Biology

Characteristics of living organism

Identification of a living organismAn organism is an individual living thing that can react to stimuli, reproduce, grow, and maintain homeostasis. It can be a virus, bacterium, protist, fungus, plant or an animal. All living organisms do the seven following:

1. Movement. All living organisms show movement of one kind or another. All living organisms have internal movement, which means that they have the ability of moving substances from one part of their body to another. Some living organisms show external movement as well - they can move from place to place.

2. Respiration. All living things exchange gases with their environment.3. Sensitivity. Ability to sense and respond to changes in its surrounding4. Growth. An increase in size, mass, complexity of an organism5. Reproduction. Producing offspring similar to the parent 6. Excretion. Excretion is the removal of waste from the body. If this waste was allowed to remain

in the body it could be poisonous.7. Nutrition. All living organisms need to take substances from their environment to obtain

energy, to grow and to stay healthy.An organism is considered “living” when it does all of these seven characteristics.

CellsDefinition: The basic structure of organisms. All cells are made by other cells.a part of the cell containing DNA and RNA and responsible for growth and reproduction

All organisms are made up of units called cells joined together. Very small living things like bacteria are made up of only one cell.

Types of cell Animal cells Plant cells Specialised cells

o Xylem cellso Leaf palisade cellso Root hair cellso Red blood cellso Nerve cellso Muscle cellso Bone cells

Single cells

o Amoeba Many cells

o Spirogyra

Animal cells

Cell part Definition Function

Cell membrane

A thin semi-permeable membrane that sur- rounds the cytoplasm of a cell, enclosing its contents.

Gives shape the cell. Cell membrane anchors the cytoskeleton (a cellular 'skeleton' made of protein and contained in the cytoplasm).

Attaching cells together to form tissue. Cell membrane is responsible for attaching the cell to the extracellular matrix (non-living material that is found outside the cells).

Transportation of materials. This is needed for the functioning of the cell organelles. Cell membrane is semi permeable and controls the in and out movements of substances. Such movement of substances may be either at the expense of cellular energy or passive, without using cellular energy.

Receive signals from other cells or the outside environment. They convert the signals to messages that are passed to the organelles inside the cell.

Group together to form enzymes. These carry out metabolic reactions near the inner surface of the cell membrane.

Proteins in the cell membrane. also help very small molecules to get themselves transported through the cell membrane, provided, the molecules are traveling from a region with lots of molecules to a region with less number of molecules.

Cytoplasm The contents outside of Fills the interior of the cell. The cytoplasm forms

the nucleus and enclosed within the cell membrane of a cell.

the ground substance of the cell. Hold cell organelles. Cell organelles control all of

the cell’s activities. These keep the cell alive.Nucleus A part of the cell

containing DNA and RNA and responsible for growth and reproduction

Regulates all cell activity. It does this by controlling the enzymes present.

Hold the DNA needed for reproduction.

Mitochondria An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur

Provide energy for the cell through respiration. Location of ATP (adenosine tri-phosphate)

Plant cell

Cell part Definition Function

Vacuole A space within a cell that is empty of cytoplasm, lined with a membrane, and filled with fluid.

Removing unwanted structural debris Isolating materials that might be harmful to

the cell Containment of waste products Maintaining internal hydrostatic pressure or

turgor within the cell Maintaining an acidic internal pH Containing small molecules

Exporting unwanted substances from the cell. Enabling the cell to change shape.

Chloroplasts An organelle found in plant cells that conduct photosynthesis

Capture light energy. Store it in the energy storage molecules ATP

and NADPH Use it in photosynthesis. It makes organic

molecules and free oxygen from carbon dioxide and water.

Cell wall The rigid outermost cell layer found in plants and certain algae, bacteria, and fungi but characteristically absent from animal cells

Provides support. Bonds with other cell walls. This forms the

structure of the plant.

Plant sap Watery fluid of plants. Cell sap is a fluid found in the vacuoles (small cavities) of the living cell

Store important substances Support the plant. The pressure of water filling

the cell vacuole pushes out against the cell wall. This gives the wall enough strength to hold up fairly large green plants.

Animal vs. Plant cellsAnimal cell Plant cell

Plasma membrane Only cell membrane Cell wall and membraneNucleus Present PresentShape Round (irregular shape) Rectangular (fixed shape)Chloroplast Animal cells don't have

chloroplastsPlant cells have chloroplasts because they make their own food (photosynthesis)

Cytoplasm* Present PresentMitochondria Present PresentVacuole One or more small vacuoles

(much smaller than plant cells).

One, large central vacuole taking up 90% of cell volume.

Storage Store energy as granules of glycogen

Store energy as starch

*Plant and animal cells have many smaller structures in the cytoplasm.

Diffusion

Diffusion: The spread of particles through random motion from regions of higher concentration to regions of lower concentration.

