A complete note covering all 17 topics stated in the Cambridge Syllabus Guide in detail with diagrams, so that you would be able to answer almost any question at your O Level examination. The covered topics include, Cell Structure and Organization, Diffusion and Osmosis, Enzymes, Plant Nutrition, A...
,Contents
Page No
1. Cell Structure and Organization 3
2. Diffusion and Osmosis 9
3. Enzymes 14
4. Plant Nutrition 17
5. Animal Nutrition 30
6. Transport in Flowering Plants 61
7. Transportation in Humans (Circulatory System) 73
8. Respiration 97
9. Excretion 111
10. Homeostasis 118
11. Coordination & Response 125
12. Support, Movement and Locomotion 140
13. The Use and Abuse of Drugs 143
14. Microorganisms and Biotechnology 153
15. Relationships of organisms with one another and with the 171
environment
16. Development of Organisms and Continuity of Life 188
17. Inheritance 224
2|Page out of 242
, 1. Cell Structure and Organization
Cell-is the smallest structural and functional unit of life. Each type with its own functions like RBC
transport oxygen and Neurons (Nerve Cells) transmit nerve impulses.
All living things have cells. Animals-Animal Cells and Plants-Plant Cells.
Unicellular organisms-one celled organisms (ex:- Amoeba, Paramecium, Yeast)
Multicellular organisms-many cells (ex:-most visible living things)
Cells are observed using a microscope (light and electron). And would look like below diagram
when observed through a light microscope.
Part of the cell Features Functions
Cell Wall Only in plant cells, made of cellulose (forms a Maintains the shape of the
crisscross fibres) and is a fully permeable cell, maintains turgidity,
membrane. prevents the cell from
bursting when taking in
water.
Cell membrane Is a very thin layer of fat and protein, Enclose the cell, only
semi/selectively/partially permeable membrane. some elements can enter
(not all).
Cytoplasm Clear jelly like structure, containing 70% water, Holds the cell organelles,
metabolic reactions take place, organelles are carry out different
submerged in it. metabolic reactions.
Vacuoles Plant cells have large vacuoles containing ‘Cell To maintain the water
Sap’, surrounded by a membrane called balance and to keep the
‘Tonoplast’. cell firm.
Animal cells have a small space called ‘Vesicle’.
3|Page out of 242
, Chloroplast In plant cells, have green pigments called Photosynthesis
Chlorophyll, photosynthesis takes place and
contains starch grains.
Nucleus Main organelle in a cell and is surrounded by the Transfer inherited
Nuclear Envelope, has Chromatin Body that characteristics from
contains the DNA (Deoxyribo Nucleic Acid), generation to generation.
during cell division (Mitosis) it to divides and
forms Chromosomes, controls the type and Controlling cell activities.
quantity of enzymes produced, regulates chemical
changes, and determines the role of a cell.
Mitochondria Oval/rod shaped structure, powerhouse of the cell, Cellular respiration
invisible to light microscope, more mitochondria is (Aerobic Respiration)
present in places which need more energy. takes place here.
(Prokaryote doesn’t have this)
Ribosome Small organelle that can be seen close to the Producing proteins
Endoplasmic Reticulum or scattered freely. It’s (Protein synthesis)
made of RNA and Proteins.
Turgidity - the internal pressure in a plant cell when water is absorbed and the cell wall acting like a
balloon. This keeps the plant stem firm and upright and its leaves flat.
Difference between Animal and Plant Cells
Plant Cell Animal Cell
Has a cell wall of Cellulose outside the Cell No Cell wall
Membrane.
Has a cell membrane, nucleus, and Has a cell membrane, nucleus, and
cytoplasm cytoplasm.
Has Chloroplasts containing Chlorophyll No Chloroplast or Chlorophyll.
Has large vacuoles containing Cell Sap. Have small or no vacuoles.
Might have starch grains. No starch but might contain Glycogen
granules.
Often regular in shape Irregular in shape
Around 40-100 μm in diameter. Around 10-20 μm in diameter.
Specialization of Cells
Most cells (after division) become specialized, so that;
They do one particular job
They develop a distinct shape
Special kinds of chemical reactions take place in their cytoplasm
This specialization of cells is also referred to as ‘Division of Labour’.
4|Page out of 242
,Root Hair Cells
The outer part of the cell wall is having a long
tubular extension, to increase the surface area
required for water and mineral absorption.
Xylem Vessel Cells
Xylem Vessel is made up of 04 main cells, which are;
1. Xylem Vessel Cell
2. Tracheids
3. Parenchyma Cells
4. Fibres
Xylem Vessels are made up of a series of long xylem cells joined end to end. Once the growth
has stopped the end walls of the cell is digested, forming long hollow tubes of joined cells.
