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54 Cards in this Set

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polarity of water
water molecules consist of two hydrogen atoms bonded to an oxygen atom, water molecules have two poles- a positive hydrogen pole and a negative oxygen pole. This feature of a molecule is called polarity
hydrogen atoms have a slight positive charge, oxygen atoms have a slight negative charge
What are the four most common chemical elements of life
carbon, hydrogen, oxygen, and nitrogen
what are the functions of lipids
energy storage- in the form of fat in humans and oil in plants

heat insulation- a layer of fat under the skin reduces heat loss

buoyancy-lipids are less dense than water so help animals to float
energy storage, heat insulation, buoyancy
What are the subunits of DNA
Phosphate group, sugar, and the "base"
Building DNA molecules
two DNA nucleotides can be linked together by a covalent bond between the sugar of one nucleotide and the phosphate group of the other.

DNA molecules consist of two strands of nucleotide wound together into a double helix, hydrogen bonds link the two strands together
what kind of bond links the antiparallel strands together
Taking in food
humans take in food through the mouth and the esophagus.

food is absorbed in the small intestine in a process called absorption. Small finger like projections from the wall of the small intestine called villi are specially adapted to absorb food molecules. After food has been absorbed it is assimilated and becomes a part of the tissues of the body.
the need for digestion
food must be broken down because food that humans eat is not suitable for human tissues.

many molecules in food are too large to be absorbed by the villi in the small intestine.

digestion of large molecules happens naturally at body temperature, but only at a very slow rate. Enzymes are essential to speed up the process
salivary amylase
Salivary Glands,
pH 7
source, substrate, products, optimum pH
wall of stomach
small polypeptides
source, substrate, products, optimum pH
Pancreatic lipase
Triglycerides (fats or oils)
fatty acids and glycerol
source, substrate, products, optimum pH
Functions of the stomach
digestion of proteins begins in the stomach, catalysed by pepsin. Bacteria, which could cause food poisoning, are most likely killed by the acid conditions of the stomach. The acidity also provides optimum conditions for pepsin to work.
Functions of the intestines
enzymes secreted by the wall of the small intestine complete the process of digestion. the end products of digestion are absorbed by the villi protruding from the wall of the small intestine.

the indigestible parts of the food, together with a large volume of water, ass on into the large intestine. Water is absorbed here leaving solid feces which are eventually egested through the anus.
relationship between structure of a villus and its function
villi increase the surface area over which food is absorbed

an apithelium, consisting of only one thin layer of cells, is all that foods have to pass through to be absorbed

protrusions of the exposed part of the plasma membranes of the epithelium cells increase the surface area for absorption.

protein channels in the microvilli membranes allow rapid absorption of foods by facilitated diffusion and pumps allow rapid absorption by active transport

mitochondria in epithelium cells provide the ATP needed for active transport

blood capillaries inside the villus are very clost to the epithelum so the distance for diffusion of foods is very small

a lacteal (a branch of the lymphatic system) in the centre of the villus carries away fats after absorption
Heart Structure
the heart is a double pump, with the right side pumping blood to the lungs and the left side pumping blood to all the other organs. the walls of the heart are composed of cardiac muscle. Contraction ofcardiac muscle is myogenic
there are many capillaries in the muscular wall of the heart. the blood running through these capillaries is supplied by the coronary arteries which branch of the aorta, close to the semilunar valve. the blood brought by the coronary arteries brings nutrients. it also brings oxygen for aerobic cell respiration, which provides the energy needed for cardiac muscle contraction
can contract on its own iwthout the stimulation of a nerve cell (muscle)
which arteries go to the lungs, to the other organs?
pulmonary goes to the lungs, aorta goes to other organs
where do the vena cava(s) go?
right atrium
they are veins
where do the pulmonary veins come from
what does the atrio-ventricular valve do?
prevent back flow into atria
what do the semilunar valves do?
allow the ventricles to fill with blood
block the arteries from the ventricles
thick outer layer of logitudinal collagen and elastic fibres to avoid bulges and leaks

thick wall to withstand high pressures

thick layers of circular elastic and muscle fibres to help pump the blood after each heart beat

narrow lumen to help maintain pressures
thick outer layer

thick wall


narrow lumen
thin layers with a few circular elastic and muscle fibres because blood does not flow in pulses so theveins wall cannot help pump it.

