A Level Biology : Module 1 - Cell Ultrastructure Flashcards
1
Q
Cell Surface Membrane
A
- Surrounds ALL cells
- Controls exchange of materials between internal environment and external environment
- Formed from a phospholipid bilayer spanning around 10nm
2
Q
Cell Wall
A
- Freely permeable to most substances
- Plant cells, NOT ANIMAL CELLS
- Offer structural support
- In plant cells, it is made of polysaccharide cellulose
- In most bacterial cells, it is made of peptidoglycan
3
Q
Nucleus
A
- In all eukaryotic cells apart from RBCs
- Separated from the cytoplasm via a double membrane (nuclear envelope)
- Nuclear envelope has many pores, allowing mRNA and ribosomes to travel out of the nucleus, as well as enzymes and signalling molecules to travel in
- Contains chromatin (making up chromosomes)
- Chromosomes are tightened around proteins called histones
3
Q
Mitochondria
A
- Site of aerobic respiration in all EUKARYOTIC cells
- Surrounded by a double membrane with the inner membrane folded inwards to form cristae
- Within the cristae is the matrix, containing enzymes needed for aerobic respiration, producing ATP
- Smaller pieces of DNA and ribosomes are found in the matrix for replication
4
Q
Chloroplasts
A
- Plant cells
- Larger than mitochondria, also surrounded by a double membrane
- Thylakoids are membrane bound compartments containing chlorophyll
- They stack to form structures called grana
- Grana join together by lamellae (thin flat thylakoid membranes)
- Site of photosynthesis
- Light dependent stage takes place within thylakoids
- Light independent stage takes place in stroma
- Small pieces of DNA and ribosomes are used to synthesise proteins needed in replication and photosynthesis
5
Q
Ribosomes
A
- Synthesised in the nucleolus
- Composed of almost equal amounts of protein and RNA
- Found in ALL cells
- Found in cytoplasm of all cells, or as part of the ENDOPLASMIC RETICULUM in eukaryotic cells
- Ribosomes are complexes of ribosomal RNA and proteins
- 80S ribosomes are found in eukaryotic cells
- 70S ribosomes are found in prokaryotes, mitochondria and chloroplasts
- Site of translation and proteinsynthesis
6
Q
Rough Endoplasmic reticulum
A
- Found in plant and animal cells
- Surface covered in ribosomes
- Formed from continuous colds of membrane continuous with the nuclear envelope
- This processes proteins made by ribosomes
7
Q
Smooth Endoplasmic Reticulum
A
- Found in animal and plant cells
- Does not have ribosomes on its surface
- Function is distinct to the RER
- Involves production, processing and storage of steroids, lipids and carbohydrates
8
Q
Golgi Apparatus
A
- Found in plant and animal cells
- Flattened sacs of membrane similar to ER
- Modifies proteins and lipids before packaging them into Golgi vesicles
- Vesicles then transport proteins and lipids to required destination
- ## Proteins go through Golgi apparatus are exported, put into lysosomes or delivered to membrane bound organelles
9
Q
Large Permanent Vacuole
A
- Sac in plant cells surrounded by the tonoplast (selectively permeable)
- Vacuoles in animal cells are not permanent and small
10
Q
Vesicles
A
- Found in plant and animal cells
- Membrane bound sacs for transport and storage
11
Q
Lysosomes
A
- Special forms of vesicles
- They contain hydrolytic enzymes (which are enzymes that break down biological molecules)
- Break down waste materials, such as worn out organelles
- Used extensively by cells of the immune system and in apoptosis
12
Q
Centrioles
A
- Hollow fibres made of microtubules
- Two centrioles formed at right angles to each other form a centrosome, which organises spindle fibres during division
- Not found in flowering plants or fungi
13
Q
Microtubules
A
- Found in all eukaryotic cells
- Makes up cytoskeleton
- Made of α and β tubulin which combine to form DIMERS
- Dimers join to form protofilaments
- 13 protofilaments in a cylinder make a microtubule
- It provides support and movement of the cell
14
Q
Microvilli
A
- Found in specialised animal cells
- Cell membrane projections
- Increase surface area of cell surface membrane in order to increase the rate of exchange of substances
15
Q
Cilia
A
- Hair like projections which are made of microtubules
- Allows movement of substances over the cell surface
16
Q
Flagella
A
- Found in specialised cells
- Similar in structure to the CILIA, but is made of longer microtubules
- Contracts to provide cell movement, for example in sperm cells
17
Q
What is the Cytoskeleton?
A
- Extensive network of protein fibres
- Made if microfilaments and microtubules
- There are intermediate filaments also found within cytoskeleton
18
Q
Function of the cytoskeleton?
A
- Strengthening and support
- Intracellular movement
- Cellular movement
19
Q
What are microfilaments?
A
- Solid strands mostly made of actin
- Fibres can cause cell movement and movement of organelles
20
Q
What are microtubules?
A
- Hollow (tubular) strands made of tubulin.
- Organelles and other cell contents are moved along these fibres using ATP to drive movement
21
Q
How does the cytoskeleton strengthen and support the cell?
A
- With mechanical strength (like scaffolding), maintaining shape of cell
- Supports organelles and keeps them in position
22
Q
How does the cytoskeleton provide intracellular movement?
A
- Aids transport by forming ‘tracks’ along which organelles can move
- Examples include movement of vesicles and chromosomes to opposite ends of a cell during cell division
23
Q
How does the cytoskeleton provide cellular movement?
A
- Via cilia and flagella
- They contain microtubules responsible for moving them
24
Q
How do prokaryotic cells differ from eukaryotic cells?
A
- Eukaryotic cells have membrane bound organelles
- Eukaryotic cells have nuclei (and not a single circular dna molecule)
- Prokaryotic cells have cell walls containing murein.
- Ribosomes are 70S (smaller) as opposed to 80S
Additional :
- Flagellum
- Plasmids (small loops of DNA)
- Capsules (protects bacteria from drying out)
- Prokaryotes divide by binary fission, Eukaryotes by mitosis or meiosis, involves spindle
- In prokaryotes, cell walls are made of peptidoglycan, Eukaryotes it is polysaccharide cellulose
- Prokaryotes are 0.5-5um, eukaryotes are up to 100um
