Unit 1: Diet and Energy

Energy

Energy

the ability to do work (transfer energy b/w forms)

Everything your body does requires...

energy. Including staying warm, moving, and thinking (the "work" in question).

Heterotroph

an organism that depends on complex organic substances for nutrition

Solar Energy

energy from the sun that is converted into thermal or electrical energy. Every single organism on earth depends on solar energy for life

Mechanical Energy

1. Kinetic- energy of movement

2. Potential- stored energy

Chemical Energy

energy stored in chemical bonds

Food is a form of...

Chemical energy. When you digest food, you break the bonds and harvest the energy to run your cellular processes

First Law of Thermodynamics

• Energy cannot be created or destroyed, but it can change forms

• Photosynthesis is not creating energy, it is converting light energy from the sun to chemical energy in the plant

• All energy in the universe existed when it first began

Second Law of Thermodynamics

Energy conversions are inefficient and some energy will ALWAYS be lost

Third Law of Thermodynamics

• Energy flows from higher (more ordered or efficient) forms to lower (less ordered or efficient) energy forms

• Disorder, or entropy, increases over time

Solar energy is converted into...

chemical energy by plants (plant sugars). Animals eat plants or other animals to convert plant sugars into ATP (energy for now) and/or stored chemicals (energy for later)

How do cells fuel chemical reactions?

Energy Conversions

• Solar Energy is converted into chemical energy by plants (plant sugars)

• Animals eat plants (or other animals) to convert plant sugars into ATP (energy for now) and/or stored chemicals (energy for later)

Cells store energy in the bonds of...

ATP

Organic Nutrients

• AKA Biological Macromolecules

• Hydrogen and other elements covalently bonded to Carbon

• Carbon is the backbone of organic molecules necessary for life- forming long chains of hydrogens and carbons − Hydrocarbon Chains

Carbon

• Most versatile element on earth • Four valence electrons means many covalent bonds

Functional Groups

• Functional groups are attached to hydrocarbon chains to provide chemical reactivity to organic molecules

• Different functional group means the molecule has a different job

Building Blocks of Organic Nutrients

Dehydration Synthesis

Joining monomers to form a polymer by removing a water molecule

Hydrolytic Reaction (Hydrolysis)

Breaking polymers down into monomers by adding a water molecule

Carbohydrates

• Chains of sugar molecules (carbon rings with 3-7 carbons)

• Quickly accessed as an energy source (preferred energy source)

• Can form long polymers that are easily broken down by digestive enzymes

Monosaccharide

Single carbohydrate units, AKA simple sugars (Ex: glucose, galactose, fructose)

Disaccharide

Combinations of two monosaccharides, one of which is usually glucose (Ex: maltose, lactose, sucrose)

Polysaccharide

Long chains of glucose molecules, may be either branched or unbranched

Sugars in your blood: 3 fates

Depending on their structure, dietary carbohydrates can...

Lead to quick-but-brief or slow-but-persistent increases in blood sugar.

Lipids

Non-polar molecules that do not dissolve in water

Saturated fats raise...

Bad cholesterol in the bloodstream which can create blockages and heart disease

Trans Fats

• Man-made fats

• One of the worst things you can eat

Structure of Fats

Sterols

• Carbon arranged in four rings instead of chains

• Cholesterol: Component of animal cell membranes−In blood, can attach to vessel walls, causing blockage

• Steroid Hormones−Regulate sexual development, maturation, and sex cell production −Estrogen: Memory/Mood −Testosterone: Muscle growth

Phospholipids

• Compose the membrane of all living cells

Proteins

• Amino group and carboxyl group bound to a chain of amino acids • Order, identity and number of amino acids determine protein function

Protein Diversity

• Structure (hair, nails)

• Protection (fight invading microorganisms, coagulate blood)

• Regulation (control cell activity, hormones)

• Contraction (allows muscles to contract, heart to pump)

• Transportation (carry molecules around body)

Protein Structure

A change in protein shape =

A change in function

Hair Protein

Keratin

Amino Acids are...

Essential. You cannot make these and you have to obtain them from food or you will die!