A substance called ‘Lignin’ (a complex organic polymer) gets deposited in their cell walls
making them strong and impermeable (which eventually kill the cell).
Lignin is formed in 03 distinctive patterns, they are spiral, ladder or reticulate (network)
shaped.
Function:- To transport water and minerals from the roots to each cell in each leaf
To provide mechanical support to the plant.
Red Blood Cells
These are very small (7μm diameter and 2μm thick), disk shaped biconcave cells that are red in
colour due to the red pigment Haemoglobin.
Haemoglobin (Hb) readily combines with oxygen and forms Oxyhaemoglobin, which is
transported throughout the body.
Hb + O2 = HbO
A nucleus cannot be seen in the RBC as it provides more space for the transportation of
Oxygen.
Every mm3 has 4 to 6 million RBC, which are produced by the bone marrow and has a life span
of 120 days (3 to 4 months) and is destroyed by specialized cells in the Spleen and Liver.
Type of Cell Where it is found Function
Ciliated cells Lining the trachea and bronchi. Moves mucus upwards.
Root hair cells Near the ends of plant roots. Absorb water and mineral salts.
Xylem vessels In stems, roots, and leaves of plants. Transports water and mineral salts;
help in support.
Palisade mesophyll Beneath the epidermis of the leaf. Photosynthesis.
cells
Nerve cells Throughout the bodies of animals Transmit information in the form of
electrical impulses.
Red blood cells In the blood of mammals. Transport oxygen.
Sperm and egg cells In testes and ovaries Fuse together to produce a zygote.
5|Page out of 242
,Cells and Organisms
A large organism contains millions of cells where each specialise in carrying out activities which are
characteristic of living things.
Tissue – a group of cells specialized in the same activity found together.
Ex; Stomach lining : these cells produce enzymes to digest the food.
Stomach muscles : moves the stomach wall in and out, churning the food and
mixing it with enzymes.
Inside a leaf, palisade tissue : carry out photosynthesis
Organs – a group of tissues that work together to achieve a common task.
Ex; Heart, stomach, kidney all have multiple tissues working together to complete its role.
Onion bulb, leaf are also organs.
Organ System – a group of organs working together for a particular task.
Ex; the mouth, intestines, stomach : all make up the digestive system.
Organisms – a group of organ systems working together carrying out the characteristic activities of
living things.
Ex; ciliated cells ciliated tissue (lining) organ (bronchus) organ system (respiratory system)
organism (human, animal)
Microscope
Is an Instrument used to see extremely tiny things that cannot be seen by the naked eye.
Generally, all specimens are stained with a dye in order to identify things clearly. Methylene
Blue is used to stain animal cells and Iodine is used to stain Plant Cells.
Is mainly of 02 types:-
1. Light Microscope - uses visible light for observations, a very good light microscope can
magnify up to x1500 times.
2. Electron Microscope – uses a beam of electrons and can magnify up to 500,000 times
Part Function
1. Eye Piece Is the ocular lens that helps you to see the magnified image, have
a power of x10 or x15.
2. Eye Piece/ Ocular/Body Connects the eyepiece lens with the nose piece.
Tube
3. Nose Piece Holds the 03 or 04 objective lenses with various powers.
4. Objective Lenses Has a magnification power of x4, x10, x40 and x100. Longest
lens has the highest power, and the smallest has the lowest power.
5. Course Adjustment Moves the body tube up and down and brings the specimen to
Knob correct focus.
6. Fine Adjustment Knob Brings the specimen into sharp focus.
7. Stage Flat surface where the specimen slide is kept for observation.
8. Stage Clips Holds the slide in place.
9. Aperture Hole in the stage that allows the passage of light to the slide.
6|Page out of 242
, 10. Diaphragm Helps in regulating the amount of light entering the
specimen/stage.
11. Mirror/ Illuminator Mirror – reflects sunlight to the specimen.
Illuminator – source of light.
12. Arm Connects the bas and the head of the microscope.
Practical Work
1. Observing a plant cell
Preparation
a) Peel of the dry outer leaves of an onion bulb.
b) Remove one of the fleshy layers beneath.
c) Using forceps peel away a thin layer of epidermis.
d) Place a few drops of Dilute Iodine solution on a clean, dry microscope slide.
e) Transfer the epidermis layer to the iodine solution. (Make sure it lies flat and is fully dipped
in Iodine)
f) Carefully place a cover slip on the preparation and remove any excess liquid using a filter
paper.
g) Transfer the prepared slide to the stage of the microscope and observe.
(The onion cells are large, so the high-power lens of the microscope is not needed.)
Observation
Conclusion
The cell wall, cell membrane, vacuole, nucleus, and starch grains can be seen in the onion cell
when observed under a light microscope with a magnification of x400 times.
7|Page out of 242
, 2. Observing an animal cell.
