bio paper 2

• Homeostasis


  The regulation of the internal conditions of either a cell or whole organism to maintain the optimum conditions for function in response to internal and external changes
• Homeostasis regulation


  1. Negative feedback loops

  2. Maintain blood glucose concentration

  3. Maintain body temperature

  4. Maintain water levels
• Receptor


  A type of cell that detects a stimulus
• Coordination center


  The brain, spinal cord, or pancreas that responds to a stimulus
• Effector


  A muscle or gland that responds to a signal
• Response systems


  • Nervous system
  • Endocrine system
• Nervous system


  Uses nerves/neurons to transfer electrical impulses, provides fast but short-lived responses
• Endocrine system


  Uses hormones released from glands, provides slower but longer-lasting responses
• Reflex reaction


  1. Stimulus detected by receptor

  2. Sensory neuron generates nervous impulse

  3. Relay neuron passes impulse through spinal cord

  4. Motor neuron passes impulse to effector

  5. Effector (muscle) responds
• The first required practical in biology paper 2 is about investigating the effect of a factor like caffeine or tiredness on reflex reaction time
• Endocrine glands


  • Pituitary
  • Pancreas
  • Thyroid
  • Adrenal
  • Ovaries (females)
  • Testes (males)
• Pituitary gland


  The "master gland" that controls other endocrine glands
• Thyroid gland


  Produces thyroxine to stimulate basal metabolic rate
• Adrenal glands


  Produce adrenaline, leading to the fight-or-flight response
• Pancreas


  Monitors and controls blood glucose levels by releasing insulin and glucagon
• Blood glucose level rises

  Pancreas secretes insulin, which stimulates glucose uptake by cells
• Blood glucose level falls

  Pancreas secretes glucagon, which stimulates the liver to release glucose
• Type 1 diabetes


  Disorder where the pancreas doesn't make enough insulin, leading to uncontrolled high blood glucose
• Type 2 diabetes


  Cells no longer respond to insulin, can often be controlled by diet and exercise
• Menstrual cycle


  1. FSH causes egg maturation

  2. LH triggers ovulation

  3. Ovaries produce estrogen and progesterone

  4. Progesterone levels fall, causing menstruation
• Fertility treatment


  1. FSH and LH drugs to stimulate egg production

  2. In-vitro fertilization - eggs fertilized in lab, embryos inserted into uterus
• Sexual reproduction


  Involves fusion of genetically unique gametes to produce genetically unique offspring
• Asexual reproduction


  Produces genetically identical clones
• Mitosis


  DNA doubles, cell divides once to produce two genetically identical diploid cells
• Meiosis


  DNA doubles, cell divides twice to produce four genetically unique haploid gametes
• Gene


  A length of DNA that codes for a specific protein
• Allele

  Different variants of the same gene
• Genotype


  The specific alleles an organism has
• Phenotype

  The observable characteristics of an organism
• Homozygous

  Having two of the same alleles
• Heterozygous


  Having two different alleles
• Recessive allele


  Only expressed when homozygous
• Expressed

  What is actually seen or observed
• Genotype


  The genetic makeup of an organism
• Recessive allele

  An allele that is only expressed when present in the homozygous state
• Dominant allele

  An allele that is expressed even when present in the heterozygous state
• The genetic material of a eukaryotic cell is contained in the nucleus and is made of DNA
• DNA is a long molecule made of two long polymer chains which together form a double helix
• Human cells have 23 pairs of chromosomes
• Genome


  The entire genetic material of an organism, including all genes and non-coding sequences