Topic 5A p3 Flashcards
(19 cards)
Model of a Process (e.g., Photosynthesis)
A model of a process is a detailed representation that explains the steps and components involved in a biological or chemical process. For photosynthesis, it might include diagrams of chloroplasts, light absorption, electron transport, and glucose production. It helps illustrate how energy and matter flow through the system.
Meaning of “Evolved” in “the structure of plants has evolved around the process of photosynthesis”
In the sentence “the structure of plants has evolved around the process of photosynthesis”, evolved means that over time, plants have developed or changed their physical features to optimise photosynthesis. This natural adaptation has improved their ability to capture light, exchange gases, and produce energy efficiently.
Chloroplast Envelope
The chloroplast envelope consists of two membranes (an inner and an outer membrane) that surround the chloroplast. It controls the entry and exit of materials such as carbon dioxide, water, and sugars. The outer membrane is permeable to small molecules, while the inner membrane is more selective. This double membrane separates the chloroplast from the cytoplasm and helps maintain the internal environment for photosynthesis.
Grana
Grana (singular: granum) are stacks of thylakoids found within the chloroplast. They are the sites where the light-dependent reactions of photosynthesis occur. Their stacked structure increases surface area for absorbing light. Grana are connected by intergranal lamellae to allow communication and molecule transport between them.
Pigment Molecule
A pigment molecule is a substance that absorbs light energy at specific wavelengths. In photosynthesis, the main pigment is chlorophyll, which captures light for use in energy conversion. Pigments are embedded in the thylakoid membranes. Different pigments absorb different wavelengths, maximising energy capture.
Lamellae
Lamellae (specifically intergranal or stromal lamellae) are thin membrane structures that connect grana to each other. They help transport materials between grana and maintain the chloroplast’s structure. They also contain chlorophyll and play a role in the light-dependent reactions of photosynthesis.
Thylakoids
Thylakoids are flattened, disc-shaped membrane sacs inside the chloroplast. They contain chlorophyll and other pigments and are the site of the light-dependent reactions. Thylakoids stack to form grana. Their membranes house the electron transport chain and ATP synthase.
Granal Membrane
The granal membrane is the membrane surrounding the thylakoids in the grana. It contains pigment molecules and proteins involved in the light-dependent stage of photosynthesis. Its large surface area allows efficient light absorption. It also plays a key role in ATP and NADPH production.
Thylakoid Membrane vs Plant Cell Membrane
The thylakoid membrane is found inside chloroplasts and forms the boundary of thylakoids.
It contains chlorophyll, enzymes, and proteins needed for photosynthesis.
The plant cell membrane (plasma membrane) surrounds the entire cell and controls what enters and exits the cell.
It is involved in general cellular transport, communication, and homeostasis, not photosynthesis.
Thus, the thylakoid membrane is specialised for photosynthesis, while the plant membrane manages cell-wide functions.
Stroma
The stroma is the fluid-filled space inside a chloroplast, surrounding the grana and thylakoids. It contains enzymes, DNA, ribosomes, and substrates needed for the light-independent reactions (Calvin cycle). It is where carbon dioxide is fixed into glucose. The stroma plays a key role in regulating the chloroplast’s internal environment.
Chloroplast Membrane (Five-Sentence Explanation)
The chloroplast membrane refers to the double membrane (inner and outer) surrounding the chloroplast, collectively known as the chloroplast envelope. The outer membrane is smooth and permeable to small molecules, while the inner membrane is selective, containing transport proteins. These membranes protect the internal structures of the chloroplast and help maintain the right environment for photosynthesis. They regulate the movement of key substances such as carbon dioxide, water, and sugars in and out of the chloroplast. Although they do not take part directly in photosynthesis, they are essential for maintaining the structure and function of the chloroplast.
Convert
To convert means to change one form of something into another. In biology, it often refers to the transformation of energy or molecules, such as light energy being converted into chemical energy during photosynthesis. Conversion processes are usually enzyme-controlled and essential for metabolic functions.
Chlorophyll
Chlorophyll is a green pigment found in the thylakoid membranes of chloroplasts. It is essential for photosynthesis because it absorbs light energy, mainly in the blue and red wavelengths. This energy is then used to power the conversion of carbon dioxide and water into glucose.
Chlorophyll Molecule
A chlorophyll molecule consists of a magnesium ion at the centre of a porphyrin ring, with a long hydrocarbon tail that anchors it to the thylakoid membrane. It absorbs light energy and transfers excited electrons to the electron transport chain. The molecule is highly efficient in capturing light for photosynthesis.
Chlorophyll a
Chlorophyll a is the primary pigment in photosynthesis. It absorbs mainly blue-violet and red light and reflects green. It plays the central role in converting light energy into chemical energy by transferring excited electrons to the reaction centre of the photosystem. All plants, algae, and cyanobacteria contain chlorophyll a.
Chlorophyll b
Chlorophyll b is an accessory pigment that broadens the range of light absorbed for photosynthesis. It mainly absorbs blue and orange light, complementing the absorption of chlorophyll a. It passes the absorbed energy to chlorophyll a to enhance photosynthetic efficiency.
Carotenoids
Carotenoids are yellow, orange, or red accessory pigments found in the thylakoid membrane. They absorb blue and blue-green light and help protect chlorophyll from damage by excess light (photoprotection). They also transfer absorbed light energy to chlorophyll a. Examples include beta-carotene and lutein.
Phaeophytin
Phaeophytin is a grey-coloured pigment and an early electron acceptor in the photosystem II reaction centre. It is a chlorophyll molecule that has lost its magnesium ion. It plays a key role in transferring electrons from excited chlorophyll a to the next carrier in the electron transport chain. It is essential for initiating charge separation in photosynthesis.
Quality vs Quantity (Scientific Comparison)
Quality refers to the type, characteristics, or effectiveness of something E.g. The wavelength of light (e.g. red vs blue) in photosynthesis
Quantity refers to the amount or number of something. E.g. The intensity or amount of light absorbed by chlorophyll
In photosynthesis, quality of light affects how effectively it can be used (e.g. red light is better absorbed than green), while quantity affects how much energy is available for the plant. Both factors influence the rate and efficiency of photosynthesis.
