topic 1 cell structure

Question 1

light microscope resolution and magnification max

Answer 1

-resolution- 0.2um
- mag - x1500

nucleus and mitochondria can be seen

Question 2

methods for sample prep

Answer 2

-dry mount - specimen placed directly
- squash slides - wet mount is prepared and cover slip is pressed to squash cells
- smear slides- edge if slide is used to smear sample to create thin even coating
- wet mount- small drop of water in centre of glass slide, forceps is used to place thin layer of specimen onto water, few drops of stain, cover slip

Question 3

what is differntial staining

Answer 3

using more than one chemical stain

Question 4

using light microscope

Answer 4

-clip microscope slide onto stage
- select objective lens to lowest power
- use coarse focus to bring the stage just below the objective lens
- look down eyepiece and use the coarse focus to move stage downwards until image is roughly in focus
- use fine focus to make image clearer
- if a higher magnification is needed swap to a more powerful objective and refocus

Question 5

what to include in biological drawings and what not to

Answer 5

✅title
✅magnification or scale
✅sharp pencil
✅smooth continuous lines
✅include labels
✅include accurate sizes of observable structures
❌shading or colouring
❌arrowhead for labels
❌lines overlapping

Question 6

magnification

Answer 6

how many times larger an image is than the object

Question 7

resolution

Answer 7

the ability to distinguish between two separate points

Question 8

image size

Answer 8

how large the object appears when you view it through a microscope

Question 9

magnification formula

Answer 9

image size/ object size

Question 10

cm to mm

mm to um

um to nm

Answer 10

x10

x1000

x1000

Question 11

nm to um

um to mm

mm to cm

Answer 11

➗1000

➗1000

➗10

Question 12

eyepiece graticule

Answer 12

small scale placed within the eyepiece used to measure length or width of a specimen

Question 13

a stage micrometer

Answer 13

used to calibrate the eyepiece graticule and is a glass slide with a scale measured in um

Question 14

how to graticule is calibrated

Answer 14

• fix the stage micrometer into place on the stage
• look through the eyepiece to line up the micrometer and the graticule
• count the number of graticuke divisions that fit into one micrometer divison
• use the formula to calculate the size of each graticule division at that magnification

graticule division = size of one micrometer division / number of graticule divisons

Question 15

2 types of electron microscope

Answer 15

• transmission electron microscope (TEM)
• scanning electron microscope (SEM)

Question 16

TEMs

Answer 16

-use electromagnets to transmit electrons through a specimen. the denser parts absorb more electrons so appear darker in the image formed
- specimen must be viewed in a vaccum
- specimen must be thin
- resolution - max of around 0.5um
- magnification- max of around x1 500 000

Question 17

SEMs

Answer 17

-scan a beam of electrons across the surface of a specimen. reflected electrons are used to form an image
- produce 3D images of the surface of specimen
- only view non living or dead specimen
- can view thicker specimen
- requires specimen to be coated in a metal ( leads to artifacts)
- max resolution 5nm
-max mag 1500 000

Question 18

laser confocal microscopy

Answer 18

-a type of fluorescence microscopy
-uses a laser bean to scan a specimen that has been tagged with a fluorescent dye. the dyed components give off light which is focused through a pinhole and onto a detector.the detector is connected to a computer which generates an image. it can be 3D
- less resolution than electron but more than light
- can be used to look at different depths within a specimen and living

Question 19

nucleus

Answer 19

-contains genetic info in the form of chromosomes
-contains structure known as a nucleolus surrounded by nuclear envelope containing pores
-controls cells activities
-synthesis of ribosomes
-exchange between nucleus and cytoplasm

Question 20

cell surface membrane

Answer 20

• found on the surface of animal cells
• mainly made up of lipids and proteins
• controls movement of substances into and out of the cell
• partially permeable
• cell signalling

Question 21

mitochondria

Answer 21

double membraned organele where aerobic respiration takes place and ATP is produced
mitochondria is made up of
-outer membrane - controls the entry and exit of materials
-inner membrane - folded into cristae to increase surface area for respiration enzymes.Cistae project into liquid matrix.It is coated with enzymes which catalyse aerobic respiration reactions to produe ATP.
-matrix- the central space containing enzymes for the Krebs cycle, mitochondrial DNA, and ribosomes.

Question 22

ribosmes

Answer 22

-ribosomes are the site of protein synthesis and is involved in the process of translation.They are composed of rRNA and proteins and are found either free in the cytoplasm or attached to the rough endoplasmic reticulum.
-ribosomes consist of 2 subunits (large and small) that come together during protein synthesis
-ribosomes read the mRNA sequence during translation to assemble amino acids into a polypeptide chain, creating proteins
-free ribosomes synthesize proteins used within the cell
ribosomes on the RER synthesize proteins for secretion or for use in membranes
-not surrounded by a membrane

Question 23

golgi apparatus

Answer 23

the golgi apparatus is composed of fluid filled, flattened membrane bound sacs (cisternae).Also contains smaller vesicles
-modifies proteins and lipids recieved from the endoplasmic reticulum, sorts them and packages them into vesicles for transport
-essential for secretion of hormones, enzymes and other molecules

Question 24

rough endoplasmic reticulum

Answer 24

-The RER is contains a network of membranous sacs called cisternae and tubules and have ribosomes attached to the outer surface enabling protein synthesis
-synthesizes proteins
-proteins enter the RER lumen for folding and initial modifications
- packages proteins into vesicles for transport to the Golgi apparatus

