Unit 1 Topic 3

krebs cycle

a

biochemical pathway

that requires oxygen

and takes place in the

mitochondria as the

second stage of aerobic

cellular respiration

Distinguish between endergonic and exergonic reactions, and explain how they link to catabolism and anabolism

• Exergonic reactions: release free energy (ΔG < 0). Example: breakdown of glucose in cellular respiration. These drive catabolism (breaking molecules down).

• Endergonic reactions: require an input of free energy (ΔG > 0). Example: synthesis of proteins or glucose. These drive anabolism (building molecules).

• Link: Energy released from catabolic (exergonic) reactions is stored in ATP, which is then used to power anabolic (endergonic) reactions.

How does light, temperature, wind, or humidity affect transpiration?

• Light: increases transpiration (opens stomata).

• Temperature: increases transpiration (faster evaporation).

• Wind: increases transpiration (removes water vapour).

• Humidity: decreases transpiration (reduces concentration gradient).

How do stomata and guard cells regulate gas exchange in plants?

Guard cells change shape to open/close stomata. Open stomata allow CO₂ in and O₂ + H₂O out; closed stomata reduce water loss.

Compare xylem and phloem structure and function.

• Xylem: vascular tissue

  in plants, consisting of

  dead cells, responsible

  for the bulk transport of

  water and minerals

• Phloem: vascular tissue

  in plants, consisting of

  living cells, responsible

  for the bulk transport

  of sugars

What is the overall photosynthesis reaction?

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Where do light-dependent reactions of photosynthesis occur, and what are the inputs/outputs?

• Location: Thylakoid membranes

• Inputs: Light, H₂O, NADP+, ADP

• Outputs: O₂, ATP, NADPH

In which direction do gases move between capillaries and muscle tissue?

• O₂ diffuses from capillaries → muscle cells

• CO₂ diffuses from muscle cells → capillaries

In which direction do gases move between alveoli and capillaries?

• O₂ diffuses from alveoli → capillaries

• CO₂ diffuses from capillaries → alveoli

How do alveoli and capillaries enable efficient gas exchange?

• Alveoli: large surface area, thin walls (1 cell thick), moist lining.

• Capillaries: close contact with alveoli, very thin walls, large network for diffusion.

Compare aerobic and anaerobic respiration.

• Aerobic: requires oxygen, produces 36–38 ATP per glucose, end products CO₂ + H₂O.

• Anaerobic: no oxygen, produces 2 ATP per glucose, end products lactic acid (animals) or ethanol + CO₂ (yeast).

Where does the electron transport chain occur and what are its inputs/outputs?

• Location: Inner mitochondrial membrane

• Inputs: NADH, FADH₂, O₂

• Outputs: H₂O, ~34 ATP

Where does glycolysis occur and what are its inputs/outputs?

• Inputs: Glucose, 2 ATP, NAD+

• Outputs: 2 Pyruvate, 2 Net ATP, 2 NADH

How does ATP link catabolic and anabolic reactions?

Energy released from catabolic reactions is stored in ATP. This ATP is then hydrolysed to release energy that drives anabolic reactions.

What is the difference between catabolism and anabolism?

• Catabolism: breaks down complex molecules into simpler ones, releasing energy (e.g., cellular respiration).

• Anabolism: builds complex molecules from simpler ones, requiring energy (e.g., protein synthesis).

What is the adaptive immune response?

• A specific, slower immune defense that develops after exposure to a pathogen.

• Involves recognition of antigens

What is the inflammatory response?

• A non-specific, innate immune reaction to tissue damage or infection.

• Its purpose is to isolate and destroy pathogens, remove damaged cells, and begin tissue repair.

What roles do prostaglandins and vasodilation play in inflammation?
A:

• They brings more immune cells and nutrients to fight infection and promotes swelling, redness, and heat.

What is the role of neutrophils in the inflammatory response?

• Neutrophils are the first white blood cells to arrive.

• They move into tissues (via chemotaxis) and perform phagocytosis, engulfing and destroying pathogens.

What is the role of macrophages in the inflammatory response?

• Macrophages arrive later and continue phagocytosis.

• They also release cytokines to recruit more immune cells.

• Importantly, they act as antigen-presenting cells (APCs), trigger the adaptive immune response.

What is the role of natural killer (NK) cells in the inflammatory response?

• NK cells target and destroy virus-infected or cancerous cells.

• They release perforin and granzymes that trigger apoptosis (cell death) in abnormal cells.

• They help limit the spread of infection until adaptive immunity is activated.

What is the three stage process of aerobic cellar respiration

[Glycolysis: glucose is converted to pyruvate, 2 ATP produced.¹]

[Krebs (cycle): pyruvate is converted to carbon dioxide, 2 ATP produced.²]

[Electron transport chain: hydrogen combines with oxygen to produce water, 32–34 ATP produced.³]

What are the inputs and outputs of the electron transport chain in an animal cell?

Inputs : NadH, ADP, oxygen and P1 and the outputs are Water, Nadh+ and ATP

What molecules transfer energy from the Krebs cycle to the electron transport chain?

NADH and FADH2