bio 103 Flashcards
What is the electromagnetic spectrum?
The electromagnetic (EM) spectrum consists of all of the radiation which is emitted by stars in the solar system. High frequency wavelengths in the EM spectrum contain more energy than low frequency wavelengths. The EM spectrum includes (from highest energy to lowest energy) gamma rays, X-rays, ultraviolet rays, visible light, infrared waves, microwaves, and radio waves. Most high energy radiation (gamma, X-rays, some ultraviolet) is stopped from reaching Earth’s surface by the ozone layer. Low energy radiation (infrared, microwave, and radio) are often shielded from Earth by water vapor and carbon dioxide. Over the years, living organisms have adapted to use the primary source of EM radiation which reaches Earth: visible light. Most animals have eyes which are used to detect visible light. Plants use the energy from visible light to photosynthesize. The various colors of visible light can be remembered using the mnemonic device “ROY G. BIV” (red, orange, yellow, green, blue, indigo, and violet).
What is photosynthesis?
Photosynthesis refers to the process by which plants use the energy from visible light, carbon dioxide, and water to produce carbohydrates (glucose) and oxygen.
What is the chemical reaction for photosynthesis?
CO2 + H2O + visible light C6H12O6 + O2
carbon dioxide plus water plus visible light produces glucose plus oxygen
What is the glucose from photosynthesis used for? How about oxygen?
Glucose is a monomer of polysaccharides (carbohydrates). They are used for food (plants), building materials (wood), fabrics (cotton), paper, fuel, pharmaceuticals, and energy (fossil fuels).
Oxygen is used for breathing and ultimately for cellular respiration. Oxygen also makes up a protective layer of ozone which covers the Earth and protects us from much higher energy electromagnetic radiation.
What are autotrophs?
Autotrophs are organisms like algae, green plants, and cyanobacteria which are able to photosynthesize and produce glucose and oxygen. They are sometimes referred to as primary producers and are located at the bottom of the food chain.
How do autotrophs get water and carbon dioxide?
Vascular plants get water from their roots. From there it travels up vascular tissue until it reaches leaf veins.
They get carbon dioxide through openings on the underside of leaves called stomata (stoma is singular). Stomata open to let carbon dioxide in and oxygen and water out of a leaf. After entering leaves through stomata, carbon dioxide diffuses into chloroplasts.
What are heterotrophs?
Heterotrophs are organisms like humans and other animals which gain their nourishment from eating autotrophs or other animals which eat autotrophs, They are sometimes referred to as consumers.
In what type of organelle does photosynthesis occur? Why?
Chloroplasts are the organelles in which photosynthesis occurs because they have pigments which are capable of absorbing visible light and capturing its energy to use in photosynthesis.
Why do green plants look green?
Green plants don’t absorb wavelengths of green light; instead, they reflect wavelengths of green light and thus appear green.
Describe the structure and function of a chloroplast.
Chloroplasts have double membranes surrounding them. Inside is a fluid-filled interior called the stroma (not to be confused with stoma). Membranes within the stroma form flattened sacs called thylakoids. Thylakoids are stacked in some areas to form grana (granum is singular).
Chlorophyll and other pigments that absorb visible light are a part of the thylakoid membranes. Carbon dioxide is reduced to form glucose in the stroma.
What are the three most important photosynthetic pigments?
Chlorophyll a, chlorophyll b, and carotenoids (which play an accessory role) are the most important photosynthetic pigments. Chlorophylls a and b absorb violet, blue, and red light best. Carotenoids absorb violet, blue, and green light best.
What is a spectrophotometer?
A spectrophotometer is an instrument which can tell you the wavelengths of light a pigment absorbs.
How does an absorption spectrum differ from an action spectrum?
An absorption spectrum shows the visible light wavelengths that various pigments can absorb. An action spectrum shows the visible light used to perform a function (such as photosynthesis).
What are the reactants of photosynthesis? the products?
Reactants: carbon dioxide and water
Products: glucose and oxygen
From which reactant does the oxygen from photosynthesis originate?
water
Photosynthesis is an oxidation-reduction (redox) reaction. What does this mean?
Carbon dioxide is reduced (electrons are added to make glucose) while water is oxidized (electrons are taken away to produce oxygen).
Photosynthesis has two sets of reactions. What are they and how do they differ?
Light reactions take place in the thylakoid membranes and involve the oxidation of water to produce oxygen.
Calvin cycle reactions take place in the stroma and involve the reduction of carbon dioxide to produce glucose.
What are the three types of photosynthesis and how do they differ?
C3: used by C3 plants (most common plants like maple trees, azaleas, wheat, and Kentucky bluegrass). Mesophyll cells in the leaves contain chloroplasts where both carbon dioxide fixation and other Calvin cycle reactions occur. This type of photosynthesis requires photorespiration (process by which light causes carbon dioxide to be taken up and oxygen to be released by stomata. A drawback is that when the stomata open during the day, water is also lost.
C4: used by C4 plants (sugarcane, corn, Bermuda grass, crab grass). Both mesophyll cells and bundle sheath cells around the leaf veins contain chloroplasts. Carbon dioxide fixation occurs in the mesophyll cells and other Calvin cycle reactions occur in the bundle sheath cells. This type of photosynthesis does not require photorespiration (stomata don’t have to open), so they can be more productive than C3 plants in hot, dry climates.
CAM (crassulacean-acid metabolism): used by flowering succulents living in warm, dry regions (pineapples, cacti, orchids). This type of photosynthesis fixes carbon dioxide into four carbon molecules during the night. It then releases carbon dioxide to the Calvin cycle reactions during the day. This means that stomata only have to open at night, which allows them to conserve water.
