B3 Flashcards
What do enzymes do?
They are proteins that catalyse reactions (speed them up). They either split apart or join together the substrates
What is the substrate?
The substance on which an enzyme acts
Name 3 variables that affect the rate of reaction in enzymes
pH, Temperature and Substrate concentration
What is the balanced symbol equation for photosynthesis?
6CO2 + 6H2O -> C6,H12,O6 + 6O2
Is photosynthesis endothermic or exothermic?
Endothermic
Name one test to measure the rate of photosynthesis
Rate of oxygen production
Name 3 factors that limit the rate of photosynthesis
CO2, Light intensity and Temperature
What is diffusion?
The movement of particles from a higher concentrated area to a lower concentrated area
What is osmosis?
The movement of water molecules across a partially permeable membrane from a higher concentrated area of water to a lower concentrated area of water
What is active transport?
The movement of molecules across a membrane from an area of lower concentration to an area of high concentration- this requires energy
What is the xylem?
Tubes which carry up water and minerals from the roots up the stem
What is the phloem?
Tubes which transport food substances up and down the stem
What is translocation?
The movement of food substances around the plant. For the most part this is taking them from the source to the sink.
What is transpiration?
The loss of water from the plant, which causes more water to be drawn from the roots up the xylem
What are stomata?
Tiny pores that allow CO2 and oxygen to diffuse in and out of the cell, and allow water vapour to escape during transpiration
Name 2 abiotic factors that affect communities in an ecosystem
Environmental changes
Toxic chemicals
Name 3 biotic factors that affect communities in an ecosystem
Amount of food
No. predators
Presence of pathogens
What are abiotic factors?
Physical rather than biological; not derived from living organisms.
What are biotic factors?
Relating to or resulting from living organisms
What are transects?
A straight line across the earth’s surface, along which observations are made or measurements taken
What can transects be used for?
To investigate distribution
Give 3 reasons why biomass is lost between each trophic layer
Animals use some of the biomass for respiration
Biomass is lost through egestion
Not all of the organism gets eaten e.g. bones
Summarize the carbon cycle
Plants use CO2 from the air for photosynthesis.
Animals then eat the plant, passing on the carbon compounds from the plant into the food web.
When animals and plants die they are decomposed by microorganisms which release CO2 back into the air as they break the material down. This also occurs when animals defecate
Alternatively, animal/plant products when burnt also release CO2 into the air
Summarize the water cycle
Energy from the sun makes water evaporate.
The warm water vapour rises until it cools and condenses to form clouds.
Water then falls from the clouds as precipitation.
Some of this water is then absorbed by the soil and taken up by plants, ready to be evaporated again.
Some of this water is used by animals and then returned to the soil through excretion.
Some of this water will not be absorbed by the soil and will run off into streams/rivers/oceans, ready for evaporation
How are chloroplasts related to photosynthesis?
Chloroplasts contain chlorophyll, and work to convert light energy of the sun into sugars
How is diffusion important for photosynthesis?
The movement of oxygen and carbon dioxide in and out of leaves during photosynthesis occurs by diffusion
Why is photosynthesis endothermic?
Plants absorb energy from sunlight
State one test for if photosynthesis is occurring
Iodine is an indicator that turns blue-black in the presence of starch. If a leaf turns blue-black, it demonstrates that the leaf has been performing photosynthesis and producing starch
State 2 ways to measure the rate of an enzyme-controlled reaction
- The rate in which the product is made
- The rate in which the substrate disappears
What is the inverse square law in relation to light intensity and distance?
Light intensity ∝ 1/Distance^2
What is the factors in photosynthesis?
Carbon dioxide, Water, Light intensity, Temperature
What does the inverse square law mean in relation to light intensity and distance?
As distance from source increases, light intensity decreases
How does pH affect rate of enzyme controlled reactions?
Enzymes have an optimal pH in which they react the quickest. If the pH is too low or too high, the rate of reaction will decrease and if it gets too low or high, the enzyme will denature
How does temperature affect rate of enzyme-controlled reactions?
Enzymes have an optimal temperature in which they react the quickest. If the temperature is too low, the rate of reaction will slow. If the temperature is too high, the rate of reaction will slow and eventually stop, as the enzymes are denaturing
How does substrate concentration affect rate of enzyme-controlled reactions?