Parts of solution Solute: A substance that is dissolved in a solvent to form a solution Solvent: A liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in

a solutionA solute is dissolved in a solvent.

Types of solutions Concentrated solution: Has a large amount of solute in the solvent. Diluted solution: Has a small amount of solute in the solvent.

OsmosisOsmosis: A special kind of diffusion. It is the net movement of solvent molecules through a partially permeable membrane (such as a cell membrane) into a region of higher solute concentration from a low solute concentration down a concentration gradient.

How does it work? Partially permeable membrane – The cell membrane is selectively permeable because it allows

certain molecules to pass through and no others. Water can pass through but dissolved substances cannot.

Different concentration of solution on each side of the membrane – water will move from the weak solution (high concentration of water) to the strong solution (low concentration of water).

Water potential gradient – when the number of molecules of water in the solution becomes less and the concentration of the solute becomes more, the water molecules move to the place where there is low concentration of water molecules.

Enzymes

Enzyme: Biological catalysts that are produced in all living organisms and control all the chemical reactions that occur. Enzymes are present in all cells not just in the digestive systems. They are protein molecules that have particular shape which are held together by weak hydrogen bonds.Catalysts: Substance which increases the rate of reactionSubstrate: The chemical compound on which the enzyme works. Active site: Part of an enzyme where substrates bind and undergo a chemical reaction.

Two types of enzymes Breakers – Break large molecules into smaller simpler ones for the cells to use. This is

especially important to digestion as some of the nutrients we get from foods are large molecules. Some examples are amylase to break down starch to form glucose molecules, protease to break down protein and lipase to lipids/fats.

Builders – Combine smaller ones to make large molecules inside our cell. These are important in plants to be used in photosynthesis, the opposite of respiration, because in photosynthesis, oxygen and water are combined together to form carbon dioxide and sugars.

Specific enzymes Carbohydreases break down carbohydrates to form polysaccharides Proteases break down proteins to form amino acids Lipases break down fats/lipids to form fatty acids and glycerol Amylase break down starch to form glucose and maltose

Properties of enzyme1. They are all proteins2. Each enzyme controls one particular reaction3. They can be used again.4. They are affected by temperature5. They are affected by PH6. They are held together by weak hydrogen bonds.

How do enzymes work?Enzymes work by lowering the activation energy (Ea or ΔG‡) for a reaction, thus dramatically increasing the rate of the reaction.

DenaturationEnzymes are proteins that are bonded with weak hydrogen bonds. When heat or acidity is applied to the enzyme, the hydrogen bonds break and the active site no longer fits the particular substrate. The enzyme is said to be denatured.

Sample questions

1. An enzyme has an ‘active site’ on its surface on which the reaction takes place. Use the idea of an active site to explain:

a. Why an enzyme is specific for a particular substrate. An enzyme is described to be ‘specific’ when it only catalyzes on particular substrate. The hydrogen bonds in the enzyme create the shape that is specific to the substrate. An enzyme is specific for that particular substrate because each enzyme’s active site has a certain shape to fit a particular substrate.

b. Why an enzyme denature at a high temperature. An enzyme ‘denatures’ when its shape does not fit its substrate because the hydrogen bonds are broken. Hydrogen bonds are weak bonds and connot stand the movement and energy created by the heat. Enzymes are denatured at high temperature due to the heat breaking the hydrogen bonds and the active site no longer is in its original shape to fit the substrate.

c. Why an enzyme can be used again and again. The enzyme isn’t broken down in the reaction but it is involved in the reaction.

2. How does amylase enzyme work? Amylase enzymes have an active site designed to break down the complex molecule of starch into the smaller globules of glucose to be absorbed into the body

Food and DigestionPurpose of food

For energy For growth For repair

Nutrition: Obtaining organic substances and mineral ions from which organisms obtain their energy and their raw materials for growth and tissue repair.

Nutritional Requirements For plants – need carbon dioxide, carbon diozide, water, sunlight, and chlorophyll to make

their own food. Also known as photosynthesis For animals – need seven essential nutrients: carbohydrates, proteins, fats, minerals, vitamins,

water and roughage.

Balanced Diet Definition:　The intake of correct amounts of food substances

Food substance

Function in body Examples Composition Deficiency Disease/Symptoms

Protein Growth/repairMaking enzymes

Meat, fish, soyabean

Amino acids Kwashiorkor: loss of hair, swollen abdomen

Fats Store of energy Dairy, nuts, meat, fish

3 fatty acids Lack of certain fatty acids may cause various diseases

Vitamin A To make light sensitive chemical

Cod liver oil Retinyl palmitate

Poor night vision

Vitamin C To make connective tissue

Citrus fruit Ascorbic acid Scurvy: poor healing of wounds and bleeding gums

Vitamin D To absorb enough calcium from the intestines

Dairy produce/sunlight

Cholecalciferol or ergocalciferol

Rickets: weak bones

Iron To produce haemoglobin for red blood cells

Liver, egg yolk N/A Anaemia: lack of red blood cells

6CO2 + 6H2O → C6H12O6 + 6O2

Carbon dioxide + Water (+ Light energy) → Glucose + Oxygen

Calcium Strengthening bones and teeth

Bread, dairy produce

N/A Rickets and poorly developed teeth

Fibre To allow correct rate of peristalsis

Wholemeal bread, fruit

Arabinoxylans, cellulose, dextrins, inulin, lignin, waxes, chitins, pectins, beta-glucans, and oligosaccharides

Constipation, appendicitis, bowel cancer.

