Ch 1 and 3 study pt2

Internal Structures

Carry Out Specific Functions

Three forms of passive transport across a cell membrane are:

Diffusion through the lipid bilayer · Diffusion through channels · Facilitated transport

Production of ATP from Glucose occurs in four stages

Glycolysis · The Preparatory Step · The Citric Acid Cycle · The electron transport system

Catabolism

Large molecules are broken down, a process that releases energy. The breakdown of glucose into water, carbon dioxide and energy is an example of a catabolic pathway

Cells use energy and transform matter and energy

Living cells release the energy stored in chemical bonds of molecules and use it to build, store and breakdown still other molecules to maintain life. · The sum of all chemical reactions in an organism is called Metabolism. · A thousand different chemical reactions are possible within a single cell at any time. · Some chemical reactions are organized in orderly and predictable patterns; some are linear in which the product (or end material) of one reaction becomes the subtrate (or starting material for another). · Other metabolic pathways form a cycle in which subtrate molecules enter and product molecules exit, but the basic cycle repeats itself over and over

Two basic types of metabolic pathways Anabolism

Molecules are assembled into larger molecules that contain more energy, a process that requires energy

Diffusion

Molecules in a gas or liquid move about randomly, colliding with other molecules and changing direction. The movement of molecules from one region to another as a result of this random motion is known as diffusion.

Fats and Proteins are additional energy sources

Most of the body's energy reserves do not take the form of glycogen. In fact, the body stores only about 1% of its total energy reserve as glycogen. About 78% are stored as fats; and 21% as protein. · After glycogen our bodies use fats and then proteins Order of fuel use o Glucose (carbohydrates) o Fats o Protein

Molecules and ions cross the plasma membrane in three major ways:

Passive transport · Active transport · Endocytosis and exocytosis

Passive Transport

Passive transport is "passive" because it transports a molecule without requiring the cell to expend energy (no energy needed). It relies on the mechanism of diffusion

Osmosis is

Passive transport moves with the concentration gradient · Most substances cross the cell membrane by passive transport. · Passive transport is always "downhill" (high to low) with respect to the concentration gradient, meaning it relies on diffusion at least in some way.

Mitochandria

Responsible for providing most of the usable energy and are called the cells' "power plants". · The number of mitochandria varies according to the cell's energy requirement. For example, a muscle cell may contain more than 1,000 mitochandria. · Energy liberated within the mitochandria is used to create high-energy moleculessuch as ATP Fat and glycogen: Sources of energy To avoid running out energy, some cells store energy as lipids (fat) · Fat cells are so specialized for this purposed that most of their volume consists of large droplet of stored lipids. · Dieting and exercise tend to reduce the amount of stored fat - making the fat cells leaner. · Dieting and exercise do not reduce the number of fat cells. Cells are able to restore fat over and over

The Nucleus

The most identifiable organelle in the cell · Serves as the information center · Contains most of the cell's DNA

Diffusion through channels

Water and many ions diffuse through channels in the plasma membrane. · Open channels are open all the time (like having a key to enter a house at anytime). · Gated channels open and close under certain conditions (like having an intercom system to let visitors in) · Facilitated transport (also called facilitated diffusion). A molecule attaches itself to a membrane protein triggering a change in the protein's shape or orientation that transfers the molecule to the other side of the membrane and releases it there (Like having to escort someone into or out of your house)

Ribosomes

are small structures composed of RNA and certain proteins and are responsible for protein synthesis.

The most immediately useful source of energy

is ATP. Glucose provides the cell with energy · Cells can use a variety of fuels to make ATP. · The most readily available fuel is glucose derived either from food recently eaten or from stored glycogen. · However, if glucose is not available, cells may turn to stored fats and even protein for fuel. · Regardless of the fuel used, most of the ATP is produced is by very similar metabolic pathways

The Endoplasmic Reticulum

is the Manufacturing Center of the Cell · The ER, in conjunction with its attached ribosomes, synthesizes most of the chemical compounds made by the cell. · If the cell where an industrial city then the ER would be the city's steel mills, saw mills and chemical plants. These materials are often not in their final form and are refined by the Golgi apparatus.

Diffusion

is the movement from high concentration to low · The net diffusion of molecules requires that there be a difference in concentration, called a concentration gradient, between two points · Once the concentration of molecules is the same the solution is in a state of equilibrium in which molecules diffuse randomly but equally in all directions.

Endocytosis

moves material into the cell. o Insulin molecules enter the cell by this method.

Extocytosis m

moves material out of the cell · Certain toxic waste products are released through extocytosis Isotonic extracellular fluid also maintains cell volume

The Golgi apparatus

refines, packages, and ships Raw materials are refined and shaped Vesicles Several types of membrane-bound storage and shipping containers

· Tonicity refers to the

relative concentrations of solutes in two fluids. Isotonic: extracellular and intracellular ionic concentration equal · Hypotonic: extracellular ionic concentration less than intracellular · Hypertonic: extracellular ionic concentration more than intracellular

Active Transport Requires Energy

· Active transport can move substances through the plasma membrane against their concentration gradient. (low to high) · Active transport requires energy to move substances from an area of lower concentration to an area of higher concentration. · Some active transport proteins use the high-energy molecule ATP. Imagine that the active transport protein is a conveyor belt moving objects uphill, powered by a gasoline engine. In this example, ATP is the gasoline and ADP the exhaust (with one difference: the ADP "exhaust" in the cell can be recycled to ATP.

The plasma membrane surrounds the cell and is like the walls and roof of a house. Although likened to a house, there are two main differences:

· Plasma membrane of animals are not rigid · Phospholipids and proteins are not anchored to specific positions in the plasma membrane and drift... like icebergs. Imagine if you woke up and your door was moved three feet towards the ceiling

When we eat more calories than we can immediately utilize, some of the excess energy is stored as glycogen and the rest converted to fat and stored in fat tissues.

· Pound for pound, fats carry more than twice the energy of carbohydrates such as glycogen Anaerobic pathways make energy available without oxygen · Cellular respiration requires oxygen to complete the chemical reactions of the citric acid cycle. · Glycolysis is an anaerobic metabolic pathway and is the only step that can occur without oxygen, glucose is the only fuel that can be used under anaerobic conditions.