B2 Flashcards
What is diffusion?
Diffusion is the net movement of particles from a region of high concentration to low concentration down the concentration gradient.
How do you increase rate of diffusion?
- Decrease distance particles must move
- Increase concentration gradient
- Increase surface area (more space for diffusion)
What is osmosis?
Net movement of water particles from an area of high water potential to low water potential, across a semi-permeable membrane down the concentration gradient.
What is active transport?
Movement of particles across a membrane against the concentration gradient (low concentration to high).
Key features of active transport
- Requires ATP
- Transported against concentration gradient
- Carrier proteins are used
Examples of active transport.
- Plants take up nutrients from the soil which has a lower concentration of nutrients than in the root hair cells
- Nervous system, carrier protein pumps sodium ions out and potassium ions in (sodium potassium pump)
What is mitosis?
- process of body cells dividing to produce 2 identical daughter cells.
Explain the period of cell growth.
G1 - Gap 1 - cell grows, new cell structures and proteins made
S - DNA replication - DNA unzips, free nucleotides attach to the strands (complementary base pairing)
G2 - Gap 2 - cell grows and protein needed for cell division is made.
M - mitosis
Explain the process of mitosis.
- DNA replicates
- Chromosomes line up in the centre of the cell.
- Cell fibres pull the chromosomes apart to the opposite ends of the cell.
- Membranes form around the two sets of chromosomes (new nuclei)
- Cytoplasm divides and there are now two genetically identical cells.
Adaptations of a sperm cell.
- Acrosome - in the head of sperm, digestive enzymes which break down the outer layers of the ovum to transfer genetic information.
- Mitochondria - lots of it, so lots of respiration and energy so allow the flagellum to move.
- Flagellum - tail to swim
Adaptations of a fat cell.
- Specialized to store fat so that animals can survive when food is short.
- Insulation provider.
- layer of cytoplasm around reservoir to allow cell expansion.
Adaptations of a red blood cell.
- Biconcave disc to increase surface area to allow quicker rate of diffusion (gaseous exchange).
- No nucleus to allow it to be packed full of haemoglobin, this protein binds to oxygen.
Adaptations of ciliated cells.
- Cilia on cells sweep mucus away from your lungs and back of throat.
Adaptations of palisade cells.
- Found near surface of cell and are full of chloroplast to allow light absorption to be quicker and photosynthesis can occur.
What are stem cells?
- Undifferentiated cells that can differentiate into any cell and perform its function.
Types of stem cells
Embryonic - found in embryos and can differentiate into any cell.
Adult - found in bone marrow and can differentiate into cells of their tissue of origin.
Stem cells in plants.
- Meristems - only part of the plant that can divide my mitosis
- Found in roots and shoots
- Differentiate into any type of cell in the plant and last the life of the plant.
Why is it harder to exchange surfaces in multi-cellular organisms?
- Poor surface area:volume ratio.
- Substances have to travel large distances to reach the desired target and won’t reach the cells demand
- They have adapted exchange surfaces to increase their SA:V ratio.
Lung adaptations for gas exchange.
- To exchange gas (transfer oxygen to blood and remove waste CO2), the lungs have millions of air sacs called alveoli.
- Alveoli have - large surface area, thin walls, moist lining to dissolve gases, good bloody supply.
Small intestine adaptations.
- The small intestine is where dissolved food molecules are absorbed.
- They have millions of tiny finger-like projections called villi.
- They increase the surface area to speed up diffusion, a good blood supply to assist quick absorption and a single layer of surface cells.
What is the structure of a double circulatory system?
- Contains the heart, blood vessels and blood.
- Deoxygenated blood pumped from the heart to the lungs to be oxygenated.
- Oxygenated blood returns to the heart and is pumped to the necessary organs of the body to give oxygen and glucose to cells.
- Carbon dioxide enters the blood
- Deoxygenated blood returns to the heart to be pumped the lungs to be oxygenated and for carbon dioxide to be removed.
What are the tree blood vessels?
