Biology of Food Midterm 2

Taste and Smell

senses that detect the presence of chemicals

Gustation

Sense of taste

5 taste qualities detected

Sweet, umami, bitter, salty, sour

Papillae

structures on our tongue that allow us to taste food; comes in different forms

What do papillae contain?

taste buds made up of 50 to 150 taste cells

Types of taste buds

circumvallate, foliate, and fungiform

What can taste buds detect?

All five tastes

What can taste cells detect?

one or two of the five tastes

How is taste detected?

through a receptor or a channel

Sugar

The only substance that elicits pleasure sensation without it being a learning experience

What do receptors bind to

Molecules

Taste Receptors

Detect sweet, umami, and bitter tastes

Taste Channels

Detect salty and sour tastes using ion channels . these channels permit the passage of very select ions

Receptors

Classified as being either type 1 or type 2 and can function as a monomer or dimer

Dimer or Type 1

Detects sweet and umami

Monomer or Type 2

Detects bitter

Olfaction

Sense of smell

What can olfaction detect

Detects 1 trillion different odors and most food flavors are detected through this sense

Where is the olfaction sense located

In the nasal cavity in a region the size of a postage stamp there are 10 million olfactory receptor cells.

Who primarily uses the olfactory sense?

Animals; primarily to identify members of the same species and needed for reproduction

What are receptor cells?

Nerve cells that attach to the olfactory bulb (part of the brain), and the limbic system of the brain (associated with memory)

Olfactory Receptors

over 400 million different types of olfactory receptors; each one can detect many odor molecules

Aroma Molecules

Countless numbers of aroma molecules and the may either be used to attract or deter other living creatures

What are some aroma molecules?

Chemical defense mechanisms and may also taste bitter; can be toxic if too much is consumed; similar aroma molecules can have similar qualities

Thermoreceptors

Send signals to our brain about the temperature of food or environment; located on the palate and the tongue

Vanilloid Receptor (VR):

activated by eat

Spiciness

chemicals in our food can give sensation of heat either mild or intense

• Example: capsaicin (chilli pepper) or gingerot (ginger); these chemicals activate VR even though heat is not really there

Cold and Menthol Receptor (CMR)

Activated by cold

Cool minty sensation

some foods have chemicals that provide a cooling sensation

• Example: menthol (peppermint); binds to CMR and activates it

Sensory Transduction

the conversion of sensory stimulus to a neurological signal

Mechanoreceptors

these receptors are activated by touch or sound. those in the mouth can provide information regarding texture of food. located on the palate and tongue

Threshold Concentration

to preserve specific taste, a minimal concentration of a taste molecule ( ex: sugar) must be present in the food

Can more than one molecule elicit the same type of taste?

Yes, they can elicit the same type of taste but different thresholds of concentration

example: fructose is sweeter than glucose

Receptor Interactions

Each taste or aroma molecule can interact with taste/aroma receptors differently. This explains why fructose is sweeter than glucose

Why is fructose sweeter than glucose?

Fructose binds to sweet receptors more strongly than glucose resulting in sweeter sensation

Where does flavor come from in food?

The aroma of foods; aroma chemicals are volatile compounds

Esters

Produce fruity smells

Aromatic/Phenolics

Spicy, earthy aromas

Terpenes

Herbal, floral, woodsy aroma

Amines

Fishy smelling

The biology of plants is centered around the fact that…

they are stationary organisms

How do plants survive as immobile lifeforms?

They produce a variety of chemicals to impact behavior of other organisms

Do plants move to get food?

No

Can plants run from predators?

No

Can plants carry seeds to new locations?

No

Photosynthesis

process by which plants produce energy. Conversion of light energy into chemical energy (ATP, sugar)

Chlorophyll

Most prominent pigment in plants to capture light energy; absorbs everything except green light

Carotenoids

accessory pigments in plants; gives fruits and veggies orange and green color

Photosynthesis Basic Reaction

Carbon dioxide + Water + Sunlight = Sugar + Oxygen

How to plants capture light energy?

• Through pigment molecules; chlorophyll is most important

• accessory pigments help capture the light that chlorophyll doesnt (ex: carotenoids)

Photosynthesis Stage One

The Light Reactions

The Light Reactions

• light energy captured by plant pigments is used to make chemical forms of energy

• light energy (photons) causes electrons to be pulled away from water

  • This turns water into oxygen

• Electrons are then used to make chemical energy (ex. ATP) for the plant which is used to provide for plants immediate energy needs

Photosynthesis Stage Two

The Calvin Cycle

The Calvin Cycle

• Chemical energy from light reactions is used to convert carbon dioxide into sugar

  • Carbon dioxide taken from the atmosphere

  • Chemical energy is used to drive forward the process that condenses carbon dioxide into sugar

    • This sugar is used to provide energy for later and stored in several places

Plant Structure

the smallest unit of life is the cell. the level of organization increases from there

• Cell→Tissues→organ→organism

Plant Cell

Surrounded by a cell wall and a membrane. Cell wall is strong and rigid. Plant cells connect to each other through their cell walls. Contained inside all plant cells are nucleus and water-filled vacuole

Where do leaf cells contain?

