products
1) oxygen and carbon dioxide are transfered between cells and the environment during gas exchange
2) urea diffuses from cells into the blood plasma for removal from the body by the kidneys
EXCHANGE SURFACES:
What is urea?
a waste product produced from the breakdown of proteins
EXCHANGE SURFACES:
How easy it is for an organism to exchange substances with their surroundings depends on what?
the organism’s surface area to volume ratio
EXCHANGE SURFACES:
How are substances transpoted in and out of single celled organisms and why?
- gases and dissolved substances can diffuse directly into or out of the cell across the cell membrane
- because they have a large surface area compared to their volume so enough substances can be exchanged across the membrane to supply the volue of the cell
EXCHANGE SURFACES:
Why can’t multicellular organisms only directly diffuse suctances in or out?
- they have a smaller surface area compared to their volume
- not enough substances can diffuse from their outside surface to supply the entire volume
EXCHANGE SURFACES:
How do multicellulr organisms efficiently diffuse substances in and out?
- they have exchange surfaces for efficient diffusion
- they allow enough od the neccessary substances to pass through
EXCHANGE SURFACES:
Name the 4 ways in which exchange surfaces are adapted to maximise effectiveness?
- they have a thin membrane, so substances only have a short distance to diffuse
- they have a large surface area so lots of substance can diffuse at once
- exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly
- gas exchange surfaces (e.g. alveoli) are often ventilated too - air moves in and out
CHROMOSOMES AND MITOSIS:
In what form does the nucleus store genetic information?
chromosomes
CHROMOSOMES AND MITOSIS:
What are chromosomes?
Coiled up lengths of DNA molecules
CHROMOSOMES AND MITOSIS:
What do the different genes in chromosomes control?
the development of different characteristics e.g. hair colour
CHROMOSOMES AND MITOSIS:
How many copies of each chromosome do body cell usually have?
2 - one from the mother and one from the father
CHROMOSOMES AND MITOSIS:
How many pairs of chromosome are found in a normal human cell?
23 pairs of chromosomes
CHROMOSOMES AND MITOSIS:
What is the cell cycle?
a series of stages where body cells in multicellular organisms divide to produce new cells
CHROMOSOMES AND MITOSIS:
What is the name of the stage in the cell cycle where the cell divides?
mitosis
CHROMOSOMES AND MITOSIS:
Why do multicellular organisms use mitosis?
to grow or replace cells that have been damaged
CHROMOSOMES AND MITOSIS:
What is the result at the end of the cell cycle?
two new cells identical to the original cell with the same number of chromosmes
CHROMOSOMES AND MITOSIS:
What are the 2 main stages in the cell cycle?
- Growth and DNA replication
- Mitosis
CHROMOSOMES AND MITOSIS:
What is the DNA like in a cell that is not dividing?
the DNA is all spread out in long strings
CHROMOSOMES AND MITOSIS:
What happens in growth and DNA replication?
- the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
- it duplicates its DNA - so there’s one copy for each new cell. The DNA is copied and forms X-shaped chromosomes.
- each arm of the chromosome is and exact duplicate of the other (the left arem has the sam DNA as the right arm of the chromosome)
CHROMOSOMES AND MITOSIS:
What happens in mitosis in the cell cycle
Once the contents and DNA have been copied, the cell is ready for mitosis
- the chromosomes line up at the centre of the cell and cell fibres pull them apart, the 2 arms of each chromosome go to opposite ends of the cell
- membranes form around the new sets of chromosomes. Theses become the nuclei of the two new cells - the nucleus has divided
- then the cytoplasm and the cell membrane divide
- the cell has produced two identical daughter cells, both with the same DNA as the parent cell
MICROSCOPY:
What are stains used for?
to highlight objects in a cell by adding colour to them
