Behavioural Biology Lecture 3: Cell Structure & Function PDF

Behavioural Biology Lecture 3 Cell Structure & Function Today’s Lecture Intro to Cells Common characteristics and features of human cells Cells are like factories Reading: Chapter 3, Concepts 3.1-3.3 and 3.5-3.6 All living organisms are made up of cells, at least 1! Microscopic si...

Behavioural Biology Lecture 3 Cell Structure & Function Today’s Lecture Intro to Cells Common characteristics and features of human cells Cells are like factories Reading: Chapter 3, Concepts 3.1-3.3 and 3.5-3.6 All living organisms are made up of cells, at least 1! Microscopic single celled organisms such as bacteria Multicellular organisms such as this puma. Characteristics shared by all cells 1. All cells are surrounded by a membrane. 2. All cells have internal mass (cytoplasm). 3. All cells contain genetic material (DNA). 4. All cells have ribosomes (for making proteins). What is Cytoplasm? The cytoplasm is the fluid that fills the cell and any structural components found within it. (except for the nucleus) ** **will be explained in the upcoming slides. Two Major Cell Types in the Living World: 1. Cells without complex organelles Bacteria 2. Cells with complex organelles (e.g. nucleus and mitochondria) Animals, plants, fungi Bacteria are cells without complex organelles Bacteria are very small single celled organisms. There are many bacteria that live on our skin and within our digestive tract in a symbiotic way. Other bacteria are known Circular DNA and ribosomes human pathogens which make are free floating in the us sick, for example strep cytoplasm throat. Cells with Complex Organelles 1. Larger in size 2. DNA is enclosed within it’s own organelle = Nucleus Several linear strands of DNA (chromosomes) 3. Contain many other membranous organelles (e.g. mitochondria). 4. Ribosomes present 5. Cytoplasm fills most of the cell, but not in the nucleus. Cells making up the tissues within humans are this cell type. Examples of organisms made up of cells with complex organelles Animals Fungi Plants Cell Size Bacterium Virus http://learn.genetics.utah.edu/content/cells/scale/ Human cell Human Cell Components and their functions 1. Plasma Membrane 2. Nucleus 3. Ribosomes 4. Endoplasmic Reticulum 5. Golgi Apparatus 6. Mitochondria 1. Plasma Membrane The plasma membrane separates the inside contents of a cell from its surroundings. Plasma Membrane Aids in homeostasis by controlling the passage of substances into and out of the cell.  Plasma Membrane Structure The plasma membrane is made up of: 1. Phospholipids Main structural components 2. Proteins 3. Cholesterol (keeps membrane flexible) 4. Carbohydrates (helps ID the cell type to other cells)  Phospholipids - A type of lipid Head - Primary component of cell (water loving membranes region) Tails (water repelling region Phospholipids self orient into a double layer as their tails (repel from water) attract one another. Membrane proteins are dispersed amongst the phospholipid bilayer. Phospholipid bilayers create compartments Compartments: - Intracellular environment (inside the cell) - Interior of organelles such as the nucleus, ER, Golgi and Mitochondria… Water Water 50 nm The plasma membrane of a cell is selectively permeable due to the nature of phospholipids. What does this mean? Some substances can pass through the plasma membrane on their own while others cannot.  PM Permeability Substances that CAN pass through the phospholipid bilayer on their own include: Small lipids (e.g. fatty acids, steroid hormones like testosterone) Respiratory gases oxygen and carbon dioxide (O2, CO2) Water (H2O) PM Permeability Substances that CANNOT pass through the phospholipid bilayer on their own: Most organic molecules (e.g. Glucose) Charged atoms/molecules (e.g. ions) So how do these substances get into and out of cells? Transport Proteins For those substances that cannot slip between phospholipids a cell may provide a transport protein it can pass through if it requires it. 1. Channel Proteins Create a corridor for a specific solute to pass through. 2. Carrier Proteins Require binding of the solute which causes them to change shape allowing the solute to cross to the other side. Highly specific to a solute. Cell Membrane Proteins are essential for Cell-to-Cell Communication Create corridors between cells allowing chemical messengers through, or act as receptors on the surface of cells to which chemical messengers can bind. Which diagram illustrates synaptic signaling and endocrine signaling? Bulk Transport: Exocytosis and Endocytosis Transport proteins work well for individual molecules but when large quantities of molecules need to be moved, all at once, in or out of a cell, bulk transport mechanisms are utilized. Bulk Transport out of cells = Exocytosis Bulk Transport into cells = Endocytosis Exocytosis: Bulk transport out of cells Allows the efficient release of large quantities of large molecules all at once. Can be regulated. Neurotransmitters and most hormones are released this way during cell-to-cell communication! Endocytosis Type 1: Phagocytosis (cellular eating) Cell engulfs a particle or parasitic cell (in the case of our immune system) forming a vesicle for digestion. Endocytosis Type 2: Pinocytosis Taking in of extracellular fluid and any dissolved solutes. This is non-specific in terms of what the cell gets. 2. Nucleus Organelle that houses the DNA (several strands of it). It is the largest and easiest organelle to identify using a microscope. Human cheek cells under the microscope. Nucleus is the dark blue spot in each cell. Each strand of DNA inside the nucleus is called a chromosome. Specific regions on each chromosome are called genes. Each gene has the instructions to make a protein which will determine a trait or set of traits you have in your body. Gene Expression The specific traits (hair, eye, skin colour, shape of features etc...) that we exhibit result directly from the DNA we have inherited from our parents. Our DNA holds the instructions (Genes) to build all the necessary structures in our bodies through protein synthesis. Cells specialize in form to fulfill their particular functions Genes can be activated or inactivated. Different cell types have a different selection of active genes and therefore make different proteins. Leads to different cell structure and function. 3. Ribosomes Ribosomes are molecular complexes that are made in the nucleolus. They must make their way into the cytoplasm via a nuclear pore. New ribosomes either remain free within the cytoplasm or become embedded in the membrane of the rough endoplasmic reticulum. Either way their function is to make proteins. 4. Endoplasmic Reticulum (ER) There are 2 regions: 1. Rough ER 2. Smooth ER Rough ER The rough endoplasmic reticulum (rough ER) surrounds the nucleus. Highly folded membranous organelle. Called rough because it’s surface is studded with ribosomes. Functions: 1. Works with ribosomes to make proteins that will be released from a cell. 2. Makes plasma membrane components (phospholipids and proteins). Smooth ER Smooth ER: Continues out from the rough ER. It is not studded with ribosomes. Functions: 1. Makes lipids 2. Detoxification of drugs and poisons 3. Storage of calcium ions 4. Carbohydrate metabolism 5. Golgi Apparatus Receives, stores and ships out the products made by the ER. Some products remain within the cell, others are released to be distributed elsewhere. E.g. hormones and enzymes. 6. Mitochondria (mitochondrion sing.) Power houses of the cell. Convert energy from food into a form that our bodies can use (ATP) to do work. Cells are like factories The nucleus houses the instructions (DNA) to make proteins. The rough ER follows these instructions to make the proteins with the help of ribosomes. Smooth ER makes lipids. Proteins and lipids are stored in the Golgi apparatus until required. Some proteins and lipids will remain within the cell while others will be released as products outside of the cell. For example neurotransmitters and hormones. Identify the nucleus, what is its role in the production of proteins? What type of bulk transport is being used to release proteins from this cell?