Cell Structure and Functions Flashcards
compare the structures
and functions of typical
animal and plant cells as
seen under the light and electron microscope
( Rough and smooth
endoplasmic reticulum,
Golgi body, mitochondria,
ribosomes, lysosomes,
chloroplasts, cell
membrane, nuclear
envelope, centrioles,
nucleus and nucleolus.)
(Differences between
electron and light
microscope and between
resolution and
magnification.)
Structures and Functions of Cell Organelles:
Rough and Smooth Endoplasmic Reticulum (RER and SER):
Function: Both types of endoplasmic reticulum are involved in protein synthesis and lipid metabolism. The RER has ribosomes attached to its surface, involved in protein synthesis, while the SER lacks ribosomes and is involved in lipid metabolism and detoxification.
Appearance: Under the electron microscope, the RER appears as flattened sacs or tubes studded with ribosomes, while the SER appears smoother without ribosomes.
Golgi Body (Golgi Apparatus):
Function: The Golgi apparatus processes, sorts, and packages proteins and lipids synthesized in the endoplasmic reticulum for secretion or delivery to other cellular compartments.
Appearance: Under the electron microscope, the Golgi apparatus appears as a stack of flattened membranous sacs called cisternae.
Mitochondria:
Function: Mitochondria are the powerhouses of the cell, responsible for producing ATP through cellular respiration.
Appearance: Under the electron microscope, mitochondria appear as double-membrane organelles with an inner membrane folded into structures called cristae.
Ribosomes:
Function: Ribosomes are involved in protein synthesis, translating mRNA into amino acid sequences.
Appearance: Under the electron microscope, ribosomes appear as small, dense granules distributed throughout the cytoplasm or attached to the surface of the endoplasmic reticulum.
Lysosomes:
Function: Lysosomes contain enzymes that break down macromolecules, cellular waste, and foreign particles through hydrolysis.
Appearance: Under the electron microscope, lysosomes appear as membrane-bound vesicles containing dense granules.
Chloroplasts (Plant Cells Only):
Function: Chloroplasts are responsible for photosynthesis, converting light energy into chemical energy (glucose) in the presence of chlorophyll.
Appearance: Under the electron microscope, chloroplasts appear as double-membrane organelles with internal membranous structures called thylakoids arranged in stacks called grana.
Cell Membrane:
Function: The cell membrane regulates the passage of molecules into and out of the cell and maintains cell integrity.
Appearance: Under the electron microscope, the cell membrane appears as a lipid bilayer with embedded proteins.
Nuclear Envelope, Centrioles, Nucleus, and Nucleolus:
These structures have similar functions in both animal and plant cells, involved in genetic regulation, DNA replication, and cell division.
Appearance: Under the electron microscope, the nuclear envelope appears as a double membrane surrounding the nucleus, centrioles appear as paired cylindrical structures, and the nucleus and nucleolus have distinct internal structures.
Differences Between Light and Electron Microscopes:
Magnification: Electron microscopes have much higher magnification capabilities than light microscopes, allowing for the visualization of smaller structures.
Resolution: Electron microscopes also have higher resolution, meaning they can distinguish between smaller objects more clearly.
Technique: Light microscopes use visible light to illuminate specimens, while electron microscopes use beams of electrons.
describe the structure of
a prokaryotic cell
Prokaryotic cells are simple, single-celled organisms that lack a true nucleus and membrane-bound organelles. Instead, their genetic material is typically concentrated in a region called the nucleoid. Let’s break down the structure of a prokaryotic cell:
Cell Wall:
Prokaryotic cells have a rigid cell wall that provides structural support and protection from osmotic changes and physical damage.
The composition of the cell wall varies among prokaryotes. Bacteria typically have cell walls made of peptidoglycan, while archaea may have cell walls composed of different materials like pseudopeptidoglycan or protein.
Plasma Membrane:
The plasma membrane surrounds the cytoplasm and regulates the passage of substances into and out of the cell.
