Lecture 5: Other Cell organelles 7- Peroxisomes: contain enzymes that transfer hydrogen from various substrates to oxygen. Functions of peroxisomes: Hydrogen peroxide (H2O2) is a poison, but the peroxisome has enzyme that converts H2O2 to water. Some peroxisomes break fatty acids down to smaller molecules that are transported to mitochondria for fuel لإنتاج الطاقة. They detoxify يبطل المفعول السُّمى alcohol and other harmful compounds. Thus, it exists extensively in the liver cells

8- Mitochondria: الميتوكوندريا They are the main energy transformers of cells as they convert energy to fuel الطاقة that cells can use for work. Mitochondria are the sites of cellular respiration التنفس الخلوي. generating تـُنتِج ATP from the catabolism هدم of sugars, fats, and other fuels مصادر طاقة in the presence of oxygen. Almost all eukaryotic cells have mitochondria. Mitochondria and chloroplasts are move around the cell along tracks in the cytoskeleton.

Mitochondria have a smooth outer membrane and a highly folded inner membrane forming cristae انثنائات. The inner membrane encloses the mitochondrial matrix, a fluid-filled space with DNA, ribosomes, and enzymes.

The cytoskeleton: الهيكل الخلوي A network of fibres شبكة من الالياف that provide structural support تدعيم to the cell. The cytoskeleton also functions in cell motility حركة الخلية and regulation. The cytoskeleton is a network of fibers extending throughout تمتد عبر the cytoplasm. The cytoskeleton organizesينظم the structures and activities of the cell.

Cytoskeleton Microfilaments Intermediate filaments Microtubules سميكة أنيبيبات دقيقة ألياف دقيقة ألياف متوسطة Thick Thin Middle سميكة رقيقة متوسطة Responsible for cell motility, and separation of chromosome during cell division. (Tubulin protein) Support cell motility and transport materials within the cell. (Actin protein) Reinforcing the cell shape and fixing position of organelles. (Fibrous protein)

Cilia الأهداب and Flagella الأسواط Microtubules are the central structural supports both cilia and flagella. Both can move unicellular and small multicellular organisms by propelling water outside the organism. Comparison between cilia and flagella: Cilia usually occur in large numbers on the cell surface. Flagella usually occur in just one or a few per cell. Cilia move more like oars مجاديف with alternating power and recovery strokes. Flagella have an adulatory movement حركة تموجية. So, they differ in their beating pattern أسلوب الحركة.

Cilia Flagellum

Cilia and flagella are formed of arms of a motor protein (dynein بروتين الداينين). Dynein arms alternately grab, move, and release the outer microtubules. Protein cross-links limit sliding and the force is expressed as bending إلتواء.

Many prokaryotes are motileمتحركة About half of all prokaryotes are capable of directional movement الحركة الموجهة by the following: By the flagella, scattered مبعثرة over the entire surface, is the most common شائعة method of movement. By two or more filaments ألياف. By threads خيوط that anchors تربط the cells to the substratum السطح الذى تعيش عليه. By cilia.

Cell membrane: The plasma membrane functions as a selective barrier حاجز إختيارى that allows passage of oxygen, nutrients, and wastes for the whole volume of the cell.

Cell membrane: Composed of lipids (phospholipids) and proteins. Carbohydrate chains Hydrophilic مُحب للماء Phospholipid Hydrophobic كاره للماء Proteins Composed of lipids (phospholipids) and proteins. Lipid layer contains hydrophilic and hydrophobic regions