B2 Flashcards
Explain why a cell’s DNA is replicated during the cell cycle.
When the cell divides during mitosis, the two new cells will contain identical DNA.
What is mitosis?
When a cell reproduces by splitting to form two identical offspring.
What is differentiation?
When a cell changes to become specialized for its job.
What are palisade leaf cells and what elements do they contain?
They do most of the photosynthesis in plants and are packed with chloroplasts. They have a large surface area to absorb CO2.
What features do sperm cells have?
Long tails and streamlined heads to help them swim.
Lots of mitochondria to provide them with energy.
Enzymes in their heads to digest through the egg cell membrane.
What do sperm cells do?
To transport male DNA to female DNA during reproduction.
What can Stem cells do?
Differentiate into different types of cells to perform specialized jobs.
What are the limitations to adult stem cells?
They are only found in the bone marrow.
They cannot turn into any cell type at all.
They are used to replace damaged cells.
What can meristems do?
Produce unspecialized cells that are able to divide and form any cells. They can divide to generate for as long as the plant lives.
What can Meristems differentiate into?
Xylem and Phloem tissues.
What is diffusion?
The movement of particles from high to low concentration.
What is active transport?
The movement of particles against a concentration gradient. From a low concentration to high concentration.
What does active transport require to function?
ATP from respiration.
Give an example where active transport is used.
When plants absorb minerals they need from the soil.
Explain Osmosis.
The net movement of water molecules from a high concentration to a low concentration.
What can water potential represent?
It can tell you how concentrated a solution is.
Explain what turgor pressure does.
Helps support the plant tissues.
List three factors affecting the movement of substances.
- Surface area to volume ratio
- Temperature
- Concentration gradient
Explain the function of the lungs.
Transfer oxygen to the blood and remove waste carbon dioxide from it.
List examples of how alveoli are specialized to maximize the diffusion of oxygen.
- enormous surface area (about 75m^2 in humans)
- very thin walls
- moist lining for dissolving gases
- good blood supply
Explain why it is beneficial for an exchange surface to be just one cell thick.
It means that the substances only have to travel short distances.
How are leaves specialized to maximize the diffusion of oxygen and carbon dioxide?
- broad, large surface area
- thin, gases travel short distances
- air spaces: lets gases move easily between cells
- stomata: increase diffusion of gases
How are plant roots adapted to be able to absorb lots of water and mineral ions from the soil?
-each branch of a root are covered in millions of microscopic hairs,, provides a larger surface area to absorb water and minerals
List the advantages of having a double circulatory system.
- blood can be pumped at a higher pressure so more oxygen can be delivered to the cells
- help maintain body temperature
Which chamber of the heart pumps deoxygenated blood to the lungs?
Right ventricle
Which chamber of the heart pumps deoxygenated blood to the lungs?
Left ventricle.
Describe the function of arteries.
Carry blood away from the heart.
What do capillaries do?
They are involved with the exchange of materials at the tissues.
What do veins do?
Carry blood to the heart.
What muscle is the heart made up of? And what do they contain of?
Cardiac muscle. They contain of loads of mitochondria to provide the cells with ATP.
What is used to help keep the blood flowing in the right direction?
Valves.
Describe the structure of arteries.
- strong, elastic and thick walls
- contain thick layers of muscle to make them strong
- elastic fibres allow them to stretch and spring back
Describe the structure of capillaries.
- carry blood close to cells to exchange substances
- permeable walls
- walls are only one cell thick
Describe the structure of Veins.
- walls thinner than artery walls
- bigger lumen to help blood flow
- valves to keep blood flowing in right direction
Give three examples of the contents in plasma
Red blood cells, water, digested food products, carbon dioxide, urea, hormones, antibodies
How are red blood cells adapted to carry oxygen?
- biconcave disc shape
- haemoglobin, contains iron
- no nucleus
- small and flexible
What do Phloem tubes transport?
Food
Describe the structure of Phloem Tubes.
-made of living cells called sieve tube elements (companion cells due to having no nucleus)
What is the direction of transport in Phloem vessels?
Both up and down the stem. This is known as translocation.
What do Xylem tubes transport?
Water.
Describe the structure of Xylem Tubes.
- made of dead cells with no gaps in between and a hole down the middle.
- thick side walls made up of cellulose strengthened by lignin
What is the direction of transport in Xylem tubes?
Carry water and minerals up from the roots to the shoots to the leaves in the transpiration system.
What is transpiration?
The loss of water from the plant.
What causes transpiration and where does it usually happen?
Evaporation and diffusion of water. Happens at the leaves.
State 3 or more benefits of plants having a constant transpiration stream.
- Keeps plant cool
- Constant supply of water for photosynthesis
- Turgor pressure to support plants
- Minerals brought in by soil
What is transpiration rate affected by?
- Light intensity
- Temperature
- Air movement
List 3 adaptations of leaves to help reduce water loss.
- Waxy cuticle - waterproof
- Stomata on lower surface - slow diffusion
- Fewer and smaller stomata
What type of cells open and close stomata?
Guard cells.
What can we use to estimate transpiration rate?
How can we estimate using the given data?
Potometer. Start stopwatch and record distance moved by bubble per unit time. Keep conditions constant. Make sure apparatus is watertight and airtight.
