Notes biology


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Intro to Energy
energy is the ability to do work
Energy exists in many forms, including,light energy, heat energy and chemical energy.
In living organisms chemical energy is stored in the organic molecules such as carbs, lipids, nucleotides etc.
Chemical energy can be converted to other forms of energy when needed.
For example: when muscles contract chemical energy is converted to mechanical energy.
All organisms need energy to live. Directly or indirectly, nearly all energy for life comes from the sun. Organisms obtain energy through food. Some organisms make their own food while others consume food.
Autotrophs are organisms that make their own food
Examples of autotrophs include:
chemoautotrophs : Uses chemicals to make food. Ex: deep sea bacteria that use hydrogen sulfide
photoautotrophs : Uses light to make food Ex: Plants, algae and protist
heterotrophs are organisms that need to ingest food in order to obtain energy.
Examples: Humans, animals and bacteria
thermodynamics is the study of the flow and transformation of energy in the universe.
Laws of Thermodynamics:
1st Law - Law of Conservation of Energy
Energy can be changed from one form to another, but it cannot created or destroyed
2nd Law - Energy cannot be converted (changed) without losing usable energy.
Energy that is lost is generally converted to thermal heat energy
The Unit of Energy
Many chemical reactions and processes in your cells are ongoing. Macromolecules are assembled and broken down, substances are transported and genetic instructions are transmitted.
All of these cellular activities require ATP energy.
In all cells, the energy necessary for cellular functions is in the form of ATP.
Think of ATP as the energy currency for all cells
ATP Energy
ATP is a biological molecule (nucleotide) that provides the most chemical energy for the cell.
ATP stands for adenosine triphosphate
ATP is a nucleotide made up of an adenine base, a ribose sugar and 3 phosphate groups.
Where does ATP come from?
The mitochondria breaks down glucose in order to obtain ATP molecules. This process is called cellular respiration.
Once we obtain the ATP molecules they can be broken down further to release energy needed to perform cellular functions such as active transport.
How is ATP Energy Harnessed?
The adenosine diphosphate ADP breaks down glucose in order to obtain ATP molecules. This process is called cellular respiration.
Once we obtain the ATP ______________________they can be broken down further to release energy needed to perform cellular functions such as active transport.
Cellular Metabolism
Cellular metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. Cellular metabolism involves complex sequences of controlled biochemical reactions, better known as metabolic pathways.
In other words, metabolism is all of the chemical reactions that occur inside a cell
A metabolic pathway is a series of steps that occur in reactions that help convert molecules or substrates, such as sugar, into different, more readily usable materials. These reactions occur inside of a cell, where enzymes, or protein molecules, break down or build up molecules
Metabolic Pathways
In this chapter we will focus on 2 metabolic pathways:
photosynthesis : metabolic pathway in which light energy from the sun is converted to chemical energy for use by the cell. In this reaction, autotrophs use light energy, carbon dioxide and water to form glucose and oxygen.
cellular respiration : metabolic pathway in which organic molecules are broken down to release energy (in the form of ATP) for use by the cell. In cell respiration oxygen is used to break down organic molecules which results in the production of carbon dioxide and water.
Most autotrophs, including plants and algae, make organic compounds such as sugars by a process called photosynthesis
Recall that photosynthesis is a metabolic pathway that converts sunlight into chemical energy.
The equation for photosynthesis is:
The Reactants of Photosynthesis are:
Light - from the sun
Carbon Dioxide (CO2)
Water (H2O) - from the roots
The Products of Photosynthesis are:
Glucose (C6H12O6)
Oxygen (O2)
Photosynthesis Con
Photosynthesis occurs in two phases
light-dependent reaction (Light reactions) occur in the thylakoids of the chloroplast
light independent reaction (Calvin cycle) occur in the stroma of the chloroplast.
Chloroplasts are organelles found mainly in the leaves of plants. Chloroplast have 2 main compartments:
thylakoids : flattened sac like membranes made of phospholipids that contain stacks called grana; where light reactions take place.
Chlorophylls are light absorbing pigments found inside the thylakoids. These give plants their green color.
stroma : Fluid-filled space outside grana; where light independent reactions take place.
Light Dependent Reactions
Step 1: Water is absorbed into the thylakoids membrane.
Step 2: Chlorophylls inside the thylakoids absorb sun light
Step 2: The sun light energy that is absorbed excites electrons in the thylakoids
Step 3: The energized (excited) electrons are used to split water (H2O) into hydrogen ions (H+) and oxygen (O2).
Step 4: The oxygen is released into the air through openings on the underside of the leaf called stomata
Step 5: The leftover H+ ions are further used inside the thylakoids to synthesize (produce) ATP and NADPH
Light Independent (Calvin Cycle
Light independent reactions also known as the calvin cycle are a series of enzyme assisted reactions in which the energy stored in ATP and NADPH is used to make plant food (glucose)
The Calvin cycle:
Takes place in the stroma of the chloroplast
Uses CO2 and organic molecules along with energy (NADP and ATP) to produce glucose.
Factors of Photosynthesis
Factors that affect photosynthesis:
The amount of light : Without enough light, a plant cannot photosynthesize very quickly, even if there is plenty of water and carbon dioxide. _increasing the amount of light a plant receives will increase the rate of photosynthesis to a point.
The _amount of CO2: Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is plenty of light, a plant cannot photosynthesize if there is insufficient carbon dioxide.
_increasing the amount of CO2 will raise the rate of photosynthesis to a certain point.
__temperature _: If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesize if it gets too hot either because temperatures above 40°C slow down photosynthesis.
Essentially, an increase in light, temperature and CO2 speeds up photosynthesis to a certain point.
Cellular Respiration
_cellular respiration is the process of breaking down glucose molecules to obtain ATP energy. This process occurs in the mitochondria
The equation for cell respiration is:

