Bioenergetics

What is respiration?

• the process living organisms use to release and transfer energy

• it is exothermic

What is the equation for aerobic respiration?

• glucose + oxygen => carbon dioxide + water (+ energy)

• C6H12O6 + 6O2 => 6CO2 + 6H2O

What does aerobic respiration require?

• oxygen

Where do reactions in aerobic respiration take place?

• mitochondria

What is respiration controlled by?

• enzymes, reactions between glucose and oxygen release energy

Why does blowing into lime water turn it cloudy?

• because our breath contains CO2 as a product of aerobic respiration

Why does breathing on a cold mirror turn it foggy?

• because water is a product of respiration, but it is breathed out as water vapour and condenses on the mirror

How does an increased heart rate during exercise help?

• during exercise the muscles need more energy for contraction so they respire faster. Heart rate increases to pump blood faster and deliver more oxygen and glucose to the muscle cells for increased respiration. carbon dioxide and lactic acid are also removed more quickly from the muscles, preventing a build up.

What are ways that energy may be used during respiration?

• building larger molecules from smaller ones

  • e.g proteins from amino acids

• to enable muscles to contract

• to maintain a steady body temperature in colder surroundings (thermoregulation)

• to build up sugars, nitrates and other nutrients into amino acids and then amino acids into proteins

What is anaerobic respiration?

• an exothermic reaction in which glucose is broken down to release energy in the absence of oxygen

What is the equation for anaerobic respiration?

• glucose => lactic acid (+energy)

Why is anaerobic respiration less efficient than anaerobic respiration?

• glucose is not fully broken down, less energy is transferred

Why can anaerobic respiration lead to muscle fatigue?

• lactic acid builds up in muscles, preventing efficient contraction

What is an oxygen debt?

• amount of oxygen needed to convert lactic acid back into glucose after anaerobic respiration

What is fermentation?

• anaerobic respiration that occurs in yeast cells

What is the equation for fermentation?

• glucose => ethanol + carbon dioxide (+ energy)

Why is the fermentation reaction important?

• used in the production of bread and alcoholic drinks

What are the differences between aerobic and anaerobic respiration?

• aerobic respiration requires oxygen; anaerobic does not.

• aerobic produces CO₂ and water; anaerobic produces lactic acid (or ethanol) + CO₂

• Aerobic respiration transfers a greater amount of energy

How do muscles store glucose?

• as glycogen

How is lactic acid transported away from the body?

• blood flow through the muscles transports lactic acid to the liver, where it is oxidised back to glucose

How do cells use the energy transferred by respiration?

• to continuously carry out enzyme controlled processes which lead to the synthesis of new molecules

What is photosynthesis?

• process by which plants synthesise glucose using light energy from the sun

• light is converted into chemical energy

• it is endothermic

Where does photosynthesis take place?

• within chloroplasts in leaf palisade cells, containing chlorophyll which absorbs light energy

What is the photosynthesis equation?

• Carbon dioxide + Water => Glucose + Oxygen

• 6CO2 + 6H2O => C6H12O6 + 6O2

How can you show that a plant gives off oxygen during photosynthesis?

• using a water plant. collect gas bubbles produced during photosynthesis. The gas will relight the glowing splint as it contains oxygen

What are some examples of leaf adaptations for photosynthesis?

• broad leaves - maximise surface area

• thin leaves - short diffusion pathway

• palisade cells contain lots of chlorophyll - to absorb sunlight for photosynthesis

• many stomata on the bottom surface of the leaf - gases to diffuse into and out of the leaf

• pair of guard cells - control the opening and closing of stomata

• network of xylem and phloem - transport water and products of photosynthesis

• air spaces and large surface area - gases diffuse efficiently between palisade and stomata

• thick waxy cuticle - prevents water loss

What are the uses of glucose during photosynthesis?

• Starch - insoluable so it is good for storage

• Cellulose - to strengthen the cell walls

• Amino acids - to build proteins

• Respiration - to release energy

• Fats - or oils, for storage (broken down in respiration to release energy)

What is the structure of a leaf? (from top to bottom)

• waxy layer

• upper epidermis

• mesophyll tissue, containing the palisade layer and the spongy layer

• xylem and phloem

• air space

• guard cells and stomata

What is the purpose of epidermal tissue?

• cover the plant

• e.g upper and lower epidermis cover the leaf

What is the purpose of the palisade mesophyll tissue?

• carries out photosynthesis

• has many chloroplasts to absorb light for photosynthesis

What is the purpose of the spongy mesophyll tissue?

• carries out photosynthesis

• have chloroplasts to absorb CO2 for photosynthesis

• they have a large surface area and are surrounded by big air spaces to make the diffusion of gases faster

What is the purpose of Xylem tubes?

• transports water and dissolved ions around the plant

What is the purpose of Phloem tubes?

• transports substances such as glucose around the plant

What is Meristem tissue?

• found growing at the tips of roots and shoots

• cells are stem cells that can differentiate into any type of plant cell throughout the life of the plant