The greater the substrate concentratoin, the greater the rate of reaction up to a point. This is because the frequency of enzyme and substrate interactions are more likely. However, when the substrate concentration reaches the point in which all enzyme active sights are occupied, adding more substrates will make no difference
How do substances travel in and out of single-celled organisms?
They can diffuse straight in and out of the partially permeable membrane
Where do CO2 and O2 diffuse in and out of during photosynthesis?
They diffuse in and out through tiny pores in the leaf called stomata, and the partially permeable membrane of the plant cells
What are root hairs?
Root hairs collect mineral ions and water from the soil. On a plant root, there are millions of tiny hairs- these means there is a huge surface area, allowing the minerals and water to be transferred at the fastest rate
What type of transportation is used in the transporting of mineral ions into root hairs?
Active transport, as the concentration of mineral ions is likely to be higher in the root hair than in the soil, therefore the minerals must travel against the concentration gradient
What type of transportation is used in the transporting of water into root hairs?
Osmosis, as the concentration of mineral ions is likely to be lower in the root hair than in the soil, and water is a liquid
Why in multi-cellular organisms are specialised exchange surfaces need?
As many cells are deep inside a organisms, it’s a long way for substances to travel
What are phloem tubes made from?
Living cells
What are xylem tubes made from?
Dead cells
What are guard cells and what do they do?
They surround the stomata and change shape, which change the size of the stomata pores
When do stomata close and why? (2 times)
When water levels are low as water is lost through the stomata in transpiration
They also close at night to lose less water without losing out on photosynthesis
What does it mean when a cell is plasmolysed?
When the cell is very low on water, and the cytoplasm starts to shrink and the membrane pulls away
What 3 things affect transpiration rate?
Light intensity
Temperature
Air movement
What is a potometer?
A piece of apparatus that measures water uptake of a plant, which can be used to formulate an estimate of rate of transpiration
Within an ecosystem, what is an individual?
A single organism
Within an ecosystem, what is a population?
All the organisms of one species in a habitat
Within an ecosystem, what is a community?
All the organisms living in a habitat
What is an ecosystem?
A community along with the abiotic conditions
How do you use quadrats and transects to measure distribution?
Place a quadrat along pre-determined points along a transect line take your measurements-
For example-
- What percent each item takes up within the frame (e.g. 75% species A, 25% species B).
- What is in each of the smaller squares (e.g. 12 squares species A, 5 squares species B, 0.5 squares species C, etc.).
Why is not all biomass transferred between trophic levels? (3 reasons)
- Energy (biomass) can be used up in respiration
- Energy (biomass) can be lots from excretion
- Energy (biomass) is lost because not all of every organisms is eaten (e.g. the bones or plant roots)
Lipids (fats and oils) are made from joining what? (2 things)
Fatty acids and glycerol
What makes up long chain carbohydrates (e.g. starch)? (1 thing)
Simple sugar (e.g. glucose)
How can you test for sugars?
You can add Benedict’s reagent to a sample and heat I in a water bath that’s set at 75 degrees Celsius. If a sugar is present, a precipitate will be formed.
The colour of the precipitate depends on the concentration of sugar present
How can you test for starch?
You can add iodine solution- if starch is present, it will change blue-black.
If starch isn’t present, it will stay browny-orange
How can you test for lipids?
Shake the test substance with ethanol, and then add it to water- if there are any lipids present, they will show up as a milky emulsion.
The greater the concentration of lipid, the more noticeable the milky colour will be
How can you test for proteins?
You can use the biuret test- add sodium hydroxide to the sample. Then add some copper (II) sulfate (which is blue)
If the solution stays blue, there is no protein present.
If the solution goes purple, there is protein present
What are the main types of decomposers?
Bacteria and fungi
What is decomposition?
The breakdown of waste material by microorganisms
What 3 things affect rate of decomposition and why?
Oxygen levels- decomposers need oxygen for aerobic respiration
Temperature- because decomposers contain enzymes which break down the waste material, and these enzymes work best in hotter temperatures
Water levels- decomposers need water to survive
What does anaerobic respiration by decomposers emit?
Methane
What happens when guard cells become turgid?
They are open for CO2 and O2 to enter, and for O2 and water to leave
What happens when guard cells become flaccid?
They are closed, so nothing can enter or leave
Why do guard cells become flaccid?
To stop losing water through transpiration, and oftentimes when it is night time, as they cannot photosynthesise
