1. Photosynthesis and ATP synthesis Flashcards
Humans, like all animals and fungi, are
heterotrophs
heterotrophs are
organisms that obtain energy from the food they eat
autotrophs are
organisms that can capture energy from sunlight or chemicals and use that energy to produce food
they are primary producers
heterotrophs means that we need to eat food containing
organic molecules, especially carbohydrates, fats and proteins.
These organic molecules are our only source of energy
Plants do not need to take in any organic molecules at all.
plants obtain their energy from
sunlight
plants can use this energy from the sunlight to build
their own organic molecules using simple inorganic substances
how plants build their own organic molecules using simple inorganic substances
1) they produce carbohydrates from carbon dioxide and water, by photosynthesis.
2) use these carbohydrates + inorganic ions such as nitrate, phosphate and magnesium, to manufacture all the organic molecules that they need.
Organisms that feed in this way are autotrophs
heterotrophs depend on autotrophs for
the supply of organic molecules on which they feed
how some heterotrophs feed (2)
1) directly on plants
2) further along a food chain
eventually all of an animal’s or fungus’s food can be traced back to (2)
1) plants
2) energy of sunlight
Respiration is
The process by which cells break down simple food molecules to release the energy they contain.
Respiration involves
the oxidation of the energy-containing organic substances, forming another energy-containing substance called ATP
Every cell has to make its own
ATP
Photosynthesis happens in what organisms (3)?
1) plants
2) algae (phytoplankton)
3) some bacteria (autotrophs)
Phytoplankton are
tiny organisms that float in the upper layers of the sea and lakes
photosynthesis in green plants takes place in
the chloroplasts of several plant tissues, especially the palisade mesophyll and spongy mesophyll tissues of leaves
diagram of the structure of a leaf (#18)
check notebook #18
diagram of the structure of inside a leaf (#19)
check notebook #19
The ultimate source of almost all of our food is
photosynthesis
Overall equation for photosynthesis
6CO2 + 6H2O ——> C6H12O6 + 6O2
Algae are
A diverse group of aquatic organisms that have the ability to conduct photosynthesis
what bring water to the photosynthesizing cells of the leaf
The xylem tissues of roots, stems and leaf vascular bundles
how carbon dioxide diffuses into the leaf
1) through stomata,
2) then diffuses through air spaces and into mesophyll cells
3) and finally into chloroplasts, where photosynthesis takes place
Chloroplasts are
organelles within the cells of plants and certain algae that is the site of photosynthesis.
it has a double membrane and contains chlorophyll to absorb light energy
what is the site of photosynthesis
chloroplasts
Xylem tissues transports
water
stomata are
the tiny holes/pores usually found in the lower epidermis of the leaf through which diffusion of gases occurs, including carbon dioxide
physical features of a leaf (4)
1) a broad, thin lamina
2) a midrib
3) a network of veins
4) a leaf stalk (petiole)
photomicrograph of a section of a typical leaf from a mesophyte
quizlet or chegg
A mesophyte is
a plant adapted for normal terrestrial conditions
(it is adapted neither for living in water nor for withstanding excessive drought).
for the mesophyte to perform its function, the leaf must (3)
1) contain chlorophyll and other photosynthetic pigments arranged in such a way that they can absorb light;
2) be able to absorb carbon dioxide and dispose of the waste product, oxygen;
3) have a water supply and be able to export manufactured carbohydrate to the rest of the plant.
The large surface area and thinness of the lamina of the leaf allows it to
absorb a lot of light
The thinness of the lamina of the leaf
minimizes the length of the diffusion pathway for gaseous exchange
The Lamina of the leaf is
the green flat part of a leaf that is specialized for photosynthesis
The arrangement of leaves on the plant helps the plant to
absorb as much light as possible
the Leaf mosaic is
The arrangement of leaves on the stem of a plant
The upper epidermis of the leaf is made of
thin, flat, transparent cells which allow light through to the cells of the mesophyll below, where photosynthesis takes place
A waxy transparent cuticle, which is secreted by the epidermal cells, provides a
watertight layer preventing water loss other than through the stomata, which can be closed in dry conditions.
