Download MADANIA (High School) Grade 10-Biology

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MADANIA (High School)
Grade 10-Biology-Handout 2
Cell Structure
09 / 08 / 2010
All living organisms on Earth are divided in pieces called cells. There are smaller pieces to cells that include
protein and organelles. There are also larger pieces called tissues and systems. Cells are small
compartments that hold all of the biological equipment necessary to keep an organism alive and succesful
on Earth. A main purpose of a cell is to organize. Cells hold a variety of pieces and each cell has a different
set of functions.
There are two kinds of cells: prokaryotic and eukaryotic.
All cells have several basic features in common:
 They are bounded by a plasma membrane
 They contain a semifluid substance called the cytosol
 They contain chromosomes
 They all have ribosomes
Plasma membrane
The cell membrane is not one solid piece. Compounds called proteins and pho
spholipids make up most of the cell membrane.
Cytoplasm
Cytoplasm or cytosol is the fluid that fills a cell. The cytoplasm has many different molecules dissolved in
solution. You will find enzymes, fatty acids, sugars and amino acids that are used to keep the cell working.
Ribosomes
Cells need to make proteins. Ribosomes are the protein synthesizers of the cell. They might be found in
cytoplasm and rough endoplasmic reticulum.
Chromosomes
Chromosomes are made up of DNA. Segments of DNA in specific patterns are called genes. Your genes
make you who you are. Chromosomes and genetic material can be found in nucleus. In prokaryotes, DNA
flotas in the cytoplasm in an area called nucleoid. Chromosemes are usually found in pairs.
Cell Nucleus
The cell nucleus acts like the brain of the cell. The nucleus is not always in the center of the cell. It will be a
big dark spot somewhere in the middle of cytoplasm (cytosol). Not all cells have a nucleus. Take for
example prokaryotic cell.
Endoplasmic Reticulum (ER)
Endoplasmic reticulum functions as the packaging system. It does not work alone. The ER works closely
with Golgi apparatus, ribosomes, RNA, mRNA and tRNA. There are two types of ER: rough and smooth ER.
Smooth ER acts as a storage organelle. It is important in the creation and the storage of steroids. Rough ER
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has ribosomes attached. Ribosomes are very important in the synthesis and packaging of proteins. Some of
the proteins might be used in the cell and some are sent out. As the ribosome build the amino acid chain,
the chain is pushed into the ER . When the protein is complete, the rough ER pinches off a vesicle (small
membrane). The vesicle can move to the cell membrane or Golgi apparatus.
Golgi apparatus
Golgi apparatus or golgi complex gathers simple
molecules and combine them to make more
complex molecules. It then takes those big
molecules, packages them in vesicles, and either
stores them for later use or sends them out of the
cell. Golgi apparatus also builds lysosomes (cell
digestion machine). Golgi apparatus receives transition vesicles contains of proteins from endoplasmic
reticulum. After the Golgi does its work on the molecules inside the vesicles, a secretory vesicle is made and
released into the cytoplasm. From there, the vesicle moves to the cell membrane and the molecules are
released out of the cell.
Vacuoles
Vacuoles are storage bubbles found in cells. They are found in both animal and plant cells but are much
larger in plant cells. Vacuoles might store food or any kinds of nutrients a cell might need to survive. They
can even store waste products so the rest of the cell is protected from contamination.
Mitochondria
Mitochondria are known as the powerhouses of the cell. They are organelles that
act like a digestive system that takes in nutrients, breaks them down and creates
energy for the cell. Mitochondria have two membranes. The outer membrane
covers the organelle and its content. The inner membrane folds over many times
(cristae). The fluid inside of the mitochondria is called the matrix.
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Prokaryotic Cell
Prokaryotic celss are small, relatively simple cells. They do not have a nucleus. A prokaryotic cell is
enclosed by a plasma membrane and is usually encased in a rigid cell wall.
Eukaryotic Cell
Eukaryotes are distinguished by the presence of a true nucleus. Eukaryotic organelles fall into four
functional groups.
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Animal Cell
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Plant Cell
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A plant cell has some structures that an animal cell lacks: Chloroplasts and a rigid cell wall.
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