35 WJEC Biology AS Level - Marianne Izen - 2nd Edition Flashcards
What is the shape and size of mitochondria?
Mitochondria are often cylindrical and 1-10 μm in length.
What do the mitochondria comprise of?
They comprise of:
- Two membranes
- An organic matrix
- A small circle of DNA
- Small (70S) ribosomes
Describe the mitochondrial membranes?
There are two membranes, separated by a narrow, fluid-filled inter-membrane space.
The inner membrane is folded inwards to form cristae.
Describe the organic matrix of the mitochondria?
It is a solution containing many compounds, including lipids and proteins.
What is the function of the small circle of DNA in the mitochondria?
It allows the mitochondrion to replicate and code for some of its proteins and RNA.
What is the function of the 70s ribosomes?
It allows protein synthesis.
What is the function of mitochondria?
The function of mitochondria is to produce ATP in aerobic respiration.
Where do the reactions of aerobic respiration take place?
Some of the reactions occur in the matrix and others on the inner membrane.
What does the cristae provide?
The cristae provide a large surface area for the attachment of enzymes involved in respiration.
Why do muscle cells have many mitochondria?
Metabolically active cells, such as muscle cells, need a plentiful supply of ATP.
They contain many mitochondria, reflecting the high metabolic activity taking place.
Why are mitochondria cylindrical and not spherical?
Being cylindrical, mitochondria have a larger surface area than a sphere of the same volume, in other words, their surface area to volume ratio is bigger.
Compared with a sphere, being a cylinder reduces the diffusion distance between the edge and the centre, making aerobic respiration more efficient.
Show that if a cylinder and sphere have the same volume, the cylinder has a smaller radius
If a cylinder and sphere have the same volume, compare their radius.
If a sphere and a cylinder have the same volume, the cylinder has a smaller radius.
Where are chloroplasts found?
Chloroplasts occur in the cells of photosynthesising tissue.
Where is the highest concentration of chloroplasts found?
In many plants the highest concentration is in the palisade mesophyll cells, just below the upper surface of the leaf.
What is each chloroplast surrounded by?
Each chloroplast is surrounded by two membranes, comprising the chloroplast envelope.
What does the stroma of the chloroplast contain?
The stroma is fluid-filled.
It contains some of the products of photosynthesis, including lipid droplets and starch grains.
These products can take up a large part of the stroma.
What are the other components of chloroplasts?
Like mitochondria, chloroplasts contain 70S ribosomes and circular DNA which enable them to make some of their own proteins and self-replicate.
Do all plant cells contain chloroplasts?
Not all plant cells contain chloroplasts.
Root cells, for example, being underground, would have no use for them.
Draw a diagram of the electron micrograph of a section of the mitochondria?
Draw a diagram of a section of mitochondria and label its parts.