Preparation
a) Cut a cube of fresh liver (approximately 1.5cm2)
b) Scrape the cube using a spatula to gather a few cells.
c) Transfer the cells to a clean microscope slide.
d) Add a drop of Methylene Blue and a drop of Glycerol.
e) Carefully place a cover slip over the preparation and remove excess fluids using a filter
paper.
f) Transfer the prepared slide to a microscope and observe.
Observation Conclusion
The cell membrane, cytoplasm and the nucleus of
the animal liver can be observed under a light
microscope with a magnification of x400 times.
Total Magnification = Magnification of Eye × Magnification of Objective
Piece lens lens
Ex:- x10 × x40 = x400
Some organelles are extremely small, and millimetres is a lot bigger so a smaller unit like micrometre
is used.
1 mm = 1000 μm
1 cm = 10,000 μm
1 m = 1,000,000 μm
8|Page out of 242
, 2. Diffusion and Osmosis
1. Diffusion
Particles (atoms, molecules, and ions) are always on the move.
In solids, particles cannot move (only vibrate) as they are held firmly with forces of
attraction.
In liquids, particles can freely bounce and rebound on each other.
In a gas, particles are far apart, no forces of attraction between them.
As particles move freely, they tend to spread themselves out as evenly as possible.
Diffusion is a result of the random motion of particles.
In a cell H2O, O2 and CO2 can pass through the cell membrane easily.
Diffusion – is the net movement of molecules and ions from a higher concentration to the region
with a lower concentration down a concentration gradient as a result of their random movement.
Examples of Diffusion
1. Absorption of Carbon Dioxide by plants for Photosynthesis. (CO2 diffuses from the air to the leaf
through the stomata)
2. Oxygen diffuses out of the leaves to the air, after photosynthesis.
3. The gas exchange in the Alveoli.
4. Absorption of nutrients after digestion by the Ilium (intestine) happens by diffusion.
Starch Glucose absorbed by blood vessels of Villi
Proteins Amino Acids
Lipids Fatty Acids and Glycerol - Absorbed by Lacteal Villi.
5. Flowers use diffusion to spread their scent to attract pollinators.
6. During respiration by cells O2 diffuses in and CO2 out.
7. Most Living things obtain O2 through Diffusion to survive.
8. N2 diffuses into the body of divers as they go further into to the sea and when they come up
diffuses out.
Concentrated (Conc.) – has more sugar particles than water.
Dilute (Dil.) – more water than sugar particles.
Result – with time, a uniform distribution of water and sugar molecules is formed as a result of
diffusion.
9|Page out of 242
, Factors That Affect the Rate of Diffusion
1. The temperature (with the increase of temperature, particles gain more energy making them
move faster which speeds up the diffusion)
2. The distance of diffusion (greater the distance, slower the diffusion)
3. The difference between the concentration gradient. (The greater the difference, faster the
diffusion)
4. Absorption by the surface area. (Larger the surface area, faster the diffusion)
2. Osmosis
Osmosis – is the passage of water molecules from a region of higher water potential to a
region of lower water potential through a partially/semi permeable membrane.
The only difference between Diffusion and Osmosis is that in Osmosis only water
molecules are allowed to pass through the semi permeable membrane unlike in diffusion
where any molecule could mix with anything.
In vertebrates, the brain checks on the concentration and is adjusted by the kidneys, so that
the cells don’t fill up excessively with water or don’t get dehydrated without water.
Partially/Semi Permeable Membrane – is a membrane that will only allow some
molecules to pass through it.
Natural Semi Permeable Membrane – Animal Cell Membrane, Plant Cell Membrane,
Egg Membrane.
Artificial Semi Permeable Membrane – Cellophane, Visking/Dialysis Tubing.
Cellophane Visking Tubing
Is a thin, transparent sheet made of regenerated cellulose. It has a low Visking/Dialysis Tubing is
permeability most molecules (including bacteria and air) and is used used in separation
for food packaging. But cellophane is highly permeable to water techniques, as it facilitates
vapour, so it is coated with a nitrocellulose lacquer to prevent this. the flow of tiny molecules in
solutions.
There is more water potential in the low
concentration side, so the water molecules
move from the low concentration side
(high water potential) to the high
concentration side (low water potential),
through the semi permeable membrane, till
both sides become uniformly concentrated.
Demonstration of Osmosis using a Visking Tubing
Observation – The visking tubing swells and becomes firm and
turgid. The level of water in the beaker decreases and the level of
liquid in the glass tube will increase.
Conclusion – the beaker has a higher water potential, and the
solution has a low water potential. The water molecules move from the
beaker to the visking tubing through the semi permeable membrane,
making the tube swell and firm.
10 | P a g e o u t o f 2 4 2
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller vivekedirisinghe1. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $50.49. You're not tied to anything after your purchase.
