PAPER 1 TOPICS 2022 Flashcards
what temperature is the body kept at and why?
37 degrees, as this is the optimum temperature for enzymes in the human body
what happens when you are too hot?
- lots of sweat is produced - when it evaporates it transfers energy from your skin to the environment, cooling you down.
- blood vessels near to the skin widen - vasodilation. it allows more blood to flow near the surface, so it can transfer more energy into the surroundings which cools you down.
- hairs lie flat/erector muscles relax
what happens when you are too cold?
- very little sweat is produced
- blood vessels near the surface of the skin constrict (vasoconstriction). less blood flows near the surface, so less energy is transferred to the surroundings.
- you shiver, which increases your rate of respiration, which transfers more energy to warm the body due to excess heat lost from chemical reactions. exercise does the same
- hairs stand on end to trap an insulating layer of air, which keeps you warm
chromosome
thread like structure in the nucleus of a cell, made of DNA. contains the genetic information (genes)
what is DNA?
- a molecule with a double helix shape, composed of two strands of nucleotides held together by pairs of bases (A&T and C&G).
- carries the genetic information in coded form, for all characteristics of an organism.
homologous pair
- a pair of chromosomes that are the same shape, same size and carry genes for the same characters in the individual
- in the same positions on each chromosome
- one of each pair came from each parent.
haploid
a cell containing one set of chromosomes (one of each pair) (n) e.g. a gamete
diploid
a cell containing two sets of chromosomes (both of each pair) (2n) e.g. body cells
gene
a region along the length of the DNA of a chromosome that contains the information to control a certain characteristic by coding for a specific protein.
allele
an alternative form of a gene- occurs at the same position on the chromosome and controls the same character, but in a different way. recessive or dominant
genotype
the alleles an organism carries for a certain characteristic
phenotype
the appearance of an organism resulting from its genotype
homozygous
genotype with the same alleles of a gene e.g. AA or aa; both dominant or both recessive
heterozygous
genotype with different alleles of a gene e.g. Aa; one dominant one recessive
dominant (allele)
an allele which is always expressed in both homozygous and heterozygous genotypes
recessive (allele)
an allele that is not expressed in the phenotype if a dominant allele of the gene is present. only expressed if homozygous with no dominant alleles.
XX
the two sex chromosomes that are found in female body cells
XY
the two sex chromosomes that are found in male body cells
mitosis
type of cell division that produces two diploid daughter cells that are GENETICALLY IDENTICAL with the same number of chromosomes as the parent cell
meiosis
type of cell division that produces four haploid gametes which are GENETICALLY DIFFERENT to one another and have half the number of chromosomes as the parent cell
gamete
male and female sex cells, formed by meiosis. haploid
zygote
single cell resulting from fertilisation of a female gamete by a male gamete.
what is diffusion?
- the net movement of particles from an area of high concentration to an area of lower concentration.
- passive
- liquids and gases
osmosis
- the net movement of water molecules from an area of high water concentration to an area of low water concentration across a partially permeable membrane.
- passive