Cell Processes & Energy Unit 3 Cell Processes & Energy

Cell Transport **The purpose of cell transport is to maintain homeostasis In other words, cells must be able to move substances into and out of the cell to maintain a stable internal environment The different kinds of cell transport are divided into two categories: those that require energy and those that do not.

I. Cell Membrane Structure A. Each cell has a membrane responsible for allowing some molecules to pass through, while keeping others out. (Selective Permeability).

I. Cell Membrane Structure B. The structure of a cell membrane is made up of a double layer of phospholipids and some scattered proteins.

I. Cell Membrane Structure C. Phospholipids are organic compounds made out of fats, or oils. These materials make up the majority of the membrane's surface.

I. Cell Membrane Structure D. Proteins are in the crevices built into the membrane. Proteins help regulate which molecules move into and out of the cell.

II. Passive Transport A. Passive transport is the movement of dissolved substances across a cell membrane without the use of energy.

B. Diffusion 1. The movement of particles from an area of higher concentration to an area of lower concentration.

B. Diffusion 2. It continues until the concentration of particles has reached equilibrium (evenly throughout the space)

B. Diffusion 3. Examples include gas exchange in cells. (O2 and CO2)

C. Osmosis 1. It is the diffusion of water through a membrane from a more concentrated solution to a less concentrated solution

2. Types of Solutions a. Isotonic - the concentration of water inside and outside the cell is equal. There is no net movement of water into or out of a cell. Most cells can be found this state.

2. Types of Solutions B. Hypotonic - Higher water concentration outside and lower concentration inside. In a hypotonic environment, water moves into the cell and the cell swells up like a balloon.

2. Types of Solutions C. Hypertonic - Higher water concentration inside and lower concentration on the outside. Water will move out of a cell that is in a hypertonic environment and the cell will shrink.

D. Facilitated Diffusion 1. The movement of molecules through channels created by proteins in the cell membrane.

D. Facilitated Diffusion 2. Sugar is a common molecule that enters the cell this way.

III. Active Transport The cell membrane is actively using energy to move molecules from one side of the cell membrane to the other.

III. Active Transport A. usually moves substances from low concentrations to high concentrations against the concentration gradient. 1. Special proteins within the cell membrane act as specific protein ‘carriers’.

III. Active Transport 2. The energy for active transport comes from ATP generated by respiration (in mitochondria).

B. Endocytosis 1. the movement of substances inward through the cell membrane that are too large to enter any other way.

B. Endocytosis 2. In this process, the cell membrane changes shape and engulfs the particle, trapping it inside.

C. Exocytosis 1. The reverse process of endocytosis.

C. Exocytosis 2. This is the releasing of large particles through the membrane.

C. Exocytosis 3. Vacuole containing particles fuse with the cell membrane.

C. Exocytosis 4. The cell membrane then forms an opening and releases the contents of the vacuole

Cell Energy

Introduction: Living organisms require energy from outside sources to perform their many tasks.

Introduction: Energy used by living organisms comes from the sun and it flows through the ecosystem. Think Food Chain!

Photosynthesis and cellular respiration are the two main processes performed by most living organisms to obtain usable energy from nature. While photosynthesis is performed by most plants to prepare their own food, most animals get their energy requirements through cellular respiration.

A. Photosynthesis Background 1. The main site of photosynthesis is in the leaves, but all green parts of the plant have chloroplasts.

A. Photosynthesis Background 2. Chlorophyll is the green pigment located inside the chloroplast of plant cells.

A. Photosynthesis Background 3. CO2 enters the leaf and O2 exits through the stomata – small openings that are on the surface of a leaf. Similar to a pore on your skin.

A. Photosynthesis Background 4. Water enters through the roots of a plant and is transported through a plant in vascular tissue. (veins)

I. Photosynthesis B. Photosynthesis is the process where plants and some other organisms absorb energy from the sun and use energy from the sun to convert carbon dioxide and water in to sugars and oxygen.

I. Photosynthesis  C. In other words, Photosynthesis is where a cell captures the energy in sunlight and uses it to make food.

I. Photosynthesis C. The food produced by plants is in the form of glucose. Glucose is an energy rich carbohydrate molecule, the primary food/energy source of cells.

I. Photosynthesis D. Stage 1 – The Light Dependent Reactions 1. Energy from sunlight is captured by the chlorophyll.

I. Photosynthesis D. Stage 1 – The Light Dependent Reactions 2. Chlorophyll changes light energy into a form that can be used in stage 2.

I. Photosynthesis D. Stage 1 – The Light Dependent Reactions 3. Water is split into hydrogen and oxygen. The hydrogen will be used in Stage 2. The oxygen is given off as a waste product in the atmosphere.

I. Photosynthesis D. Stage 2 – The Light Independent Reactions / Dark Reactions / Calvin Cycle 1. Plant cells produce sugar (Glucose)

I. Photosynthesis D. Stage 2 – The Light Independent Reactions / Dark Reactions / Calvin Cycle 2. Through a series of chemical reactions, the energy and hydrogen from Stage 1 are combined with carbon dioxide to produce Glucose.

I. Photosynthesis E. Chemical Equation is 6CO2 + 6H2O + light → C6H12O6 + 6O2

II Respiration A. During Cellular Respiration, cells break down glucose and other molecules in the presence of oxygen, releasing energy (ATP)

II Respiration B. In other words, respiration is the process of by which cells obtain energy from glucose.

II Respiration C. The chemical equation for respiration is the mirror image of the chemical equation for photosynthesis. C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

II Respiration  D. Nearly all cellular processes depend on ATP as their energy source.

III. Fermentation A. Fermentation is a process where cells release energy from food without the use of oxygen.

III. Fermentation B. Fermentation produces far less energy than respiration.

III. Fermentation C. The two most common types of fermentation: 1. Alcohol fermentation – the glucose is converted into ethanol. Most common in yeast, bacteria and plant cells (usually fruits). 2. Lactic acid fermentation – glucose is converted into lactic acid. Most common in animal muscle cells.