Pathway of Energy

Functions of Digestive System

1. Break down incoming nutrients to be transported to cells of the body

2. Supply cells with water

3. Remove undigested waste material

Mechanical Digestion

• Physically breaking food down to increase its surface area

• Mouth and stomach

Chemical Digestion

• Break down nutrient molecules using enzymes to harvest energy

• Small intestine

Digestive Tract Organs

Mouth – breaks up food by mechanical and chemical digestion

Esophagus – transports food to stomach

Stomach – mechanical mixing of food

Small intestine – major organ of digestion and absorption

Large intestine – eliminates indigestible materials, reabsorbs water

Accessory Organs

Salivary glands – lubricates food and provides enzymes

Liver – produces bile, processes and stores nutrients

Pancreas– produces digestive enzymes for the small intestine, regulates blood sugar levels

Gallbladder – stores bile

Small Intestine

Folds, Villi: Increase surface area to maximize nutrient absorption

Capillaries inside villi connect small intestine to circulatory system

Lacteals inside villi transport fat-soluble molecules to lymphatic system

Enzymes

Metabolic catalyst that speed up chemical reactions or allow them to occur at all

Activation Energy: The amount of energy required to make a chemical reaction occur

Enzymes lower activation energy

How Enzymes work

1. Substrate (nutrient) binds to active site of enzyme

2. Enzyme changes shape, which changes the shape of the nutrient molecule (thus lowering reaction activation energy)

3. Once reaction is complete, nutrient unbinds from enzyme

Enzyme Regulation

Conditions can change the shape of the active site and its ability to interact with its substrate

Feedback Inhibition

• Product of the enzyme pathway tells enzyme to stop working

• Only the needed amount of product will be produced

Digestive Enzymes

Break down carbohydrates, proteins, and lipids into molecules that can move into circulatory or lymphatic system

Amylases

• Break down carbohydrates

• Sends simple sugars to blood stream

Peptidases

• Break down proteins

• Sends amino acids to blood stream

Lipases

• Break down fats

• Sends simple fats (monoglycerides) to lymphatic system

Cells

The smallest unit that still displays all the properties of life

All cells have...

Cytoplasm, Plasma Membrane, DNA, Ribosomes

Prokaryotic Cells

• Simple, single-celled (unicellular) organism

• Lacks a nucleus, or any other membrane-bound organelle

• DNA is found in the nucleoid

Prokaryotes: Bacteria and Archaea

There are how many cells in the body?

• 30 trillion human cells

• 39 Trillion bacteria, archaea, and fungi cells

• That’s more cells than there are stars in the milky way galaxy

Eukaryotic

Nucleus and membrane bound organelles

Eukaryotic Cells & Membrane Bound Organelles

• Membrane-bound compartments inside cells with specific functions

• What is the advantage of compartmentalization?

Mitochondria

• Act as all-purpose energy converters

• Harvest energy to be used for cellular functions

Mitochondria Structure

• “Bag-within-a-bag”

• Two areas inside: Intermembrane space, Mitochondrial matrix

Origin of Mitochondria

• Symbiosis: Individuals of two different species live in physical contact, often for mutual benefit

• Endosymbiosis: Occurs when an individual of one species lives inside an individual of another species

Endosymbiosis
 Hypothesis

Mitochondria originated from bacterial cell that took up residence inside another cell (developed by Lynn Margulis)

Plasma Membrane

• Defines the boundary of the cell

• Determines the nature of its contact with the environment

• Can exclude, allow in, or remove different substances

• Regulates internal environment of cell

• Made of a phospholipid bilayer

Phospholipid Bilayer Structure in a Cell

Fluid-Mosaic Model

• Describes the structure of the plasma membrane as a mosaic of components that are able to flow and change position, while maintaining the basic integrity of the membrane

• Phospholipids

• Cholesterol—regulates fluidity based on temperature

• Proteins—serve as channels or pumps, enzymes, structural attachments

• Carbohydrates—on exterior of cell surface

Molecules must move across membranes

• Cells take in food/nutrients, export wastes, and communicate with their environment

• Passive Transport: No energy required

• Diffusion (simple or facilitated)

• Osmosis (water only)

• Active Transport: Energy Required

• Bulk Transport: Special vesicles used to move large quantities at the same time

Passive Transport: Diffusion

• Solute: What molecule is being dissolved

• Solvent: What molecule is dissolved in

• Concentration Gradients: Differences in number of molecules solute per mL solvent across a membrane

Concentration Gradient

• Molecules will move from areas of high concentration to areas of low concentration until the concentrations are the same

• This happens without input of energy

Passive Transport: 
Simple Diffusion

Small molecules that carry no charge can pass directly through the membrane

Passive transport:
 Facilitated Diffusion

Large or charged molecules must pass through a channel or carrier molecule to get across PM

