Cell structure Flashcards
Describe the structure and function of the nucleus
Surrounded by a nuclear envelope
Nuclear pores allow substances to enter/exit
Contains DNA coiled into chromosomes
Controls the cell
Describe the structure and function of mitochondria
Cristae (site of ETC)
Matrix (contains DNA, lipids and proteins)
Site of aerobic respiration
Produces ATP
Describe the structure and function of the chloroplasts
Thylakoids (flattened stacked discs)
Stroma (fluid-filled matrix)
Site of photosynthesis
Converts solar energy to chemical energy
Describe the structure and function of the Golgi apparatus
Stack of membrane-bound, flattened sacs
Synthesises glycoproteins
Transports and stores proteins
Describe the structure and function of a lysosome
Sac surrounded by a glycoprotein coat
Exocytosis of digestive enzymes
Digests contents of phagosome
Describe the structure and function of a ribosome
Site of protein synthesis
In cytoplasm or attached to ER
Describe the structure and function of the endoplasmic reticulum (ER)
Rough ER = many ribosomes attached for protein synthesis
Smooth ER = lipid synthesis
Describe the structure of the cell wall in different organisms and functions it has
Bacteria = murein
Plants = cellulose microfibrils
Mechanical support
Physical barrier against pathogens
Enables easy diffusion
Describe the structure and function of the cell vacuole in plants
Absorbs and hydrolyses harmful substances
Acts as a temporary food source
State the role of plasmids, the flagella and the capsule in prokaryotes
Plasmids = small ring of DNA carrying non-essential genes
Flagella = tail that propels the organism
Capsule = provides mechanical support + acts as a food reserve
Compare and contrast eukaryotic and prokaryotic cells
Both have a cell membrane, ribosomes and cytoplasm
Eukaryotes: Prokaryotes:
multicellular unicellular
nucleus no nucleus
larger ribosomes smaller ribosomes
cellulose cell wall murein cell wall
What are viruses?
Viruses are acellular and non-living
Describe the structure of a virus
Attachment proteins on the surface
Capsid
Linear genetic material
What are the advantages and disadvantages of using an optical (light) microscope?
+ image in colour
+ relatively cheap equipment
- lower resolution than electron microscopes
- 2D image
What are the advantages and disadvantages of using a scanning electron microscope (SEM) ?
+ 3D image
+ higher resolution than optical
- requires a vacuum
- black and white image
- expensive
What are the advantages and disadvantages of using a transmission electron microscope (TEM) ?
+ higher resolution than optical
+ higher magnification than optical
- 2D image with no colour
- expensive
- longer process
What happens during cell fractionation?
- Homogenize the tissue to release organelles
- Filter homogenate to remove debris
- Spin homogenate in centrifuge
- Most dense organelles form a pellet than can be filtered off
- It’s then spun again at a higher speed to remove any other organelles
What are the stages in the cell cycle?
Interphase
Mitosis (nuclear division)
Cytokinesis (cytoplasmic division)
What are the 3 stages that happen during interphase?
G1 = cell synthesises proteins for replication
S = DNA replicates
G2 = organelles divide
What happens during the first phase of mitosis?
PROPHASE:
Chromosomes condense, becoming visible
Spindle fibres form
What happens during the second phase of mitosis?
METAPHASE:
Sister chromatids line up along equator
Attached to spindles by their centromere
What happens during the third stage of mitosis?
ANAPHASE:
Sister chromatids separate into 2 chromosomes
Centromeres divide
What happens during the fourth stage of mitosis?
TELOPHASE:
Chromosomes decondense, becoming invisible
Spindle disintegrates
How do cancer treatments control the rate of cell division?
Prevent DNA replication
Disrupt spindle formation
How do prokaryotic cells replicate?
BINARY FISSION:
1. DNA loop replicates
2. Cell elongates, separating DNA loops
3. Cell membrane contracts
4. Cell splits into 2 identical cells with a DNA loop and varying number of plasmids
How do viruses replicate?
- Attachment proteins attach to receptors on host cell
- Viruses fuse with cell membrane
- Host cell synthesises new viral proteins
- Components of the new viral particle assemble
Why is it difficult to treat viruses?
They replicate inside living cells, making them difficult to kill without harming the host cell
