exam #3 bio

Photoautotrophs

 organisms capable of producing their own organic compounds from sunlight.

heterotrophs

organisms that consume organic substances or other organisms for food

heterotrophs

organisms that consume organic substance or other organisms for food

chemoautotrophs

organisms that can build organic molecules using energy derived from inorganic chemicals instead of sunlight

stomata

aids in water balance- gas exchange occurs through small openings

gaurd cells

found on either side of a stomata, and regulate the openings and closing thy

thylakoid

disc-shaped, membrane bound structure inside a chloroplast where the light dependent reactions of photosynthesis take place; stacks of thylakoids are called grana

chlorophyll

a pigment, or molecule that absorbs light

carotenoid

photosynthetic pigment (yellow-orange-red) that functions to dispose of excess energy

garum

stack of thylakoids located inside a chlorpplast

stroma

fluid filled space surrounding the grand inside a chloroplast where the light-independent reactions of photosynthesis take place

photosynthetically active radiation

plant pigment molecules absorb only light in the wavelength range of 700nm-400nm

absorption spectrum

range of wavelengths of of electromagnetic radiation absorbed by a given substance

photoact

ejection of an electron from a reaction center using the energy of an absorbed photon

photosystem

group of proteins, chlorophyll and other pigments that are used in light-dependent reactions of photosynthesis to absorb light energy and convert it into chemical energy

photorespiration

respiratory process in many higher plants take up oxygen in the light and give out carbon dioxide

Name the 3 major types of organisms on earth that can photosynthesize.

plants, algae, cyanobacteria

why do chemoautotrophs use for energy to make sugar molecules?

they make sugars from inorganic chemical compounds

name the three basic elements required for photosynthesis

sunlight, carbon dioxide, water

name the two basic products of photosynthesis

oxygen and glyceraldehyde-3-phosphate

name the general tissue in the leaf where photosynthesis takes place

mesophyll

How are gasses (CO₂ and O₂) exchanged through the surface of the leaf?

through the stomata 

Be able to describe in detail the structure of the organelle where photosynthesis takes place in eukaryotes.

In eukaryotic autotrophs, photosynthesis takes place in an organelle called  a chloroplast. Chloroplast has a double membrane (outer and inner) system. stacks of disc-shaped structures called thylakoids fill the chloroplast. The thylakoid membranes contain chlorophyll, a pigment, or molecule that absorbs light. The thylakoid membrane also contains proteins that make up the cell's electron transport chain. The internal space in the thylakoids is called the lumen. A stack of thylakoids is called a granum. surrounding the granum is a liquid-filled space called the stroma.

name two major classes of pigments that absorb light in plants

chlorophyll and carotenoids

Understand the differences between the light-dependent and light-independent reactions of photosynthesis.  Why are they called this?

light dependent reactions - first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH) 

light-independent reactions- second stage of photosynthesis, through which carbon dioxide is used to build carbohydrate molecules using energy from ATP and NADPH   

light-dependent reactions, energy from sunlight is absorbed by chlorophyll and that energy is converted into stored chemical energy. In the light-independent reactions, the chemical energy harvested during the light-dependent reactions drives the assembly of sugar molecules from carbon dioxide.

where does the light dependent reaction take place

thylakoid membrane

what are the major products of the light dependent reaction

ATP and NADPH

the sun emits solar energy in the form of?

electromagnetic radiation

how is solar radiation categorized

its categorized based on its wavelength, or the distance between two consecutive peaks on the waveform

How is the length of the wavelength of solar radiation related to its potential energy?

The longer the wavelength, the less energy is carried. short, tight wavelengths carry the most energy 

what is the wavelength range of light energy that plant pigments can absorb

range of 700nm-400nm

what are the main two types of chlorophyll pigments found in plants

chlorophylls A and B are the main types in plant chlorplasts

what is the role of carotenoid pigments in plants?

they play a major function in the disposal of excess energy absorbed by plant tissues

*they are also used to attract seed dispersers

Relate the concept of the absorption spectrum of pigments with the green color of most plant tissue.

this is related with the green color of most plant tissue because many organisms have a mixture of pigments, allowing them to absorb a broader range of energy.

Describe the parts of a photosystem and where they are found.

they have a light harvesting complex and a reaction center.

in the light harvesting complex there is 300-400 chlorophyll molecules (and other pigments) bound to antenna proteins in the reaction center it's a specialized pair of chlorophyll a molecules of being oxidized (giving up e-)

What are the names of the proteins that house the chlorophyll pigments?

Antenna protein 

What is special about the two molecules of chlorophyll that are found in the reaction center?

a specialized pair of chlorophyll a molecule is capable of being oxidized  (giving up e-)

How is light energy transferred by the chlorophyll molecules before reaching the reaction center? 

excited energy– same wavelength 

What happens to the captured energy once it has been passed to the specialized chlorophyll a molecules?

delivers it high-energy electron to the primary electron acceptor, passed down to the electron transport chain

What is the primary electron acceptor in plants?

Phototact

What is so unique about what happens during a “photoact?”

it's the step in photosynthesis where light energy is actually converted into an excited electron 

In Photosystem II, where does the electron come from to replace the one lost in the oxidation of the two chlorophyll a molecules in the reaction center?

The splitting of water, releasing oxygen as a waste product

In Photosystem I, where does the electron come from to replace the one lost in the oxidation of the two chlorophyll a molecules in the reaction center?

It is replaced but not from water, but from the ETC 

Where does the high energy electron go after it leaves Photosystem II?  

Its passed down the electron transport chain 

What are the waste products produced from Photosystem II?

