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Year 11 Human Biology notes
Topic 1. Cells and Tissues
Animal and plant cells are eukaryotic cells, meaning it contains a nucleus and many other
various organelles, surrounded by a plasma membrane
Cell Membrane
The cell membrane is a structure described as a ‘fluid mosaic’
Fluid: made up of phospholipids which are like liquid and
move easily within each layer
Mosaic: form the surface of the membrane and looks like a
mosaic picture made up of tiles.
Functions of the cell Membrane
1. forms a barrier for water soluble substances between cytoplasm and extracellular
2. Are permeable to non-polar molecules like fatty acids and oxygen, and to small polar
molecules like water and carbon dioxide
3. are impermeable to ions and non-polar molecules
4. allow movement so vesicles can form and/or re-join
Types of movement across a membrane
Diffusion: passive transport across a membrane from high concentration to low
Facilitated diffusion: type of passive transport that allows substances to cross a membrane
with the assistance of special transport proteins, some molecules (like glucose) are unable
to just simply pass through lipid membranes.
Active Transport: dissolved molecules move across a cell membrane from a low to high
concentration (against/opposite), which requires an input of energy from the cell
Osmosis: the movement of water molecules from a high concentration to a low
Carrier Mediated Transport: Carrier proteins transport molecules across a plasma
membrane. They bind the particles on their active sites and release them on the other side
of the membrane. Carrier proteins can only transport molecules in one direction.
Vesicular Transport: mechanism for exchange of proteins and lipids between membranebound organelles.
Endocytosis: the cell internalises non particulate materials such as proteins by
engulfing them in an energy dependent matter by pinocytosis (cell drinking) or
phagocytosis (cell eating)
Exocytosis: the fusion of secretory vesicles with the plasma membrane and results in
the discharge of the vesicle content into extracellular space and the incorporation of
new proteins and lipids into the plasma membrane
Tissue types
Epithelial: Cells that line the surfaces of your body. They make up the lining of your skin,
blood vessels, urinary tract and organs. Functions of epithelial cells include; protection,
secretion, absorption, excretion, filtration, diffusion, and sensory reception.
Connective: this group of cells that supports, protects and gives structure to other tissues
and organs in the body. Connective tissue also stores fat, helps move nutrients and other
substances between tissues and organs
Muscular: responsible for movement, maintenance of posture, joint stabilisation and heat
Nervous: main function is to send and receive information from stimuli and communicate
with the spina chord and brain via electrical impulses
Metabolism refers to the process by which your body converts what you eat and drink into
energy. During this complex process, calories in food and beverages are combined with
oxygen to release the energy your body needs to function.
Catabolic: Large molecules broken down into smaller ones – energy is released. Think of the
breaking down of your food.
Anabolic: Small molecules assembled into larger molecules – energy is required. Think of the
anabolic pathway where macromolecules are created.
Cellular Respiration
Cellular respiration is the process by which organisms combine oxygen with food molecules
in a chemical reaction which releases energy, resulting in wastes of carbon dioxide and
water. The catabolic breakdown of glucose releases ATP.
Aerobic Respiration
1. Glycolysis
- Occurs in the cytoplasm of the cell. During
this process, a glucose molecule is broken
down (catabolism) into two pyruvate
molecules (pyruvate acid)
2. Citric Acid Cycle (Kreb’s Cycle)
- Occurs in the Mitochondria of the cell.
This process turns the pyruvate molecules
into carbon dioxide. This releases 2 ATP .
3. Electron Transport Chain
- Also occurs in the Mitochondria, and
produces 32 ATP from the Conversion of
NADH and FADH. The electron Transport
chain works as a proton pump, pumping
hydrogen ions through the membrane
Anaerobic Respiration
Anaerobic respiration does not use oxygen,
Only glycolysis can occur, so it only
produces 2 ATP. Single celled organisms
(bacteria and yeast) can survive
anaerobically. Large animals, like humans build up an oxygen debt when anaerobic.
Pyruvate builds up and is converted into lactic acid.
Enzyme function
1. substrate binds to the active site of the enzyme – some enzymes have two
substrates that bind to different parts of the active site
2. while the substrates are bound to the active site they change into different chemical
substances, which are the product of the reaction
3. the products separate from the active site, leaving it vacant for substrates to bind
4. the substrate molecules can only bind to the active site if it moves very close to it –
coming together of a substrate molecules and an active site is known as collision
5. most reactions the substrates are dissolved in water around the enzyme because
water is in a liquid states its molecules and all the particles dissolved in it are in
contact with each other and are in continual motion – each particle can move
6. the direction for movement changes and is random, basis of diffusion in liquids
7. both substrates and enzymes with active sites are able to move, though most
substrate molecules are smaller than the enzyme so their movement is faster
8. collisions between substrate molecules and the active site occur because of random
movements of both substrate and enzyme – the substrate may be at any angle to
the active site when the collision occurs. successful collisions are ones in which the
substrate and active site are correctly aligned to allow binding to take place
Factors affecting Enzyme activity
Temperature: low temperatures result in insufficient thermal energy for activation to occur.
