CELL STRUCTURE AND CELL ORGANISATION

UNDERSTANDING CELL STRUCTURE AND FUNCTION LEARNING OUTCOMES A student is able to: –Identify the cellular components of an animal cell –Identify the cellular components of a plant cell –State the functions of the cellular components in an animal cell –State the functions of the cellular components in a plant cell –Compare and contrast an animal cell and a plant cell –Relate the density of certain organelles with the functions of specific cells.

PLASMA MEMBRANE THE STRUCTURE  It covers the protoplasma  It is extremely thin  It is made up of proteins and phospolipids

Nucleolus nucleus Nuclear membrane Nuclear pore NUCLEUS

THE STRUCTURE o The largest cell organelles with a spherical shape o It is enclosed by a nuclear membrane which is perforated by the nuclear pores. o It contains nucleolus and nucleoplasm which has chromosomes in it.

NUCLEUS THE FUNCTIONS o It controls all the activities in a cell. o The nuclear pores allow exchange between the nucleus and the cytoplasm. o Chromosomes in the nucleoplasma carry genetic materials which determine the characteristics and functions of a cell

VACUOLE THE STRUCTURE o It is a fluid-filled sac surrounded by a membrane called a tonoplast. o The fluid contained in a vacuole is called cell sap. o It appears as a large central structure in a plant cell. o Can also be found in certain unicellular organisms like Paramecium as contractile vacuoles and food vacuoles

VACUOLE THE FUNCTIONS o It acts as a storage place in a cell o The cell sap in the vacuoles contains water, organic acids, sugars, amino acids, mineral salts, waste substances, pigments and metabolic by-products. o It also gives support esp. to herbaceous parts of a plant to prevent it from wilting.

MITOCHONDRIA THE STRUCTURE o Is a spherical or cylindrical – shaped organelle. o Surrounded by two membranes. o The inner membrane is folded to form finger- like cristae ( gives large surface area for enzyme attachment)

MITOCHONDRIA THE FUNCTIONS o It is involved in the cellular respiration which produces energy which later stored in the form of ATP (adenosine triphosphates)

CHLOROPLAST THE STRUCTURE o Having a double unit membrane surrounding it. o It contains a matrix called stroma in which are stacks of lamellae (grana)

Inner membrane Stroma Outer membrane Granum CHLOROPLAST

THE FUNCTION o It involves in photosynthesis as it contains green pigment called chlorophyll in the grana. o The chlorophyll is important in trapping sunlight before converting it into chemical energy

RIBOSOMES THE STRUCTURE o They are found attached to the surface of rough endoplasmic reticulum or suspended freely in the cytoplasm  They are made up of small RNA molecules and protein

Ribosomes Endoplasmic Reticulum

RIBOSOMES THE FUNCTION o They involve in the protein synthesis by using the information carried by the chromosomes.

ENDOPLASMIC RETICULUM THE STRUCTURE o A network of folded membrane which forms interconnected tubules. o The membrane is physically attached to the nuclear membrane o Rough endoplasmic reticulum has ribosomes attached to its surface; whereas, smooth endoplasmic reticulum has no ribosomes attached to the surface

ROUGH ENDOPLASMIC RETICULUM THE FUNCTION o Transport the protein formed by the ribosomes to the golgi apparatus. o The protein is first enclosed in transport vesicles before it is transported by the vesicles to the golgi apparatus. o Upon reaching the golgi apparatus, the vesicles will fuse with its membrane and empty their contents into the membranous space

SMOOTH ENDOPLASMIC RETICULUM THE FUNCTION o Involves in the synthesis of lipids and steroid

GOLGI APPARATUS THE STRUCTURE o Composed of a stack of flattened membranous sacs.

GOLGI APPARATUS

THE FUNCTION o It modifies the products such as protein carried by the transport vesicles o Then the modified products are sorted before being packaged into secretory vesicles o The secretory vesicles will then bud off from the Golgi membrane and travel to the other parts of the cell or to the plasma membrane. o The vesicles will fuse with the plasma membrane before releasing their contents outside the cell

PLASMA MEMBRANE

THE FUNCTIONS  It controls the movement of necessary substances needed by the cells such as water, oxygen and nutrients into the cells  It also controls the movement of waste products such as carbon dioxide out of the cells  As it lets some substances through, but not others, therefore, the plasma membrane is also known as a partially permeable membrane

CELL WALL THE STRUCTURE o A rigid outer layer surrounding the plasma membrane of a plant cell o It is made up of cellulose

CELL WALL THE FUNCTIONS o It allows movement of all fluids through its permeable wall. o It gives shape and provides mechanical support to the plant cells o It protects the plant cell from being ruptured due to the excessive intake of water

CYTOPLASM THE STRUCTURE  Semi fluid (jelly –like matrix) in nature between the nucleus and the plasma membrane  It contains organelles, organic and inorganic substances THE FUNCTIONS  It acts as a medium for biochemical reactions to take place in a cell.

Cytoplasm

LYSOSOMES THE STRUCTURE o Membrane-bound sacs containing hydrolytic enzymes.

LYSOSOMES THE FUNCTIONS o Digesting complex organic molecules o Eliminating worn out mitochondria and damaged cell organelles. o Digesting bacteria engulfed by a white blood cell o Secreting enzymes in food vacuoles of unicellular organisms to help them digest the food taken.

CENTRIOLES THE STRUCTURE o Found only in animal cells as a pair of small cylindrical structures. THE FUNCTION o Forming spindle fibres during cell division in animal cells

COMPARISON BETWEEN THE STRUCTURE OF ANIMAL AND PLANT CELLS SIMILARITIES Both have a nucleus, a plasma membrane, mitochondrion, cytoplasm, golgi apparatus, endoplasmic reticulum and ribosomes

DIFFERENCES BETWEEN THE STRUCTURE OF ANIMAL AND PLANT CELLS ANIMAL CELLSTRUCTURESPLANT CELL SHAPE CELL WALL VACUOLES CHLOROPLAST FOOD STORAGE IrregularRegular PresentAbsent Present LargeInsignificant In the form of starch In the form of glycogen

THE DENSITY OF ORGANELLES IN SPECIFIC CELLS The density or abundance of certain organelles is related to the functions of specific cells. For example: The function of palisade cells is to carry out photosynthesis. Due to this, the cells have a high density of chloroplast in them Do the activity on page 21 of your textbook

Types of cellsOrganelles found abundantly in the specific cells Function Sperm CellsMitochondriaEnable the sperm to swim towards the ovum Flight muscle cells in in insects and birds MitochondriaEnable the muscle cells to contract to allow the insects and birds to fly Cells in the meristemsMitochondriaEnable the cells to divide mitotically Mesophyll palisade cells ChloroplastAbsorbs sunlight carry out potosynthesis Pancreatic cellsRER and Golgi Apparatus Synthesize and secrete enzymes and hormones THE DENSITY OF ORGANELLES IN SPECIFIC CELLS