study of a cell
DESCRIPTION
STUDY OF AN CELLTRANSCRIPT
cells – the basic units of life
WHAT IS A CELL?
A cell is the basic unit of structure and function in organisms hence basic unit of life.
Cells differ in size, shape and in function.
A cell made up of smaller structures called organelles.
Two types of cellsProkaryotic 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.
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
DIFFERENCES BETWEEN PLANT- AND ANIMAL CELL
PLANT CELL ANIMAL CELL
CELL WALL CELL MEMBRANE
CHLOROPLAST NO CHLOROPLAST
BIG IN PLANTS SMALL IN ANIMALS
CAN PHOTOSYNTHESIZE CANNOT PHOTOSYNTHESIZE
MAKE THEIR FOOD DEPENDENT ON PLANTS IN CASES OF FOOD
STRUCTURE AND FUNCTIONS OF THE DIFFERENT ORGANELLS OF CELLS
Chapter 6 p. 98 – 131
CELL WALL(ONLY IN PLANT CELLS)
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 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 sacFilled with cell sap.Causes turgor pressure in the
vacuole.Function: Stores various
substances, including waste.Helps with osmotic potential
of cell.
OTHER SMALLER ORGANELLESEndoplasmic Reticulum – Transport
system in cellRibosomes – Protein synthesisGolgi-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
PERMEABILITY OF THE CELL MEMBRANEThe 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.
MICROSCOPYThe microscope is an instrument designed to observe objects too small to be seen with the naked eye.
The human eye cannot distinguish objects much smaller than 0.1mm.
The microscope act as an extension of the eye, allowing one to see smaller objects.