General Biology 1 Week 6 PDF

GENERAL BIOLOGY 1 WEEK 6 LESSON 1: FERMENTATION AND AEROBIC RESPIRATION LESSON 2: “COOL BUT FEARFUL” CELL MEMBRANE Activity 1: LET’S DEFFERENTIATE? Direction: Differentiate the two pictures below.. Activity 1: LET’S DEFFERENTIATE? Direction: Differentiate the two pictures...

GENERAL BIOLOGY 1 WEEK 6 LESSON 1: FERMENTATION AND AEROBIC RESPIRATION LESSON 2: “COOL BUT FEARFUL” CELL MEMBRANE Activity 1: LET’S DEFFERENTIATE? Direction: Differentiate the two pictures below.. Activity 1: LET’S DEFFERENTIATE? Direction: Differentiate the two pictures below.. Is it wonderful to see plants, animals and other living organisms? Have you ever questioned how these living organisms grow? How water from soil enter the roots? How oxygen and carbon dioxide enter and leave the lungs? Also how glucose from the small intestine enter the blood?  In this lesson you will find out that there are simple and complex activities that are happening in the cell. The cell has transport mechanisms namely the Passive and active transport that allow selective materials to come in and come out of the cell. You will be able to understand how passive transport and active transport works. LESSON 1: TRANSPORT MECHANISMS IN CELL LESSON 2: EXOCYTOSIS AND ENDOCYTOSIS OBJECTIVES: a. Explain transport mechanisms in cells (diffusion osmosis, facilitated transport, active transport) and b. Differentiate exocytosis and endocytosis. LESSON 1: TRANSPORT MECHANISMS IN CELL LESSON 2: EXOCYTOSIS AND ENDOCYTOSIS  Membrane transport refers to the collection of mechanisms that regulate the passage of solutes such as ions and small molecules through cell/plasma membranes, which are lipid bilayers that contain proteins embedded in them.  The regulation of passage through the membrane is due to selective membrane permeability - a characteristic of biological membranes which allows them to separate substances of distinct chemical nature. In other words, they can be permeable to certain substances but not to others.  The movements of most solutes through the membrane are mediated by membrane transport proteins which are specialized to varying degrees in the transport of specific molecules. As the diversity and physiology of the distinct cells is highly related to their capacities to attract different external elements, it is postulated that there is a group of specific transport proteins for each cell type and for every specific physiological stage.  This differential expression is regulated through the differential transcription of the genes coding for these proteins and its translation, for instance, through genetic-molecular mechanisms, but also at the cell biology level: the production of these proteins can be activated by cellular signaling pathways, at the biochemical level, or even by being situated in cytoplasmic vesicles. There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. PASSIVE TRANSPORT This process does not require energy for molecules to pass through the plasma membrane. Molecules move down their concentration gradient. A gradient is any imbalance in the concentration. Passive transport moves molecules from higher concentration to lower concentration.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. PASSIVE TRANSPORT This process is carried out to maintain an equilibrium level in a cell. Passive transport moves molecules by Simple Diffusion, and Facilitated Diffusion or Osmosis.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. PASSIVE TRANSPORT Simple Diffusion allows non polar molecules such as oxygen (O2) and carbon dioxide (CO2) to pass directly on the membrane. Facilitated Diffusion does not require energy but needs a membrane transport channel or carrier protein to transport ions such as sodium (Na+) and potassium (K+).  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. PASSIVE TRANSPORT Osmosis is a special type of diffusion specifically associated with the movement of water molecules. A solution with higher concentration of solutes is said to be hypertonic while a solution with a lower concentration of solutes is hypotonic. Water crosses the membrane until the solute concentrations are equal on both sides. Solutions of equal solution concentration are said to be isotonic.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. PASSIVE TRANSPORT Osmosis is a special type of diffusion specifically associated with the movement of water molecules. A solution with higher concentration of solutes is said to be hypertonic while a solution with a lower concentration of solutes is hypotonic. Water crosses the membrane until the solute concentrations are equal on both sides. Solutions of equal solution concentration are said to be isotonic.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. ACTIVE TRANSPORT is the movement of molecules from region of low concentration to high concentration. It occurs against a concentration gradient that is why it requires energy released from ATP (Adenosine triphosphate) for molecules to pass through the cell membrane.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. ACTIVE TRANSPORT Primary active transport uses energy usually through ATP hydrolysis. Secondary active transport relies on primary active transport, it requires energy and moves against a concentration gradients.