PC101

homeostasis, osmosis etc

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

where does hydrogen within oxidative phosphorylation come from (step 3 in making ATP)

glycolysis and citric acid cycle strip hydrogen from carbohydrates

Final step in making ATP

Oxidative phosphorylation combines the hydrogen with oxygen to make water - this process provides the energy to run ATPase which produces ATP

phosphorylation

adding phosphate

coordinated processes/variables

body’s internal environment

core principles

* feedback loops
* structure function
* cell-cell communication
* gradients

potential energy

energy that is stored

2 basic types of passive transport

diffusion and osmosis

properties of water

water absorbs heat without changing significantly in temperature itself

water carries heat with it when it changes from a liquid to a gas

water cushions and protects the body’s structure

water as a lubricant between 2 adjacent surfaces

yield of glycolysis

spent 2 ATP

produces 4 ATP

produced 2 NADH

splits glucose into 2-3 carbon pyruvate

which pathways produce acetyl CoA

glycolysis and beta oxidation

what are the metabolic cycles used for glucose metabolism

glycolysis, citric acid cycle, oxidative phosphorylation

what pathway metabolises acetyl-CoA

citric acid cycle

how does water move in regards to concentration gradient

water moves down the concentration gradient

what causes cells to swell

hypotonic solutions

what causes cells to shrink

hypertonic solutions

what reaction produces the most ATP

oxidative phosphorylation