The waxy transparent cuticle and epidermis together form
a protective layer against microorganisms and some insects.
The structure of the lower epidermis in mesophytes is similar to that of the upper, except that
most mesophytes have many stomata in the lower epidermis. (Some have a few stomata in the upper epidermis also.)
Each stoma is bounded by
two sausage shaped guard cells
guard cells are
The two cells that flank the stomatal pore and regulate the opening and closing of the pore.
diagram of a photomicrograph of stomata and guard cells in Tradescantia leaf epidermis (#45)
check notebook #45
Changes in the turgidity of these guard cells cause them to
change shape so that they open and close the pore
explain when guard cells gain or lose water
When the guard cells gain water, the pore opens
When the guard cells lose water, the pore closes
explain the walls in guard cells
guard cells have unevenly thickened cell walls.
The wall adjacent to the pore is very thick, whilst the wall furthest from the pore is thin
what is arranged as hoops around each guard cell
Bundles of cellulose microfibrils are arranged as hoops around each guard cell
as the cell becomes turgid, these hoops ensure that the cell mostly increases in length and not diameter
cellulose microfibrils are
Long, thin strand of cellulose that helps strengthen plant cell walls.
what makes guard cell curve
Since the ends of the two guard cells are joined and the thin outer wall bends more readily than the thick inner one, the guard cells become curved.
This makes the pore between the cells open
Guard cells gain and lose water by
osmosis
what is needed before water can enter the cells by osmosis
A decrease in water potential is needed before water can enter the cells by osmosis.
This is achieved by the active removal of hydrogen ions, using energy from ATP, and then intake of potassium ions (indirect active transport)
diagram of a photomicrograph of palisade cells (#54)
check notebook #544
The main site of photosynthesis is the
palisade mesophyll because there are more chloroplasts per cell in the palisade mesophyll than in the spongy mesophyll.
spongy mesophyll is a
layer of loose tissue found beneath the palisade mesophyll in a leaf
palisade mesophyll is a
Layer of tall, column-shaped mesophyll cells just under the upper epidermis of a leaf
how Palisade cells show several adaptations for light absorption (3)
1) They are long cylinders arranged at right-angles to the upper epidermis.
2) The cells have a large vacuole with a thin peripheral layer of cytoplasm.
3) The chloroplasts can be moved (by proteins in the cytoplasm, as they cannot move themselves) within the cells,
how Palisade cells having long cylinders arranged at right-angles to the upper epidermis show adaptations for light absorption
This reduces the number of light-absorbing cross walls in the upper part of the leaf so that as much light as possible can reach the chloroplasts.
how Palisade cells having a large vacuole with a thin peripheral layer of cytoplasm show adaptations for light absorption
This restricts the chloroplasts to a layer near the outside of the cell where light can reach them most easily
how chloroplasts being able to move within Palisade cells is a adaptations for light absorption
it absorbs the most light or to protect the chloroplasts from excessive light intensities.
How palisade cells show adaptations for gaseous exchange (2)
1) The cylindrical cells pack together with long, narrow air spaces between them.
2) The cell walls are thin and moist, so that gases can diffuse through them more easily.
how palisade cells having cylindrical cells pack together with long, narrow air spaces between them show adaptations for gaseous exchange
This gives a large surface area of contact between cell and air.
how palisade cells having thin and moist cell walls show adaptations for gaseous exchange
gases can diffuse through them more easily.
how living organisms gain their energy?
