FLAGELLA “ SPERM ”

Issues Addressed What is Sperm (flagella)? What is its structure? What is its function?

Sperm (Flagella) Flagella are whip like appendages of many cells that are used to move fluid or to propel the cells in a snake like motion. Flagella are whip like appendages of many cells that are used to move fluid or to propel the cells in a snake like motion. Sperm production takes place in the testes of male mammalian and also in other animals and plants. Sperm production takes place in the testes of male mammalian and also in other animals and plants.

Structure Sperm consist of a head which contain a haploid set of chromosomes in a compact inactive state Sperm consist of a head which contain a haploid set of chromosomes in a compact inactive state A mid-piece containing mitochondria, a single centriole and a tail A mid-piece containing mitochondria, a single centriole and a tail The Geometric Clutch Model of flagella beating is a hypothesis that attempts to explain the way the flagella work The Geometric Clutch Model of flagella beating is a hypothesis that attempts to explain the way the flagella work

Structure The molecular motors (dynein arms) power the beat of flagellum and when activated they pull and push on the outer doublets and induce a strain on the structure that causes flagellum to bend. Each doublet creates a sideways force that is transverse to the doublet. The transverse (t-force) pushes some of the doublets closer together and others apart. The motors that are pushed close together go into action and generate force. The motors that are pulled apart are forced to stop pulling.

Structure The central sheath consist of central microtubules, which is in turn connected to the radial spokes. The doublets are connected by the interdoublet bridge made of elastic protein (nexin) The pair of arms (inner and outer) project from microtubules in a clockwise direction.

Structure The motors act as swinging cross bridges that generate forces of flagella movement. The central mitochondrial pairs and radial spokes are thought to determine which arms are active at a given instant

Structure ( Swimming Spermatozoa)

Structure (Sperm Fertilization of a Fern) The Arch canal cells undergo autolysis (self lysis) at maturity and provide an open channel for the sperm to reach the egg. Many sperm arrive but only one reaches the egg and achieves fertilization.

Structure (Fern)

The first division of the Zygote is transverse and produces an upper (epibasal) and a lower (Hypobasal) cell. If an embryo is formed in the upper basal it is exoscopic. If it is formed in the lower basel it is endoscopic and grows into the gametophyte (simple plants that produce both sexually and asexually) this gives it protection from the environment and nutrition.

Function Sperm flagella can generate a variety of bending patterns. Two dimensional patterns that can be approximated as planar bending waves and three dimensional bending patterns that are approximately helical waves.

Function Sperm cells use flagellum as a propeller to move the cell through fluid of the female oviduct to reach an egg. Mammalian sperm movement is a function of sperm length and mitochondrial output. The mitochondria provide energy in the form of ATP for the flagellum to propel the cell. Movement of flagellum depends on properties of the sperm and surrounding medium in which it resides.