wide lumen is needed to accomodate the slow flowing blood

thin wall allows the vein to be pressed flat by adjacent muscles, helping to move the blood

thin outer layer of logitudinal collagen and elastic fibres because there is littledanger of bursting
thin layers

wide lumen

thin wall

thin outer layer
wall consists of a single layer of thing cells so the distance for diffusion in or out is small

pores between cells in the wall allow some o the plasma to leak out and form tissue fluid. phagocytes can also squeee out

very narrow lumen so that the capillaries can fit into small spaces. many small capilarries have a larger surface area than fewer wider ones
single layer wall

pores between cells

very narrow lumen

collecting chambers
pumping chambers
action of the heart
the walls of the atria contract, pushing blood from the atria into the ventricles through the atrioventricular valves, which are open. the semi lunar valves are closed, so the ventricles are filled with blood

the walls of the ventricles contract powerfully and the blood pressure rapidly rises inside them. this rise in pressure first cuases the atrioventricular valves to close, preventing back-flow of blood to the atria and then causes the semilunar valves to open, allowing blood to be pumped into the arteries. at the same tiem the atria start to refill as the collect blood from the veins

the ventricles stop contracting and as pressure falls inside them the semilunar calves close, preventing back-flow of blood from the arteries to the ventricles. when the ventricular pressure drops below the atrial pressure the atrioventricular valves open. Blood entering the atrium from the veins then flows on to start filling the ventricles.
what controls the heart beat?
what can transmit messages to the pacemaker
one nerve carries messages from the brain to the pacemaker that tell the pacemaker to speed up the beating of the heart

another nerve carries messages from the brain to the pacemaker that tell the pacemaker to slow down the beating

adrenalin carried to the pacemaker by the bloodstream, tells the pacemaker to speed up the beating of the heart
what kind of cells are in blood
plasma, erythrocytes, leukocytes and platelets
what is an erythrocyte
red blood cell
what is a leukocyte?
white blood cell
functions of blood
transport and defense against infectious disease
what do red blood cells transport
oxygen from lungs to respiring cells
what does blood plasma transport

carbon dioxide



what are antibodies
antibodies are proteins that recognize and bind to specific antigens
what are antigens
antigens are foreign substances that stimulate the production of antibodies
what is the main function of antibodies
to defend the body against pathogens by binding to antigens on the surface of a paathogen and stimulating its destruction
what are natrual barriers to infection
the skin and mucous membranes
how does skin function as a barrier to infection
the outer layers are tough and form a physical barrier. sebaceous glands in the skin secrete lactic acid and fatty acids, which make the surface of the skin acidic.
how do mucous membranes function as barriers to infection
they do not form a strong physical barrier, but many bacteria are killed lysozyme, an enzyme in the mucus.

bacteria can also get caught in the sticky mucus and cilia push the mucus and bacteria out
where are mucous membranes found
nose, trachea, vagina, and urethra
what are antibiotics
chemicals produced by microorganisms to kill or control the growth of other microorganisms
why do antibiotics not work on viruses
viruses carry out very few processes themselve. they rely instead on a host cell such as a human cell to carry out the processes for them. it is not possible to block these precesses with an antibiotic without also harming hte human cells.
what do phagocytes do?
identify and ingest pathogens
what is a pathogen
an organism or virus that causes disease
production of antibodies
antibodies are made by lymphocytes, one of the two main types of leukocyte

a lymphocyte can only make one type of antibody so a huge number of different lymphocyte types is needed. Each lymphocyte puts some of the antibody that it can make into its plasma membrane with the antigen-combining site projecting outwards

when a pathogen enters the body, its antigens bind to the antibodies in the plasma membrane of one type of lymphocyte

when antigens bind to the antibodies on the surface of a lymphocyte, this lymphocyte becomes active and divides by mitosis to produce a clone of many identical cells

the clone of cells starts to produce large quantities of the same antibody- the antibody needed to defend the body against the pathogen.
cell respiration
happens in the cytoplasm and mitochondria of cells and releases energy in the form of ATP for use inside the cell
gas exchange
swapping of one gas for another. gas exchange happens in the alveoli of human lungs. oxygen diffuses from the air in the alveoli to the blood in the capillaries. carbon dioxide diffuses in the opposite direction.

this can happen because there are concentration gradients of oxygen and carbon dioxide between the air and the blood.
to maintain the concentration gradients the air in the aveoli must be refreshed frequently.

the process of bringing fresh air to the alveoli
tube going into the lungs
branches off the trachea
branches off bronchus
muscle that allows breathing
what are the adaptations of the alveolus to gas exchange?
the lungs contain hundreds of millions of alveoli in total, which gives huge surface area for gas exchange

the wall of the alveolus consist of a single layer of very thin cells. the capillary wall also is a single layer of thin cells so the gas only has to diffuse a short distance

alveolus covered by a dense network of blood capillaries

cells in the alveolus wall secrete a fluid which keeps the inner surface of the alveolus moist, allowing the gases to dissolve. The fluid also contains a natural detergent, which precents the sides of the alveoli from sticking together