B3. Cell Structure (DONE)

Question 1

What is the definition of resolution?

Answer 1

The ability to distinguish two points on an image

Question 2

What are the differences between electron microscopes and optical microscopes?

Answer 2

Optical: Uses light; Limited resolution due to using light; Max useful magnification 1500x; Cheap; Specimens alive
Electron: Uses electrons; Very high resolution; Useful max magnification 1.5 million x; Expensive; Specimens dead

Question 3

What are the two type of electron microscopes?

Answer 3

Transmission electron microscopes TEMs; Scanning electron microscopes SEMs

Question 4

How do TEMs work?

Answer 4

Uses electromagnets to focus beam of electrons; Beam transmitted through specimen

Question 5

What are the advantages and disadvantages of TEMs?

Answer 5

Advantages: High resolution; Allows internal structures to be seen;
Disadvantages: Only works on thin specimens; Cannot observe living specimen due to being in vacuum; Long treatment time to prepare specimen, artefacts can appear; Non coloured image

Question 6

What are the advantages and disadvantages of SEMs?

Answer 6

Advantages: Can be used on thick or 3D specimens; Allow external 3D structure to be observed;
Disadvantages: Lower resolution than TEMs; Cannot observe live specimens; Non coloured image

Question 7

How do SEMs work?

Answer 7

Scans a beam of electrons across the specimen; Beam bounces off surface of specimen and electrons are detected; Forms image;

Question 8

What is the equation for calculating magnification?

Answer 8

Size of image / Actual size of specimen

Question 9

What is cell fractionation?

Answer 9

Process of separating cell organelles from each other; Three stages, Homogenisation, filtration, ultracentrifugation

Question 10

What is homogenisation?

Answer 10

Biological term describing the breaking up of cells

Question 11

What condition solution are tissue samples placed in before homogenisation?

Answer 11

Place tissue in: Cold, reduce activity of enzyme; Isotonic, prevent water moving into cell via osmosis; Buffered, add buffer solution to prevent denaturing of proteins;

Question 12

What is a homogeniser?

Answer 12

Blender like machine that grinds cells up, breaks plasma membrane releasing organelle into solution (homogenate)

Question 13

What occurs in filtration of cell fractionation?

Answer 13

Homogenate filtered through gauze; Separates large unbroken debris; Solution of mixed organelles left (filtrate)

Question 14

What is a centrifuge?

Answer 14

Machine that separates organelle by spinning at high speeds

Question 15

What occurs in the ultracentrifugation stage of cell fractionation?

Answer 15

Filtrate placed in centrifuge: spun at low speed, heavy organelles settle at bottom of tube (pellet); Supernatant drained and placed in another tube; Centrifuge spun at higher speeds; Organelle settle at bottom (pellet); Repeated till desired organelle extracted

Question 16

What is supernatant?

Answer 16

The solution the rest of the organelles stay suspended in above the pellet

Question 17

What are the order of heavy to light organelle?

Answer 17

Nuclei, Chloroplasts, Mitochondria, Lysosomes, Endoplasmic Reticulum, Ribosomes

Question 18

What does the cells surface membrane do and what does it consist of?

Answer 18

Surrounds all cells; Controls exchange of materials between internal and external environment; Partially permeable; Consists of a phospholipid bilayer

Question 19

What does the cells wall do and what does it consist of?

Answer 19

Formed outside of cell membrane; Offer structural support to cell; Polysaccharide cellulose in plants, peptidoglycan in bacteria cells

Question 20

What are the parts of a nucleus?

Answer 20

Nucleolus, chromatins, nucleoplasm, nuclear pores, nuclear envelope,

Question 21

What does the nucleus do?

Answer 21

Contains genetic material; Contains instructions for protein synthesis; Nuclear envelope, double membrane that surrounds the nucleoplasm and has pores; Nuclear pore channels allow mRNA, ribosomes to leave nucleus and enzymes, signaling molecules to enter; Nucleolus, dark spot, sites of ribosome production

Question 22

What is a chromatin?

Answer 22

Complex of DNA and histone proteins

Question 23

What are chromosomes?

Answer 23

Sections of linear DNA tightly wound around histone proteins

Question 24

What are the parts of mitochondria and what are its functions?

Answer 24

Inner membrane, cristae, matrix, outer membrane; Site of aerobic respiration; Surrounded by double membrane, inner membrane folded to form cristae; Matrix formed by cristae contains enzymes for aerobic respiration, producing ATP; Mitochondrial DNA, ribosomes are found in matrix

Question 25

What is the structure of Chloroplast?

Answer 25

Surrounded by double membrane; Membrane bound components, thylakoids containing chlorophyll stack to form grana; Grana joined by lamellae; Light-dependant stages in thylakoids; Light-independent stages in stroma; Chloroplast DNA; Starch granules; Ribosomes; Drops of lipids

Question 26

What is the purpose of chloroplast?

Answer 26

Site of photosynthesis; Light energy used to derive carbohydrate molecules from carbon dioxide

Question 27

Describe ribosomes and their purpose.