1) from light or
2) they use the energy transferred from reactions involving elements, simple inorganic compounds or complex organic compounds
Phototrophs are
organisms that gain their energy by absorbing light
how Chemotrophs gain their energy
from chemical reactions
not from light reactions
The simplest form of carbon that organisms can use is
carbon dioxide.
energy flows through living systems and is not
recycled
Metabolic pathway is
a series of small reactions controlled by enzymes
e.g. respiration and photosynthesis
Life depends on continuous transfers of
energy
how this energy enters an organism depends on its type of nutrition
eg- In plants, energy in light is absorbed by chlorophyll and then transferred into the chemical energy of the molecules formed during photosynthesis
Spongy mesophyll is mainly adapted as
a surface for the exchange of carbon dioxide and oxygen.
because it contain chloroplasts, but in smaller numbers than in palisade cells
why photosynthesis don’t often occur in the spongy mesophyll
the spongy mesophyll has smaller numbers of chloroplasts compared to the palisade mesophyll
Photosynthesis occurs in the spongy mesophyll only at high light intensities.
Photosynthesis occurs in the spongy mesophyll only at
high light intensities.
xylem brings in the water necessary for (2)
1) photosynthesis
2) cell turgor
what the phloem does
the phloem takes the products of photosynthesis to other parts of the plant.
adaptations of the leaf for it to bring together the three raw materials of photosynthesis (water, carbon dioxide, and light and remove its products (oxygen and glucose)
large surface area that absorbs as much sunlight as possible and thin for diffusion
an arrangement of leaves on the plant that minimizes overlapping
transparent cuticle and epidermis that let light through to the photosynthetic mesophyll cells beneath
long, narrow upper mesophyll cells packed with chloroplasts that collect sunlight numerous stomata for gaseous exchange
stomata that open and close in response to changes in light intensity
many air spaces in the lower mesophyll layer to allow rapid diffusion in the gas phase of carbon dioxide and oxygen
a network of xylem that brings water to the leaf cells, and phloem that carries away the sugars produced during photosynthesis
lifetime of leaves
Leaves have a limited lifetime – they are replaced at growing seasons
Plants usually have numerous leaves and they are borne at
the nodes of a stem
The leaf blade is connected to the plant stem by a
petiole
Leaves have different shapes and sizes and may be modified to suit particular functions. For example
they may be modified with spines as protection for a plant, or for climbing as tendrils in vines
Leaves are arranged on plant stems in three major patterns called (3)
alternate opposite or whorled
The arrangement of the leaves on the plant is organised so as to
maximise the capability of the plant to capture sunlight
Leaves consist of different types of cell with particular functions. The major types of cell in a leaf are (4)
epidermal cells,
parenchyma cells,
mesophyll cells and
guard cells
epidermal cells are
a single layer of dermal tissue with covers the outside of a plant.
parenchyma cells are
a relatively unspecialized plant cell that carries out
various functions
Leaves have an outer layer of epidermal cells which are covered with a cuticle that is designed to
limit water loss
Trichomes are
Epidermal hairs
Epidermal hairs (trichomes) may be present where?
on the upper and lower surfaces of the leaf and these can also help retard water loss
In dicotyledonous leaves, stomata are normally restricted to
the lower epidermis
The guard cells regulate the opening of the stomata according to
environmental conditions
e.g. hot, dry or humid
The mechanism for the opening and closing of the stoma is dependent on
changes in the osmotic concentration of the vacuoles of the guard cells
Radioactive water is injected into the stem of a plant that is actively photosynthesising. Outline the route that a water molecule travels before exiting through a stoma
Stem into petiole, veins, mesophyll cells or palisade cells, intercellular spaces, exit stomata
Open stomata allow what? (3)
the carbon dioxide necessary for photosynthesis to enter the leaf and
let out the oxygen produced by photosynthesis.
Water vapour which has evaporated from the surfaces of the mesophyll cells into the intercellular spaces also exits the leaves
The irregular shapes of spongy mesophyll in the lower epidermis result in
large intercellular air spaces which make for efficient gaseous exchange
The mesophyll layer has numerous veins (vascular bundles) consisting of
xylem and phloem
that are continuous with the vascular system of the stem and the entire plant
The vascular tissues of the leaf veins are surrounded by
parenchyma cells that have a small number of chloroplasts and they form a structure called the bundle sheath
The bundle sheaths extends where?
right to the end of the smallest veins making sure that no parts of the veins are exposed to the air in the intercellular spaces
what must happen for substances entering or leaving the vascular bundle?
