These Grade 9 Biology notes are specifically designed to align with the South African CAPS (Curriculum Assessment Policy Statement) system. Comprehensive and well-structured, these notes provide a thorough understanding of cells and organelles, a fundamental topic in biology.
Topics Covered:
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Organelles
Organelle Description Function
Cell Wall - Tough, fibrous, non-living structure that surrounds protoplasm - Protects and supports the cell
- It is present in only cells Provides shape + strength + support
- Composed of cellulose; outer layer of cellulose or chitin
Cell Membrane - Forms a thin outer boundary for contents of the cell - Controls the entry/exit of substances in and out.
(Plasma membrane) -Controls the movement of. substances in and out of the cell (it - Useful substances are allowed and unwanted …substances are blocked
is selectively permeable) - Regulates the movement of substances
- Surrounded by a rigid cell wall for additional support - Receptor molecules respond to chemicals
- Substances move by osmosis …across the cell membrane.
Cytoplasm -Jelly like fluid matrix inside the cell …membrane. - Maintains shape of cell
- Medium in which chemical …reactions occur - Substances are dissolved or suspended in cytoplasm
- Food is stored in cytoplasm
- Maintains shape of cell
Nucleus - Dark, round/oval structure in the cytoplasm - Carries inherited characteristics on DNA (deoxyribonucleic acid) which is
- It is enclosed by a nuclear membrane. coiled to form chromatin threads in the …nucleoplasm:
- Contains fluid called nucleoplasm. - DNA contains the coding for the structure and functioning of a
- Controls all the activities of a cell. cell.
- DNA coding is arranged in units called genes and occurs in the
nucleus of every cell in the body of an organism.
- DNA causes variation within a species: ~DNA in people is
unique.
Mitochondrion - Animal and plant cells - Cite of aerobic respiration
(single) Mitochondria - Cigar/cylinder shaped, double membrane - Transforms energy in fuel into accessible forms of energy
(plural) - Folded in membrane
- Releases energy from food
- Uses oxygen releases CO2
Vacuole - Fluid filled sac in the cytoplasm; Filled with liquid called cell sap Basically, a membrane enclosed sac that can be filled with anything the
- Enclosed by the tonoplast – a selectively permeable membrane cell needs to keep separate. Stores food, water, etc. In plants the vacuole
- Plant cells have larger vacuoles that provide support, storage, also helps the cell maintain its rigidity.
and shape for the plant cell
- Animal cells have smaller vacuoles called contractile vacuoles
that regulate the water balance
Chloroplast - Oval shaped, green organelle called a plastid - Converts light energy from the sun, water, and carbon dioxide to
- Occurs in photosynthesising parts of a plant carbohydrates for food.
- Surrounded by a double membrane filled with liquid
Lysosome Small, round structures, containing enzymes - Breaks down large molecules and old cell parts into their components
that can be recycled to build new cell parts
Golgi Complex Small bags with tubes connecting them - Receives products from the ER and adds final modifications. It also
sorts these products and sends them to their final destinations.
Nuclear membrane Thin covering over the nucleus
Nucleolus Site of genes for rRNA synthesis - Assembles ribosomes
Ribosome Small specks made of RNA. Found in cytoplasm or on the - Smallest organelle found in ALL cells. Builds proteins by putting
endoplasmic reticulum together long chains of Amino Acids according to the mRNA
message (a copy of a piece of DNA) Thousands in each cell.
Rough endoplasmic Network of internal membranes - Large, folded membrane system studded with Ribosomes.
reticulum - Ribosomes build proteins and the ER helps fold or modify
them.
- Products are shipped to the Golgi
Smooth endoplasmic Network of internal membranes - Large, folded membrane system studded with ribosomes.
reticulum - Ribosomes build proteins and the ER helps fold or modify them.
- Products are shipped to the Golgi
Centriole Small cylindrical - The centrosome is responsible for organizing the microtubules
(made of proteins) in the process of mitosis,
- therefore, it is also known as microtubule organizing centre of
cell.
- It also plays a major role in cell division and helps in providing
the shape and structure to the cell.
, GLOSSARY
Glossary
Cells: Organelles the structure of cells
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