IGCSE 0653 Combined Science Biology Notes

Biology Quick
Revision Guide




Notes for 0653 Combined Science
Written by BN Mupeti
Email
2nd Edition © 2024

,CONTENTS………. PAGE NUMBER………….

Biology

B1. Characteristics of living organisms 01
B2. Cells 01
B3. Movement into and out of cells 04
B4. Biological molecules 06
B5. Enzymes 07
B6. Plant nutrition 11
B7. Human nutrition 13
B8. Transport in plants 16
B9. Transport in animals 17
B10. Diseases and immunity 23
B11. Gas exchange in humans 24
B12. Respiration 26
B13. Drugs 26
B14. Reproduction 27
B15. Organisms and their environment 32
B16. Human influences on ecosystems 35




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, Brian Nathan Mupeti email:

B1: Characteristics of living organisms

Movement: an action by an organism or part of an organism causing a change of position or
place.

Respiration: chemical reactions in cells that break down nutrient molecules and release
energy for metabolism.

Sensitivity: ability to detect and respond to changes in the internal or external environment.

Growth: permanent increase in size and dry mass.

Reproduction: processes that make more of the same kind of organism.

Excretion: removal of waste products of metabolism and substances in excess of
requirements

Nutrition: taking in of materials for energy, growth and development.

The seven characteristics could be memorized by the term “Mrs. Gren”:

Movement Growth

Respiration Reproduction

Sensitivity Excretion

Nutrition



B2: Cells

Cell structure

Living organisms are made of cells. Cells are very small; hence, they can only be seen under
a microscope. We have two types of cells namely plant and animal cells.

Comparing the structure of a plant and animal cell

Plant cell vs animal cell: Structural comparison

Organelle Plant Cell Animal Cell
Cell Membrane Yes Yes
Cytoplasm Yes Yes
Nucleus Yes Yes
Mitochondria Yes Yes
Ribosomes Yes Yes
Cell Wall Yes No
Chloroplasts Yes No
Vacuole Yes No



0653 Quick Revision Biology 2 nd Edition written by B.N Mupeti © 2024 Page 1 of 36

, Brian Nathan Mupeti email:

Differences:
 Plant cells have a cell wall, chloroplasts, and a vacuole, which are absent in animal
cells.




Differentiating ribosomes, mitochondria and chloroplasts in diagrams

Using size

 Ribosomes are the  Mitochondria are  Chloroplasts are
smallest, medium in size the largest.
and
Using shape
 Ribosomes are  Mitochondria are  Chloroplasts are
dots or clusters, oval or rod shaped oval or disk
and shaped

Functions of the structures found in cells

 Cell Wall: Provides support and protection to the cell
 Cell Membrane: Controls the movement of substances in and out of the cell due to it
being semi or partially permeable.
 Nucleus: Contains genetic material (DNA). Controls cell activities.
 Cytoplasm: Supports metabolic processes. Provides a medium for chemical reactions
 Chloroplasts: Site of photosynthesis. Contains chlorophyll
 Ribosomes: Site of protein synthesis
 Mitochondria: Site of cellular respiration (energy production)
 Vacuoles: Storage organelles



0653 Quick Revision Biology 2 nd Edition written by B.N Mupeti © 2024 Page 2 of 36

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The structure of a bacterial cell Specialized cells




Functions of certain specialized cells:

Specialised cell Function

Root hair cell Absorption of water and mineral salts

Palisade mesophyll cells photosynthesis

Red blood cells Transport oxygen



Meanings of key terms

Here are the meanings of some key terms that you need to know:

Cell
A cell is the smallest unit of life, consisting of a nucleus surrounded by cytoplasm and a cell
membrane. Cells are the basic structural and functional units of living organisms.

Tissue
A tissue is a group of similar cells that work together to perform a specific function.
Examples of tissues include muscle tissue, nerve tissue, and epithelial tissue.



0653 Quick Revision Biology 2 nd Edition written by B.N Mupeti © 2024 Page 3 of 36