Oxygen

Understand what the energy derived from the electron transport chain is used for in plants.

light dependent reactions 

used to reduce NAPD and create a protein gradient to make ATP

Where in the chloroplast is the chemiosmotic gradient established?

in thylakoid lumen 

What is the hydrogen ion gradient potential energy used for?  How is it harnessed?

hydrogen ion stream allows ATP synthase to attach a third phosphate group to ADP, which forms a molecule of ATP 

– add phosphate to ADP to form ATP

What is the purpose of Photosystem I?

It initiates one of the first steps of solar energy conversion by light driven electron transport

What are the products of Photosystem I?

ATP

What is the captured chemical energy (ATP and NADPH) used for during photosynthesis?

It's used to produce organic molecules

Where does the carbon come from that is used to build carbohydrates in the light-independent reaction of photosynthesis?

The calvin cycle 

Understand what happens in each of the three major stages of the Calvin Cycle.

fixation, reduction, and regeneration  

What is the enzyme that most plants (C₃) use for carbon fixation?

RuBisCo

What is the name of the high-energy 5-carbon molecule carbon is fixed to?

RuBP

What is the name of the molecule formed by carbon fixation?

RuBP

What is the name of the molecule formed by the reduction of 3-PGA?  What is the fate of this product?

 becomes G3P or glyceraldehyde 3- phosphate 

What enzyme causes the problem, and why does this occur?

the build up of O2 and CO2 

Under what conditions does photorespiration usually occur?

under normal conditions, it has a higher affinity for carbon. However when concentrates of oxygen build, it will switch to its “oxygenase”

Why is photorespiration so detrimental to the plant?

it can cause a problem in light-independent photosynthetic pathways 

Be able to describe in detail how C₄ plants and CAM plants have evolved to overcome photorespiration.

CAM plants use temporal separation, C4 plants use spatial separation of carbon and fixation. They have evolved to overcome photorespiration by separating the functions of the stomata and the fixation of the carbon into day and night cycles which then minimizes photorespiration.

What is the name of the enzyme C₄ plants use in place of RuBisCo?

PEP Carboxylase

What is the name of the molecule that first fixes carbon in C₄ plants?

oxaloacetate

What are the benefits of using PEP Carboxylase instead of RuBisCo?

It has a much higher affinity for Co2 then RuBisCo does, and it also does not have the oxidase activity 

How do C₄ plants use spatial separation of the light-independent process to overcome photorespiration?

they reduce the exposure of RuBisCO to oxygen

What are the costs associated with performing C₄-type photosynthesis?

it requires 2 ATP to convert pyruvate back into PEP 

How do CAM plants avoid photorespiration?

they capture CO2 using C4 enzymes -PEP carboxylase – but at night 

What are the intermediary compounds that store the fixed CO₂ until daytime?

organic acids converted from oxaloacetate 

Which enzymes do CAM plants use to initially fix carbon?

PEP carboxylase to produce oxaloacetate 

Where does the Calvin cycle take place in CAM plants?

it takes place in the stroma of the chloroplasts 

mesophyll cells 

ligand

a molecule that binds another specific molecule, delivering a signal in the process 

target cell

cells that are affected by chemical signals

neurotransmitter

chemical ligand that carries a signal from one nerve cell to the next 

hormone

signals mainly move through the bloodstream as ligands

gap junction

 in some animal tissues, small watery channels exist between cells

plasmodesmata

in plants, these channels are found throughout 

intracellular mediator

small molecules move between cells

signal transduction

conversion of an extracellular signal into an intracellular signal.

signaling cascade

After the ligand binds to a cell-surface receptor the intracellular signal sets off a signaling cascade that results in some change.

Why do cells need communication?

to respond to external stimuli and to each other 

What are the four categories of chemical signaling in multicellular organisms?

paracrine signaling 

endocrine signaling 

autocrine signaling

direct signaling

What is the main difference between the four categories?

Be able to describe each of the four categories in terms of the distance the signal travels, how quickly it elicits a response, and how long the effect lasts.

Give examples of each of the four categories of chemical signaling in the human body. 

What is the benefit of using intracellular mediators in gap junctions and plasmodesmata in tissues of animals and plants?  

What are the two major types of cell receptors?

internal receptors 

cell-surface receptors

Do internal receptors typically respond to hydrophobic or hydrophilic molecules within the cell?

hydrophobic

Most signaling in multicellular organisms uses which type of receptor?

cell surface receptors  

What is signal transduction?

conversion of an extracellular signal into an intracellular signal ?

What are the three major categories of cell-surface receptors?  How are they different?  How are they similar?

ion channel-linked receptors - when a ligand binds to the extracellular region of the receptor, there is conformational change to the protein structure 

G-protein-linked receptors - when a ligand binds to the extracellular region of the receptor, the A sub unit is separate from the B and Y sub units 

enzyme- linked receptors- cell surface receptors that are associated with an enzyme on the intracellular surface.

They are similar because they are linked receptors

Once a ligand has bound to its specific receptor, how is the communication usually conveyed throughout the cell?

through the signaling cascade

What are some typical examples of cellular responses to signal propagation?

protein synthesis, change in cellular metabolism, cell growth, death, or division

genome

a cells DNA

Chromosome

in our species, the genome is in 23 discrete pieces, or strands of DNA

Ploidy

refers to how may complete sets(copies) of the genome an organism carries in its cells

homologues

matched pairs of chromosomes in a diploid organism

locus

a position of gene on a chromosome

Histone

proteins at regular intervals along the entire length of the chromosome

nucleosome

the resulting histone DNA structure resembles beads

Chromatin