Bioenergetics test Year 10 Flashcards
Parts of the leaf
- palisade mesophyll
- epidermal tissue
- spongy mesophyll
- guard cells
- stoma/ stomata
- ploem
- xylem
Features of palisade mesophyll
- cell shape allows them to be tightly packed
- has lots of chloroplasts to maximise amount of light energy that can be captured in photosynthesis
Features of epidermal tissue
- single outer layer of flattened cells that protect the leaf
- waterproof waxy layer on upper epidermis - prevents water loss
- lower epidermis contains stomata and guard cells
Features of spongy mesophyll
- loosely packed
- large surface area
- lots of air gaps
- maximises rate of gas exchange for photosynthesis
- allows gases to diffuse easily through leaf to and from stomata
features of guard cells
open and close stomata
What are stomata/ stoma
pores in the leaf that gases can diffuse through
(turgid = close and flaccid = open)
What is meristem tissue?
- made of unspecialised cells that can divide repeatedly to make other cells
- new cells can differentiate into other types of plant cell, allowing for the plant to grow
What do phloem cells do?
transport sugars made in leaves to the rest of the plant
features of phloem
- elongated cells to transport sugars over long distances
- companion cells have many mitochondria for active transport
- end walls have pores to allow sugar solution to pass from cell to cell easily
What do xylem cells do?
transport water and mineral ions through the plant
Features of xylem cells
- hollow tubes (lumen) with no end walls to allow water and minerals to flow easily
- lignin in walls to provide strength and support
Describe the transport of water and minerals
- root hair cells take up water from the soil by osmosis
- takes up minerals by activie transport
- xylem carries mineral and water solution from roots to stem to leaves
- flow of water up through the plant is called the transpiration stream
- water is lost from leaves by evaporation and diffusion (transpiration)
- loss of water from leaf pulls up more water through xylem
Describe the proccess of transporting dissolved food
- movement of dissolved food molecules through phloem is called translocation
1. food molecules are produced in leaves by photosynthesis
2. food transported in phloem to the rest of the plant as dissolved sugars
3. sugar may be used by cells immediately or converted into starch for storage
4. food molecules can be transported upwards towards growing shoots or down towards roots and storage organs
What is the role of the stomata?
- without stomata there would be too little CO2 for photosynthesis and oxygen could not be released
- a major source of water loss
- water evaporates from spongy mesophyll
- water vapour diffuses out of the stomata
- water loss is controlled by pairs of guard cells
What are the environmental factors that affect the rate of transpiration?
- humidity (decrease concentration gradient)
- temperature (increases kinetic energy)
- air movement (increasees concentration gradient)
- light intensity (photosynthesis opens stomata, water is lost through open stomata)
How do you investigate the rate of transpiration?
- potometer
- measure distance that air bubble moves and divide by time in minutes
Why is photosynthesis so important?
- transfers energy from surroundings into living things
- plants use photosynthesis to make glucose molecules that provide the energy that they need
- glucose molecules are used to build all other materials that make up a plant (plant biomass)
- biomass and store of energy passes into food chain when animals feed on plants
photosynthesis supplies energy to food chain
what occurs during photosynthesis?
- takes place in chloroplasts which have chlorophyll
- traps energy tranferred by light
- allows glucose to be made with water and carbon dioxide
- glucose is a simple sugar
- oxygen is produced
- products have more energy than reactants
- energy is transferred from the environment by light
- endothermic reaction
What is the word equation for photosynthesis
carbon dioxide + water -> light glucose + oxygen
Balanced symbol equation for photosynthesis
6 CO2 + 6 H2O → C6H12O6 + 6 O2
How do you calculate the rate of photosynthesis?
amount of oxygen produced/ time taken to collect it
What are the factors that affect photosynthesis?
