B2 Flashcards
(42 cards)
Name the four stages of cell cycle and briefly outline what happens
1) gap phase one- cell grows and organelles are replicates
2) synthesis- DNA is replicated by splitting and complementary free floating nucleotides pair up and form cross links
3) gap phase 2 cell grows and proteins needed for mitosis are made
4) mitosis- chromosome are pulled to either end by cell fibres, the nucleus divides and cytoplasm and cell membrane divides
Why do cells have a cell cycle?
Cells have a cell cycle because they need to replicate cells for growth, replace and repair
Name two specialised animal cells and his they are specialised to carry out their function
Sperm
Nerve
Sperm cells- have a long tail and streamline head for swimming, their nucleus only contains half the genetic material, they are packed with mitochondria for energy for swimming and they have enzymes which digest egg cell membrane in their heads
Nerve cells- have dendrites which increase the surface area so connecting to other nerve cells is easier, they have a long axon which speeds up impulses as opposed to shifter ones with many connections, a myelin sheath covers the axon to insulate it and they have synapses which send transmitter chemicals to set of the impulse in the next neuron
Name one plant cell and how it is specialised to do its function
Palisade leaf cell
Palisade leaf cells have a tall shape so they have a high surface area exposed to absorb CO2, they have a thin shape so gases have a short path, they have air spaces to let gases move easily between cells and have stomata underneath to let gases in and out and allow transpiration
What is a stem cell?
A stem cell is an undifferentiated cell which can differentiate to form other types of specialised cells
Name three places we can find stem cells
1) human embryos- can turn into any cell for growth and development
2) bone marrow- can turn into any cell from its original tissue to replace damaged cells like skin or blood
3) Meristem tissue plant - can turn into any cell as long as the plant lives
Definition of diffusion
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient
Which three things increase the rate of diffusion?
Temperature, concentration gradient and cell membrane surface area increase the rate of diffusion
How does a cell membrane use diffusion?
Cell membranes only let small molecules like oxygen glucose and amino acids diffuse through while big molecules like starch and proteins can’t fit
Definition of active transport
Active transport- the movement of particles from a more dilute solution to a more concentrated solution against a concentration gradient using ATP.
What is ATP
ATP is the energy released by the mitochondria in respiration
Give two examples of where active transport is used in plants and animals
1) in the lumen in the small intestines to move sugars into the cells where they diffuse in to the bloodstream
2) In Root hair cells where active transport is used to move ions from the soil into the root hair cell where they are moved into the plant for making chlorophyll
Osmosis definition
Osmosis is the net movement of water molecules from an area of high water concentration to an area of low water concentration across a partially permeable membrane
How does osmosis work?
Water molecules in a dilute solution with a higher concentration of water molecules diffuse across a partially permeable membrane to an area with a higher concentration but a lower concentration of water molecules down a water potential gradient
How does osmosis effect animal cells? Describe the effect of putting an animal cell in water then in a concentrated solution
If you put an animal cell in water osmosis will move in the net direction into the cell because the cytoplasm has a relatively low water concentration. The cell will swell and eventually burst
If you put an animal cell in a concentrated solution (with a low water concentration) osmosis will move in the net direction out of the cell and the cell will shrink
How does osmosis effect plant cells? Describe the effect of putting a plant cell in water then in a concentrated solution
If you put a plant cell in water osmosis will move in the net direction into the cell because the cytoplasm has a relatively low water concentration. The cell will expand and become turgid but will not burst due the cell the wall. This turgid pressure helps support plant tissues.
If you put a plant cell in a concentrated solution (with low water concentration) osmosis will work in the net direction out of the cell so the cell will shrink and become flaccid. The plant will wilt
Describe an experiment to investigate osmosis
1) peel a potato
2) use a cork borer to cut three symmetrical cylinders
3) use a scalpel to cut them to the same length
4) measure their mass
5) put the each in a test tube the first with 0.5 molar sugar solution. The second with 0.25 molar sugar solution and the last in distilled water
6) leave overnight
7) take them out pat them dry and measure their mass and work out the percentage change of mass for each concentration
Which three factors effect osmosis, diffusion and active transport?
1) surface area to volume ratio- smaller objects have larger surface area to volume ratios so substances have more surface area to diffuse across so the rate is faster
2) temperature- the warmer particles in a substance are the more energy they have so there diffuse faster in out cells
3) concentration gradient- the larger the concentration gradient the more particles they are to move across so rate is faster
How is exchanging substances in single celled organisms different to multicellular organisms.
In single celled organisms substances can diffuse straight across the outer membrane because they only have to travel a short distance and SA:V is high
In multicellular organisms substances can’t diffuse across the outer membrane because some cells are deep inside and SA:V ratio is low. Thus multicellular organisms have specialised exchange organs with specialised exchange surfaces and transport systems to carry substances to these organs
What is the function of the lungs and how are they adapted to this function?
The function of the lungs is to transfer oxygen into the blood and remove waste from it the adaptions include
- millions of alveoli (huge SA)
- alveoli have thin walls (short diffusion path)
- good blood supply (ensures a high concentration gradient)
What is the function of the small intestine and how are they adapted to this function?
The function of the small intestine is to absorb nutrients and minerals from food into the blood. Adaptions include
- long around 5m (high SA)
- covered in villi (high SA)
- villi covered in microvilli (high SA)
- villi have thin membrane (short diffusion path)
- villi have a good blood supply (ensures a Hugh concentration gradient)
What is the function of leaves and how are they adapted to their function?
The function of the leaves are to take in carbon dioxide, oxygen and water vapour and to also release these substances. Adaptions include:
- broad (large surface area for diffusion)
- thin (short path for gases)
- transparent upper epidermis (light can get to photosynthetic cells)
- air space (for O2 and CO2 increase SA for gas exchange)
- stomata (let gases and water vapour diffuse in/ out)
What is the function of roots and how are the my adapted to their function?
The function of roots is to absorb water and mineral ions from the soil. Adaptions include:
- covered in thousands of root hair cells which each have a root hair (increases SA)
- contain root hair cells which contain large amounts of mitochondria (to provide energy for active transport of minerals)
Describe the function of the circulatory system and how it works
The circulatory system is responsible for pumping blood around the body using the heart and blood vessels:
1) the heart pumps deoxygenated blood to the lungs where the blood become oxygenated
2) the oxygenated blood returns to the heart where it is pumped to the organs
3) the blood gives its oxygen to the organs and becomes deoxygenated
4) the blood returns to the heart where it is pumped back to the lungs
