1
,
,OCR A-level Biology summary notes
Module 2-Foundations in biology
2.1.1 CELL STRUCTURE
★ Microscopes
Max Max
Image
Microscope Type Magnifica Resolut Observes Live/Dea Colour?
Type
tion ion
Whole
×1500– 2D, Usually live Yes (with
Light Microscope (LM) 200 nm cells,
2000 coloured or dead staining)
tissues
2D, Internal
Transmission Electron ×1,000,00 Dead, thin
0.1 nm black & ultrastruct No
Microscope (TEM) 0 sections
white ure
3D,
Scanning Electron 1–10 Surface
×500,000 black & Dead No
Microscope (SEM) nm topology
white
Slide
Description Use Case Advantages Limitations
Type
Wet Specimen suspended in Viewing live cells, Quick, observes Thin specimens
mount liquid under coverslip motility living cells needed
Squash Wet mount pressed to Root tip cells, Cells spread in Can damage
slide spread cells dividing cells one layer delicate cells
Smear Specimen spread thinly on Blood smears, May not be
Thin even layer
slide slide bacterial samples uniform
Section Thin sliced tissue, often Plant or animal Detailed cell Requires special
slide stained tissue structure structure equipment
Use of staining: to identify different cellular components and cell types
Magnification- how big the image is compared to its actual size
Resolution- the ability to distinguish between 2 separate points
3
, Cellular
Structure Function
Component
Large spherical, double membrane with
Nucleus Contains DNA, controls cell activities
pores
Produces ribosomal RNA and
Nucleolus Dense region inside nucleus
assembles ribosomes
Nuclear Controls movement of substances
Double membrane with pores
Envelope in/out of nucleus
Rough ER Network of flattened sacs with ribosomes Synthesizes and transports proteins
Network of tubular membranes without Synthesizes lipids and detoxifies
Smooth ER
ribosomes substances
Golgi Modifies, sorts, and packages proteins
Stacks of flattened membranous sacs
Apparatus and lipids
Small, dense particles made of RNA and
Ribosomes Site of protein synthesis
protein
Double membrane with folded inner Produces ATP through aerobic
Mitochondria
membrane (cristae) respiration
Membrane-bound vesicles with digestive
Lysosomes Digests waste materials and pathogens
enzymes
Double membrane with stacks of
Chloroplasts Site of photosynthesis in plants
thylakoids (grana)
Plasma Controls movement of substances into
Phospholipid bilayer with proteins
Membrane and out of cell
Cylindrical structures made of Organize spindle fibers during cell
Centrioles
microtubules division
Provides structural support and
Cell Wall Rigid layer made of cellulose (in plants)
protection
Flagella Long whip-like projections Enables cell movement
Move fluids over cell surface or enable
Cilia Short hair-like projections
locomotion
,
,OCR A-level Biology summary notes
Module 2-Foundations in biology
2.1.1 CELL STRUCTURE
★ Microscopes
Max Max
Image
Microscope Type Magnifica Resolut Observes Live/Dea Colour?
Type
tion ion
Whole
×1500– 2D, Usually live Yes (with
Light Microscope (LM) 200 nm cells,
2000 coloured or dead staining)
tissues
2D, Internal
Transmission Electron ×1,000,00 Dead, thin
0.1 nm black & ultrastruct No
Microscope (TEM) 0 sections
white ure
3D,
Scanning Electron 1–10 Surface
×500,000 black & Dead No
Microscope (SEM) nm topology
white
Slide
Description Use Case Advantages Limitations
Type
Wet Specimen suspended in Viewing live cells, Quick, observes Thin specimens
mount liquid under coverslip motility living cells needed
Squash Wet mount pressed to Root tip cells, Cells spread in Can damage
slide spread cells dividing cells one layer delicate cells
Smear Specimen spread thinly on Blood smears, May not be
Thin even layer
slide slide bacterial samples uniform
Section Thin sliced tissue, often Plant or animal Detailed cell Requires special
slide stained tissue structure structure equipment
Use of staining: to identify different cellular components and cell types
Magnification- how big the image is compared to its actual size
Resolution- the ability to distinguish between 2 separate points
3
, Cellular
Structure Function
Component
Large spherical, double membrane with
Nucleus Contains DNA, controls cell activities
pores
Produces ribosomal RNA and
Nucleolus Dense region inside nucleus
assembles ribosomes
Nuclear Controls movement of substances
Double membrane with pores
Envelope in/out of nucleus
Rough ER Network of flattened sacs with ribosomes Synthesizes and transports proteins
Network of tubular membranes without Synthesizes lipids and detoxifies
Smooth ER
ribosomes substances
Golgi Modifies, sorts, and packages proteins
Stacks of flattened membranous sacs
Apparatus and lipids
Small, dense particles made of RNA and
Ribosomes Site of protein synthesis
protein
Double membrane with folded inner Produces ATP through aerobic
Mitochondria
membrane (cristae) respiration
Membrane-bound vesicles with digestive
Lysosomes Digests waste materials and pathogens
enzymes
Double membrane with stacks of
Chloroplasts Site of photosynthesis in plants
thylakoids (grana)
Plasma Controls movement of substances into
Phospholipid bilayer with proteins
Membrane and out of cell
Cylindrical structures made of Organize spindle fibers during cell
Centrioles
microtubules division
Provides structural support and
Cell Wall Rigid layer made of cellulose (in plants)
protection
Flagella Long whip-like projections Enables cell movement
Move fluids over cell surface or enable
Cilia Short hair-like projections
locomotion
