Summary
Grade 9 Natural Sciences Summary
- Course
- Natural Science
- Institution
- 9th Grade
'A complete summary of "Natural Science" at grade 9 level, document meets the requirements as set out in the CAPS/CAPS.
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Natural sciences, CHAPTER 1 : THE CELL
CELL MEMBRANE, ORGANELLES
Microscopic- cannot be seen with the naked eye
Organelles- structures in the cytoplasm that carry out the functions of the cell
Cell membrane- is thin and surrounds the cell contents; functions are selectively
permissive
Cytoplasm- jelly-like medium surrounded by the cell membrane.
The cell nucleus is present in all plant and animal cells.
(plant cells more on the side of the cell)
(Animal cells more in the center of the cell)
PLANT CELL LAYOUT :
Plant cells are eukaryotic cells (cells with a membrane-bound nucleus)
[prokaryotic cells = the DNA in a plant cell housed within a nucleus surrounded by a
membrane ]
The nucleus of plant cells also contains other membrane-bound organelles (small cellular
structures) that perform specific functions necessary for normal cellular operation.
2 Noted © NATURAL SCIENCES GRADE 9 www.notedsummaries.co.za
,Structures and organelles:
Cell (Plasma) a thin, semipermeable membrane that surrounds the cytoplasm
Membrane of a cell, enclosing the contents.
cell wall outer covering of the cell that protects the plant cell and gives it
shape.
Chlorine solution the sites of photosynthesis in a plant cell. They contain
chlorophyll, a green pigment that absorbs energy from sunlight.
Cytoplasm gel-like substance in the cell membrane that contains water,
enzymes, salts, organelles, and various organic molecules.
Cytoskeleton a network of fibers throughout the cytoplasm that helps the cell
maintain its shape and supports the cell.
Endoplasmic extensive network of membranes consisting of both regions with
Reticulum (ER) ribosomes (rough ER) and regions without ribosomes (smooth ER).
The ER synthesizes proteins and lipids.
Golgi Complex responsible for the production, storage, and shipping of certain
cellular products, including proteins.
Microtubules (hollow rods) = function to support and shape the cell. They are
important for chromosome movement in mitosis and meiosis, as
well as cytosol movement within a cell.
Mitochondria (organelles) = generate energy for the cell by converting glucose
(produced by photosynthesis) and oxygen to ATP. This process is
known as respiration.
Nuclear membrane bound structure that contains the cell's hereditary information
(DNA)
Nucleolus structure within the nucleus that helps in the
synthesis of ribosomes.
Nucleopores a small hole in the nuclear membrane that allows
nucleic acids and proteins to move in and out of
the nucleus.
Peroxisomes small structures bound by a single membrane containing enzymes
that produce hydrogen peroxide as a by-product[involved in plant
processes such as photorespiration].
Plasmodesmata pores or channels between plant cell walls that allow molecules
and communication signals to pass between individual plant cells.
Ribosomes consisting of RNA and proteins, ribosomes are responsible for
protein assembly. They can either be attached to the rough ER or
free in the cytoplasm.
Vacuoles structure in a plant cell that provides support and participates in
a variety of cellular functions, including storage, detoxification,
protection, and growth. When a plant cell decays, it typically
contains one large fluid-filled vacuole
3 Noted © NATURAL SCIENCES GRADE 9 www.notedsummaries.co.za
, TYPES OF PLANT CELLS:
Parenchyma cells Typical plant cell [highly specialized]. These cells synthesize
(through photosynthesis) and organize organic products in the
plant. Parenchyma cells make up the middle layer of leaves, as
well as the outer and inner layers of stems and roots.
Collenchyma cells These cells help support plants while not restricting growth due
to their lack of secondary cell walls and the absence of a
hardening agent in their primary cell walls.
Sclerenchyma cells Support function in plants, they have a hardening agent and are
strict. These cells are thick and contain different shapes.
Sclerenchyma cells form the hard outer shell of nuts and seeds.
Water conductance Water-conducting cells of xylem also have a support function in
of cells plants. Two types of cells make up xylem. They are narrow, hollow
cells, called tracheid’s and vessel members.
Sig tube members Sieve cells of phloem carry organic nutrients such as sugar
throughout the plant. Other cell types found in phloem include
capsule cells, phloem fibers and parenchyma cells.
There are three types of tissue systems: dermal tissue, vascular tissue, and ground
tissue systems.
ANIMAL CELL LAYOUT:
Animal cells are eukaryotic cells (cells with a membrane-bound nucleus)
DNA in animal cells = housed in the nucleus.
4 Noted © NATURAL SCIENCES GRADE 9 www.notedsummaries.co.za
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