Increasing the temperature can increase the speed/motion of both enzyme and substrate
resulting in more frequent collisions. And an optimal temperature, the rate of enzyme
activity will be at its peak. Too high temperatures can cause the stability of the enzyme to
decrease causing it to denature.
pH – Acidity and Basicity:
changing the pH will alter the
charge of the enzyme, which inturn will alter protein solubility
and shape. Changing the shape
or charge can change the shape
of the active site, which
therefore decreases the ability
of the substrate to bind to the
active site. Enzymes have an
optimal pH, and moving outside
this range can alter its efficacy.
Small changes outside the
optimal change may not have a
permanent change in shape,
however larger pH changes can.
Substrate concentration: increasing substrate concentration increases the rate of reaction.
This is because there are more substrate molecules available to collide with the enzyme, so
more product will be formed.
Enzyme Concentration: increasing enzyme concentration will initially increase reaction rate
as more enzymes will be colliding with substrate, however this will only have an effect up to
a certain point. Once saturation occurs, the limiting factor will change, this same process
also occurs with an increase in substrate concentration.
Musculoskeletal System
Types of Joints
Osteoporosis: a disease that weakens the bones to the point where the break easily. Most
often the bones in the hip, spine and wrist. Osteoporosis is caused by a lifelong lack of
calcium. Low calcium intake results in low bone density. You can prevent bone loss with
regular exercise, this can also help keep your bones strong and reduce the risk of fracture on
the future.
Osteoarthritis: occurs when the protective cartilage that cushions the ends of the bones
wears down over time. This disease can damage any joint however it is most common in
hands, knees, hips and spine. It is an age related disease that cannot be cured but there are
many treatments available to maintain pain.
Sliding Filament theory
The sliding filament theory describes the mechanism that allows muscles to contract.
Myosin (a motor protein) binds to actin. The myosin then alters its configuration which
results in a power stroke that pulls on the actin filament and causes it to slide across the
myosin filament, the overall process shortens the sarcomere structure, but does not change
the actual length of each filament.
1. The sarcoplasmic reticulum is stimulated to release calcium ions
2. Calcium ions bind to troponin which causes troponin to drag tropomyosin off cross
bridge binding sites. Cross bridges bind to actin
3. Cross bridges on myosin pull on actin = power stroke. Actin filaments slide to the
middle of the sarcomere, muscle shortens and contracts.
4. Cross bridge detaches from binding sites on actin
5. Muscle fibre lengthen and relaxes
6. Calcium ions are actively pumped back into sarcoplasmic reticulum. Troponin is
released from tropomyosin. Tropomyosin covers cross bridge binding site.
Respiratory System
- Air that moves from the external environment
into the body must pass through the nasal cavity
where it is warms, humidified and surveyed for
- As air moves out of the nasal cavity, it moves
into the pharynx, larynx, trachea, the primary
bronchi (left and right lung), secondary and
tertiary bronchi, bronchioles, terminal then
respiratory bronchioles, alveolar ducts and then
alveolar sacs where gas exchange occurs with
the capillaries.
- Mucus production and the presence of cilia
help to protect the lungs from foreign material.
Circulatory System
Function is to move blood throughout the body. This blood circulation keeps organs,
muscles and tissues heathy and working to keep you alive.
The circulatory system also helps your body get rid of waste products;
- carbon dioxide from respiration
- chemical by-products from your organs
- wastes from things you eat and drink
Composition of Blood
- Plasma: watery fluid section. It
transports nutrients as well as
wastes throughout the body.
Contains proteins, electrolytes,
carbohydrates, minerals and fats
- Erythrocytes: aka red blood
cells, biconcave discs. The shape
provides flexibility, maximum
surface area. Primary function is
to transport oxygen
- Leukocytes: aka white blood
cells. They are larger than red
blood cells. Some are phagocytic
(cell eater), other produce
antibodies – defence against
organisms that cause disease.
-Thrombocytes: aka platelets, are
cell fragments that become sticky
and clump together to form plugs
that close breaks/tears in blood
vessels, they initiate the
formation of blood clots.
