Detailed summaries of the Grade 12 Life Sciences / Biology syllabus (CAPS & IEB SAGS). Can be used for exam and test preparation. Compiled from various sources to enhance the learning experience and enrich the content of the summaries.
, DNA
THE BASIC 9(
[ANIMAL] CELL
Contains [organic compounds]:
NUCLEIC ACID:
u Proteins ⇨ chains of amino acids, an organic compound containing the
u lipids and elements carbon, hydrogen, oxygen,
u carbohydrates
nitrogen and phosphorus. ⇨Polynucleotide
[DNA & RNA]
Two types of nucleic acids:
u deoxyribonucleic acid (DNA)
u ribonucleic acid (RNA)
TYPICAL LAYOUT:
Animal cells are eukaryotic cells (cells with a membrane-bound nucleus)
Cell (Plasma) thin, semi-permeable membrane that surrounds the cytoplasm of a
Membrane cell, enclosing its contents.
Centrioles cylindrical structures that organize the assembly of microtubules
during cell division.
Cili and flagella specialized clusters of microtubules that protrude from some cells
and aid in cellular locomotion.
Cytoplasm gel-like substance inside the cell.
Cytoskeleton a network of fibers through the cell's cytoplasm that gives the cell
support and helps maintain its shape.
Endoplasmic an extensive network of membranes consisting of both regions with
Reticulum ribosomes (rough ER) and regions without ribosomes (smooth ER).
Golgi Complex [Golgi apparatus]
structure responsible for manufacturing, storing and shipping
certain cellular products.
Lysosomes pockets of enzymes that digest cellular macromolecules such as
nucleic acids.
Microtubules hollow rods that function primarily to support and shape the cell.
Mitochondria cell components that generate energy for the cell and are the sites
of cellular respiration.
Nuclear bound structure that contains the cell's hereditary information.
membrane
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 Enzymes contain structures that help detoxify alcohol, form bile
acids, and break down fats.
Ribosomes consisting of RNA and proteins, ribosomes are responsible for
protein assembly.
DNA FUNCTION:
u Portions of DNA
W WHERE? = chromosomes in the nucleus of eukaryotic cells carry hereditary
W Chromosomes carry the hereditary material in the form of genes information
u DNA contains coded
W DNA FOUND IN mitochondria and chloroplasts [eukaryotic cells]
information for
W extranuclear DNA = DNA found outside the cell nucleus protein synthesis
W LOCATION = In the cytoplasm [organelles] u Controls the
functioning of cells
CHROMOSOME Z [a thread-like molecule of DNA made up of many genes]
EUKARYOTIC CELL Z [a cell with a nucleus surrounded by a membrane and organelles
surrounded by membranes]
GENE Z [a specific part of a strand of DNA that carries the information for a specific
trait to produce a specific protein, such as haemoglobin]
CHROMATIN NETWORK Z [the form in which chromosomes are found in the nucleus of a
non-dividing eukaryotic cell. The chromatin network consists of a mass of long,
interwoven strands of DNA]
EXTRANUCLEAR DNA Z [DNA found outside the cell nucleus]
, COMPLEMENTARY BASES Z[nucleotide
bases that can be bonded by
STRUCTURE OF A DNA [DEOXYRIBONUCLEOTIDE] hydrogen bonds and therefore hold
the double-stranded nucleic acid
& It is a double strand in a helix shape
together]
& It consists of building blocks/monomers [nucleotides]
& The three components of a nucleotide are as follows: nitrogen bases, phosphate
part and deoxyribose sugar part
& The 4 nitrogenous bases are Adenine (A), Thymine (T), Cytosine (C) and Guanine (G)
& The bases are divided into two groups: Purines (double-ring structures) are A and G
and Pyrimidines (single-ring structures) are T and C - adenine (A) binds with thymine
(T) - cytosine (C) binds with guanine (G) - through weak hydrogen bonds
DNA ⇨ carbon, hydrogen, oxygen, nitrogen and phosphorus
DNA ⇨ double-stranded polynucleotide
A SPECIFIC PYRIMIDINE ALWAYS BONDS WITH A SPECIFIC PURINE:
& adenine matches thymine (is bonded by two hydrogen bonds)
& cytosine matches guanine (is bonded by three hydrogen bonds)
u The sugar-phosphate backbone is on the outside of the double helix and purines and
pyrimidines form the "CENTRAL" of the DNA helix.
u The two DNA strands are antiparallel to each other.
u The direction of each strand is identified by numbering the carbons (1 to 5) in each sugar
molecule. The 5ʹ end is the one where carbon #5 is not attached to another nucleotide; the 3ʹ
end is the one where carbon #3 is not attached to another nucleotide.
GENES & NON-CODING DNA
GENE = the part of a DNA molecule with the code to produce a specific protein
noncoding DNA: DNA that does not code to produce proteins
DNA sequencing: the process used to work out the base sequence in a segment of DNA
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