Eukaryotic Membranes Golgi complex The Golgi complex is

Eukaryotic Membranes: Golgi complex • The Golgi complex is a specialized set of membranous sacs derived from the endoplasmic reticulum.

Eukaryotic Membranes: Golgi complex • In fact it looks like discs of smooth ER stacked on top of one another. • The vesicles that we talked about budding off from the smooth ER now fuse with the sacs on one side of the Golgi complex. – Adding membrane to the Golgi complex – Emptying their context into the Golgi complex.

Eukaryotic Membranes: Golgi complex

Eukaryotic Membranes: Golgi complex • While some vesicles are joining the Golgi complex on one side others are leaving the other side. • These vesicles are carrying proteins, lipids and other complex molecules.

Eukaryotic Membranes: Golgi complex • The Golgi complex performs the following three major functions. 1. It separates proteins and lipids received from the ER according to their destinations; for esample, the Golgi separates digestive enzymes that are bound for lysosomes from hormones that will be secreted from the cell.

Eukaryotic Membranes: Golgi complex 2. It modifies some molecules – for instance, adding sugars to proteins to make glycoproteins 3. It packages these materials into vesicles that are then transported to other parts of the cell or to the plasma membrane for export.

Eukaryotic Membranes: Golgi complex

Eukaryotic Membranes: Lysosomes • Some of the proteins manufactured in the ER and sent to the Golgi are intracellular digestive enzymes that can break down proteins, fats, and carbohydrates into their component subunits.

Eukaryotic Membranes: Lysosomes • In the Golgi, these enzymes are packaged in membraneous vesicles called lysosomes

Eukaryotic Membranes: Lysosomes • The major function of lysosomes is to digest food particles, which range from individual proteins to complete microorganisms

Eukaryotic Membranes: Lysosomes • As we will discuss in the future many cells “eat” by phagocytosis (engulfing extracellular particles with extensions of the plasma membrane. • These membranous sacs are called food vacuoles

Eukaryotic Membranes: Lysosomes • Lysosomes recognize these food vacuoles and fuse with them. • The contents of the two vesicles mixes, and the lysosomal enzymes digest the food into amino acids, monosaccharides, fatty acids, and other small molecules, which then diffuse into the cytoplasm

Eukaryotic Membranes: Lysosomes

Eukaryotic Membranes: Lysosomes • It is still not understood how lysosomes recognize these food vacuoles, but research is being done in this field • Lysosomes also digest defective or malfunctioning organelles, such as mitochondria or chloroplasts. Doing so in the same manner as food vacuoles.

Eukaryotic Membranes: Chloroplasts and Mitochondria • Each cell has specific needs – – – manufacture materials, pick things up from the environment throw other things out to move to reporduce

Eukaryotic Membranes: Chloroplasts and Mitochondria • Mitochondria and chloroplasts are responsible for providing energy for the cell. • They are exxentially foreign creatures thought to have evovled from bacteria that took up residence long ago within a fortunate eukaryotic cell.

Eukaryotic Membranes: Chloroplasts and Mitochondria

Eukaryotic Membranes: Chloroplasts and Mitochondria • There are many similarities between the two organelles – Both are usually oblong – Surrounded by double membranes – Have enzyme assemblies that synthesize ATP – DNA unique to themselves

Eukaryotic Membranes: Chloroplasts and Mitochondria • At the same time they are different due to different functions. – Chloroplasts capture the energy of sunlight during photosynthesis and store it in sugar – Mitochondria convert the energy of sugar into ATP for use by the cell

Eukaryotic Membranes: Chloroplasts and Mitochondria • The endosymbiotic hypothesis gives an explanation of the possible incorporation of bacteria into the cytoplasm of host cells, and the possible origin of the double membrane surrounding mitochondria and chloroplasts

Eukaryotic Membranes: Chloroplasts and Mitochondria

Eukaryotic Membranes: Chloroplasts • Chloroplasts are found only in plants and certain protist, notable the unicellular algae. – They are surrounded by two membranes, though there is very little space between them – The inner membrane encloses a semifluid material called the stroma.

Eukaryotic Membranes: Chloroplasts • Embedded within the stroma are interconnected stacks of hollow membranous sacs. • The individual sacs are called thylakoids and a stack of sacs is a granum • The green pigment, chlorophyll, which captures light energy is stored in the thylakoid.

Eukaryotic Membranes: Chloroplasts • • • Energy from sun Thylakoid ATP Stroma Sugar

Eukaryotic Membranes: Mitochondria • Whereas chloroplasts convert solar energy into chemical energy, mitochondria extract energy from food molecules and tore it in the high-energy bonds of ATP • A cell digests food by both aerobic and anaerobic metabolism.

Eukaryotic Membranes: Mitochondria • Anaerobic (without oxygen) occurs in the cytosol. • Aerobic (with oxygen) occurs with in the mitochondria, and is 18 -19 times more efficient.

Eukaryotic Membranes: Mitochondria • Because mitochondria are energy producing they are found in higher concentrations in certain cells such as muscle, and less abundant in others such as bone. • Mitochondria are the power house of the cell and will be discusses further later in the course.

Eukaryotic Membranes: Mitochondria • Cistae, deep folding loops • Matrix, inner compartment • Intermembrane Compartment, space between membranes

Eukaryotic Membranes: Plastids and Vacuoles • There are times when a cell will find itself in a favourable environment, where food can be stored rather than used. • Because of this cells have evolved organelles in which to store such valuable molecules.

Eukaryotic Membranes: Plastids and Vacuoles • Plastids are used as storage containers for various types of molecules • They are double membraned organelles

Eukaryotic Membranes: Plastids and Vacuoles • Especially important, particularly for perennial plants (year after year) are plastids that store photosynthetic products from the summer for use during the following winter and spring. • Starch is usually the means of storage, potatoes being an example of this.