Lymphatic System
The lymphatic system is out body’s sewerage system. It maintains fluid levels in our body
tissues by removing all fluids that leak out of our blood vessels. The lymphatic system is
important for the optimal functioning of our general and specific immune system.
Blood Transfusions and Types
A blood transfusion is a safe procedure that replaces blood lost due to injury or surgery. Tt
can also help treat certain medical conditions. Blood Transfusions can be lifesaving, but they
can cause some mild side effects. Although infections are very rare, it is possible for the
body to react to the new blood. In most cases, however, these reactions are mild
Four blood Types: A, B, AB, O. O is compatible with all blood types (universal donor)
Digestive System
- Made up of the gastrointestinal tract, liver, pancreas and gallbladder
- The hollow organs that make up the GI tract include the mouth, oesophagus, stomach,
small intestine, large intestine and anus.
- The small intestine is made up of three parts; (in order) duodenum, jejunum and ileum.
- The large intestine includes (in order) the appendix, cecum, colon and rectum. The
appendix is attached to the cecum.
- Bacteria (gut flora/microbiome) in the GI tract help with digestion along with the nervous
and circulatory systems, and hormones.
- Your digestive system breaks down proteins into amino acids, fats into fatty acids and
glycerol, and carbohydrates into simple sugars.
Chewing physically breaks down food. Salivary amylase (enzyme) begins to
chemically break down food
Oesophagus Once you begin swallowing, the process becomes automatic – peristalsis
Stomach muscles help to mix the food with digestive juices. Becomes a slop
called Chyme and it passed into the small intestine. The stomach has glands
that secrete stomach acid and enzymes
Muscles of the small intestine mix the food with digestive juices from the
liver (bile stored in gall bladder, to digest fats and vitamins) and pancreas
(digestive juices direct from ducts to the small intestine, breaks down fat,
carbohydrates and proteins). The walls of the small intestine absorb
nutrients and some water from the chyme and pass it into the blood
Waste products from the digestive process include indigested food, fluid
and old cells from the lining of the GI tract. The large intestine absorbs the
remainder of the water and turns the waste into a stool. Peristalsis helps
move the stool into your rectum
The lower end of your large intestine, the rectum stores the stool until you
- water is essential to extract nutrients from digested food into the blood stream. The small
intestine uses diffusion to extract water and water soluble nutrients – glucose, amino acids,
water soluble vitamins (b/c) and minerals
- fats and fat soluble vitamins (a, d, e and k) require energy to
Excretory System
Components = Kidneys, liver lungs and skin
- Cells produce water and carbon dioxide as by-products of metabolic breakdown
- the continuous production of metabolic wastes creates a steep concentration gradient
across the cellular membranes, causing wastes to diffuse out of cells and into the
extracellular fluid
- excretory systems regulate the chemical composition of body fluids by removing metabolic
wastes and retaining the proper amounts of water, salts and nutrients
- nitrogen wastes are a by-product of protein metabolism. Amino groups (NH2) are removed
from amino acids, combines with hydrogen to form NH3 = ammonia
- ammonia is very toxic, and is then converted to urea with help from the liver
- The urinary system is made up of kidneys, ureters, bladder and urethra.
- all vertebrates have paired kidneys. Their primary duty is to regulate body fluids, second to
removal of wastes
- Kidney Function
1. maintain volume of extracellular fluid
2. maintain ionic balance in extracellular fluid
3. maintain pH and osmotic concentration of the extracellular fluid
4. excrete toxic metabolic by-products such as urea
- The Nephron
- Consists of a cup shaped capsule containing capillaries and the glomerulus and a
long renal tube.
- blood flows into the kidney through the renal artery which branches into capillaries
associated with the glomerulus.
- arterial pressure causes water and solutes from the blood to filter into the capsule
- fluid flows through the proximal tubule, which include the loop of Henle and then
into the distal tubule
- the distal tubule empties into a collecting duct
- fluids and solutes are returned to the capillaries that surround the nephron tube
- Three main functions of the nephron
1. Glomerular filtration of water
and solutes from the blood
2. tubular reabsorption of
water and conserved molecules
back into the blood
3. tubular secretion of ions and
other waste products from
surrounding capillaries into the
distal tubule
- Components of the Nephron
- Glomerulus: mechanically filters blood
- Bowmans capsule: mechanically filters blood
- Proximal Convoluted Tubule: reabsorbs 75% of water, salts, glucose and
amino acids
- Loop of Helne: Counter current exchange – maintains concentration
- Distal Convoluted Tubule: secrets H ions, potassium and certain drugs