Biology Unit 5: Cellular Structure & Function Study Guide

This can happen in three ways. How do each of these ways work? Can any molecule use any of those ways to travel into or out of the cell?

Simple diffusion is when ions or molecules diffuse down the concentration gradient, that means, from an area of high concentration to an area of low concentration. Examples of simple diffusion are the gaseous exchange that occurs during photosynthesis, and the evaporation of water in plants during transpiration. In osmosis, the particles moving are water molecules. They move from a region of low solute concentration to one of high solute concentration, across a semipermeable membrane. It allows polar and charged molecules to cross the membrane. Facilitated diffusion is the movement of hydrophilic molecules or ions across the plasma membrane. The difference is, the diffusion is facilitated by transport proteins(i.e. carrier proteins or pore proteins)

Phagocytosis

Phagocytosis is a process wherein a cell binds to the item it wants to engulf on the cell surface and draws the item inward while engulfing around it. The process of phagocytosis often happens when the cell is trying to destroy something, like a virus or an infected cell, and is often used by immune system cells.

Pinocytosis

Pinocytosis, a process by which liquid droplets are ingested by living cells. Pinocytosis is one type of endocytosis, the general process by which cells engulf external substances, gathering them into special membrane-bound vesicles contained within the cell. In pinocytosis, rather than an individual droplet of liquid traveling passively through the cell membrane, the droplet first becomes bound, or adsorbed, on the cell membrane, which then invaginates (forms a pocket) and pinches off to form a vesicle in the cytoplasm. It is believed that a vesicle may carry extracellular fluid to the opposite side of the cell, where it undergoes exocytosis.

Passive transport has 3 main types. Know the difference among these

Simple diffusion - movement of small or lipophilic molecules (e.g. O2, CO2, etc.) Osmosis - movement of water molecules (dependent on solute concentrations) Facilitated diffusion - movement of large or charged molecules via membrane proteins (e.g. ions, sucrose, etc.)

What is facilitated diffusion

Transport of substances across a biological membrane from an area of higher concentration to an area of lower concentration by means of a carrier molecule. Since the substances move along the direction of their concentration gradients, energy is not required.

What are carrier proteins, ion channels, and channel proteins?

A carrier protein is a protein that transports specific substance through intracellular compartments, into the extracellular fluid, or across the cell membrane. An ion channel is a cell membrane channel that is selectively permeable to certain ions (as of calcium or sodium). Channel proteins are a protein that allows the transport of specific substances across a cell membrane.

Active transport- what is it and why does it occur? What prevents molecules from crossing the cell membrane and thus requiring active transport?

Active transport is usually associated with accumulating high concentrations of molecules that the cell needs, such as ions, glucose and amino acids. If the process uses chemical energy, such as from adenosine triphosphate (ATP), it is termed primary active transport.Small nonpolar molecules, such as O2 and CO2, are soluble in the lipid bilayer and therefore can readily cross cell membranes. ... Charged molecules, such as ions, are unable to diffuse through a phospholipid bilayer regardless of size; even H+ ions cannot cross a lipid bilayer by free diffusion.

What organelles do they share?

Both cells have a plasma membrane, ribosomes, cytoplasm, and DNA.

Know the difference between eukaryotic and prokaryotic cells

Eukaryotic cells contain membrane-bound organelles, including a nucleus. Eukaryotes can be single-celled or multi-celled, such as you, me, plants, fungi, and insects. Bacteria are an example of prokaryotes.Prokaryotic cells do not contain a nucleus or any other membrane-bound organelle.

Exocytosis

Exocytosis is the process by which material is transported from the cell to the extracellular environment.

What is cellular transportation?

Cell transport is movement of materials across cell membranes. Cell transport includes passive and active transport.

What is plasmolysis?Crenation?Cytolysis?Turgor pressure?

Plasmolysis is the shrinking of the cytoplasm away from the wall of a living cell due to outward osmotic flow of water. Crenation is a phenomenon which occurs when cells of animal origin are exposed to a hypertonic solution, meaning that the solution which bathes the cells has a high concentration of solutes. In crenation, the cells shrink and their shapes become distorted, often with a ruffled or scalloped edge. The change in cell shape can be seen in microscopy of the cells, and can be a sign that someone is experiencing a medical problem. These cells may die as a result of impairments in cell function. Cytolysis is the usually pathologic dissolution or disintegration of cells. Turgor pressure is the actual pressure developed by the fluid in a turgid plant cell as a result of endosmosis as contrasted with the potential maximum pressure that fluid of the same concentration could theoretically develop.

Selectively permeable

A selectively permeable cell membrane is one that allows certain molecules or ions to pass through it by means of active or passive transport. Some solutes cross the membrane freely, some cross with assistance, and others do not cross at all. A few lipophilic substances move freely across the cell membrane by passive diffusion.

What is equilibrium? How does solute/ions/water travel in regards to reaching equilibrium?

Equilibrium happens when a chemical reaction does not convert all reactants to products: many reactions reach a state of balance or dynamic equilibrium in which both reactants and products are present. Another way of defining equilibrium is to say that a system is in equilibrium when the forward and reverse reactions occur at equal rates. When water molecules react with a solute they are no longer free to cross the membrane. The more solute, the fewer molecules left that are free to diffuse across the membrane. Therefore a highly concentrated solution (one with lots of solute) has a low effective concentration of water. Therefore water will tend to diffuse across a membrane from areas of low solute concentration to areas of high solute concentration - until the concentration of the solution is equal on both sides. This is only true if the solute cannot cross the membrane.

