Cell Structure and Function Notes
A. The structure of the cell -
be able to identify the following organelles from the diagrams below:
golgi, rough and smooth ER,
nucleolus, nucleus, mitochondria, vesicles, ribosomes, cell membrane, membrane
channels.
B. Cell Organelles
1. Cell Membrane
Function - It regulates what enters and leaves the cell (also called
selective permeability). It also gives the cell shape and protection.
Structure - Made up of two layers of phospholipids with proteins embedded
randomly in the layers. Lipid soluble substances, like alcohol, easily pass
across the membrane by dissolving in it. Lipid insoluble substances cannot pass,
and water passes through protein lined pores. See
Fluid Mosaic Model of Cell Membrane structure
2. Rough Endoplasmic Reticulum
Function -Primarily concerned with protein synthesis and transport. Most
highly developed in protein exporting cells (eg. liver and pancreatic cells)
Structure - It is a series of interconnected membranes which spread
throughout the cytoplasm forming channels of flattened sacs, with ribosomes
attached to them. The channels formed by the membranes transport the proteins
made by the ribosomes.
See
Protein synthesis
3. Smooth Endoplasmic
Reticulum
Function - synthesizes and transports lipids and steroids. Some kinds of
smooth E.R. accepts, modifies, and transports proteins from the rough E.R. and
still other kinds break down energy rich glycogen and fats.
Structure - The smooth E.R. is free of ribosomes so has a smooth
appearance. The channels formed are similar to those formed by the rough E.R.
but are tubular and are concerned with making and transporting lipids and
steroids.
4. Golgi apparatus (body)
Function - Proteins exported from the rough and smooth E.R. are modified
and enclosed in secretory or lysosomal vesicles and transported out of the
cell.
Structure - The golgi appear as flattened stacks of membranes. The
proteins enter these membranes are modified, concentrated and packaged into
small spherical membrane bound structures called vesicles.
5. Lysosomes
Function - digests and disposes of foreign particles, malfunctioning
structures, and worn out organelles.
Structure - The contents of the lysosome are contained within vesicles. The
lysosome contains 40 or so different enzymes that are capable of breaking down
virtually every large biological molecule, including DNA, RNA, proteins, and
certain lipids.
6. Mitochondria
Function - The chemical reactions which produce energy and the storage of
that energy as ATP occur in this organelle. Glucose and Oxygen are used to produce ATP, carbon dioxide and water. Collectively these reactions are called aerobic
respiration.
Structure -The structure is characterized by a double membrane which
creates two areas within the organelle. The area between the membranes houses
the enzymes of the Kreb's cycle and is called the matrix. The other area, on the
surface of the membranes, contains the enzymes of the electron transport system
and is called the cristae. Be able to recognize the cristae and matrix in the
diagram of the mitochondria below
Below is an electron microscope
picture (micrograph) of a mitochondrion
7. Nucleus
Function - acts to control the metabolic activities of the cell. Is the
central control centre which monitors internal and external conditions and turns
on or off different genetic programs.
Structure - is surrounded by a membrane which is similar in structure to
the plasma or cell membrane. Nuclear pores or holes occur at intervals along the
membrane. These holes provide a way for the nucleus to communicate with the
cytoplasm. Substances pass in and out of the nucleus through these openings.
8. Nucleolus
Function - Rich in RNA and is the site of the synthesis of ribosomes
Structure - consists of densely packed chromosomes, protein and precursor
RNA strands from which the subunits of ribosomes are formed.
9. Vacuole
Function - In plants it can act as a storage area for ions, metabolic
products such as sugars and amino acids, and toxic compounds. Its main function
however is to increase cell size and surface area so that the absorption of ions
is enhanced.
Structure - Fluid pressure builds up in the vacuole causing the cell to
become elongated and extended increasing surface area and cell size. It is
bounded by a cell membrane.
10. Chromosome
Function - Carries the genetic code which determines characteristics of
an organism.
Structure - made up of genes which are in turn made up of DNA. The
chemical components and the order of the of the chemical components determine
the specific characteristics.
11. Cell wall
Function - allows plant cells to withstand high internal pressure without
bursting.
Structure - made of cellulose (provides the rigidity) cemented together
with lignin.
12. Vesicles
Function - Contain products that have been packaged/modified by the golgi.
(eg. proteins like enzymes, plasma proteins, peptide hormones etc.) It has the
same structure as a vacuole only it is smaller in size. Structure W in the first
diagram and structure Z in the second, show vesicles.
Structure - Contents are surrounded by a membrane
Cell structure and function quiz
1. What is a function of the following organelles: cell membrane, vacuole,
golgi, lysosome, mitochondria, nucleus, nucleolus, rough ER, ribosome,
chromosome, vesicles, smooth ER, nuclear envelope, chromosomes
2. Name two internal structures of mitochondria and describe their functions.
3. Name one structural feature of the rough ER
4. What organelle is rich in RNA
5. What organelle is characterized by:
a. flattened stacks of membranes
b. storage of pigments or starch
c. has ribosomes embedded in its surface
d. a membrane bound enzyme bag
6. Give a structural feature of the following organelles:
a. nucleolus b.
smooth ER c. cell membrane
7. Be able to labeled and describe
the functions of all the organelles in the following diagrams of cells
Cell Structure Subjective Questions
1. The functions of the Endoplasmic Reticulum, Golgi and Ribosome are all
related during a specific cellular process. Name this process and describe how
each organelle functions to contribute to the completion of this process.
a. Name of process _____________________
b. Function of:
Golgi -
Rough E. R. -
Ribosomes -