Notice that the equation for cell respiration is_opposite __to that of photosynthesis.

The Reactants of Cell Respiration :
Glucose (C6H12O6) - eat
Oxygen (O2) - breathe in

The Products of Cell Respiration :
Energy- release throughout your body
Carbon Dioxide (CO2) - breathe out
Water (H2O) - breathe out
Cellular Respiration Cont
Cellular respiration occurs in two main parts.
__glycolysis - Occurs in the cytoplasm
_aerobic respiration _when there is oxygen present- occurs in the mitochondria
_anaerobic respiration_____when there is no oxygen present- occurs in the mitochondria
The cellular respiration process begins with the food you eat. More specifically, it begins with the starchy food you eat. That's because starch breaks down into a sugar called _glucose _. This glucose is needed to kick start glycolysis.
__glycolysis is a process that happens in the cytoplasm.
Step 1: Glucose enters the cell and splits _glucose __, a six-carbon compound, into two pyruvate molecules, each of which has three carbons.
Step 2: The process of splitting glucose makes 2 ATP
Aerobic Respiration
Respiration happens inside the _mitochondria ___ and it is the process where the majority of the ATP is obtained. When organism have oxygen present they perform aerobic respiration
Step 1: After glycolysis, the __pyruvate ____ sugars are transported to the mitochondria. The three-carbon pyruvate is converted into a molecule called acetyl-CoA. This molecule moves through the Krebs cycle and produces _2 ATP and Co2__which we breathe out.
Four ATP molecules are produced by glycolysis and the Krebs cycle combined.
Step 2: Next electrons inside the mitochondria along with oxygen (we breathe in) will move through the _electron transport chain__and produce water and 32 ATP molecules.
So in total aerobic respiration makes 36 ATP (2 glycolysis and 34 in Krebs/ETC)
Anaerobic Respiration
_anaerobis respiration __is a process that occurs when there is either no oxygen present or no mitochondria present.
In the absence of oxygen, organisms continue to carry out glycolysis, since glycolysis does not use oxygen in its chemical process.
However, after glycolysis, cells undergo a process called fermentation.
_fermentation _ is an anaerobic process in which energy can be released from glucose even though oxygen is not available. Fermentation makes NO ATP.
Fermentation differs from __cellular respiration __in a way that it uses organic compounds such as carbohydrates instead of molecular oxygen. Fermentation occurs in fruits, bacteria, yeasts, fungi, as well as in mammalian muscle.
Lactic Acid Fermentation
There are 2 kinds of fermentation:
lactic acid fermantation_: Lactic acid fermentation is common in fungi and bacteria. Lactic acid fermentation also takes place in human muscle cells when strenuous exercise causes temporary oxygen shortages. Since lactic acid is a toxic substance, its buildup in the muscles produces fatigue and soreness. A process that occurs in animal cells.
Plants and animal cells cannot survive off anaerobic respiration
Alcohol Fermentation
alcohol fermentation _: Occurs mostly in yeast and some bacteria and it is the source of ethyl alcohol present in wines and liquors. It also accounts for the bubbles in bread. When yeast in bread dough runs out of oxygen, it goes through alcoholic fermentation, producing carbon dioxide. These carbon dioxide bubbles create spaces in the dough and cause it to rise.
Like lactic acid, the ethanol produced by alcoholic fermentation is toxic. When ethanol levels rise to about 12 percent, the yeast dies.
Cell Respiration & Photosynthesis are interrelated
If you haven't noticed the relationship between photosynthesis and cellular respiration is such that the products of one process are the reactants of the other
Molecules such as O2 and CO2 are recycled through the environment, however the energy is not.
Energy enters our environment as light and leaves back into outer space as heat.