- light intensity (energy transfer increases)
- Temperature (increases speed that molecules collide and react, but denatures enzymes at high temperatures)
- carbon dioxide concentration (if all other factors are favorable it can become a limiting factor)
- amount of chlorophyll (can limit the rate of photosynthesis if there isn’t enough)
How do farmers use the limiting factors to produce more crops?
- introduce CO2 artificially
- increase temperature using heaters
- artificial lights increase “daylength” and intensity of light
- expensive but gives higher yields & more income
How do limiting factors interact?
at some point when the limiting factor is no longer the limiting factor other factors become the limiting factor, meaning that the rate of photosynthesis plateaus even if you continue to increase the previous limiting factor
What is the inverse square law?
light intensity is inversely proportional to the square of the distance
I = 1/d^2
I = light intensity
d = distance from lamp
How do you measure the effect of light intensity on the rate of photosynthesis of pondweed?
- water and sodium hydrogen carbonate solution in a beaker
- funnel with pondweed in the beaker
- measuring cylinder to measure the volume of water displaced
- or counting bubbles
- metre ruler to measure distance from light source
- change distance from light source
What is glucose made from photosynthesis used for?
- energy release and storage
- make molecules for growth
How does energy release and storage work?
- respiration to release energy
- produce fat or oil molecules for storage
- glucose molecules can be linked together into insoluble stach for storage
- starch, fat & oil can be stored in cells
- when needed they are broken down and converted back into glucose
How does making molecules for growth work for plants?
- produce cellulose to strengthen cell walls
- produce amino acids that are needed for protein synthesis
- nitrate ions absorbed from the soil are used to make (synthesise) protein
What is respiration?
an exothermic reaction that releases the energy stored in molecules such as glucose so that the energy is available for living processes
Why do organisms need to respire?
- chemical reactions to build larger molecules from smaller ones
- movement (eg muscle contraction)
- active transport where substances are moved against a concentration gradient
- keeping warm in some animals
What is aerobic respiration?
- glucose can be completely oxidised with enough oxygen available
- a lot of energy is released
- takes place in mitochondria
What is the word equation of aerobic respiration?
glucose + oxygen -> carbon dioxide + water
What is the balanced symbol equation of aerobic respiration?
C6H12O6 + 6O2 -> 6 CO2 + 6 H2O
What is anaerobic respiration?
- when oxygen levels are too low anaerobic respiration takes place
- less energy is released per molecule of glucose
- glucose is not completely oxidised
Word equation of anaerobic respiration in animals
glucose -> lactic acid
Word equation for aerobic respiration in plants and yeast
glucose -> ethanol + carbon dioxide
What is anaerobic respiration in yeast called?
fermentation
- important for making bread + alcoholic drinks
How does the body change during exercise?
- heat rate increases to supply more oxygenated blood to the muscles
- increase breathing rate and breath volume to increase oxygen supply from the air
What happens when you are in oxygen debt?
- heart and breathing can’t keep up with aerobic respiration and switches to anaerobic
- anaerobic respiration causes a build up of lactic acid in the muscles
- extra oxygen is needed to remove lactic acid when exercise stops
- muscles can become fatigued and stop contracting efficiently
- oxygen debt is the amount of oxygen needed after exercise to react with the lactic acid and remove it
How does the body remove lactic acid?
- blood removes lactic acid from muscles and take it to liver
- converted back into glucose
- glucose can be stored as glycogen or used in respiration
What is metabolism?
The sum of all chemical reactions in the cells of an organism
can synthesise new molecules or break down
controlled by enzymes
relies on energy from respiration
What reactions involve carbohydrates?
- plants = cellulose and starch
- animals = glycogen
- both can be broken down into glucose when needed for respiration
What reactions involve proteins in plants and animals?
- plants = nitrates from soil + glucose from photosynthesis -> animo acids
- animals = animo acids from food -> new proteins
- excess proteins -> urea + excreted
What reactions involve lipids?
- synthesised from one molecule of glycerol and three fatty acid molecules
- lipase can break down lipids again
- made from the products of photosynthesis/ digestion