It is composed of a phospholipid bilayer embedded with proteins and may contain specialized structures like transport proteins and receptor molecules.
Cytoplasm:
The cytoplasm is a gel-like substance that fills the interior of the cell and contains various cellular structures and molecules.
It houses the cell’s metabolic machinery and supports cellular processes.
Nucleoid:
The nucleoid is a region within the cytoplasm that contains the cell’s genetic material, typically a single, circular DNA molecule.
Unlike eukaryotic cells, prokaryotic cells lack a true nucleus, so the DNA is not enclosed within a membrane-bound nucleus.
Ribosomes:
Ribosomes are the cellular structures responsible for protein synthesis.
In prokaryotic cells, ribosomes are smaller (70S) than those found in eukaryotic cells (80S) and are free-floating in the cytoplasm or attached to the plasma membrane.
Flagella (Optional):
Some prokaryotic cells may possess flagella, which are long, whip-like appendages used for locomotion.
Flagella are composed of protein subunits and rotate like propellers to propel the cell through its environment.
Pili (Optional):
Pili are hair-like appendages found on the surface of some prokaryotic cells.
They can serve various functions, including attachment to surfaces, exchange of genetic material (conjugation), or adherence to host cells.
Capsule (Optional):
Some prokaryotic cells may have a capsule, a protective layer external to the cell wall.
Capsules are composed of polysaccharides or proteins and provide protection from desiccation, phagocytosis, and host immune defenses
compare the structure
of prokaryotic cells with
that of eukaryotic cells
(The basis of the
endosymbiotic
development of
eukaryotic cells. Can
mention plants, animals,
fungi and protista)
Prokaryotic Cells:
Size and Complexity:
Prokaryotic cells are typically smaller and simpler in structure compared to eukaryotic cells.
They lack membrane-bound organelles and a true nucleus, with their genetic material localized in the nucleoid region.
Cellular Organization:
Prokaryotic cells have a cell wall made of peptidoglycan (in bacteria) or other materials (in archaea), providing structural support and protection.
The plasma membrane surrounds the cytoplasm and regulates the passage of substances into and out of the cell.
Ribosomes are the sites of protein synthesis and are smaller (70S) compared to eukaryotic ribosomes (80S).
Genetic Material:
The genetic material in prokaryotic cells consists of a single, circular DNA molecule located in the nucleoid region.
They lack histones and do not undergo mitosis or meiosis.
Optional Structures:
Some prokaryotic cells may possess flagella for locomotion, pili for attachment, and capsules for protection.
Eukaryotic Cells:
Size and Complexity:
Eukaryotic cells are larger and more complex than prokaryotic cells.
They have membrane-bound organelles, including a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and chloroplasts (in plants).
Cellular Organization:
Eukaryotic cells have a cytoskeleton composed of microtubules, microfilaments, and intermediate filaments, providing structural support and facilitating intracellular transport.
The plasma membrane surrounds the cell and is selectively permeable.
The nucleus contains the cell’s genetic material, organized into linear chromosomes and enclosed within a double membrane.
Genetic Material:
Eukaryotic cells have multiple linear chromosomes composed of DNA associated with histone proteins.
They undergo mitosis for cell division and meiosis for the formation of gametes (in sexually reproducing organisms).
Endosymbiotic Theory:
The endosymbiotic theory proposes that mitochondria and chloroplasts within eukaryotic cells originated from ancestral prokaryotic cells that were engulfed by a host cell.
This theory is supported by evidence such as the similarity between the size and structure of these organelles and prokaryotic cells, their independent replication through binary fission, and the presence of their own DNA and ribosomes.
explain the concepts of
tissue and organ using
the dicotyledonous root
and stem.
(Use of transverse section
of a dicotyledonous root
and stem to illustrate
tissues including
parenchyma, xylem and
phloem. The root is used
as an organ.)