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. ACTIVE TRANSPORT Exocytosis, endocytosis and sodium-potassium pump are a few examples of active transport.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. ACTIVE TRANSPORT Large molecules enter the cell by generalized non-selective process known as ENDOCYTOSIS. Phagocytosis is endocytosis of a particulate material while pinocytosis is endocytosis of liquid material. In this process, the plasma membrane engulfs the particle or fluid droplet and pinches off a membranous sac or vesicles with a particular fluid inside into the cytoplasm.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. ACTIVE TRANSPORT Large molecules enter the cell by generalized non-selective process known as ENDOCYTOSIS. Phagocytosis is endocytosis of a particulate material while pinocytosis is endocytosis of liquid material. In this process, the plasma membrane engulfs the particle or fluid droplet and pinches off a membranous sac or vesicles with a particular fluid inside into the cytoplasm.  There are two major ways in which molecule or particles can move across a membrane. It is either by passive or active transport. ACTIVE TRANSPORT EXOCYTOSIS is the reverse process where a membrane- bound vesicle filled with bulky materials moves to the plasma membrane and fuses with it. In this process, the vesicles contents are released out of the cell. DIFFERENCES BETWEEN ENDOCYTOSIS AND EXOCYTOSIS LESSON 2: EXOCYTOSIS AND ENDOCYTOSIS  In addition to moving small ions and molecules through the membrane, cells also need to remove and take in larger molecules and particles. Some cells are even capable of engulfing entire unicellular microorganisms. You might have correctly hypothesized that the uptake and release of large particles by the cell requires energy. A large particle, however, cannot pass through the membrane, even with energy supplied by the cell.  In this lesson, we'll discover how some cells can eat, drink, and digest their dinner through the process of endocytosis and a structure called the lysosome. Furthermore, we'll learn how a cell can throw out the leftovers across the cell membrane during exocytosis  In this lesson, we'll discover how some cells can eat, drink, and digest their dinner through the process of endocytosis and a structure called the lysosome. Furthermore, we'll learn how a cell can throw out the leftovers across the cell membrane during exocytosis DIFFERENCES BETWEEN ENDOCYTOSIS AND EXOCYTOSIS  ENDOCYTOSIS AND EXOCYTOSIS: DIFFERENCES AND SIMILARITIES Endocytosis and exocytosis are the processes by which cells move materials into or out of the cell that are too large to directly pass through the lipid bilayer of the cell membrane. Large molecules, microorganisms and waste products are some of the substances moved through the cell membrane via exocytosis and endocytosis. Why is bulk transport important for cells? Cell membranes are semi-permeable, meaning they allow certain small molecules and ions to passively diffuse through them. Other small molecules are able to make their way into or out of the cell through carrier proteins or channels. Why is bulk transport important for cells? Endocytosis and exocytosis are the bulk transport mechanisms used in eukaryotes. As these transport processes require energy, they are known as active transport processes. WHAT IS ENDOCYTOSIS? Endocytosis is the process by which cells take in substances from outside of the cell by engulfing them in a vesicle. These can include things like nutrients to support the cell or pathogens that immune cells engulf and destroy. Endocytosis occurs when a portion of the cell membrane folds in on itself, encircling extracellular fluid and various molecules or microorganisms. The resulting Endocytosis serves many purposes, including: Taking in nutrients for cellular growth, function and repair: Cells need materials like proteins and lipids to function. Capturing pathogens or other unknown substances that may endanger the organism: When pathogens like bacteria are identified by the immune system, they are engulfed by immune cells to be destroyed. Disposing of old or damaged cells: Cells must be safely disposed of when they stop functioning properly to prevent damage to other cells. These cells are eliminated through endocytosis. Types of endocytosis There are two types of endocytosis: phagocytosis and pinocytosis. PHAGOCYTOSIS Phagocytosis, also known as cell eating, is the process by which cells internalize large particles or cells, like damaged cells and bacteria. 