2.1.1 Cell Structure

Question 1

What are the differences with how genetic material is organised in eukaryotic and prokaryotic cells?

Answer 1

DNA is linear in eukaryotes. DNA is circular/non-linear in prokaryotes.
DNA forms chromatin/is associated with protein/ host ones in eukaryotes. DNA is naked in prokaryotes.
DNA is stored in the nucleus in eukaryotes. DNA is free floating in the cytoplasm in prokaryotes.
Genes split into exons by introns in eukaryotes. There are only exons no introns in prokaryotes.

Question 2

What are the differences between SEMs and TEMs?

Answer 2

SEM produce 3D images of the sample. TEM only produce 2D images.
Both have a higher resolution and magnification than optical light microscopes.
Electrons bounce off the sample in SEM but in TEM, electrons are passed through the sample to create an image.

Question 3

Structure and function of the nucleus

Answer 3

Structure:
Double nuclear envelope - double membrane-compartmentalises the nucleus + prevents damage
Nuclear pores-allow molecules to enter + leave the cell
Nucleolus- site of ribosome production, composed of RNA + proteins

Function:
Controls activity of the cell, where DNA is stored + copied into RNA
Close to rough ER so can easily get to ribosomes

Question 4

Structure and function of endoplasmic reticulum

Answer 4

Rough ER:
Stacks of membrane sacs which form sheets (cisternae).
Attached to nucleus + covered with ribosomes.
Interconnected system of cisternae
- site of protein synthesis + transports proteins made by ribosomes.

Smooth ER:
Stacks of sacs called cisternae.
No ribosomes attached.
System of interconnected tubules.
- responsible for carbohydrate + lipid synthesis.

Question 5

Structure + function of Golgi apparatus

Answer 5

Structure:
Stacks of flattened sacs (cisternae).
Continuously formed from ER on one end + buds off as Golgi vesicles at the other.

Function:
Received proteins from RER in vesicles.
Modifies them (adds sugar/enzyme chain-folds inti a specific shape).
Repackaged and sent off in vesicles to cell surface membrane to diffuse into blood.
Makes lysosomes + lipid synthesis.

Question 6

Structure and function of ribosome

Answer 6

Structure:
2 subunit organelle.
Made from RNA + protein.
Free floating in cytoplasm or attached to rough ER.
Not membrane bound.

Function:
Where proteins are made (protein synthesis)
Assemble amino acids into protein chains using mRNA.

Question 7

Structure and function of mitochondria

Answer 7

Structure:
Oval shape, double membrane.
Inner membrane - finger-like structure (cristae) increases SA.
Solution called matrix - has enzymes for respiration.
Mitochondrial DNA - enable to reproduce + create enzymes.

Function:
Site of aerobic respiration
Release ATP (energy carrier in cells) as a result.

Question 8

Structure and function of lysosomes

Answer 8

Structure:
Spherical sacs with a single membrane.

Function:
Contain powerful hydrolytic digestive enzymes.
Break down worn out components of the cell + digests invading cells.

Question 9

Structure and function of centrioles

Answer 9

Structure:
Component of the cytoskeleton - many microtubules.
Small hollow cylinders that in pairs next to nucleus.
Each centriole has a ring of 9 microtubules.

Function: makes a copy of itself during cell division + helps to form the spindle in cell division.

Question 10

Structure and function of cillia

Answer 10

Structure:
“Hair-like” extension that profuse from some animal cell types.
Outer membrane + ring of nine pairs of protein microtubules with two microtubules in the middle.
Allows movement.

Function:
Sensory function - beat + waft in one direction in unison to move mucus/objects for locomotion.

Question 11

Structure and function of plasma membrane

Answer 11

Structure:
Membrane found on the surface of animal cells and inside the cell wall of plant cells.
Composed of proteins and lipids.
Phospholipid bilayer.

Function:
Regulated movement into an out of the cell.
Receptor molecules that allow it to respond to chemicals like hormones.