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homeostasis

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homeostasis, osmosis etc

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homeostasis

the ability of an organism to maintain constant internal conditions despite changes in the external environment

all levers of organisation contribute to homeostasis

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steady state

another term for homeostasis

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Things to keep stable

  • body temp

  • blood pH

  • blood glucose levels

  • amount of wastes in blood

  • blood pressure

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3 step process in maintaining stable body conditions

  • change must be detected somehow

  • solution must be developed

  • adjustments must be made

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receptors

step 1 in maintaining stable body conditions

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what occurs within receptors

cells receive messages about a change which is known as the stimulus

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examples of receptors

sense organs:

  • eyes

  • ears

  • nose

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chemoreceptors

detect chemicals such as glucose levels

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baroreceptors

detect pressure such as full bladder

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control centre

involved in step 2 of maintaining stable body conditions

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what occurs within the control centre

received info from receptors, then sends messages back out to fix the problem

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effectors

step 3 in maintaining stable body conditions

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what occurs within effectors

cells, tissues and organs follow instructions from the control centre and make changes to produce a response

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negative feedback loop

reduces or opposes the intensity of the stimulus

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set point

the physiological value around which the normal range fluctuates

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normal range

the restricted set of values that is optimally stable and healthful

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what does homeostasis aim to reach

homeostasis aims to keep the body at the set point

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positive feedback

the response increases the stimulus rapidly until end point is reached

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components of cell membrane

has 2 layers of lipids

has a phospholipid inlayer

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structure of lipids

polar heads

non polar and hydrophobic tails

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function of phospholipid bilayer

allows water inside and outside of the cell

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membrane proteins

peripheral and integral proteins

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peripheral proteins

do not go all the way through the membrane, acts likes assistants to integral proteins

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integral proteins

goes all the way through the membrane

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3 types of integral proteins

transporter, cell surface identity maker, cell surface receptor

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transporter cell surface

moves things in and out of the cell

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cell surface identity maker

cell recognition eg. antigen

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cell surface receptor

brings a message into the cell

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what can cross the phospholipid bilayer

non-polar, hydrophobic molecules that have no charge

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polar

electrons aren’t shared evenly

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how do non-polar hydrophobic molecules cross through the phospholipid bilayer

dissolves in membrane and goes through

smaller molecules cross more quickly

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what cannot cross the phospholipid bilayer

polar hydrophilic molecules mostly cannot cross

water and ethanol are polar but small - some get through

large polar molecules eg. glucose

charged molecules

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2 methods of transport across the cell

active transport and passive transport

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active transport

the movement of substances across the membrane using energy, usually against concentration gradient

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passive transport

movement of substances across the membrane without the use of cellular energy, usually with the concentration gradient

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concentration gradient

occurs when a substance is more concentrated in one area than another

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diffusion

movement from high to low concentration

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passive diffusion

does not require energy

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movement of ions or smaller polar molecules

cannot pass through the phospholipid bilayer but there are channels made of protein

moves along the concentrated gradient through facilitated diffusion

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active transport requirements and method : primary

against concentration gradient and requires energy and special protein channels

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active transport : secondary

uses the electrochemical gradient of an ion to move something else against its gradient

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antiporter

membrane protein that transports two molecules at the same time in the opposite direction

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symporters

proteins that transports two molecules across a membrane in the same direction

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where do large molecules move in and out of the cell

through vesicles and vacuoles

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endocytosis

moves large molecules to the inside of a cell

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exocytosis

moves large molecules to the outside of a cell

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osmosis

diffusion of water through a semi-permeable membrane

from a high concentration to a low concentration

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hypertonic

more solutes and less water in a solution

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hypotonic

less solute and more water in a solution

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isotonic

equal in solute and water in a solution

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passive transport

movement of substances across the membrane without the use of cellular energy, with the concentration gradient

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metabolism

sum of all biochemical reactions occurring in the cells

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2 types of metabolism

anabolic and catabolic

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anabolic reactions

building/making molecules

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catabolic reactions

breaking down molecules/breaking bonds

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what do biochem reactions require

most biochem reactions need enzymes to increase the speed of the reaction to sustain life

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methods to make particles collide

  • make particles smaller

  • add heat energy to increase movement causing more collisions

  • alter concentration/pressure

  • using catalysts

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enzymes

proteins that act as a catalyst to increase the rate of reactions

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active site

area on the enzyme where the substrate attach

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size of enzymes and active site

enzymes are usually very large proteins and the active site is just a small region

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function of active site

males enzymes specific to particular substrates

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pathways

metabolic reactions occur in a series of these pathway reactions

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3 reasons cells need energy

chemical, mechanical and electrochemical

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energy for chemicals

to aid the building/rearranging/breaking apart of substances

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energy for mechanicals

to aid the movement of cell structure eg.cilia

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energy for electrochemical

to aid the movement of charged particles across membranes

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how do cells get energy (1)

breaking down high energy moles in food through metabolic pathways

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how do cells get energy (2)

law of conservation of energy

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how is ATP used

  • energy in phosphate bonds

  • bonds broken = energy released

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cellular respiration

glucose + oxygen - water + carbon dioxide + ATP

describing the metabolism of carbohydrates

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metabolism of carbohydrates

over 3 metabolic pathways:

  • glycolysis

  • citric acid cycle

  • oxidative phosphorylation

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beta oxidation

a metabolic pathway where fatty acids are used to produce energy

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glycolysis

  • series of chemical reaction

  • occurs in cytoplasm

  • does not need oxygen

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substrate and product of glycolysis

substrate = glucose

product = pyruvate

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ATP within glycolysis

uses 2 ATP and produces 4 ATP

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TCA/Citric acid/Krebs cycle

in the presence of oxygen

pyruvate is converted to Acetyl-CoA inside the mitochondria

Acetyl-CoA enters the cycle

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link reactions

where pyruvate is converted to Acetyl-CoA inside the mitochondria

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where does oxidative phosphorylation occur

occurs in the mitochondria

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2 parts of oxidative phosphorylation

electron transfer chain

chemiosmosis

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fermentation

following glycolysis, if oxygen is absent then pyruvate is converted into lactate - lactic acid

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how is ATP produced

By breaking down glucose metabolic pathways

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breakdown of glucose (step 1 in making ATP)

begins with glycolysis which can be aerobic or anaerobic

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what reaction is lactate produced in

anaerobic

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aerobic reaction of glycolysis (step 2 in making ATP)

both glycolysis and beta oxidation feed their products into the citric acid cycle which produces carbon dioxide

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