8 Within the human body, and in other mammals, phagocytosis is how immune cells engulf and destroy dangerous microorganisms or toxic compounds. Macrophages and neutrophils, types of white blood cells, are the two primary phagocytes. These white blood cells are responsible for clearing out aged and damaged cells, as well as disposing of infectious microorganisms. Types of endocytosis There are two types of endocytosis: phagocytosis and pinocytosis. Pinocytosis Pinocytosis, also known as cell drinking, is common in plant and animal cells. During pinocytosis, the cell takes in substances from the extracellular fluid that it needs to function. These include things like water and nutrients The steps of endocytosis The following is an outline of the basic steps of the two types of endocytosis. Phagocytosis: A particle or substance binds to receptors on the cell’s surface, stimulating the release of pseudopodia (extensions of the plasma membrane filled with cytoplasm). Pseudopodia surround the object until their membranes fuse, forming a phagocytic vesicle. The phagocytic vesicle pinches off from the cell membrane, entering the cell. The phagocytic vesicle fuses with lysosomes, which recycle or destroy the vesicle’s contents. The steps of endocytosis The following is an outline of the basic steps of the two types of endocytosis. Pinocytosis: Molecules bind to receptors located along the surface of the cellular membrane. The plasma membrane folds in, forming a pinocytic vesicle that contains the molecules and the extracellular fluid. The pinocytic vesicle detaches from the cell membrane inside the cell. The vesicle fuses with early endosomes where the contents found within Endocytosis example Macrophages are a type of white blood cell that play a central role in protecting mammals against pathogens like bacteria and viruses. When a macrophage comes into contact with a virus, say a cold virus in the bloodstream, it can bind to the virus’s cell surface. Next, the macrophage will form a vesicle around the virus, completely ingesting it. The vesicle then travels to the cytosol and fuses with the lysosome, where the virus is broken down. Some viruses replicate by “tricking” host cells into endocytosing them, at which point the cell is hijacked by the virus and is instructed to replicate the virus genome and capsid. WHAT IS EXOCYTOSIS? Exocytosis is the process by which cells move materials from within the cell into the extracellular fluid. Exocytosis occurs when a vesicle fuses with the plasma membrane, allowing its contents to be released outside the cell. Exocytosis serves the following purposes: Removing toxins or waste products from the cell’s interior: Cells create waste or toxins that must be removed from the cell to maintain homeostasis. For instance, in aerobic respiration, cells produce the waste products carbon dioxide and water during ATP formation. Carbon dioxide and water are removed from these cells via exocytosis. Exocytosis serves the following purposes: Facilitating cellular communication: Cells create signaling molecules like hormones and neurotransmitters. They are delivered to other cells following their release from the cell through exocytosis. Facilitating cellular membrane growth, repair, signaling and migration: When cells absorb materials from outside the cell during endocytosis, they use lipids and proteins from the plasma membrane to create vesicles. When certain exocytotic vesicles fuse with the cellular membrane, they replenish the cell membrane with these materials. TYPES OF EXOCYTOSIS: REGULATED EXOCYTOSIS Most exocytotic vesicles contain substances created within the endoplasmic reticulum for use elsewhere in the body, such as neurotransmitters or hormones. These molecules are then packaged within a layer of membrane called a vesicle. TYPES OF EXOCYTOSIS: REGULATED EXOCYTOSIS Once excreted from the endoplasmic reticulum, these vesicles are transported to the Golgi apparatus (also known as the Golgi complex) for further modification. The molecules are then packaged once again in a vesicle that makes its way to the plasma membrane. TYPES OF EXOCYTOSIS: REGULATED EXOCYTOSIS The release of these molecules from the cell is termed regulated exocytosis because the expulsion of the materials is controlled, or regulated, by extracellular signals that cause membrane depolarization. TYPES OF EXOCYTOSIS: CONSTITUTIVE EXOCYTOSIS Constitutive exocytosis, in contrast, doesn’t require any extracellular signals. The majority of molecules traveling to the plasma membrane do so using this pathway. TYPES OF EXOCYTOSIS: CONSTITUTIVE EXOCYTOSIS After exocytosis, some exocytotic vesicles are incorporated into the plasma membrane (full vesicle fusion), while others return to the interior of the cell after their contents have been released (this is termed the “kiss-and- run” pathway). Others remain docked to the membrane, where they can be used multiple times (the “kissand-stay” pathway). THE STEPS OF EXOCYTOSIS: 1. A vesicle is formed, typically within the endoplasmic reticulum and the Golgi apparatus or early endosomes. 2. The vesicle travels to the cell membrane. 3. The vesicle fuses to the plasma membrane, during which the two bilayers merge. 4. The vesicle’s contents are released into the extracellular space. 5. The vesicle either fuses with or separates from the cell membrane. Exocytosis example Let’s take the macrophage that we discussed in our endocytosis example. Once the white blood cell has engulfed a foreign pathogen eliminate it, certain parts of the pathogen are no longer needed. The macrophage gets rid of this waste material through exocytosis, during which vesicles carry out the unwanted pathogen material.