Cells

Core concepts

How does Scanning Electron Microscopy work? What type of image does it produce?

The cell is coated in gold and scanned with a beam of electrons. It creates a 3D image of the cell, which has limitations as you can not see the inside of the cell.

How does Transmission Electron Microscopy work? What type of image does it produce?

It is covered in resin and then thinly sliced. Electrons and shot at it and it created an 2D image. It can have different orientations.

Is mitochondria plant or animal? What is the function of a Mitochondria?

Both. It is the site of aerobic respiration (Krebs Cycle and electron transport chain)

What is the approximate size of a mitochondria

1 micrometer by 7 micrometers. (one of the larger organelles)

Draw and label a mitochondria cell.

-Kidney bean shape for outer membrane

-folded inner membrane

-squiggle for loop on DNA
-circles for Ribosomes-

-larger circles for granules

-lines with dots for stalked particles/ ATP synthase particle

What are the folds on the inner membrane called?

The Cristae (pl) / Crista (sing)

What is the liquid inside the inner membrane called?

The matrix.

What is the matrix for? (2)

contains a DNA loops and ribosomes so it can replicate (mitosis)

it also contains enzymes to control biochemical reactions (Kreb’s cycle)

What are the cristae for?

Increase the surface area for enzyme reactions (ETC) and allow enzymes and substrates to be concentrated and for pH to be optimised

What is the double membrane for?

To seperate reactions like the Krebs cycle and the Electron transfer chain from general reactions in the cytoplasm.

What are stalked particles for?

Respiration

What is the function of chloroplasts?

It is the site of photosynthesis where light energy is converted into chemical energy

What is the size of a chloroplast?

5-10 micrometers in diameter. bigger

Draw a chloroplast.

• Two ovals for membranes

• stretched ovals for Thylakoids and many of top of eachother for a granum.

• longer ovals between granums for intergranal thylakoids.

• squiggle for loop of DNA

• circles for starch granules

• smaller circles for lipid droplets

• dots for ribosomes

What do starch granules do?

They temporarily store carbohydrates as sugars until they diffuse out during photosynthesis

What do thylakoids and grana do?

create a large surface area to store chlorophyll (absorb light) and electron carrier molecules so more light dependant reactions can occur

What do intergranal thylakoids do?

They contain quantasomes in their membranes which is the Light Dependant Reactions of photosynthesis take place

What is the function of the Stroma?

It contains enzymes for Light Independent Reactions and DNA and Ribosomes so it can self replicate.

What is the thylakoid lumen?

It contains a reservoir of hydrogen ions that are broken off of water molecules.

What are the lipid droplets?

Store energy as lipids.

What is the function of the nucleus?

Controls cell function and contains the DNA of the cell

What is the size of the nucleus?

10-20 micrometers

Draw a nucleus

1. Two circles with gaps for the membranes and nuclear pores

2. circle for the nucleolus

3. squiggle for chromatin

4. rectangle/ oval sections for the rough endoplasmic reticulum

5. dots on the rough endoplasmic reticulum for the ribosome

What is the benefit of the double membrane?

encloses and protects the DNA as not to damage the genetic code

What is the function of the nuclear pores?

To allow large molecules (mRNA and nucleotides) to transport.

What is the function of the nucleolus?

It makes rRNA (ribosomal RNA) and packs it into the 2 subunits of ribosomes which eventually leave the nucleus through the nuclear pores.

What happens in nucleoplasm?

DNA is wrapped around histone proteins and condensed into chromosomes. It contains the bases (nucleotides)

What is chromotin?

In non-dividing cells chromosones are not visible and loosely coiled and so seen as chromotin

What are the two types of chromotin?

Heterochromatin-densley packed and darker

Euchromatin- loosely packed and lighter

What are the two membranes called collectively?

The nuclear envelope

What is the endoplasmic reticulum and where are they found?

A system of flattened membranous sacs called cisternae. They are found in all Eukaryotes (prokaryotes don’t have membranes) and are continuous with the nuclear membrane and sometimes connected to the Golgi Body

What happens in the rough endoplasmic reticulum?

They have ribosomes and are where proteins and produced and transported.

What happens in the smooth endoplasmic reticulum?

(no ribosomes and more tubular) produces and transports lipids and steroids and also breaks down toxins

What is the Golgi Body?

A stack of flattened curved sacs (looks like rainbows kind of), present in all eukaryotes

What happens in vesicles?

Modified proteins that are made in the RER are collected by vesicles and transported through the golgi body where they are folded and then travel through a ventricle around the cell or to the membrane for secretion.