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CELLS AND CELL PROCESSES InfoPacket SECTION 1: CELL PARTS AND FUNCTIONS The Nucleus controls the cell. It holds all the genetic material known as chromosomes (which are made up of DNA). The nucleus functions as the ―brain‖ of the cell. Inside the nucleus is the Nucleolus. This structures main function is to make ribosomes. Ribosomes main function is to make the proteins for the cell. These are floating around the cell and attached to the Rough endoplasmic reticulum (giving the adjective ―rough‖). A cell may have as many as 500,000 ribosomes. On the outskirts of the cell is the Cell Membrane. This is a structure made up of two layers of phospholipids and serves many purposes. The cell membrane gives the cell its shape, holds the cytoplasm within the cell, and controls what moves into and out of the cell. Within the cell membrane is a gelatinous (or jelly-like) liquid known as the Cytoplasm. This is where most of the cell's chemical reactions take place and it stabilizes the organelles. Vacuoles are found in both animal and plant cells, however play less of a role in animal cells. Vacuoles are liquid-filled and can be used to store food, water, minerals, or wastes. It is considered the ―stomach‖ of the cell. In plants it also plays a critical role in stiffening the stems by creating turgor pressure (water pressure that holds up the cell walls). See image to the right. Without a full vacuole, plants can wilt. Cell Walls are also in plant cells as well as bacteria. It forms a thick covering outside the cell membrane and gives the plant support and shape. In plants, cell walls are made up of polysaccharide known as cellulose which is used for many things such as making paper, shampoo and is an excellent source of fiber. Also only found in plant cells are Chloroplasts. This organelle is the place where photosynthesis takes place and contains chlorophyll which gives the plants its green color. The cell needs energy and gets it from the powerhouse of the cell, also known as the Mitochondria. This structure produces energy in the form of ATP. The Endoplasmic Reticulum – is an extension of the nuclear membrane and can connect it with the cell membrane. Its main purpose is to process lipids and proteins. Don’t worry about remembering the different functions for the smooth and rough, just know the rough ER is studded with ribosomes. Centrioles are found only in animal cells, is used in cell reproduction to help the chromosomes arrange before cell division. There are roaming ―garbage trucks‖ known as Lysosomes that digest, kills and transports waste. The Golgi apparatus is considered the ―post office‖ of the cell because it ―packages‖ (surrounds) cell molecules in lipids so they can be used in the cell. The cytoskeleton is make up of microfilaments and microtubules that give the sell structure as well as help mechanically to move the cell by moving the flagella, pili, or cilia. CELL PARTS PRACTICE: Label the parts with the correct terms SECTION 2: MEMBRANE TRANSPORT THE CELL MEMBRANE - The cell is surrounded by a lipid bilayer (―bi-‖ means two meaning there are two layers of phospholipids) membrane that is SEMI- PERMABLE. This membrane protects the cell and also regulates what goes in the cell and what leaves the cell. Nutrients and fluids are constantly moving in and out of the cell and it’s the membrane’s responsibility to filter the needs of the cell. This lipid bilayer membrane is made up of two layers of phospholipids. The hydrophilic (likes water) heads of the lipids face the inside (intracellular) fluid and outside (extracellular) fluid of the cell while the hydrophobic (fears water) tails attract each other. Refer to the diagram of the membrane above. DIFFUSION– imagine a bunch of atoms in one space. They are constantly moving and bumping off one another. Naturally, would they stay close to each other or spread out? The molecules will naturally spread out because they are bouncing off each other. They are trying to reach a state called equilibrium – where the molecules are equally spread out. Molecule naturally move along a concentration gradient. A concentration gradient is simply a difference in concentration of molecules in a space. Molecules will move from a high concentration of molecules (too crowded) to a low concentration of molecules (they have more space to roam). IMAGINE – you are walking into a elevator and there is a rude man lighting a cigar. Before he lights the cigar, the air is at equilibrium – all the air molecules are separated equally. He lights the cigar, takes a puff, and releases it into the air. The action created a concentration gradient: there are more molecules (higher concentration) close to the cigar and fewer molecules (lower concentration) everywhere else. With time, the smoke diffuses to spread to the areas of lower concentration until the entire elevator reaches a smelly equilibrium where the smoke molecules are even throughout the space. The smoke went with the concentration gradient. This process requires no energy and is called PASSIVE TRANSPORT. With the same idea, when molecules are moving across a membrane, they will go to where there are fewer molecules. For example, the diagram below shows there are less molecules on the inside than the outside, so the molecules will passively diffuse inside the cell. ACTIVE TRANPORT – in contrast to passive transport, active transport requires energy because you are going AGAINST a concentration gradient. For example: IMAGINE - you have an empty trunk. It takes no energy to simply toss some clothes in there when it is empty. However, when it gets fuller and fuller to the point where clothes are hanging over the side, it gets harder and harder (takes more energy) to stuff clothes inside the trunk. This is the same as the cell. Look at the diagram below. Say the cell requires more calcium inside the cell to create more proteins, but the outside of the cell has fewer than the inside. The cell will have to use ATP (energy) to force the molecules inside the cell (going against the gradient). It takes energy to go against, no energy to go with. FACILITATED DIFFUSION – you are going to want to read this since we didn’t discuss this in class. Facilitated diffusion is used when a molecule cannot diffuse over the membrane due to its size, shape or solubility. Proteins that lie in areas of the cell