Osmosis

• Passive transport of water

• Water diffuses across a membrane via channel molecule to equalize the concentration of solute inside and outside the cell

Osmosis Part 2

Active Transport

• Movement of molecules across the plasma membrane that requires energy

• Molecules being pumped against their chemical gradients

Sodium-Potassium Pump

• Important active transport example

• Creates a charge gradient (or resting potential) that helps maintain cell conditions

Bulk Transport:
 Endocytosis

• A type of active transport that moves large particles into a cell

• The plasma membrane of the cell forms a pocket around the target particle

• The pocket pinches off from the membrane

• The particle becomes contained in a newly created vacuole formed from the plasma membrane

Once Molecule is inside the cell

• Cellular respiration converts sugar molecules to ATP

• Needs Oxygen

• Releases water and Carbon Dioxide

Three steps of cellular respiration

Glycolysis Step 1

• Step 1: ATP is used to destabilize a glucose molecule.

• Makes energy in bonds easier to harvest

Glycolysis Step 2

• Step 2: Glucose broken in to two pyruvate molecules.

• Energy stored in ATP

• Electrons stored in NADH

Glycolysis uses...

• Uses 2 ATP

• Results in 4 ATP (2 Net ATP) and 2 NADH and 2 Pyruvate

• For small organisms, this is all they do!

• Larger organisms must harvest more energy from the pyruvate

Prep Reactions:
 Acetyl-CoA production

• Before proceeding to the citric acid cycle, the molecules needed for that process must be modified

• This occurs in the mitochondrion before the citric acid cycle begins

Acetyl-CoA production Step 1

• Step 1: Break down pyruvate, and in the process donate two electrons to NAD+, creating NADH

Acetyl-CoA production Step 2

• Step 2: CO2 is formed and released

• The CO2 diffuses out of the cell into the blood stream, and you eventually breathe it out

Acetyl-CoA production Step 3

Step 3: A molecule called coenzyme-A attaches itself to the remaining portion of pyruvate

What results from Acetyl-CoA production?

• Resulting molecule, called Acetyl – CoA, is sent to the Citric Acid Cycle

• This happens twice per original glucose molecule

Citric acid cycle (krebs cycle)

1. acetyl-CoA molecule enters the cycle and binds to oxaloacetate, creating a six-carbon molecule.

2. The six-carbon molecule donates electrons to NAD+, creating NADH. Two carbon dioxide molecules are released into the atmosphere.

3. The remaining four-carbon molecule is rearranged to form oxaloacetate. In the process, ATP is formed, and electrons are passed to NADH and FADH2.

Mitochondrial electron transport chain

Recall:

• Glycolysis stores high-energy electrons in NADH

• The Citric Acid Cycle stores high-energy electrons in NADH and in FADH2

• How to extract that energy?

Transport chain used to harvest energy stored in electrons in NADH and FADH2

Mitochondrial electron transport chain Step 1

At each step in the electron transport chain’s sequence of handoffs, the electrons fall to a lower energy state, releasing a little bit of energy.

Mitochondrial electron transport chain Step 2

The energy is used to power proton pumps, which pack hydrogen ions from the mitochondrial matrix into the intermembrane space.

Mitochondrial electron transport chain Step 3

At the end of the chain, the lower energy electrons are handed off to oxygen, which then combines with free H+ ions to form water.

Mitochondrial electron transport chain Step 4

The protons rush back to the mitochondrial matrix with great kinetic energy, which can be used to build ATP

How much ATP per glucose molecule?

36-38 total

Alternative pathways of energy acquisition

• Aerobic Respiration requires oxygen

• Anaerobic Respiration (Fermentation) does not require oxygen

• Cells performing anaerobic respiration must use another molecule as the final electron acceptor

What happens if our bodies fall behind in delivering oxygen?

Lungs ➡ Bloodstream ➡ Cells ➡ Mitochondria

• Many organisms have a backup method for breaking down sugar when oxygen is not present

Alternative 
energy pathways

Lactic acid build up in muscles causes cramping and burning

Fermentation in Yeast

• Sugars from grapes yields wine

• Sugars from barley yields beer

• Sugar from potatoes yields vodka

• Sugars in dough yields bread

Alternative energy 
sources

Energy drinks contain...

• No carbohydrates, proteins or fats

• contain vitamins, minerals, food additives, and stimulants

• NOT considered food by the FDA