Chloroplast-where chlorophyll is found and the site of photosynthesis

Where is starch located?

Kept inside of structures called amyloplasts

Plant Tissue

Plant cells work together to form 4 basic plant tissues, each having specific functions

Types of Plant Tissue

• Ground Tissue

• Vascular Tissue

• Dermal Tissue

• Secretory Tissue

Ground Tissue

the tissue that is used for energy production/storage (photosynthesis, starch storage)

Vascular Tissue

Transports water and nutrients throughout plants. often tough/fibrous

Dermal Tissue

Forms the outer surface of the plant. protects interior and retains water. forms exterior of all parts of plant

Secretory Tissue

Produces aroma molecules. located throughout plant (inferior and exterior)

Plant organs

Two or more tissues working together for a common purpose. Six major plant organs

Leaf

Organ most responsible for photosynthesis. Flat surface maximized sun and carbon dioxide exposure. Typically become herbs

Root

Most are tough/fibrous, barely edible. Those that are edible are rich in ground tissue. Typically become spices

Stem

Transport nutrients between the roots and leaves. tend to be fibrous

Flower

Reproductive organ

Fruit

derived from flowers ovary. promotes seed dispersal

Seed

product of plant reproduction. produces new plant when germinated

Herbs

Primarily come from plant leaves

Spice

Typically come from seed, bark, and roots

Grain

Seeds that are not used for their flavoring but rather caloric content (contain more starch)

Fruit

Plant that carries/contains/protects the seed

Vegetable

Any part of the plant that is neither fruit nor seed

Coffee and Caffeine

Coffee is a seed and a spice. coffee is a popular source of a molecule called caffeine

Caffeine

• example of a plants chemical defense mechanism

• partly responsible for bitter flavor of coffee

• increases alertness, fat metabolism, and locomotor activity

• Caffeine is an antagonist to adenosine (depressant neurotransmitters) but promotes dopamine function

Fiber

Polysaccharide, but not digestible. Classified into two types – Soluble and Insoluble fiber.

Soluble Fiber

Forms viscous gel. traps, slows absorptions of carcinogens, sugar, cholesterol

Insoluble fiber

has “bulking” effect. stimulates water and mucous to be secreted into intestines

Polyphenols

plant metabolites that come in various forms and sizes. being studied for their ability to potentially have an important impact on human health

How do polyphenols work?

bind to specific protein targets in the body which influence particular health benefits

Animal Protein

• most efficient source of protein

• all animal sources of protein are complete protein

• our body needs 20 amino acids to make all of the proteins in our body. complete protein contains all nine essential amino acids in the proportion our body needs them

Plant Protein

some plant sources provide complete protein but most plant sources provide incomplete protein

Incomplete Protein

contains insufficient amounts of one (or more) of the essential amino acids

Protein Complementation

Combining incomplete protein sources. Requires incomplete protein sources to be deficient in different essential amino acids

Plant Fat

Relative to calories/protein provided, plants tend to contain less fat than animal sources of calories/protein

Plant Fat Info

• plants contain a less saturated fat and more saturated fat

• plants contain essential fats such as omega-6 and omega-3 (examples of polyunsaturated fats

Animal Fat

Relative to calories/protein provided, animals tend to contain more fat than plant sources of calories/protein

Animal Fat Info

generally contains higher proportion of saturated fat than plant foods

• cholesterol is only found in animal-based foods (liver required)

• Some animal based foods provide essential fats (omega-6 in eggs/poultry and omega-3 in fish)

Why are fish rich in Omega 3

Fish are rich sources of omega-3 because to maintain fluid fats in the cold ocean water

How are omega-3’s important in human health

maintaining cell membrane structure, reducing inflammation, and regulating cardiovascular/endocrine systems

Animal Structure

The smallest unit of life is the cell. the level of organization increases from there

• Cell→tissue→organ→organism

Most common animal cell types consumed

Blood cell and muscle cell

Blood Cell

red blood cells make up approximately 1/4th of all cells int he human body. principle job is oxygen tranport (from lungs to interior of body), and carbon dioxide transport (from interior of body to lungs)

Hemoglobin

iron-containing protein in red blood cells that binds to the oxygen and carbon dioxide molecules. this oxygen is required for aerobic metabolism

Muscle

Long tubular muscle cells that work together to form muscle tissue

Myofibril

Basic unit of muscle cell

What is myofibril composed of?

Actin and Myosin