membrane work as bridges for these molecules to cross the membrane. This is still passive transport so facilitated diffusion is going with the concentration gradient and no energy is needed. OSMOSIS – is a type of diffusion, so it is PASSIVE transport. However, osmosis refers ONLY to the diffusion of water molecules. More specifically, osmosis happens across a semi-permeable membrane like the cell membrane. Water molecules are attracted to IONS (charged atoms). An example of an ion is SALT. REMEMBER: SALT SUCKS! Water will always flow in the direction of the higher concentration of salts or toward denser liquids full of solutes (including sugars). The water will dilute the area of higher concentration of salts. Let us use the Egg Lab as an example. After we took off the shell, with our few samples that didn’t break, we put water on top of one egg and maple syrup on top the other. The egg itself has a certain concentration of salts, solutes and water within its membrane (which is semi-permeable). When we added the water to the egg, the salts INSIDE the egg attracted the water and pulled the water inside the egg. As a result, the egg became bloated like a water balloon. When we added the syrup to the egg, the concentration of solutes was higher on the OUTSIDE of the egg’s membrane, so the solutes in the syrup sucked the water that was inside of the egg to outside. As a result, we had more liquid left inside the cup than we started with and the egg itself has shriveled up. The water in the egg was pulled out by the syrup. We are going to use this same lab to discuss tonicity – which in its simplest form means relative concentrations of liquids separated by a semi- permeable membrane. See diagram to left. When comparing liquids, if one liquid has MORE solutes (higher concentration - which means it has less water) it is considered HYPERtonic. If one liquid has LESS solutes (lower concentration - which means it has more water) it is considered HYPOtonic. If the concentrations are equal, it is ISOtonic. In the Egg lab, the water was hypotonic compared to the liquid inside the raw egg. The syrup was hypertonic to the liquid inside the egg. Now you can think of osmosis in one of two ways: Water is moving to side that has less water OR Water is moving to the side with the higher concentration of solutes. Both of these statements are correct. Follow which explanation works for you, but try not to get them confused. EGG LAB DIAGRAMS WATER SYRUP SECTION 3: MICROBIOLOGY Bacteria are microscopic organisms categorized under prokaryote. Because they are prokaryotes, they do not have a nucleus or any membrane bound organelles. Bacteria not only coexist with us all the time, but help us do an amazing array of useful things like make vitamins, break down garbage, and even maintain our atmosphere. Bacteria consist of only a single cell, but don't let their small size and seeming simplicity fool you. They have the ability to help and destroy. As we discussed in class, bacteria can be harmless, beneficial or harmful. Examples of beneficial bacteria are the E. coli in our intestines that help with digestion and the probiotics in yogurt that aid in regularity. Bacteria are also used to preserve and make many products we use on a daily basis such as vinegar, coffee, milk, pickles, etc. harmless and beneficial bacteria make up the vast majority of known prokaryotes. The smaller portion, harmful bacteria, are considered to be PATHOGENIC (or disease causing) and can cause much devastation. Examples of pathogenic bacteria are Yersinia pestis – the bacteria carried by rodents and fleas that killed 1/3 of the Europe population during the bubonic plague; Clostridium botulinium that was used as a deadly weapon during World War 2 that paralyzed and killed soldiers which is currently used to perk up faces of insecure actors and has-been models; and Bacillus anthracis, the white power substance known as ANTHRAX that causes respiratory failure and was used to scare Americans through the mail after the attacks in New York. Some bacteria are rod-shaped (these are called bacilli), some are round (called cocci, like streptococcus bacteria), and some are spiral-shaped (spirilli). These shapes help name some bacteria; Bacillus anthracis is a BACILLI or rod-shaped bacteria. Bacteria have been found that can live in temperatures above the boiling point and in cold that would freeze your blood. They "eat" everything from sugar and starch to sunlight, sulfur and iron. There's even a species of bacteria—Deinococcus radiodurans— that can withstand blasts of radiation 1,000 times greater than would kill a human being. MEMBRANE TRANSPORT PRACTICE: MICROBIOLOGY PRACTICE 1. Why do you think you feel thirsty after eating 1. What do we call disease causing bacteria? salty foods? 2. What are some good things bacteria can do for the 2. Why do slugs die when you pour salt on them? world? 3. Why is salt water bad for you, even deadly at 3. What shape would lactobacillus acidophilus be? some amounts??? 4. Are most bacteria harmless, beneficial or harmful? 4. What is a lipid bilayer and what purpose does it 5. What are some examples of beneficial bacteria? have in the cell? Harmless? Harmful? 5. What would happen if the cell membrane was 6. Know the diagram of the prokaryote in your notes fully permeable? (practice diagram on a later page) 6. What is facilitated diffusion and why is it 7. List some differences between animal cells and important? bacterial cells. EXTRA PRACTICE QUESTIONS 1. It’s structure is an extension of the nuclear 8. Yersinia pestis causes what disease? membrane 9. What does the golgi apparatus do? 2. It provides turgor pressure for plant cells 10. How do you know if a solute is soluble? What 3. type of transport that requires no energy but needs does it mean to be insoluble? help from a protein to enter cell 11. A balloon has a semi-permeable membrane. If I 4. Exhaust from a car is what kind of diffusion? put a water ballon in a bucket of salt water, what 5. This type of cell doesn’t have membrane bound would happen to the balloon? Draw it and label organelles what sides are hypotonic/hypertonic and which 6. This type of cell has cell walls way water is flowing. 7. E. coli is what type of bacteria? (think hard, not 12. What is the significance of the Ring Around the obvious answer). Rosie song?
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