Cell- It’s Structure and Functions

Made by- Digvijay SinghClass- IG-1

What is Cell? The cell (from Latin cella, meaning "small room") is the

basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently, and are often called the "building blocks of life". The study of cells is called cell biology.

Cells consist of a protoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids.

Organisms can be classified as unicellular (consisting of a single cell; including most bacteria) or multicellular (including plants and animals). While the number of cells in plants and animals varies from species to species, humans contain about 100 trillion (1014) cells. Most plant and animal cells are visible only under the microscope, with dimensions between 1 and 100 micrometres.

Eukaryotic and Prokaryotic Cells• Prokaryotic cells were the first form of life on Earth. They

are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus. Prokaryotes include two of the domains of life, bacteria and archaea. The DNA of a prokaryotic cell consists of a single chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid.

• Eukaryotic cells are about fifteen times wider than a typical prokaryote and can be as much as a thousand times greater in volume. The main distinguishing feature of eukaryotes as compared to prokaryotes is compartmentalization: the presence of membrane-bound compartments in which specific metabolic activities take place. Most important among these is a cell nucleus, a membrane-delineated compartment that houses the eukaryotic cell's DNA. This nucleus gives the eukaryote its name, which means "true nucleus."

The Cell Theory• It was proposed by two German biologists, Theodor Schwann

and Matthias Schleiden in 1839• It consists of the following points:

All known living things are made up of one or more cells.All living cells arise from pre-existing cells by division.The cell is the fundamental unit of structure and function in

all living organisms.The activity of an organism depends on the total activity of

independent cells.Energy flow (metabolism and biochemistry) occurs within

cells.Cells contain DNA which is found specifically in the

chromosome and RNA found in the cell nucleus and cytoplasm.

All cells are basically the same in chemical composition in organisms of similar species .

Plasma Membrane

• The cell membrane (also known as the plasma membrane or cytoplasmic membrane) is a biological membrane that separates the interior of all cells from the outside environment.

• The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells.

• The basic function of the cell membrane is to protect the cell from its surroundings.

• It consists of the phospholipid bilayer with embedded proteins. Cell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signalling and serve as the attachment surface for several extracellular structures, including the cell wall, glycocalyx, and intracellular cytoskeleton. Cell membranes can be artificially reassemble

• It helps in exocytosis and endocytosis

Cell Organelles• Organelles are parts of the cell which are adapted

and/or specialized for carrying out one or more vital functions, analogous to the organs of the human body

• Different OrganellesMitochondriaEndoplasmic reticulumGolgi apparatusLysosomes and PeroxisomesRibosomesCentrosomeVacuolesNucleusPlastids

Cell Organelles- Functions• Mitochondria

Energy conversion Performs Pyruvate and the citric acid cycle NADH and FADH2: the electron transport chain Heat production

• Endoplasmic reticulum Protein transport Synthesis Lipids, Steroids Performs detoxification reactions Synthesis proteins

Cell Organelles- Functions (contd.)• Golgi apparatus

Synthesis Carbohydrate and Glycoprotein Modify, sort, and pack macromolecules Transports material around the cell Helps in exocytosis

• Lysosomes and Peroxisomes Break down waste materials and cellular debris Destroy foreign particles Helps in apoptosis Breaks down very long chain fatty acids

Cell Organelles- Functions (contd.)• Centrosome

Helps in cell division Assures equal distribution of chromosomes in both daughter cells

• Ribosomes Translates mRNA into protein

Cell Organelles- Functions (contd.)• Vacuoles

Act as a transport in exocytosis and endocytosis Regulates the movements of ions around the cell Isolates materials that are harmful to cell Acts as a ‘store house’ of the cell

• Plastids Performs photosynthesis Synthesis pigments Monoterpene synthesis stores and modifies protein

Cell Organelles- Functions (contd.)• Nucleus

Cell compartmentalization Helps in Gene expression Process pre-mRNA Transfers genetic material from parents to offspring Doesn't let genetic material to flow into cytoplasm Helps in cell division Synthesis DNA and RNA (genetic material)

Cell Division• Cell division is the process by which a parent cell

divides into two or more daughter cells. • Cell division usually occurs as part of a larger

cell cycle. In eukaryotes, there are two distinct type of cell division: a vegetative division, whereby each daughter cell is genetically identical to the parent cell (mitosis), and a reductive cell division, whereby the number of chromosomes in the daughter cells is reduced by half, to produce haploid gametes (meiosis). Meiosis results in four haploid daughter cells by undergoing one round of DNA replication followed by two divisions: homologous chromosomes are separated in the first division, and sister chromatids are separated in the second division.

Animal Cell

Plant cell

The End