Question 25

smooth endoplasmic reticulum-

Answer 25

-SER has same structure as RER without ribosomes - synthesizes, stores and transports lipids and carbohydrates

Question 26

lysosomes

Answer 26

-contains hyrolytic enzymes - surrounded by a membrane to keep enzymes separate from the cytoplasm of the cell - digests invading cells and breaks down waste material

Question 27

cytoskeleton

Answer 27

-a network of protein fibres in eukaryotic cells that provides structural support and facalitates movement and transport -made up of : -microfilaments - made of 2 interwined strands of a globular protein actin which wors with motor protein called myosin ,involved in cell shape and movement.They can disassemble and reform quickly, allowing the cell to change its shape and move.provides rigidity. involved in cell movement and locomotion such as crawling and muscle contraction.Thicken the cortex around the the inner edge of a cell and like rubber bands they resist tension. Narrowest of the protein fibres in the cytoskeleton -intermediate filaments- made of several strands of fibrous proteins that are wound together. provide mechanical strength and shape. has no role in cell movement.They bear tension maintaining the shape of the celland anchor organelles in place.THey are found throughout the cell -microtubules - hollow tubes made of tublin, important for maintaining cell shape, intracellular transport, and cell division.They form  scaffold like struuctres throughout the cell.They form the main component of the mitotic spindle used for cell divisioon.The widest component.Can dissamble and reform quickly.act as tracks for intracellular transport of vesciles and oeganelles.found in the interior of the cell where they maintain cell shape by resisting compressive forces.microtubules are structural elements in cilia flagella and centrioles

Question 28

cell wall

Answer 28

-a rigid outer layer surrounding the cell membrane in plats, fungi, bacteria, and some protists -made of mainly polsacharide cellulose held together by hydrogen bonds in plants (plants) can act as a carbohydrate store by varing amount of cellulose it holds.contains gaps/channels called plasmodesmata.prevents cell from bursting( cell wall can withstand high osmotic pressure) -made of mainly chitin in fungi -made of mainly peptidoglycan (composed of sugars and amino acids) in bacteria -maintains cell shape and resists internal pressure (structural support) -acts as a physical barrier

Question 29

chloroplasts

Answer 29

-outer membrane- permeable to small molecules -inner membrane - selective, regulates substance passage -thylakoids- flattened sacs where light dependent resctions occur, stacked in gana ( linnked by lamellae) and contain chlorophykll -stroma- gel like matrix where light dependent reactions occur, contains enzymes, ribosomes, and chloroplast dna -has starch grains  -site of photosynthesis

Question 30

vacuole

Answer 30

surrounded by a tonoplast ( selectively permeable membrane) filled with cell sap which includes water, ions,sugars, enzymes,and sometimes pigments helps maintain pressure within the cell and stops the plant from wilting

Question 31

centrioles

Answer 31

-cylindrical structures found in animal cels, crucial for cell division and microtuble organisation -made up of 9 parallel microtubles that surround a central cavity -usually found in pairs called centrosomes and arranged at right angles near the nucleus - only found in isolation when in the basal regions of flagella and cilia -not surrounded by a membrane -part of the cytoskeleton -small tubes of protein fibres (microtubles) -organise the spindle fibres that seperate chromosomes during mitosis and meiosis -assist in forming the mitotic spindle for chromosome movement -serve as basal bodies for the development of cilia and fkagella, aiding in cell movement

Question 32

amyoplasts

Answer 32

a type of plastid stores starch found primarily in plant cells and some algae

Question 33

flagella

Answer 33

-a long whip like structure that extend from he surface of certain cells used for locomotion in cells -made of a 9 + 2 microtuble arrangement (9 pairs of microtubles surrounding a  central pair of microtubles) -all of the microtbles are made from the protein tubulin -bacterial flagella are helical( coil shape) and are mainly made up of the protein flagellin -propel cells trhough fluids via a whip like motion  -powered by motor proteins like dynein

Question 34

pili

Answer 34

short hair like structures on the cell surface of prokaryotic cells to attach to other cells or surfaces

Question 35

capsule

Answer 35

extra later around the cell wall made up of polysaccharides and protects the cell from attack by antibiotics or white blood cells

Question 36

2 categories of bacteria

Answer 36

gram positive gram negative

Question 37

gram positive bacteria

Answer 37

thicker cell wall 1 lipid membrane

Question 38

gram negative bacteria

Answer 38

thin cell wall 2 lipid membranes

Question 39

explain why the counter stain turns gram negative pink/red

Answer 39

-the iodine treatment sticks to cell walls - gram negative turns colorless when decolurised using ethanol bcs the iodine was not able to get to the cell wall but was able to get to the gram positive -the counterstain turns gram negative pink red bccs their thinner inner cell walls and lipid membranes allow ethanol to wash off all the crystal violet purple stain and retain the pink saffrin stain

Question 40

centrioles

Answer 40

Component of the cytoskeleton present in most eukaryotic cells. Small hollow cylinders containing microtubules. Two associated centrioles form the centrosome, which is involved in the assembly and organisation of the spindle fibres, and therefore the splitting chromosomes during cell division. Structure = sets of three microtubules with one in the center.