Term 3 Homeostasis

What are the factors that affect enzyme activity?

Temp

Optimum temp - maximum rate of enzyme activity

Above optimum - alter the structure of active sites of enzymes - denature - substrates are unable to bind - no longer complementary active site

pH

Above or below - enzyme denatures

Changing pH can alter the structure of the active site of enzyme or the substrate itself

What do membrane proteins have to do with hormones?

FOR WATER-SOLUBLE HORMONES - PEPTIDES/PROTEINS - which cannot pass thru the cell membrane

Hormone binding sites - many hormones travelling in the blood can only act on cells by binding to complementary protein receptors on the outside of the membrane to stimulate a response

e.g. insulin or adrenaline

Where do steroid hormones bind?

Intracellular receptors - lipid soluble - they travel through the plasma membrane

e.g. oestrogen or testosterone

How can cell communication occur?

Direct contact between cell membrane proteins of adjacent cells

Hormones

Neurotransmitters

What is the equation for aerobic respiration? Both.

Glucose + Oxygen → Water + Carbon dioxide + 36 ATP

C₆H₁₂O₆ + 6O₂ → 6H₂O + 6CO₂ + 36ATP

What is aerobic respiration?

Type of cell respiration used to release energy stored in chemical bonds of glucose when oxygen is available - more efficient process than anaerobic as it produces more ATP

What are the 3 stages of aerobic respiration? Where does each stage occur

Glycolysis - cytosol

Krebs cycle - mitochondria

Electron transport chain - mitochondria

What happens during the stages of aerobic respiration?

Glycolysis

Glucose is broken down into pyruvate (2C₃H₃O₃^-)

IN THE PRESENCE OF OXYGEN

Pyruvate enters the mitochondria

After pyruvate enters the mitochondria it becomes Acetyl-CoA before it can enter the main energy cycle (the Krebs cycle). 2-carbon molecule attached to a special helper (Coenzyme A).

• Krebs Cycle - citric acid cycle - mitochondrion

• Electron transport chain - mitochondrion - oxygen is the final electron acceptor that allows the production of ATP to occur efficiently

What is the stimulus response model?

6 stages

Stimulus - change in the internal/external environment that can be detected by the organism

Receptor - cells or tissues that detect the stimulus

Transmission - relay of information via nerves and/or hormones to an effector

Effector - organ/muscle or gland brings about a response after recieving the information

Response - the action which occurs as a result of the initial stimulus

Feedback - OCCURS WHEN the response has an impact on the initial stimulus - positive (reinforces/increases) or negative (reverses)

Is homeostasis constant?

NO - NOT STATIC

dynamic equilibrium - internal conditions fluctuate within tolerance limits - active adjustment

What are examples of positive feedback?

When a newborn sucks on the mother’s breast nipple - releases hormones to further stimulate the release of milk - which was the initial response

Breastfeeding can release oxytocin in the mother’s brain, promoting affection and bonding between the mother and child - the oxytocin can pass thru the breast milk to the baby - further promoting the bond.

REINFORCING THE INITIAL STIMULUS

What 2 systems detect and respond to stimuli from the internal and external environments? When is each usually involved?

Nervous - more rapid/direct communication

Endocrine

What is the nervous system made up of? What are their primary roles?

CNS - brain (controls the CNS) and spinal cord (link between brain and peripheral nerves) - processes, interprets, stores info; transmits messages to the muscles, glands and organs

PNS - nerves and ganglia located outside CNS - transmitting the info to and from the CNS - relay info from sensory receptors to the CNS and from the CNS to the effectors

How can the PNS be further subdivided?

Somatic (voluntary) - nerves are under conscious control e.g. influencing the skeletal muscles

Autonomic (involuntary) - nerves involved in unconscious responses; regulates glands, blood vesselse.g. changes in heart rate - further divided into:

Sympathetic - controls fight/flight/freeze/fawn response - mobilises body for action; energy output

Parasympathetic - rest and digest - conserves energy

What can the sympathetic and parasympathetic systems do?