B1 cell biology Flashcards
what are the different parts of a cell called?
subcellular structures
what are the five main subcellular structures of an animal cell?
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
what subcellular structures do plant cells have that animal cells don’t?
rigid cell wall, permanent vacuole, chloroplasts
what is a cell wall made of
cellulose
what is the difference between a prokaryotic cell and a eukaryotic cell?
Eukaryotic cells are complex and include all animal and plant cells.
Prokaryotic cells are smaller and simpler, e.g. bacteria
what are the main differences between a bacteria cell and a eukaryotic cell?
- Bacteria don’t have chloroplasts or mitochondria.
- Bacterial cells don’t have a ‘true’ nucleus - instead they have a single circular strand of DNA that floats freely in the cytoplasm, and could also contain one or more small rings of DNA called plasmids.
what is the process that cells go through to become specialized?
differentiation
what are undifferentiated cells called?
stem cells
what are 5 examples of specialized cells?
sperm cells, nerve cells, muscle cells, root hair cells, phloem and xylem cells
what are sperm cells specialised for?
reproduction
what is the function of a sperm?
to get the male DNA to the female DNA
what are the adaptations of a sperm cell?
it has a long tail and a streamlined head to help it swim to the egg.
there are a lot of mitochondria in the cell to provide the energy needed.
it also carries enzymes in its head to digest through the egg cell membrane
what are nerve cells specialised for?
rapid signalling
what is the function of nerve cells?
to carry electrical signals from one part of the body to another
what are the adaptations of nerve cells?
they are long (to cover more distance) and have branched connections at their ends to connect to other nerve cells and form a network throughout the body
what are muscle cells specialised for?
contraction
what is the function of a muscle cell?
to contract quickly
what are the adaptations of muscle cells?
they are long so that they have space to contract
they contain lots of mitochondria to generate the energy needed for contraction
what are root hair cells specialised for?
absorbing water and minerals
what is an adaptation of root hair cells?
they have a large surface area
what are phloem and xylem cells specialised for?
transporting substances
what are chromosomes?
coiled up lengths of DNA molecules. Each chromosome contains a large number of genes
how many copies of each chromosome does the body normally have?
two - one from the ‘mother’ and one from the ‘father’
how many pairs of chromosomes are there in a human cell?
23
what is the cell cycle?
a series of stages where body cells in multicellular organisms divide to produce new cells
what is the stage of the cell cycle when the cell divides called?
mitosis
what are the three stages of growth and DNA replication?
- In a cell that’s not dividing, the DNA is all spread out in long strings
- Before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
- It then 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 an exact duplicate of the other
what do multicellular organisms use mitosis for?
to grow, or replace cells that have been damaged
what are the two main stages of the cell cycle?
- Growth and DNA replication
2. Mitosis
what are the three stages of mitosis?
- The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell
- Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has been divided
- Lastly, the cytoplasm and cell membrane divide
what is differentiation?
the process by which a cell changes to become specialised for its job
what are clones?
genetically identical cells
what is a risk involved in using stem cells in medicine?
stem cells grown in the lab may become contaminated with a virus which could be passed on to the patient and so make them sicker
why are some people against stem cell research?
some people feel that human embryos shouldn’t be used for experiments since each one is a potential human life, whereas others think that curing existing patients who are suffering is more important than the rights of an embryo
where are stem cells found in plants?
in the meristems
can plant stem cells differentiate into any type of plant cell throughout the plants entire life?
yes
what are some uses of plant stem cells?
plant stem cells can be used to produce clones of whole plants quickly and cheaply.
They can be used to grow more plants of a rare species to prevent them being wiped out
they can be used to grow crops of identical plants that have desired features for farmers, for example, disease resistance
if an organism gets larger, does the surface area get bigger or smaller compared to the volume?
smaller
what are four adaptations of exchange surfaces?
- They have a thin membrane, so substances only have a short distance to diffuse
- They have a large surface area so lots of a substance can diffuse at once
- Exchange surfaces in animals have lots of blood vessels
- Gas exchange surfaces in animals (e.g. alveoli) are often ventilated too - air moves in and out
how do gills work?
water (containing oxygen) enters the fish through its mouth and passes out through the gills. As this happens, oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood into the water.
what are some adaptations of fish gills?
Each gill is made of lots of thin plates called gill filaments, which give a big surface area for exchange of gases.
The gill filaments are covered in lots of tiny structures called lamellae which increase the surface area even more.
The lamellae have lots of blood capillaries to speed up diffusion. They also have a thin surface layer of cells to minimise the distance that the gases have to diffuse.
Blood flows through the lamellae in one direction and water flows over in the opposite direction. This maintains a larger concentration gradient between the water and the blood.
The concentration of oxygen in the water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood.
Name four substances that can diffuse through cell membranes
oxygen, glucose, amino acids and water
name two molecules that can’t fit through cell membranes
starch and proteins
describe a practical to observe the effect of sugar solutions on plant tissue (osmosis required practical)
- cut a potato into identical cylinders
- get some beakers with different sugar solutions in them. one should be pure water and another should be a very concentrated sugar solution (e.g. 1mol/dm^3)
- measure the mass of the cylinders, then leave one cylinder in each beaker for 24 hours or so
- then take them out, dry them with a paper towel and measure their masses again
- if the cylinders have drawn in water by osmosis, they’ll have increased in mass. if water has been drawn out, they’ll have decreased in mass. you can calculate the percentage change in mass, then plot a few graphs and things
what is the dependent variable of the osmosis required practical?
the chip mass
what is the independent variable of the osmosis required practical?
the concentration of the sugar solution
what are some control variables of the osmosis required practical?
the volume of the solution, temperature, time, type of sugar used
what are some errors that may arise when doing the osmosis required practical? how can you reduce the effect of these errors?
if some potato cylinders were not fully dried, the excess water would give a higher mass, or if water evaporated from the beakers, the concentrations of the sugar solutions would change. you can reduce the effect of these errors by repeating the experiment and calculating a mean percentage change at each concentration.
