Unit : cells – the basic units of lifeCreated BY: Ms Mwelase
The study of cells and micro organisms has changed over time with the change in technology.
These were studied in the beginning with hand lenses, single lens microscope, light microscope
Today we have electron microscopes. Two types of electron microscopes are used today:
SEM – Scanning electron microscope and TEM – Transmission electron microscope.
HOW to study cells.
1632-1723ANTON VAN LEEUWENHOEK
Developed a microscope with one lens.
Discovered - bacteria- blood cells-
spermatozoa- protozoa
1662 – ROBERT HOOK
Uses the concept cell for the first time.
He used it when he looked at the microscopic structure of cork cells.
1831 – ROBERT BROWN (Botanist)
Describes the nucleus of a cell
Developed the cell theory:- Plants and animals are made of groups
of cells.- The cell is the basic unit of living
organisms
1838-1839MATTHIAS SCHLEIDEN (Botanist)THEODOR SCHWANN (Zoologist
1855 – RUDOLPH VIRCHOW
Expanded the cell theory: He said that new cells formed by
the division of existing cells
1880 – AUGUST WEISMANN
Expanded the cell theory more:
He said that all cells can be traced to their origin
All living organisms are made out of cells New cells are formed by the division of
existing cells The cell houses genes, which are the
blueprint for growth, functioning and development of cells
The cell is the functional unit of life because all chemical reactions of life take place inside the cell
Schleiden, Schwann and Virchow compiled the cell theory
WHAT IS A CELL?
A cell is the basic unit of structure and function in organisms.
Cells differ in size, shape and in function.
A cell consist of smaller structures called organelles.
Prokaryotic or Eukaryotic cells. Only organisms of the domains Bacteria
and Archaea consist of prokaryotic cells – cells without a membrane bound nucleus.
Protists, fungi, animals and plants all consist of eukaryotic cells – cell with a membrane bound nucleus.
Two types of cells
General structure of an animal cell as seen under a light microscope
(called a micrograph)
Line diagram of a general animal cell
Micrograph of a general plant cell
Line diagram of a general plant cell
PLANT CELL ANIMAL CELL
DIFFERENCES BETWEEN PLANT- AND ANIMAL CELL
STRUCTURE AND FUNCTIONS OF THE
DIFFERENT ORGANELLS OF CELLS
Chapter 6 p. 98 – 131
Porous Varies in thickness Consist of pectin (elasticity), cellulose fibrils held
together with non-cellulose substances (hardens the cell when mature) and lignin (adds strength to cell especially in woody plants)
Cell wall is permeable and protects the inside of the cell.
Middle lamella (layer of adhesive substances) – holds the cells together
Plasmodesmata (pores) that connects the cytoplasm of the connecting cells – selectively permeable
CELL WALL(ONLY IN PLANT CELLS)
CELL WALL WITH PLASMODESMATA AND INTERCELLULAR SPACES
CELL MEMBRANE/PLASMA- (ANIMAL- AND PLANT CELLS)
Consist of 2 phospholipid layers and proteins in between.
The phospholipid layers are part hydrophillic and part hydrophobic
NUCLEUS
+/- 5µm, largest organelle in cell.
Enclosed by a nucleomembrane with nuclear pores. Function: Protection and add to selective permeability.
Filled with nucleoplasma, a nucleolus and chromatin. Function of chromatin: carries genetic material in the form of chromosomes.
Function of nucleolus: Produce r-RNA
MITOCHONDRION Consist of 2 membranes:
Outer – and a highly convoluted inner membrane- These folds are called cristae – they increase the surface area.
Filled with matrix called stroma that contains DNA and ribosomes.
Function: Produce energy in the form of ATP by means of cellular respiration
CHLOROPLAST (PLANT CELL ONLY)
Enclosed by a double membrane
Filled with stroma and thylakoids filled with chlorophyll arranged in groups called grana.
Ribosomes and starch grains in stroma.
Function: Photosynthesis
VACUOLE(Large in plant-, small in animal-)
Membranous sac Filled with cell sap. Causes turgor pressure in the
vacuole. Function: Stores various
substances, including waste. Helps with osmotic potential
of cell.
Endoplasmic Reticulum – Transport system in cell
Ribosomes – Protein synthesis Golgi-apparatus – Make lysosomes and
acts as transport system. Lysosomes – Intracellular digestion. Plastids e.g.– Leucoplasts – Stores
starch - Chromoplast – gives colour
to flowers and fruit.* Centrioli – Mitosis in animal cells
OTHER SMALLER ORGANELLES
The cell membrane has the ability to regulate transport molecules across its structure.
This function is essential to the cell’s existence.
The fluid mosaic model helps to explain how membranes regulate the cell’s molecular traffic.
PERMEABILITY OF THE CELL MEMBRANE
Hydrocarbons, carbon dioxide and oxygen – non-polar
So they can dissolve in the lipid bilayer of the membrane.
They can cross the membrane without the aid of membrane proteins.
Polar molecules like, water and glucose move slowly across the membrane and need the aid of proteins to get across the membrane.
Permeability of the lipid bilayer
Hydrophyllic substances can avoid contact with the hydrophobic lipid bilayer by passing through transport proteins that span the membrane.
Channel proteins – tunnel for polar molecules to pass through membrane
Aquaporins – channel proteins for the transport of water
TRANSPORT PROTEINS
Carrier protein: Hold onto solutes that want to move across the membrane and changes shape as it moves through the membrane.
Each carrier protein is specific to what it transports.
1. If the Golgi-apparatus of a cell is destroyed, that cell would _____________
stop releasing cellular products. become a dictyosome. release digestive enzymes in the cytoplasm
for self-digestion. behave normally.
2. Which of the following characteristics does not apply to mitochondria?
Double unit membrane. Connected to the ER. Inner membrane is folded. Larger than ribosomes.
1. Which is not a key point in the cell theory?
All living cells consist of one or more cells. The cell is the basic unit of life. No cell can exist unless at least one other cell is present. New cells arise only from cells that already exist.
2. The main constituent of most cell walls in plants is_____. glucose. glycogen. proteins and phospholipids. Cellulose.
3. Which of the following is found in both plant and animal cells?
Chromosomes Chromoplasts Chondrocytes Leucoplast
Part of the nucleus that mainly consist of RNA. The inner plasma membrane in the cell
surrounding the vacuole. Organelles in living cells that contain enzymes, Give 2 functions of the plasma membrane. What is Archaea?
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