This set of study notes covers the topic of cells in A-Level Biology, with a focus on the key concepts in cell biology, including the cell theory, types of cells, the cell membrane, organelles, and cellular processes. The significance of cell biology is also discussed, including its importance in u...
V. Organelles
A. Introduction to Organelles
Organelles are specialized structures within cells that perform specific functions.
Each organelle has a distinct structure and composition, and together they work together to
maintain the homeostasis of the cell.
B. Nucleus
The nucleus is the largest organelle in most eukaryotic cells, and is the site of DNA
replication and transcription.
It is surrounded by a nuclear envelope, which is a double membrane that contains nuclear
pores that allow for the transport of molecules in and out of the nucleus.
The nucleolus is a region within the nucleus where ribosomal RNA is synthesized and
assembled into ribosomes.
C. Endoplasmic Reticulum (ER)
The ER is a network of membranes that extends from the nuclear envelope throughout the
cytoplasm.
The rough endoplasmic reticulum (RER) is studded with ribosomes and is involved in
protein synthesis and folding.
The smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in lipid synthesis,
detoxification, and calcium storage.
D. Golgi Apparatus
The Golgi apparatus is a stack of flattened membranes that receives proteins and lipids from
the ER and modifies and sorts them for transport to their final destination.
It is divided into a cis face, which receives vesicles from the ER, and a trans face, which
sends vesicles to other parts of the cell.
E. Mitochondria
Mitochondria are organelles that are responsible for cellular respiration, the process by
which cells generate energy in the form of ATP.
They have an outer membrane and an inner membrane, which contains cristae that increase
the surface area for ATP synthesis.
Mitochondria also contain their own DNA and ribosomes, which are similar to those found
in prokaryotic cells.
F. Chloroplasts
Chloroplasts are organelles found in plant cells that are responsible for photosynthesis, the
process by which plants generate energy from sunlight.
They have an outer membrane and an inner membrane, which contains thylakoids that
contain chlorophyll.
Chloroplasts also contain their own DNA and ribosomes, which are similar to those found in
prokaryotic cells.
G. Lysosomes
Lysosomes are organelles that contain digestive enzymes and are involved in the breakdown
of macromolecules, cellular waste, and foreign material.
, They are formed by the fusion of vesicles from the Golgi apparatus and are important for
recycling cellular components.
H. Peroxisomes
Peroxisomes are organelles that contain enzymes that are involved in the breakdown of fatty
acids and the detoxification of harmful substances.
They are involved in the production of hydrogen peroxide, which is then broken down by
the enzyme catalase.
I. Cytoskeleton
The cytoskeleton is a network of protein fibers that provides structural support and
maintains the shape of the cell.
It is composed of microfilaments, intermediate filaments, and microtubules, which are
involved in a variety of cellular processes including cell division, movement, and
organization.
I. Introduction
Importance of cells in biology
Brief history of cell theory
II. Cell Theory
The three components of cell theory
The significance of cell theory in biology
III. Types of Cells
Prokaryotic cells
Eukaryotic cells
The differences between prokaryotic and eukaryotic cells
IV. Cell Membrane
The structure of the cell membrane
The function of the cell membrane
The importance of the cell membrane in maintaining homeostasis
V. Organelles
The structure and function of the major organelles in eukaryotic cells, including:
Nucleus
Endoplasmic reticulum
Golgi apparatus
Mitochondria
Chloroplasts (in plant cells)
Lysosomes
Peroxisomes
VI. Cellular Processes
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