Arteries - carry blood away from the heart.
Veins - carry blood back to the heart
Capillaries - Exchange of materials at tissues.
Structure of an artery
- Blood is pumped away from the heart at high pressure so the walls are thick, strong and elastic (outer wall and layer of muscle and elastic fibres).
- Small lumen to allow pressure to increase.
- Arteries branch into arterioles.
Structure and adaptations of a capillary
- Arterioles branch into capillaries
- Network of capillaries - capillary bed
- Carry blood close to every cell and exchange substances.
- One layer thick permeable wall to allow for quick diffusion.
- Capillaries branch into venules.
Structure, function and adaptations of veins.
- Venules join up to make valves
- Blood is at lower pressure, no thick walls but larger lumen.
- Valves to prevent backflow of blood.
Blood flow at the right side of the heart.
Deoxygenated blood enters at the vena cava (superior/inferior) > right atrium > (atria contract pushing blood into the right ventricle) tricuspid valve > right ventricle > (ventricle contracts) pulmonary valve > pulmonary artery to the lungs.
Blood flow at the left hand side of the heart.
Oxygenated blood from the lungs through the pulmonary vein > left atrium > atria contract > bicuspid valve > left ventricle > aortic valve > aorta > blood to the rest of the body.
What are the 4 components of blood?
Plasma
Red Blood Cells
White Blood Cells
Platelets
What is in plasma?
- Straw coloured liquid (where blood cells float)
- 90% water
- Digested food products
- Urea, hormones, antibodies and waste (e.g. CO2)
What are white blood cells.
White blood cells - contain nucleus, fight diseases: making antibodies or engulfing microorganisms.
What are plateles?
Tiny structures that help blood clotting.
What makes up the vascular bundle system and what are their basic functions?
Xylem - transport water and mineral ions (via active transport) from the roots to stems, leaves and flowers (up the plant).
Phloem - transport soluble food molecules and dissolved sugars made during photosynthesis from the leaves. Called translocation. Sugars taken to the meristem to make new plant cells.
Structure of a xylem.
- Made of dead xylem cells.
- No cell walls
- One way flow of water and dissolved mineral ions
- Cell walls are strengthened with lignin, stiff and strong giving the plant support.
Structure of a phloem.
- Made of columns of living cells
- They have perforated sieve plates to allow dissolved sugar, water and foods through.
- Transport both up and down the plant.
How do the vascular bundles provide support?
- Network at leafs that support soft leaf tissue
- Situated around the stem, to provide strength and resist bending in the breeze.
- Centre of the root to anchor it.
What is the transpiration stream?
- Loss of water through the plants leaves and the uptake of water from the roots through osmosis and the xylem tissue.
- Constant flow of water called the transpiration stream.
How is water lost from leaves?
- In bright conditions (during the day) and during photosynthesis, the guard cells take up water and swell to become turgid opening the stomata.
- Water then diffuses out of the leaf and water is lost.
How do stomata control water loss?
- Most stomata is found on the underside of the leaf = lack of light = stay flaccid and won’t open
- Waxy cuticle at the top of the leaf to prevent water loss
- No stomata on the upper epidermis.
Factors affecting rate of transpiration.
Light intensity
Temperature
Humidity
Air movement (wind)
How does light intensity affect rate of transpiration?
Increases rate of transpiration as the stomata will open, until all the stomata open and rate of transpiration is at its maximum.
How does temperature affect rate of transpiration?
Increasing temperature increasing rate of water evaporation increasing the rate of transpiration constantly.
How does air movement affect rate of transpiration?
- Air moves over the surface of a leaf taking away water molecules. Faster the air, faster the movement of water molecules, faster the rate of transpiration.
- Also increases rate of diffusion of water as the concentration gradient is increased as water leaves the leaf.
How does humidity affect rate of transpiration?
Humidity = concentration of water in the air.
- Decreasing humidity increases rate of transpiration as the concentration gradient between the leaf and air is increased so water can diffuse out.
- High humidity = low rate of transpiration.
