biology Flashcards
chromosomal dna
strand dna found in bacteria
nerve cell
long conduct nerve impulses
palisade mesophyll
photosynthesis
Water and kidney
Water is reabsorbed in the kidney tubules by osmosis.
animals cells and water
If animal cells lose water, they become flaccid. Red blood cells, for example, would be less efficient at carrying oxygen.
turgid plants
When plant cells are turgid, their rigidity can keep the whole plant firm and upright. Leaves can be held in the best position possible to trap (absorb) sunlight for photosynthesis.
mitosis role
allows organisms to grow in size by increasing their total number of cells allows worn-out and dead cells in a tissue to be repaired and replaced allows some species to reproduce by asexual reproduction.
diagraphm
cell cycle
mutations and asexual reproduction
causes genetic variation
a sexual vs sexual reproduction
fertilisation and zygote
When a Y chromosome is delivered to the egg by the sperm the zygote will develop into a male.
When an X chromosome is delivered to the egg by the sperm the zygote will develop into a female.
dna
DNA is stored in the nucleus as long, thread-like structures called chromosomes.
All of the genetic material found in each cell of an organism is the organism’s genome.
intron
mutations have no impact
what is genetic engineering
Genetic engineering involves taking a copy of a gene from one organism and inserting that gene into the DNA of another organism, to create a genetically modified organism (GMO) or a transgenic organism.
what enzymes are involved in genetic engineering
restriction enzyme. to cut
enzyme ligase to insert
staggered dna strand
leaves sections of single strand dna known as the sticky end this is done to the plasmid also
sticky end
complementary bases form h bonds enzyme ligase forms condensation reaction.
recombinant plasmid.
recombinant plasmid. It is a plasmid that has been altered and now has DNA from more than one source.
gmo
infects indivual and adds gene to plant etc
gmo plants
totipotent stem
Totipotent stem cells can differentiate and develop into any of the wide variety of specialised cells found in an adult human.
pluripotent cells
The embryo is made up of embryonic stem cells which are pluripotent. Like the totipotent zygote, these cells can differentiate into any of the specialised cells in an adult. However, pluripotent cells cannot produce the cells that will become the placenta. Only totipotent cells can do this.
stem cells and medicine
Stem cells and medicine
Bone marrow contains stem cells that can be transplanted into patients to treat some diseases, e.g. certain cancers.
This treatment with stem cells carries risks which include:
an increased risk of cancer developing
rejection by the immune system, because the transplanted cells are identified as foreign.
genetic variation
Natural selection is the process whereby some organisms (variants) in a population are preferentially selected for and others selected against.
Due to mutations, there will be genetic variation in a population. This is usually extensive as the species is likely to have been in existence for a long time.
In a population, the genetic variation present means that not all individuals will be the same. Individuals will have different characteristics (and show different phenotypes), such as differing fur colours in mammals or heights in pea plants.
evolution
If this continues over many generations then the advantageous allele will become more common in the population and disadvantageous alleles less common. This is evolution.
. This can be expressed in the phenotype.
As referred to above, mutations within a population are a source of variation. As mutations are changes in the sequence of bases in DNA, they can be inherited and so passed on to subsequent generations. The mutations may alter the functioning of the protein the mutant gene codes for, leading to an altered characteristic.
types of reactions
A substrate may be broken by the addition of water = hydrolysis reaction.
A product may be formed by the removal of water = condensation reaction.
Induced fit theory of enzyme action
The active site of the enzyme is a specific shape and only catalyses one reaction.
The substrate with the correct shape enters the active site.
It is thought that the active site changes shape slightly once the substrate has entered it.
This makes the active site fit more closely around the substrate and helps the reaction to take place more efficiently.
enzyme effiency factors
- extreme pressure
- high sodium chloride levels
- high levels of various metals
- low water availability.
Respiration
Respiration is a chemical reaction which occurs in cells to release energy. It is catalysed by enzymes and so the rate of respiration is sensitive to changes in temperature and pH.
purposes of respiration
protein synthesis and making other new molecules
active transport
cell division
muscle contraction.
where does respiration takes place in organism s
In eukaryotic cells (including plants and animals), aerobic respiration occurs inside mitochondria. In prokaryotes (bacteria), aerobic respiration occurs in the cytoplasm
The oxygen debt is the volume of oxygen needed for cells to respire
False. The oxygen debt is the extra oxygen taken in during rapid breathing after exercise. It is used to oxidise toxic lactic acid, removing it from the body.
Anaerobic respiration takes place in mitochondria in plants and animals.
False. Anaerobic respiration takes places in the cytoplasm. Aerobic respiration takes place in mitochondria.
In bacteria, carbon dioxide will be produced inside mitochondria.
This is not correct. Bacteria do not possess mitochondria and respiration producing carbon dioxide will occur in the cytoplasm.
The pH of animal cell cytoplasm may decrease during anaerobic respiration.
Correct. Anaerobic respiration occurs in the cytoplasm and produces lactic acid. This would lower the pH of the cytoplasm as it is acidic.
What is the nervous system?
What is the nervous system?
The nervous system is a rapid communication system in the bodies of animals.
It is made up of several different cell types that use electrical impulses to send cellular messages, producing quick but short-lived responses.
how does the nervous system works ?
The nervous system uses a system of nerves that connect to the organs and tissues.
These link to the central nervous system which co-ordinates the inputs from the other nerves.
what is a neurone?
A neurone is one of the cells of the nervous system. Nerves are made of bundles of the axons of neurones.
What is the central nervous system made from?
the brain, and the spinal cord, a collection of nerves that run down the spine through the vertebrae.
what are nerves?
Nerves from the receptors in the sense organs bring impulses to the spinal cord which then sends them to the brain for processing.
what does the brain does with received impulses?
The brain interprets the impulses and then responds by sending an impulse via the spinal cord to the nerves which connect to the organs and tissues of the body.
What is a neurone?
A nerve cell is called a neurone. These transmit electrical impulses. There are different types of neurone which all contain a single nucleus in their cell body, and extensions of their cytoplasm that allow electrical impulses to travel through them.
What are the types of neurone?
Three types of neurone are sensory, relay and motor neurones.