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uitgebreide Samenvatting hoofdstuk 4 silverthorn human physiology
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Fleur sam ch4Emergent properties= distinctive traits that cannot be predicted from the simple sum of the
component parts.
Fundamental concept of biology is the energy cycling between environment and living
organisms. All cells use energy from their environment to grow, make new parts and
reproduce.
- Plants trap radiant energy from sun and store it as chemical bond energy through
process of photosynthesis. They extract carbon and O2 from CO2, Nitrogen from soil
(bodem) and hydrogen and O2 from H2O to make biomolecules like glucose and
amino acids.
- Animals cannot trap energy from sun or use carbon/nitrogen from air/soil to
synthesize biomolecules. They must import chemical-bond energy by ingesting
biomolecules of plants or other animals. Energy trapped by photosynthesis is the
energy source for all animals including humans.
Animals extract energy from biomolecules through the process of respiration:
consumes O2 and produces CO2 + H20. If animals ingest more energy than needed
for immediate use stored in chemical bonds (as in plants).
Glycogen and lipid molecules are main energy sources in animals. Those molecules
available for use when animal’s energy exceed food’s intake.
Energy= capacity to do work.
Biological system’s definition of work:
- Chemical work: making/breaking of chemical bonds. Enables cells and organisms to
grow, maintain suitable internal environment, store information needed for
reproduction/other activities. Bv. Forming chemical bonds of protein
- Transport work: enables cells to move ions, molecules and larger particles through
cell membrane and membranes of organelles inside cell. particularly useful for
creating concentration gradients, distributions of molecules in which the
concentration is higher on one side of membrane than on the other. Bv. Types of ER
use energy to import Ca2+ from cytosol. Ion transport creates high Ca2+ conc. in the
cytosol. If Ca2+ is then released back into cytosol Ca2+ signal that causes cell to
perform action bv. Muscle contraction.
- Mechanical work: used for movement. Cellular level: bv. Moving organelles around in
cell, changing cell shape, cilia/flagella beating. Macroscopic level: bv. Muscle
contraction. Most mechanical work is mediated by motor proteins that make up
certain intracellular fibers and filaments of cytoskeleton.
Energy can be classified in various ways, often: thermal, electrical, mechanical, etc.
Energy is stored in chemical bonds.
Each type of energy has own characteristics.
All types of energy have ability to appear in 2 forms:
, - Kinetic energy: energy of motion. Bv. Ball rolling down hill/perfume molecules
spreading in air/ electric charge flowing through power lines/ heat warming frying
pan/molecules moving across biological membrane.
- Potential energy: stored energy. Bv. ball poised at top of hill (bc it has potential to
start moving down the hill)/molecule positioned in high-conc side of conc. gradient
(bc has potential to move down the gradient). In chemical bonds, potential energy is
stored in the position of electrons that form the bonds.
All types of energy can reverse between potential and kinetic energy.
‘work’ always involved movement, therefore often associated with kinetic energy. Potential
energy can also be used to perform work but must first be converted into kinetic energy.
Conversion from potential energy kinetic energy, never 100% efficient, certain amount is
lost to environment (bv. heat). Amount of energy lost depends on efficiency of process.
Many physiological processes in human body not very efficient. Bv. 70% of energy used in
physical exercise is lost as heat rather than transformed into work of muscle contraction.
In biological systems potential energy is stored in concentration gradients and chemical
bonds. It’s transformed into kinetic energy when needed to do chemical, transport,
mechanical work.
2 basic rules govern the transfer of energy in biological systems and universe as a whole:
1. First law of thermodynamics/ law of conservation of energy: states that total amount
of energy in universe is constant. Universe is a closed system- nothing enters/leaves.
Energy can be converted form one type to another but total amount of energy in
closed system never changes.
Human body is not closed but open system exchanges materials/energy with
surroundings. Bc bodies cannot create energy the energy is imported from outside in
form of food. Bodies lose energy in especially form of heat to environment. Energy
that stays within body can be changed from one type to another or can be used to do
work.
2. Second law of thermodynamics: natural spontaneous processes move from a state of
order (non-randomness) to a condition of randomness/disorder= entropy.
Creating/maintaining order in open system like body requires input of energy.
Disorder occurs when open systems lose energy to surroundings without regaining it.
When this happens, the entropy of open system has increased.
Without continual input of energy, cell is unable to maintain its ordered internal
environment. As the cell loses organisation, its ability to carry out normal function
disappears, and it dies.
Using chemical reactions, cells transform potential energy of chemical bonds into kinetic
energy for growth, maintenance, reproduction and movement.
Characteristic living organism= they extract energy from environment and use it to support
life processes.
Bioenergetics= study of energy flow through biological systems
In biological system, chemical reactions are critical means of transferring energy from one
part of the system to another.
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