Carbohydrate Supply of energy Bread, rice, potatoes

Glycogen Lack of carbohydrates is linked to lack of food (e.g. starvation)

Plant Nutrition

Photosynthesis – The fundamental process by which plants manufacture carbohydrates from raw materials using energy from light.

Formula for photosynthesis]

Formula for respiration in plants

Process of photosynthesis1. Green plants take in CO2 through the stomata in the leaves by diffusion2. Water is obtained through the root hair by osmosis from the soil and this is transported

through the xylem to leaves.3. Chloroplasts present in the leaf, trap light energy which is used to break down water molecules

into hydrogen and oxygen ions4. Hydrogen and CO2 combine to form glucose5. Glucose usually changes into sucrose for transport and is stored as starch6. Oxygen is released as a waste product or is used for respiration.

C6H12O6 → 2CO2 + 2C2H5OH (+ Energy)Glucose → Carbon Dioxide + Ethanol (+ Energy)

C6H12O6 + 6O2 → 2CO2 + 6H2O (+ Energy)Glucose + Oxygen → Carbon Dioxide + Water (+ Energy)

C6H12O6→2C3H6O3 (+ Energy)Glucose → Lactic acid (+ Energy)

RespirationDefinitionRespiration: Chemical reactions that break down nutrient molecules in living cells to release energy.

Aerobic Respiration: The release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen. It mainly occurs when there is sufficient oxygen

Anaerobic respiration: The release of a relatively small amount of energy by the breakdown of food substances in the absence of oxygen.

Equation of aerobic and anaerobic exerciseAerobic respiration

Anaerobic respiration

Difference between aerobic and aneaerobic respiration

Aerobic AnaerobicTakes place in the presence of oxygen Oxygen not requiredGlucose is broken down into CO2 and H2O CO2 and C2H5OH38 ATPs are produced 2 ATPs are producedTakes place in the cytoplasm and mitochondria Only in the cytoplasm

Oxygen Debt

What is it?When your cells don't receive enough oxygen during exercise they start respiring without it, creating lactic acid as a result. Debt is simply breathing in the required amount of oxygen needed to get rid of the lactic acid that built up.

Gas exchange

The respiratory system

Alveoli and gas exchange

Function of the alveoliThe basic function of the alveoli is gas exchange. The alveoli structure is the site where the gaseous exchange during respiration takes place. These structures are surrounded by capillaries carrying blood. The exchange of carbon dioxide in the blood from these capillaries occurs through the walls of alveolus.

The alveoli begins to function when we breathe in air through our nostrils. The air passes through a long route consisting of various organs of the respiratory system. These organs include the nasal

passages, pharynx, larynx, trachea, main bronchi, small bronchial tubes, bronchioles and finally reaching the alveolus through tiny air sacs. The air contains oxygen that is absorbed by the blood flowing through the capillaries. This oxygen is then passed on to the circulatory system, thus completing the gaseous exchange cycle.

How gas exchanges take place in the alveoli?

The pulmonary gaseous exchange takes place by passive diffusion. During this gas exchange, no energy is required to be burned by the cells. The gases move through a concentration gradient that is high concentration to low concentration. This means that oxygen in the alveolus is in the high oxygen concentration gradient. It diffuses into the blood that is in the low oxygen concentration gradient. This is because of the continuous oxygen consumption in the body. The same thing happens in case of carbon dioxide. Blood contains high carbon dioxide concentration and alveoli contains low carbon dioxide concentration. Thus, the gaseous exchange takes place through passive diffusion as a part of respiratory system function.

The circulatory system

Heart ChambersThe internal cavity of the heart is divided into four chambers:

Right atrium Right ventricle Left atrium Left ventricle

The two atria are thin-walled chambers that receive blood from the veins. The two ventricles are thick-walled chambers that forcefully pump blood out of the heart. Differences in thickness of the heart chamber walls are due to variations in the amount of myocardium present, which reflects the amount of force each chamber is required to generate.

The right atrium receives deoxygenated blood from systemic veins; the left atrium receives oxygenated blood from the pulmonary

veins.