All substances (water, mineral ions, photosynthesis products, metabolic products) must pass through the bundle sheath when entering or leaving the vascular bundle
The leaves of most dicotyledonous plants have more stomata on the lower surface than on the upper.
Many have none at all on the upper epidermis.
However, leaves that float on water have
almost all their stomata on the upper surface
what would happen if leaf cells were arranged in layers horizontally rather than vertically
Light would be scattered by cell walls
advantage of having large air spaces in leaves
Diffusion through air is much faster than diffusion through cell walls and cytoplasm
what do chloroplast in the palisade mesophyll cells do on hot, bright days
chloroplasts move around in the cell so that they are not all exposed to the most intense light
the palisade mesophyll providing a large surface area of moist cell wall for gaseous exchange is due to (2)
1) irregular packing of the cells and the large air spaces thus produced
2) The veins in the leaf that help to support the large surface area of the leaf. They contain xylem and phloem
photosynthesis is a complex
metabolic pathway
a metabolic pathway is a
series of chemical reactions linked to each other that either builds a complex molecule or breaks down a complex molecule into simpler compounds.
metabolic pathway are catalysed by enzymes
Photosynthesis reactions takes place in 2 stages
light dependent stage and the light independent stage
where do both the light dependent and light independent stage of photosynthesis takes place
inside chloroplasts within cells of the leaves and often stems of plants
diagram showing the stages of photosynthesis
chegg
diagram showing the Electron micrograph of a chloroplast
chegg
Diagram of a chloroplast
chegg
diagram showing the electron micrograph of part of a chloroplast
chegg
how many chloroplasts does each cell in a photosynthesising tissue have inside it
each cell in a photosynthesising tissue may have ten or even 100 chloroplasts inside it.
A chloroplast is surrounded by
two membranes, forming an envelope
There are membranes inside the chloroplast, which are arranged so that
they enclose fluid-filled sacs between them.
The membranes are called lamellae and the fluid filled sacs are thylakoids
membranes found inside chloroplasts are called
lamellae
A thylakoid or lamellae is
a membrane-bound compartment inside chloroplasts
singular and plural of lamellae and lamella
lamella is singular and
lamellae is plural
the membranes chloroplast have are (2)
1) a double membrane
2) a lamellae
Grana are
A stacked portion of the thylakoid membrane in the chloroplast. (stacked up like a pile of pancakes)
grana function in
the light reactions of photosynthesis
Stroma is
The ‘background material’ inside the chloroplast
Embedded tightly in the thylakoid membranes inside the chloroplast are
several different kinds of photosynthetic pigments
photosynthetic pigments are
coloured substances that absorb light energy from certain wavelengths (colours) of light and use it to carry out photosynthesis.
The most abundant photosynthetic pigment is
chlorophyll
the 2 forms of chlorophyll
- chlorophyll a
- chlorophyll b
why the stacked thylakoid membranes inside the chloroplasts can capture light very efficiently
they have a large surface area so their photosynthetic pigments can capture light very efficiently.
The transformation of light energy into chemical energy in the thylakoid membranes is carried out by
other chemicals in the membranes closely associated with the photosynthetic pigments
thylakoid membranes of chloroplasts functions (2)
1) holds chemicals allowing them to function correctly
2) create the thylakoid spaces.
thylakoid lumen is
the fluid-filled space inside a thylakoid created by the thylakoid membrane
the thylakoid lumen is needed for
the accumulation of hydrogen ions, H+, used in the production of ATP
Chloroplasts often contain starch grains, because
starch is the form in which plants store the carbohydrate that they make by photosynthesis
the form that plants store the carbohydrate that they make by photosynthesis
starch
Chloroplast contains (9)
1) outer and inner membrane
2) lipid droplet
3) lamella
4) thylakoid
5) granum
6) stroma
7) starch grains
8) ribosomes
9) small circular strand of DNA
Chloroplasts are thought to have evolved from
Bacteria that first invaded eukaryotic cells over a thousand million years ago
Thylakoids (fluid-filled sacs) are stacked up in the chloroplast into structures called
rana (singular = granum).