Answer 27

Site of translation; Found freely in cytoplasm of cells or part of RER in eukaryotic cells; Ribosomes are a complex of ribosomal RNA and proteins; Eukaryotic cells - 80s; Prokaryotes, mitochondria and chloroplasts - 70s

Question 28

Describe the structure of the endoplasmic reticulum?

Answer 28

Consists of flattened membrane-bound sacs; Rough endoplasmic reticulum; Smooth endoplasmic reticulum

Question 29

Describe the structure and purpose of the rough endoplasmic reticulum.

Answer 29

Surface covered in ribosomes; Formed from continuous folds of membrane, continues from nuclear envelope; Process proteins made by ribosomes

Question 30

Describe the structure and purpose of smooth endoplasmic reticulum.

Answer 30

No ribosomes on surface; Involved in production, processing and storage of lipids, carbohydrates and steroids

Question 31

Describe the structure and purpose of the golgi apparatus.

Answer 31

Flattened sacs of membranes; Modifies protein and lipids before packaging them into golgi vesicles; Vesicles transport protein and lipids to destination

Question 32

Describe structure of the large permanent vacuole.

Answer 32

Sac in plant cells surrounded by tonoplast; Selectively permeable membrane; Vacuoles in animal cells are not permanent and are small

Question 33

Describe purpose and structure of vesicles.

Answer 33

Membrane bound sac for transport and storage;

Question 34

Describe the structure and purpose of lysosomes.

Answer 34

Specialist vesicles; Contains hydrolytic enzymes (break biological molecules down); Breaks down waste material; Used by immune system cells and in apoptosis (programmed cell death)

Question 35

Describe the structure of centrioles.

Answer 35

Hollow fibres made of microtubules; 2 centrioles at right angle to each other, form centrosomes; Organise and form spindle fibres in cell division; Not in flowering plants and fungi

Question 36

Describe the structure of microtubules.

Answer 36

Cytoskeleton of cell, provide support and movement; Made of α and β tubulin combine forming dimers; Dimers join into protofilaments; 13 protofilaments in cylinder makes a microtubule

Question 37

Describe the purpose of microtubules.

Answer 37

Cell membrane projections, increase surface area for absorption

Question 38

Describe the purpose of cilia.

Answer 38

Hair-like projections made from microtubules; Allows movement of substances over cells

Question 39

Describe the purpose of flagella.

Answer 39

Made from longer microtubules; Contract to provide cell movement

Question 40

What is a tissue?

Answer 40

Collection of cells that perform a specific function

Question 41

What is an organ?

Answer 41

Combination of tissues that are coordinated to perform a variety of functions

Question 42

Which organelles are always in prokaryotes and which organelle are sometimes in prokaryotic cells?

Answer 42

Always: Cell wall (murein) , cell surface membrane, cytoplasm, circular DNA, ribosomes;
Sometimes: Flagella, capsule, plasmid, pili

Question 43

How are prokaryotic cells different to eukaryotic cells?

Answer 43

Smaller; Cytoplasm lacks membrane bound organelle; Ribosomes 70s; No nucleus, circular DNA instead; Cell wall made of murein; Binary fission

Question 44

Describe the structure of viruses.

Answer 44

Acellular non-living infectious particles; Smaller than prokaryotes; Nucleic acid core; Capsid, protein coat; Membrane phospholipid envelope; Parasitic

Question 45

What is mitosis?

Answer 45

Cell division forming 2 genetically identical daughter cells

Question 46

What are the phases of mitosis?

Answer 46

Prophase, metaphase, anaphase, telophase

Question 47

What occurs in interphase?

Answer 47

Cell increases in mass & size; 3 phases G1 - cell makes RNA , enzymes and other proteins needed for growth, S - nucleus DNA replicates, G2 - cell continues to grow and DNA is checked;

Question 48

What are the phases of the cell cycle?

Answer 48

Interphase, nuclear division, cytokinesis

Question 49

What occurs in prophase?

Answer 49

Chromosomes condense (visible when stained); Sister chromatids join at centromere; 2 centrosomes move to opposite poles; Spindle fibres begin to emerge from centrosomes; Nuclear envelope breaks down into small vesicles

Question 50

What are sister chromatids?

Answer 50

2 identical chromatids that make up chromosomes

Question 51

What occurs in metaphase?

Answer 51

Centrosomes reach opposite poles; Spindle fibres continue to extend from centrosomes; Chromosomes line up at equator of spindle; Spindle fibres attach to centromeres of chromosomes; Each sister chromatid is attached to spindle fibre from opposite poles

Question 52

What occurs in anaphase?

Answer 52

Sister chromatids separate at centromere; Spindle fibres shorten; Separated sister chromatids (now chromosomes) are pulled to opposite poles

Question 53

What occurs in telophase?

Answer 53

Chromosomes arrive at opposite poles, begin to decondense; Nuclear envelope forms around each set of chromosomes; Spindle fibres break down

Question 54

What occurs in binary fission?

Answer 54

Circular DNA molecule undergoes replication; Plasmids undergo replication; Parent cell divides into 2 cells w/ cytoplasm halved; Daughter cells have 1 copy of circular DNA and a variable number of plasmids