homeostasis
the ability of an organism to maintain constant internal conditions despite changes in the external environment
all levers of organisation contribute to homeostasis
steady state
another term for homeostasis
Things to keep stable
body temp
blood pH
blood glucose levels
amount of wastes in blood
blood pressure
3 step process in maintaining stable body conditions
change must be detected somehow
solution must be developed
adjustments must be made
receptors
step 1 in maintaining stable body conditions
what occurs within receptors
cells receive messages about a change which is known as the stimulus
examples of receptors
sense organs:
eyes
ears
nose
chemoreceptors
detect chemicals such as glucose levels
baroreceptors
detect pressure such as full bladder
control centre
involved in step 2 of maintaining stable body conditions
what occurs within the control centre
received info from receptors, then sends messages back out to fix the problem
effectors
step 3 in maintaining stable body conditions
what occurs within effectors
cells, tissues and organs follow instructions from the control centre and make changes to produce a response
negative feedback loop
reduces or opposes the intensity of the stimulus
set point
the physiological value around which the normal range fluctuates
normal range
the restricted set of values that is optimally stable and healthful
what does homeostasis aim to reach
homeostasis aims to keep the body at the set point
positive feedback
the response increases the stimulus rapidly until end point is reached
components of cell membrane
has 2 layers of lipids
has a phospholipid inlayer
structure of lipids
polar heads
non polar and hydrophobic tails
function of phospholipid bilayer
allows water inside and outside of the cell
membrane proteins
peripheral and integral proteins
peripheral proteins
do not go all the way through the membrane, acts likes assistants to integral proteins
integral proteins
goes all the way through the membrane
3 types of integral proteins
transporter, cell surface identity maker, cell surface receptor
transporter cell surface
moves things in and out of the cell
cell surface identity maker
cell recognition eg. antigen
cell surface receptor
brings a message into the cell
what can cross the phospholipid bilayer
non-polar, hydrophobic molecules that have no charge
polar
electrons aren’t shared evenly
how do non-polar hydrophobic molecules cross through the phospholipid bilayer
dissolves in membrane and goes through
smaller molecules cross more quickly
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
2 methods of transport across the cell
active transport and passive transport
active transport
the movement of substances across the membrane using energy, usually against concentration gradient
passive transport
movement of substances across the membrane without the use of cellular energy, usually with the concentration gradient
concentration gradient
occurs when a substance is more concentrated in one area than another
diffusion
movement from high to low concentration
passive diffusion
does not require energy
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
active transport requirements and method : primary
against concentration gradient and requires energy and special protein channels
active transport : secondary
uses the electrochemical gradient of an ion to move something else against its gradient
antiporter
membrane protein that transports two molecules at the same time in the opposite direction
symporters
proteins that transports two molecules across a membrane in the same direction
where do large molecules move in and out of the cell
through vesicles and vacuoles
endocytosis
moves large molecules to the inside of a cell
exocytosis
moves large molecules to the outside of a cell
osmosis
diffusion of water through a semi-permeable membrane
from a high concentration to a low concentration
hypertonic
more solutes and less water in a solution
hypotonic
less solute and more water in a solution
isotonic
equal in solute and water in a solution
passive transport
movement of substances across the membrane without the use of cellular energy, with the concentration gradient
metabolism
sum of all biochemical reactions occurring in the cells
2 types of metabolism
anabolic and catabolic
anabolic reactions
building/making molecules
catabolic reactions
breaking down molecules/breaking bonds
what do biochem reactions require
most biochem reactions need enzymes to increase the speed of the reaction to sustain life
methods to make particles collide
make particles smaller
add heat energy to increase movement causing more collisions
alter concentration/pressure
using catalysts
enzymes
proteins that act as a catalyst to increase the rate of reactions
active site
area on the enzyme where the substrate attach
size of enzymes and active site
enzymes are usually very large proteins and the active site is just a small region
function of active site
males enzymes specific to particular substrates
pathways
metabolic reactions occur in a series of these pathway reactions
3 reasons cells need energy
chemical, mechanical and electrochemical
energy for chemicals
to aid the building/rearranging/breaking apart of substances
energy for mechanicals
to aid the movement of cell structure eg.cilia
energy for electrochemical
to aid the movement of charged particles across membranes
how do cells get energy (1)
breaking down high energy moles in food through metabolic pathways
how do cells get energy (2)
law of conservation of energy
how is ATP used
energy in phosphate bonds
bonds broken = energy released
cellular respiration
glucose + oxygen - water + carbon dioxide + ATP
describing the metabolism of carbohydrates
metabolism of carbohydrates
over 3 metabolic pathways:
glycolysis
citric acid cycle
oxidative phosphorylation
beta oxidation
a metabolic pathway where fatty acids are used to produce energy
glycolysis
series of chemical reaction
occurs in cytoplasm
does not need oxygen
substrate and product of glycolysis
substrate = glucose
product = pyruvate
ATP within glycolysis
uses 2 ATP and produces 4 ATP
TCA/Citric acid/Krebs cycle
in the presence of oxygen
pyruvate is converted to Acetyl-CoA inside the mitochondria
Acetyl-CoA enters the cycle
link reactions
where pyruvate is converted to Acetyl-CoA inside the mitochondria
where does oxidative phosphorylation occur
occurs in the mitochondria
2 parts of oxidative phosphorylation
electron transfer chain
chemiosmosis
fermentation
following glycolysis, if oxygen is absent then pyruvate is converted into lactate - lactic acid
how is ATP produced
By breaking down glucose metabolic pathways
breakdown of glucose (step 1 in making ATP)
begins with glycolysis which can be aerobic or anaerobic
what reaction is lactate produced in
anaerobic
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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