biology paper 2

• Homeostasis


  An organism's ability to regulate internal conditions even when external conditions change
• Importance of homeostasis

  • Allows crucial chemical reactions involving enzymes to happen at an Optimum rate
  • Regulates blood glucose concentration, temperature, and water levels
• Nervous system regulation of homeostasis

  1. Receptor detects change

  2. Electrical signal travels to spine through sensory and relay neurons

  3. Signal travels across synapse by neurotransmitter

  4. Signal goes to brain

  5. Conscious decision to act

  6. Signal goes back to effector via relay and motor neurons
• Reflex


  Signal bypasses the brain and goes straight through the spine to the effector
• Effectors


  Glands that produce specific chemicals the body needs
• Investigating reaction time

  1. Hold ruler between finger and thumb

  2. Drop ruler without warning

  3. Measure distance fallen before caught

  4. Repeat multiple times and take mean average
• Endocrine system


  System of glands that produce hormones that travel to effectors via the blood
• Pituitary gland


  Main or master gland that produces hormones in response to stimuli
• Pancreas

  Produces insulin to regulate blood glucose levels
• Type 1 diabetes


  Pancreas can't produce enough insulin
• Type 2 diabetes


  Cells no longer absorb glucose properly
• Menstrual cycle


  FSH causes egg maturation and estrogen production

  LH causes egg release

  Progesterone maintains uterus lining
• IVF

  In vitro fertilization - eggs fertilized in lab then implanted
• Adrenaline


  Hormone that increases heart and breathing rate in stressful situations
• Thyroxin

  Hormone secreted by thyroid that controls metabolic rate
• Meiosis

  Chromosomes copied, paired, and genes swapped

  Cell divides twice to produce haploid gametes
• Asexual reproduction


  Daughter cells genetically identical to parent
• Genome

  All the genetic material in an organism
• Gene


  Section of DNA that codes for a specific protein
• Genotype


  Genetic code stored in DNA
• Phenotype


  How the genetic code is expressed in characteristics
• Asexual reproduction

  Only one parent is needed, e.g. a plant on its own can still reproduce
• Parasite that causes malaria

  Can do both sexual and asexual reproduction
• Genome

  The term given to all the genetic material in an organism
• DNA


  A two-stranded polymer in a double helix shape that stores the genetic code
• Gene


  A section of DNA that codes for a specific protein
• Genotype


  The term given to the code stored in your DNA
• Phenotype


  How the genetic code is expressed in your characteristics and physiology
• Monomers between the two DNA strands

  • Nucleotides (made from a sugar and phosphate group, of which there are 4 types: A, T, C, G)
• A and T, and C and G always match to each other in the DNA sequence</b>
• Triplet code


  Every three DNA bases code for an amino acid
• Protein synthesis


  1. DNA sequence is copied by mRNA

  2. mRNA taken to ribosome

  3. Amino acids connected in order to make protein

  4. Protein folding affects function
• Harmful mutation


  Can change a gene so much that it results in a protein being synthesized that doesn't do its job
• Alleles


  Different types of the same gene
• Dominant allele


  Results in a characteristic being expressed even if there is another recessive allele present
• Recessive allele


  Only expressed when there is no dominant allele present
• Homozygous


  Having only one type of allele
• Heterozygous


  Having two different types of alleles
• Punnett square


  Used to predict the probability of a certain phenotype
• Polydactyly (extra fingers/toes) is caused by a dominant allele, cystic fibrosis by a recessive allele