Topic 1: Photosynthesis

Describe an autotroph

Living things that obtain energy from the environment by producing organic molecules using simple inorganic ones.

Explain the process of photosynthesis

Plants absorb water, carbon dioxide, and sunlight from their environment. Inside the leaves, chlorophyll takes this sunlight to split water molecules. This generates cellular energy (ATP and NADPH) and consequently releases oxygen as a byproduct. Specialised enzymes then utilize this energy to rearrange carbon dioxide and hydrogen into glucose.

State the definition of the spongy mesophyll layer

It consists of spongy mesophyll cells loosely packed with air spaces at the leaf's lower section.

Summarise the process of photosynthesis

The process by which plants and other autotrophs convert light energy into chemical energy.

Describe the role of Chlorophyll during photosynthesis

The chemical responsible for absorbing sunlight to split water molecules, which generates the cellular energy needed to produce glucose.

Describe the process of photosynthesis

An anabolic metabolic pathway.

Describe the structure of a chloroplast

Thylakoids: Site of chlorophyll in a chloroplast

Granum: A stack of thylakoids

Stroma: The fluid inside the chloroplast

What does photosynthesis require, and subsequently, what is required to keep a plant alive?

To conduct photosynthesis, sunlight, water, and carbon dioxide is required. This implies that plants also require water, light and carbon dioxide (as well as chlorophyll) to survive.

Describe the role of Chlorophyll in plants

The chemical responsible for the green pigment in plants.

State the definition of the term, tissue

A collection of cells that work together to perform a specific function

Describe a chloroplast

A double-membraned organelle where the process of photosynthesis occurs

What occurs when a plant lacks thylakoids?

The plant loses the ability to perform photosynthesis and cannot produce sugar.

State the definition of the Mesophyll

The mesophyll consists of 2 layers known as the palisade mesophyll layer and spongy mesophyll layer.

State the definition of the palisade mesophyll layer

It consists of palisade mesophyll cells tightly packed under the leaf surface to maximise sunlight absorption.

State the function of the palisade mesophyll layer

It is the primary site for photosynthesis because most chloroplasts reside in this layer.

State the function of the spongy mesophyll layer, and specifically name the characteristic that enables this function

Air spaces allow oxygen, carbon dioxide, water vapor to diffuse easily throughout the leaf, supporting gas exchange required for photosynthesis and cellular respiration.

Describe the stoma

An opening at the bottom of the leaf that allows gas exchange (i.e. oxygen and carbon dioxide) to enter and exit.

What else can the stoma release but not absorb?

Water vapor

What surrounds a stoma?

A pair of guard cells

State the function of a guard cell

Guard cells are responsible for regulating gas exchange and water loss by opening and closing the stoma.

Describe the function of a guard cell

Guard cells fill up with water to make the stomata swell and open. Conversely, to make the stomata flaccid and close, guard cells lose water.

State the definition of vascular bundles

Vein-like structures known as the Xylem and Phloem which are responsible for transporting water and sugar.

Describe the term, xylem

Hollow, tube-like cells responsible for carrying water and minerals from the roots into the plant

Describe the term, phloem

Tubes responsible for carrying glucose (sucrose) created from photosynthesis throughout the plant.

What is the difference in transport direction in a xylem and phloem?

The transportation of water is always up in a xylem whereas food transported through the phloem is two-way.

Provide an example of "food" that the phloem transports

Glucose (technically, sucrose)

State the function of the epidermis

Its primary responsibility is to protect the leaf from water loss, injury and infection.

Explain the difference between the functions of the lower and upper epidermis

The upper epidermis sits at the top of the leaf and protects the leaf from heat.

The lower epidermis protects alongside including the stoma and guard cells.

Describe the structure that surrounds the epidermis

Cuticle - a waxy, water resistant, and transparent layer.

Explain how the different features of the cuticle support its function

Acting as an outer layer, it prevents moisture loss through evaporation while its transparency allows sunlight to pass through for photosynthesis.

Explain the difference between the cuticles of the upper and lower epidermis

The cuticle surrounding the upper epidermis is thicker than the lower epidermis because the upper epidermis faces the sun, making it more prone to evaporation.

State the definition of the word, optimum

The most favorable, or best degree or amount possible under given circumstances

State the definition of the word, denature

To alter the fundamental properties of a substance, typically by destroying its natural structure.

Briefly summarise osmosis

The tendency of water to move from low solute concentrations (unsalted) to high solute concentrations (salty).

When does a plateau occur?

When one factor increases until another essential factor runs out.

Name all the factors that can influence the rate of photosynthesis

Carbon dioxide

Light intensity

Temperature

Explain how the concentration of carbon dioxide influences the rate of photosynthesis

As carbon dioxide concentration increases, the rate of photosynthesis increases. However, if there is not sufficient light for chlorophyll to absorb or if temperatures are too low for enzymes to work efficiently, the rate of photosynthesis approaches a plateau.

Explain how light intensity influences the rate of photosynthesis

As light intensity increases, the rate of photosynthesis increases. However, if there is not sufficient carbon dioxide to produce glucose or if temperatures are too low for enzymes to work efficiently, the rate of photosynthesis approaches a plateau.

Explain how temperature influences the rate of photosynthesis

As temperature rises towards the optimum, the rate of photosynthesis increases. However, unlike the other two factors, when temperature is too low or too high, enzymes begin to work too slowly or denature (respectively). This slows the rate of photosynthesis, creating a curve rather than a plateau.

State the function of the mitochondria

The site for aerobic respiration and ATP synthesis.

State the function of ribosomes

The site for protein synthesis.

State the function of the endoplasmic reticulum

To support the production or transportation of proteins

State the function of the golgi apparatus

To modify, sort, and package proteins and lipids for transportation inside or outside the cell