1.3: Cellular Energy, Gas Exchange and Plant Physiology

Unit 1 Topic 3

Aerobic Respiration

Takes pleace in the mitochondria where glucose is broken down and 36-38 mols of ATP is formed.

Anaerobic Respiration

When no oxygen is used so it produces CO₂ and lactic acid. less efficient than Areobic respiration and only produces 2 ATP

Clycolysis

The process in which 1 glucose mol is halved and produces 2 mols of pyruvic acid. Occurs in the mitochondria/cytoplasm. Produces 2 ATP

Stage 1 of respiration

Krebs cycle

Where pyruvic acid is broken down into carbon dioxide, in series of energy-extracting reactions. Occurs in the matrix of the mitochondria. Produces 2 ATP

Stage 2 of respiration

Electron Transport Chain (ETC)

Converts ADP to ATP by using the high-energy electrons from previous stages. Occurs in the cristae of the mitochondria. Produces 32-34 ATP

Stage 3 of respiration

Cell Respiration

the controlled release of energy in the form of ATP (Adenosine Triphosphate) from organic compunds (fat or carbs) in cells

Alcoholic Fermentraion

Produces Alcohol and CO₂ and is done with yeast

Lactic acid Fermentaion

produced by muscles during rapid exercise when the body can’t supply enough oxygen.

Ventilation

the pumping mechanism of moving air into and out of the lungs

Gas exchange

exchange of gases between an organism and its surroundings. takes place by diffusion.

• large surface area (300 million alveoli)

• Moist: gases can dissolve and travel easier

• Once cell thick

Capillary system

• CO₂ diffuses from the capillaries into the alveolus

• O₂ diffuses from the alveolus into the capillaries

• Many capillaries allows for high rate of diffusion of gases

Cell Respiration

Controlled release of energy in the form of ATP from organic compunds in cells.

Arteries

• Function = carry blood away from the heart at high pressure

• Structure of wall = thick, strong, contains muscles, elastic fibres and fibrous tissue

• Lumen = narrow, varies with heartbeat

• Valves = -

• How structure fits function = strength and elasticity is needed to withstand the pulsing of the high blood pressure to prevent bursting and maintain pressure

Capillaries

• Function = supply all cells with their requirements and take away waste products

• Structure of wall = very thin, only one cell thick

• Lumen = very narrow, only wide enough for red blood cells to pass through.

• Valves = -

• How structure fits function = most of the blood pressure has been lost, so the walls aren’t strong. thin walls and narrow lumen allows for the blood to be broughtinto close contact with body tissue which allows diffusion of materials between capillaries and surrounding tissues. White lood cells can squeeze between the cells of the wall.

Veins

• Function = Return blood to the heart at low pressure

• Structure of wal = thin, mainly fibrou tissue, contains less muscle and elastic tissue than arteries.

• Lumen = wide

• Valves = + (prevents backflow)

• How structure fits function = most of the blood pressure has been lost so the walls don’t need to be strong. Wide lumen offers less resistance to blood flow.

Photosynthesis

• Basic carbs in food chain come from Green plants from H₂O and CO₂, using the sun’s energy.

• Plants are producers/autotrophs

• An anabloic, endergonic, CO₂ requiring process that uses Photons (light energy) and H₂O to produce organic macromolecultes (glucose)

• Takes place in Chloroplast

6CO₂ + 6H₂O —> C₆H₁₂O₆ + 6O₂

Light Dependent Reactions

Produces energy from photons in the form of ARP and NADPH. Uses H₂O and Produces O₂.

Light Independent Reaction

Calvin cycle - Carbon Fixation

Uses CO₂ and energy from light dependent reactions to make glucose.

Calvin Cycle

• C₃ plants (80% of plants on earth)

• occurs in the stroma

• uses ATP and NADPH from light dependent reactions

• Uses CO₂

• takes 6 turns and uses 18 ATP and 12 NADPH to produce glucose

Stomata (stoma)

Pores in a plants cuticle where water and gases are exchange between plants and the atmosphere.

Leaf Structure

Guard Cells

• Stomata are surrounded by two modifies epidermal cells (guard cells).

• Can only occupy a small space on the leafs surface, and plays an important role in the diffusion of gases and water vapour in and out of the leaf.

Xylem

• Water is carried via the xylem, which forms one part of the vascular bundle in plants.

• Xylem is a mixture of tracheids, vessels (dead cells) and parenchyma (living cells).

• have no cell content when mature, meaning they offer little resistance to water movement.

• transports water and dissolved minerals

• unidirectional (from roots to shoots)

• cell wall = thickened and often lignified

Phloem

• The second type of vascular tissue

• transports organic molecules and minerals throughout the plant, in a process called translocation.

• Molecules such as glucose and amino acids, which are produced by photosynthetic cells, are transported throughout the plant to areas that are actively growing (apex, branches, roots, buds).

• Transports sugars, amino acids, hormones, etc

• can be bidirectional, depending on the source and sink

• cell wall = thinner primary cell walls

Structure:

• Sieve tubes = transport sugars (few cell components)

• Companion cell = required for the metabolic needs of the sieve tube

• Sieve plate = perforated wall between sieve elements

Transpiration Stream

• Directly linked to the stroma

• movement of water in one direction, from the roots, stems, to evaporate out of the leaves

• cohesion of water molecules

Affecting factors:

• Lights - stroma opens in light and closes in the dark

• Temperature - increases in temp increase the rate of transpiration

• Humidity - an increase in humidity causes a decrease in transpiration due to a decreased gradient

• Wind - increases transpiration rate by the removal of water vapour from around the stomatal pore