The grana are linked together by bits of thylakoid membrane called lamellae (singular = lamella).
Chloroplasts are found in
cotyledons, leaves, stems, fruits, and flowers, depending on the plant species and its stage of development from seedling to mature plant
Dicotyledonous refers to
the group of flowering plants that have embryos with two cotyledons.
Many also have broad leaves with a net like pattern of veins
Chloroplasts are green because
they contain the pigment chlorophyll, which is vital for photosynthesis
the major pigments found in higher plants and green algae are
Chlorophyll a and b
The most advanced photosynthetic bacteria are
the cyanobacteria
Chloroplasts are distinguished from other types of plastids by
their green colour, which results from the presence of two pigments, chlorophyll a and chlorophyll b
Plastids are
cytoplasmic organelles that often contain photosynthetic pigments.
What is a complex organ composed of several tissues organized to optimize photosynthesis?
the leaf
What type of cells surround the stomata?
guard cells
A pigment is a
a substance whose molecules absorb some wavelengths (colours) of light, but not others.
(absorbs light and has colour)
The wavelengths pigments does not absorb are either
reflected or transmitted through the substance.
These unabsorbed wavelengths reach our eyes, so we see the pigment in these colours.
the color of pigments arises because they
absorb only certain wavelengths of visible light
Plants contain many pigments, giving rise to
the various colors we see.
Flowers and fruits obviously contain a large number of organic molecules that absorb light.
Leaves, stems and roots also contain a variety of pigments
organisms that contain pigments which give them their colors (3)
1) Flowers
2) corals
3) animal skin
Photosynthetic pigments are the only pigments that have the ability to
absorb energy from sunlight and make it available to the photosynthetic apparatus.
In land plants, the two classes of photosynthetic pigments are
1) chlorophylls
2) carotenoids
In plants, algae, and cyanobacteria pigments are the means by which
the energy of sunlight is captured for photosynthesis
difference between chlorophyll a and chlorophyll b absorb
Both chlorophyll a and chlorophyll b absorb similar wavelengths of light, but chlorophyll a absorbs slightly longer wavelengths than chlorophyll b.
This can be shown in a graph called an absorption spectrum
diagram showing the absorption spectra for chlorophyll and carotene
chegg
function of carotenoids, such as carotene and xanthophylls (5)
1) absorb a wide range of short wavelength light, including more blue-green light than the chlorophylls.
2) being accessory pigments.
3) help by absorbing wavelengths of light that would otherwise not be used by the plant.
4) pass on some of this energy to chlorophyll.
5) probably also help to protect chlorophyll from damage by very intense light.
Carotenoids are
Accessory pigments that broaden the spectrum of colors that can drive photosynthesis.
Carotene are
Carotenes are yellow-orange photosynthetic pigments important for photosynthesis
xanthophylls are
xanthophylls are yellow/brown pigments important for photosynthesis
What is located between the upper and lower epidermis packed with chloroplast, and photosynthetic parenchyma?
Mesophyll
What are the two sublayers of mesophylls?
Palisade and Spongy
What type of mesophyll is the main sight of photosynthesis within a leaf?
Palisade mesophyll
What type of mesophyll functions primarily for gas exchange?
Spongy mesophyll
What opens during the day for gas exchange needed for photosynthesis and closes during the night to conserve water when photosynthesis is not occurring?
stomata
explain why chlorophyll looks green
Green plants are green because they contain a pigment called chlorophyll
As shown in detail in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum.