Hypertonic solution

If concentrations of dissolved solutes are greater outside the cell, the concentration of water outside is correspondingly lower. As a result, water inside the cell will flow outwards to attain equilibrium, causing the cell to shrink. As cells lose water, they lose the ability to function or divide. Hypertonic environments such as concentrated brines or syrups have been used since antiquity for food preservation because microbial cells that would otherwise cause spoilage are dehydrated in these very hypertonic environments and are unable to function.

Hypotonic solution

If concentrations of dissolved solutes are less outside the cell than inside, the concentration of water outside is correspondingly greater. When a cell is exposed to such hypotonic conditions, there is net water movement into the cell. Cells without walls will swell and may burst (lyse) if excess water is not removed from the cell. Cells with walls often benefit from the turgor pressure that develops in hypotonic environments.

Endocytosis

In endocytosis, the material to be internalized is surrounded by an area of plasma membrane, which then buds off inside the cell to form a vesicle containing the ingested material.

What does it mean to be a "membrane-bound" organelle? Are all organelles membrane-bound?

Membrane-bound organelles are surrounded by a plasma membrane to keep their internal fluids separate from the cytoplasm of the rest of the cell. No, some examples of non-membrane bound organelles are ribosomes, the cell wall, and the cytoskeleton.

What organelles do they NOT share?

Prokaryotic cells lack a nucleus and membrane-bound structures. Eukaryotic cells have a nucleus and membrane-bound structures called organelles.

Know the difference between plant and animal cells

Size: Animal cells are generally smaller than plant cells. Animal cells range from 10 to 30 micrometers in length, while plant cells range from 10 and 100 micrometers in length. Shape: Animal cells come in various sizes and tend to have round or irregular shapes. Plant cells are more similar in size and are typically rectangular or cube shaped. Energy Storage: Animals cells store energy in the form of the complex carbohydrate glycogen. Plant cells store energy as starch. Proteins: Of the 20 amino acids needed to produce proteins, only 10 can be produced naturally in animal cells. The other so-called essential amino acids must be acquired through diet. Plants are capable of synthesizing all 20 amino acids. Growth: Animal cells increase in size by increasing in cell numbers. Plant cells mainly increase cell size by becoming larger. They grow by absorbing more water into the central vacuole. Cell Wall: Animal cells do not have a cell wall but have a cell membrane. Plant cells have a cell wall composed of cellulose as well as a cell membrane. Animal cells may have many small vacuoles. Plant cells have a large central vacuole that can occupy up to 90% of the cell's volume.

Sodium-Potassium pumps

Sodium and potassium ions are pumped in opposite directions across the membrane building up a chemical and electrical gradient for each. These gradients can be used to drive other transport processes. In nerve cells the pump is used to generate gradients of both sodium and potassium ions.

What is meant "fluid mosaic model"?

The Fluid Mosaic Model states that membranes are composed of a flexible Phospholipid Bilayer interspersed with various protein channels floating around within it. The 'Fluid' part represents how some parts of the membrane can move around freely, if they are not attached to other parts of the cell.

What organelles do they NOT share?

The lysosomes are the animal cell's "garbage disposal", while in plant cells the same function takes place in vacuoles. Plant cells have a cell wall, chloroplasts and other specialized plastids, and a large central vacuole, which are not found within animal cells.

What's the structure of the cell membrane?

The plasma membrane is a fluid mosaic. This means that it is flexible and made up of many different types of molecules. Phospholipids form the basic structure of a cell membrane, called the lipid bilayer. Scattered in the lipid bilayer are cholesterol molecules, which help to keep the membrane fluid consistent.Phospholipids are amphiphilic with the hydrocarbon tail of the molecule being hydrophobic; its polar head hydrophilic. As the plasma membrane faces watery solutions on both sides, its phospholipids accommodate this by forming a phospholipid bilayer with the hydrophobic tails facing each other. Biological bilayers are usually composed of amphiphilic phospholipids that have a hydrophilic phosphate head and a hydrophobic tail consisting of two fatty acid chains. Biological membranes typically include several types of molecules other than phospholipids.

What organelles do they share?

They share the nucleus, mitochondria, cytoplasm, ribosomes, and Golgi apparatus.

What are three main types of active transport?

There are three main types of Active Transport: The Sodium-Potassium pump, Exocytosis, and Endocytosis.

Isotonic solutions

When cells are in isotonic solution, movement of water out of the cell is exactly balanced by movement of water into the cell. A 0.9% solution of NaCl (saline) is isotonic to animal cells. When exposing animal tissues to solutions, it is common to use an isotonic solution such as Ringer's buffered saline so as to prevent osmotic effects and consequent damage to cells.

Know the difference between active and passive transport. Why do we need transportation into the cell?

While active transport requires energy and work, passive transport does not. There are several different types of this easy movement of molecules. It could be as simple as molecules moving freely such as osmosis or diffusion. ... Sometimes, proteins are used to help move molecules more quickly.