Download Basic features of all cells

Organisms
Acellular
Viruses
Cellular
Prokaryotes
Eukaryotes
The Cell Theory
 All living organisms are composed of cells. They
may be unicellular or multicellular.
 The cell is the structural and functional unit of
life.
 Cells arise from pre-existing cells.
 All cells have the same basic chemical
composition.
Basic features of all cells
Plasma membrane
Semifluid substance called cytosol
Organelles
Genetic material
The organelle is a specialized subunit within a
cell that has a specific function.
Non-membrane bound organelles: ribosomes,
centrioles, cytoskeleton, chromosomes
Single-membrane: endoplasmic reticulum (rough
and smooth), Golgi apparatus, lysosomes,
peroxisomes, vacuoles
Double-membrane: nucleus, mitochondrion, plastid
(chloroplast)
Ribosomes
Ribosomes are composed of RNAs and proteins.
Ribosomes are found in cytoplasm, on rough ER, in mitochondria and
plastids.
Their function is protein synthesis.
Centrioles
Centrioles are made of 9 triplets of microtubules that are arranged in a
ring.
They form spindle fibers during cell division.
Cytoskeleton
Maintain and change cell shape, move organelles within the cell
Chromosomes
The function of chromosomes is to carry hereditary information
The mitochondrion
The site of cellular respiration and energy production
The Nucleus
a control center of the cell because it contains genetic material
Endoplasmic reticulum
Network of membranous channels
Synthesis of proteins, carbohydrates and lipids and steroids and their
transport
Golgi apparatus
Modification, sorting and packaging of proteins.
Lysosomes formation.
Lysosomes
Membrane vesicles containing hydrolytic proteins (digestive enzymes).
Breakdown of large molecules (proteins, lipids, nucleic acids, carbohydrates)
Peroxisomes
Membrane vesicles containing oxidative enzymes.
The enzymes break down molecules and as result produce hydrogen
peroxide molecules.
Hydrogen peroxide is immediately converted by the enzyme called catalase
to water and oxygen.
Prokaryotic cell
Absence of internal membrane-bound organelles!!!
Plasma membrane
Fluid mosaic model (Nicolson and Singer, 1972)
 Plasma membrane encloses cell and cell organelles
 Made of hydrophobic and hydrophilic components
 Semi-permeable and fluid-like
Components
 lipid bilayer
 Sterols stabilize the lipid bilayer.
 Integral (transmembrane) proteins penetrate the hydrophobic
core.
 Peripheral (exterior) proteins are bound on the surface of the
membrane.
 Carbohydrates as part of glycolipids and glycoproteins.
Functions
 Separating intracellular components from environment
 To maintain homeostasis within the cell (a stable
internal environment)
 Transport (passage) of materials into or out of the cell.
The cell membrane has selective permeability.
 Signal transduction (reception of information) by cell
surface receptors .
 Cell-cell recognition.
 Physical connection with other cells.
Transport
Passive transport: materials move from
high concentration to low concentration and
doesn’t require energy.
Active transport: molecules move through
the membrane from areas of low
concentration to areas of high concentration
with the help of energy. It uses energy to
move solutes against their gradients.
Passive transport
• Simple diffusion: small molecules (gases
such as oxygen, carbon dioxide, water)
diffuses across a membrane from the region
of higher concentration to the region of lower
concentration.
• Facilitated diffusion: big and/or polar
molecules (ions through channel proteins,
sugars, amino acids by transmembrane
transporters; aquaporins for facilitated
diffusion of water).
Active transport
• Ion pumps (sodium potassium pump).
• Endocytosis: the membrane encircles and
engulfs a food particle. The membranes fuse
together, forming a vesicle. If the material
brought into the cell is solid – phagocytosis,
liquid – pinocytosis.
• Exocytosis is the reverse of endocytosis.