B2.1 - Supplying The Cell Flashcards
What is diffusion?
The net movement of particles from a higher concentration to a lower concentration until they reach equilibrium.
Where does diffusion occur in the body?
And what is being diffused?
Between blood and the cells in your body
Diffuses glucose and oxygen into cells that need them
How do you increase the rate of diffusion?
Decrease the distance the particles need to move
Increase the concentration gradient
Increase the surface area
What is osmosis?
The special type of diffusion of water molecules across a selectively permeable cell membrane
What is water potential?
The concentration of free water molecules
What substance has the highest possible water potential?
Pure water
What is active transport?
Allows cells to move substances from an area of low concentration to high concentration against their concentration gradient
How can particles move against the concentration gradient in active transport?
Energy must be transferred from an energy store
What are the three key features of active transport?
Particles transported against concentration gradient
ATP required - comes from respiration
Makes use of carrier proteins in the cell membrane
How do cells adapt to carrying out active transport?
More mitochondria
What does the rate of active transport depend on?
Rate of respiration to produce the required ATP
What are carrier proteins?
Special proteins that span across the width of the cell membrane that can change shape or rotate to transport the molecule into the cell
What are some examples of active transport?
Digestion - glucose transferred into the bloodstream via the villi
Nerve cells - pumps sodium ions out and potassium ions in for creating nerve impulses
Root hair cells - taking in water and mineral ions
What is mitosis?
The process by which body cells divide to produce two identical daughter cells
Why do humans need mitosis?
It grows the cells we need to grow bigger and to replace the dead cells
What is the cell cycle?
The process of cell growth and division
What are the four stages of the cell cycle?
DNA replication, movement of chromosomes, cytokinesis and the growth of the daughter cell
Stage 1 of the cell cycle:
How is DNA replicated?
The DNA molecule unzips, forming two separate strands
Free nucleotides in the nucleus line up against each of the strands, forming base pairs
When the strand is complete, there are two identical molecules of DNA
Stage 2 of the cell cycle:
How do the chromosomes move?
The chromosome line up across the centre of the cell
Two identical copies of each chromosome (formed when the DNA is replicated) separate and move to opposite ends of the cell. Each end has a full set of identical chromosomes
Two new nuclei form
Stage 3 of the cell cycle:
What is cytokinesis?
Following the movement of chromosomes, the cell membrane pinches inwards to separate and enclose the two nuclei, and then pinches off to split the original cell into 2 new daughter cells, which will grow independently
Stage 4 of the cell cycle:
What happens to the individual daughter cells?
They begin replicating their DNA, and they cell cycle continues
What is special about stem cells?
They are undifferentiated cells, and they become specialised after being formed by mitosis. This means they can develop into any type of specialised cell, and help grow tissues and organs
When are stem cells used by the body?
During development, growth and repair
What are the two types of stem cell?
Embryonic and adult stem cells
What is the function of embryonic stem cells?
Found in embryos where they divide by mitosis to produce all the cells needed to make an organism.
They have the ability to differentiate into all types of cells
What is the function of adult stem cells?
Found in various body tissues, and they can differentiate into some cells, but not as many as embryonic cells
Once an animal is fully grown, many adult stem cell remain in a non-dividing state for years. What can activate them?
Disease or tissue injury can activate the for mitosis
What are the only parts of a plant that grow for the plant’s whole life?
Meristems
