B2.1 Supplying The Cell Flashcards
Diffusion
Passive net overall movement of particles from a region of high concentration to a region of low concentration down a concentration gradient
Transports Carbon dioxide, oxygen, water, food substances, wastes: urea
No energy needed
Particles move ……. and …….. by diffusion
Particles move constantly and randomly by diffusion
Key gas we need to diffuse from our lungs to our blood stream
Oxygen
Key nutrient diffused from our blood stream to muscle cells
Glucose
Factors affecting diffusion
Surface area
Temperature
Concentration gradient
Distance
Key adaptations of the body to facillitate diffusion
Alveoli
Very thin - small distance to diffuse over
Covered by a network of fine capillaries - diffuse straight into bloodstream, maintains concentration gradient
Moist - allows gases to dissolve
Large combined surface area
Small intestines
Villi - increases surface area, therefore increases volume of nutrients that can be absorbed
Good blood supply – substances diffuse straight into the bloodstream, maintains concentration gradient
Role diffusion plays in nerve impulses
Diffusion allows a nerve impulse to travel between two neurones at a synapse
Neurotransmitter molecules diffuse from vesicles towards the neurotransmitter receptors, moving from an area of high concentration to low concentration
How the placental organ is adapted to maximise diffusion
A large surface area between it and the uterus wall
Villi (finger like projections that extend into the uterus wall), which further increase the surface area of the placenta
A rich supply of maternal blood vessels
Role diffusion plays in enabling photosynthesis
Carbon dioxide diffuses in through stomata
Oxygen and water diffuse out of stomata
During photosynthesis, level of CO2 is low inside leaf, creating a big concentration gradient so CO2 diffuses into the cell
Time of day affects the state of stomata
At night, they close because, in the absence of sunlight, carbon dioxide is not required for photosynthesis
At this time only objective is preventing water loss
Osmosis
Special type of diffusion
Diffusion of water molecules across a partially (selectively) permeable membrane from an area of high water concentration to an area of lower water concentration down a concentration gradient
Transports ONLY WATER
No ATP energy needed
Hypertonic
Fluid has a higher osmotic pressure (lower water potential) than a particular fluid, typically a body fluid or intracellular fluid
Hypotonic
Fluid has a lower osmotic pressure (higher water potential) than a particular fluid, typically a body fluid or intracellular fluid
Turgid
When water enters the cell by osmosis and fills the vacuole
This pushes against the cell wall, making the cell turgid
Flaccid
When water moves out of the cell by osmosis
Vacuole shrinks and cell becomes flaccid
Plasmolysis and crenation
Plasmolysis happens if too much water leaves a PLANT cell, and cytoplasm moves away from cell wall
Crenation is same as above but for animal cells
Isotonic solution
Has same osmolarity, or solute concentration, as another solution
Lysis
When an ANIMAL cell is placed in a hypotonic solution,
causing too much water to enter cell by osmosis and the cell to swell and burst
Crenation
When an animal cell is placed in a hypertonic solution,
causing too much water to leave the cell by osmosis making the cell shrink and shrivel
Osmosis takes place over a…
Selectively/semi-permeable membrane
Active transport
Transport of particles from an area of low concentration to an area of high concentration,
against a concentration gradient
ATP energy needed
Examples:
Transports mineral ions into plant roots
Glucose from the gut into intestinal cells, from where it moves into the blood
Carrier proteins
Protiens embembedded within the cell surface membrane
They bind with useful molecules and then use ATP to rotate or change shape to transport the molecule into the cell
Allow transport of useful molecules against a concentration gradient
Example of active transport in plants
Root hair cells - Transport of mineral ions from low concentration in soil to higher concentration in root hair cell
2 examples of active transport in animals
Nerve cells - active transport used to pump sodium & potassium ions required to create nerve impulses
Digestion - active transport used to transport the final products of digestion into the bloodstream through villi
Why do cells that carry out active transport contain a lot of mitochondria
Mitochondira produce energy and energy is required for active transport to take place
Mitosis
Nuclear cell division that is used by cells for growth, repair, and healing and asexual reproduction
Stage within cell cycle
Cell cycle
Process of cell growth and division for growth and repair of body cells
Has three main stages interphase, mitosis, cytokinesis
Results in 2 identical daughter cells