Green light is not absorbed but reflected, making the plant appear green
The plasma membrane of the chloroplast is arranged so that the
outer membrane separates the inside of chloroplast from the cytoplasm of the plant cell
Immature chloroplasts develop into mature chloroplasts due to
factors like light availability, chloroplast gene transcription and proteins.
chloroplasts have their own DNA and can
produce some of their own proteins as well as multiply independently inside the cell in which they live
Where does the light dependent stage of photosynthesis take place
on the thylakoids inside the chloroplast
The light dependent stage of photosynthesis involves
the absorption of light energy by chlorophyll, and
the use of that energy and the products from splitting water to make ATP and reduced NADP
The chlorophyll molecules are arranged in clusters called
photosystems in the thylakoid membranes
Photosystems are
large complexes of proteins and pigments (light-absorbing molecules) that are optimized to harvest light, play a key role in the light reactions
Each photosystem contains what?
200 molecules of a green pigment called chlorophyll and
50 molecules of another family of pigments called carotenoids
diagram showing a photosystem in a thylakoid membrane showing photoactivation of chlorophyll
Energy is captured from photons of light that hit the photosystem, and is funnelled down to a pair of molecules at the reaction centre of the photosystem complex.
each photosystems in the thylakoid membranes spans the membrane and contains
protein molecules and pigment molecules
reaction centre is
The site in the chloroplast that receives the energy trapped by chlorophyll and accessory pigments and initiates the electron transfer process.
The two different sorts of photosystem are
photosystem I (PSI) and
photosystem II (PSII),
both with a small number of molecules of chlorophyll a at the reaction centre
The light-dependent reactions of photosynthesis
produce
ATP and NADPH
NADPH is a
reducing agent used in metabolic reactions
reduction is the
addition of electrons
oxidation is the
removal of electrons
what is both a reactant and a product of photosynthesis
water
The full name for NADP is
nicotinamide adenine dinucleotide phosphate
NADP has one more phosphate molecule than NAD.
In PSI the chlorophyll molecule has a maximum absorption at
700nm
In PSII the chlorophyll molecule has a maximum absorption at
680nm
photosystems are responsible for capturing the solar energy to be used in the light-dependent reactions.
The photosystems pass electrons from one molecule to another and some of this electron flow is used for
ATP synthesis
The reaction centre chlorophyll a of PSII is called
P680 because this pigment is best at absorbing light with a wavelength of 680 nm
The reaction centre chlorophyll b of PSI is called
P700 because this pigment is best at absorbing light with a wavelength of 700 nm
Electron transport within the chloroplast can follow either
a cyclic pathway or a non-cyclic pathway.
The cyclic electron pathway generates ATP and is called cyclic photophosphorylation because light is necessary.
The non-cyclic electron pathway generates ATP and NADPH.
The production of ATP from the non-cyclic electron pathway is called non-cyclic photophosphorylation
NADPH is used to provide
energy for biosynthetic pathways that occur in cells.
The reduction of NADP is catalysed by
NADP reductase, which is on the outer surface of the thylakoid membrane
Photophosphorylation means
‘phosphorylation using light’.
It refers to the production of ATP, by combining a phosphate group with ADP, using energy that originally came from light:
ADP + phosphate ➝ ATP
Photophosphorylation happens when
an electron is passed along a series of electron carriers, forming an electron transport chain in the thylakoid membranes.
The electron starts off with a lot of energy, and it gradually loses some of it as it moves from one carrier to the next.
The energy is used to cause a phosphate group to react with ADP
electron carriers (electron shuttles) are
small organic molecules/proteins that can easily accept electrons (i.e., be reduced) or lose them (i.e., be oxidized)- transfer electrons
The electron carriers take the electrons to a group of proteins in the inner membrane of the mitochondrion, called the electron transport chain.
what happens as electron move through the electron transport chain
they go from a higher to a lower energy level and are ultimately passed to oxygen (forming water)
electron carriers provide a
controlled flow of electrons that enables the production of ATP
what would happen without electron carriers
the cell would cease to function
eg of two electron carriers are
NAD+ and FAD, which are both derived from B vitamins
electron transport chain is a
cluster of proteins through which electrons flow
that transfer electrons through a membrane within mitochondria to form a gradient of protons that drives the creation of adenosine triphosphate (ATP).
Cyclic photophosphorylation involves what photosystem?
only PSI, not PSII
Cyclic photophosphorylation results in
the formation of ATP, but not reduced NADP