Valves of the Heart

The right atrioventricular valve is the tricuspid valve. The left atrioventricular valve is the bicuspid valve. The valve between the right ventricle and pulmonary trunk is the pulmonary semilunar valve. The valve between the left ventricle and the aorta is the aortic semilunar valve.

When the ventricles contract, atrioventricular valves close to prevent blood from flowing back into the atria. When the ventricles relax, semilunar valves close to prevent blood from flowing back into the ventricles.

Flow of BloodIt is important to realize that both atria and ventricles contract at the same time. Blood flows from the right atrium to the right ventricle, and then is pumped to the lungs to receive oxygen. From the lungs, the blood flows to the left atrium, then to the left ventricle. From there it is pumped to the systemic circulation.

How does the heart circulate blood around the body?

Coronary circulation

1. Waste-rich blood fills the right atrium

2. It then contracts and pushes the blood into the right ventricle.

3. From the right ventricle, the blood is pumped into the lungs via the pulmonary artery.

Pulmonary circulation1. Waste-rich blood enters the lung2. It fills the lung capillaries. It is within these capillaries that the carbon dioxide in the blood is

exchanged for oxygen. 3. The new, oxygen-enriched blood continues its journey through the pulmonary veins in the

lungs and returns to the heart through the left atrium. 4. From the left atrium, the blood is pumped to the left ventricle and then leaves the heart by

way of the aorta. 5. Valves keep the blood flowing in the proper direction, preventing any blood from flowing

backward and causing problems.

Systemic circulation1. Oxygenated blood is pumped through the aorta2. Blood is forced through the arteries, which forces the blood through smaller arteries called

arterioles. 3. The arterioles carry the blood and nutrients to the even smaller capillaries, where the blood

makes contact with the cells in the body. 4. Oxygen is delivered and waste cells are picked up to make the journey back to the heart. 5. The waste-rich blood is pumped through the veins. 6. The veins reach the heart, where the waste-filled blood flows into the right atrium

Veins, Arteries, Capillaries Structure Adaptation

Veins Wide lumen Thin endothelium (single layer of cells) Has valves Smooth muscles Elastic tissue

takes blood back to the heart so a high pressure is not required.

It also allows ease of flow. reduces friction of the flowing

blood keeps blood flowing towards the

heart and prevents backflow. can constrict to improve exchange

of gas at the alveoli works as the smooth muscles

relaxes to return the vessel to its orignal size and shape

Arteries Receive blood under high pressure from the ventricles of the heart.

The walls of arteries consist of three layers, namely an outer layer, a thick middle layer and an inner layer.

Outer layer consist of white fibrous connective tissue which merges to the outside with the loose connective tissue in which artery is found.

thick middle layer consist of elastic connective tissue and involuntary muscle tissue.

this layer is supplied with two sets of nerves, one stimulating the muscles to relax so that the artery is allowed to widen, and the other one causing the circular muscles to contract, making the artery become narrower.

The inner layer of endothelium consists of flat epithelial cells which are packed closely together and which is continuous with the endocardium of the heart.

The flat cells make the inside lining of the arteries smooth.

Outer layer helps to anchor the arteries because the heart pumps the blood through the arteries at a great pressure.

Flat cells limit friction between the blood and the lining to a minimum.

Must be able to stretch each time the heart beats, without collapsing under the increased pressure.

Capillaries Very small Thin walls (one-two cells thick) Microscopic holes (in kidney/liver capillaries)

Allows diffusion to occur Microscopic holes allow proteins

and nutrients to be excreted.

Blood

Structure FunctionRed blood cell(Erythrocytes)

To carry oxygen/carbon dioxide to cellso Concave shape allows large surface

area in order for large amounts of oxygen per cell

Contains hemoglobin which stick onto oxygen gas

Lymphocytes Responsible for immune responses Two main: B cells and T cells

o B cells: make antibodies that attack bacteria and toxins

o T cells: attack body cells themselves when they have been taken over by viruses or have become cancerous

Secrete lymphokines that modulate the functional activities of many other types of cells

Present at sites of chronic inflammationNeutrophils granulocytes

First immune cells to arrive at a site of infection

o Arrived through a process called chemotaxis

Ingest pathogens Protect the body against pathogens

Platelets Prevent excessive internal/external bleeding by clotting after an injury

Maintenance of homeostasis (process which causes bleeding to stop)

Makeup of Blood

Nervous SystemDefinition

Central Nervous System: Often abbreviated as CNS. It comprises of the brain and spinal cord. The CNS receives sensory information from the nervous system and controls the body's responses.

Peripheral Nervous System: Often abbreviated as PNS. It is the division of the nervous system containing all the nerves that lie outside of the CNS

Receptors: A sensory nerve ending that responds to a stimulus in the internal or external environment of an organism.

Sense organ: A group of receptor cells responding to a specific stimulus, such as light, sound, touch, temperature, chemicals