2.1.1 Cell Structure Flashcards
What are the differences with how genetic material is organised in eukaryotic and prokaryotic cells?
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.
Types of microscopes
Light:
Poor resolution due to long wavelength of light
Living samples can be examined + colour image obtained.
TEM:
High magnification + resolution
Sample is thin
Electrons pass through specimen to create image.
SEM:
High magnification + resolution
Sample doesn’t have to be thin
Electrons bounce off the surface of specimen to create 3D image.
Laser scanning confocal:
High resolution + 3D imaging
Laser light used to create image.
What are the differences between SEMs and TEMs?
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.
Structure and function of the nucleus
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
Structure and function of endoplasmic reticulum
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.
Structure + function of Golgi apparatus
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.
Structure and function of ribosome
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.
Structure and function of mitochondria
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.
Structure and function of lysosomes
Structure:
Spherical sacs with a single membrane.
Function:
Contain powerful hydrolytic digestive enzymes.
Break down worn out components of the cell + digests invading cells.
Structure and function of centrioles
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.
Structure and function of cillia
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.
Structure and function of plasma membrane
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.
Structure + function of cytoskeleton
Structure:
Network of fibres within cytoplasm.
Consists of microfilaments, microtubules and intermediate fibres.
Function:
Provides mechanical strength, maintain shape + stability of a cell.
Microfilaments - responsible for cell movement.
Microtubules - responsible for creating a scaffold-like structure.
Intermediate fibres - provide mechanical strength.
Structure + function of chloroplasts
Structure:
Surrounded by double membrane
Contains thylakoids
Fluid filled stroma contains enzymes for photosynthesis.
Function:
Site of photosynthesis
Structure + function of Cell wall
Structure:
Plants - made of microfibrils of cellulose
Fungi - made of chitin.
Function:
Provide structural strength to the cell.
Production + secretion of proteins
- Polypeptide chains synthesised in RER
- These polypeptide chains move to cisternae in RER and are packaged into vesicles to be sent to the Golgi via cytoskeleton.
- In Golgi, the proteins are modified + re-packaged into vesicles.
- The secretory vesicles carry the proteins to the cell surface membrane where it fuses and releases the protein by exocytosis.
Differences between Eukaryotic and Prokaryotic cells
P - Cells are much smaller
No membrane-bound organelles
Smaller ribosomes 70S<80S
DNA not contained within a nucleus
Cell wall made of peptidoglycan.
Also may contain:
Plasmids
(Slime) capsule around cell
Flagella
