Cell Structure

Question 1

What are the four types of microscopes?

Answer 1

light microscopes, transmission electron microscopes, scanning electron microscopes and laser scanning confocal microscopes

Question 2

adv and dsv of light microscope

Answer 2

bad resolution because of long light wavelength
living samples can be examined and a colour image can be seen

Question 3

how does transmission electron microscope work

Answer 3

high magnification and resolution as electron gun creates electron beam which is focused by an electromagnet which then passes through the thin layer of sample to create a 2d image. Some parts of the sample absorbs the electron making them darker

Question 4

how does a scanning electron microscope work

Answer 4

high magnification and resolution. sample doesn’t have to be thin.
electrons bounce off the surface of the sample based on the contours to create a 3d image

Question 5

how does a laser scanning confocal microscope work

Answer 5

high resolution and 3d imaging
a laser light with a high light intensity is used to illuminate sample that has been stained with a fluorescent dye

Question 6

resolution definition

Answer 6

the minimum distance between two objects where they can still be distinguished as separate. resolution is determined by wavelength of either light or beam of electrons depending on the microscope used

Question 7

magnification definition

Answer 7

how many times larger the image is compared to the object

Question 8

what are the four types of slide preparation for light microscopes

Answer 8

dry mount, wet mount, squash slide and smear slide

Question 9

what is dry mount prep

Answer 9

when a thin slice or whole specimen is viewed with a cover slip on top

Question 10

what is wet mount prep

Answer 10

when water or a stain is added to a specimen before putting the cover slip on with a mounted needle to prevent air bubbles

Question 11

what is squash slide prep

Answer 11

are wet mounts however you push down on the cover slip to squash sample to make it thinner to enable light to pass through

Question 12

what is smear slide prep

Answer 12

use the edge of another slide to smear the sample across to create a smooth thin evenly distributed layer of sample. place a cover slip on top. e.g. examining blood cells

Question 13

what is differential staining

Answer 13

the use of many chemical stains being used to stain different parts of a cell in different colours

Question 14

how does differential staining work

Answer 14

the positively charged stains (crystal violet or methylene blue) are attracted to and stain negatively charged components of the cell.
the negatively charged stains (nigrosin and congo red) can’t enter the cells as cytosol (liquid part of cytoplasm) repels them creating a stained background so the unstained cells stand out

Question 15

what is gram staining used for

Answer 15

used to identify types of bacteria.

Question 16

what are the stains used in gram staining

Answer 16

crystal violet and safranin

Question 17

how does gram staining work

Answer 17

crystal violet is added then iodine to fix the stain. alcohol is used to wash away any stain that didn’t bind. gram positive bacteria turn purple/blue as they have a thick peptidoglycan cell wall which absorbs dye. gram negative bacteria don’t absorb the dye as they have thin cell walls that don’t retain the dye. So safranin is used as a counter stain turning them red.

Question 18

why do electron microscopes have a high resolution

Answer 18

because they have a short wavelength

Question 19

how are the images created in electron microscopes

Answer 19

an electromagnet focuses the beam of electrons to create image

Question 20

why can only non-living samples be examined in an electron microscope

Answer 20

electrons are absorbed by air so the sample has to be in a vacuum so that the air doesn’t absorb the electrons. living things can’t survive in a vacuum

Question 21

what are the 13 organelles in a eukaryotic cells

Answer 21

cell-surface membrane, nucleus, mitochondria, choroplasts, golgi apparatus and golgi vesicles, lysosomes, cytoskeleton, centriole, flagella, cilia, ribosomes, rough and smooth endoplasmic reticulum and cell wall

Question 22

what does the nucleus contain

Answer 22

has a nuclear envelope surrounding it with a double membrane structure. has nuclear pores for the mRNA to move out of it. The DNA wraps around the proteins creating chromosomes, linear in shape.
nucleolus- small sphere inside where rRNA and ribosomes are created.

Question 23

function of nucleus

Answer 23

-site of DNA replication and making mRNA
-contains genetic code for each cell
-site of ribosome synthesis in the nucleolus

Question 24

what is flagella

Answer 24

found on some eukaryotic cells
whip like structure
used for mobility

Question 25

what is cilia

Answer 25

hair like projections either stationery or mobile mobile cilia help sweep substances along stationery cilia are used in sensory organs (nose)

Question 26

what are centrioles

Answer 26

made of microtubules they are in pairs to form a centrosome produces spindle fibre which organises chromosomes in cell division

Question 27

What is the cytoskeleton, and its role in cells?

Answer 27

The cytoskeleton is a network of fibers providing mechanical strength, maintaining cell shape, and holding organelles in place. It includes microfilaments, microtubules, and intermediate fibers.

Question 28

What is the endoplasmic reticulum, and its two types?

Answer 28

The endoplasmic reticulum (ER) consists of folded membranes called cisternae. Rough ER (RER) has ribosomes and is involved in protein synthesis, while smooth ER (SER) synthesizes lipids and carbohydrates.

Question 29

What is the Golgi apparatus's function?

Answer 29

The Golgi apparatus processes, modifies, and packages proteins, transports/stores lipids, and creates lysosomes. Secretory vesicles release proteins via exocytosis.

Question 30

What are lysosomes and their function?

Answer 30

Lysosomes are vesicles containing digestive enzymes that hydrolyze bacteria, break down dead cells, and release their contents outside the cell after digestion.

Question 31

What is the structure and function of mitochondria?

Answer 31

Mitochondria have a double membrane with folded inner membranes (cristae) and a fluid center (matrix). They are the site of aerobic respiration and ATP production, containing their own DNA and ribosomes.

Question 32

What are ribosomes and their function?

Answer 32

Ribosomes are made of two subunits of protein and RNA. In eukaryotic cells, they are 80S ribosomes, and in prokaryotes, they are smaller 70S ribosomes. They are the site of protein synthesis.

Question 33

What are chloroplasts, and where are they found?

Answer 33

Chloroplasts are found in plant cells. They have a double membrane, thylakoids (stacked into grana), and fluid (stroma) for photosynthesis.

Question 34

What are the differences in cell walls between plants and fungi?

Answer 34

Plant cell walls are made of cellulose for structural strength, while fungal cell walls are made of chitin, a nitrogen-containing polysaccharide.

Question 35

What is the plasma membrane and its function?

Answer 35

The plasma membrane is made of a phospholipid bilayer with embedded proteins and cholesterol. It controls what enters and exits the cell and regulates the permeability.

Question 36

What is the pathway for protein production and secretion?

Answer 36

Proteins are synthesized in the RER, folded and packaged into vesicles, sent to the Golgi apparatus for modification, and transported in vesicles to the cell membrane for exocytosis.

Question 37

What are the main differences between prokaryotic and eukaryotic cells?

Answer 37

Prokaryotic cells are smaller, lack membrane-bound organelles, have circular DNA (not in a nucleus), 70S ribosomes, and a cell wall made of murein.

Question 38

What are plasmids, and where are they found?

Answer 38

Plasmids are additional loops of DNA in prokaryotes, carrying genes like antibiotic resistance. Not all bacteria have plasmids, and they vary in number.

Question 39

What is the function of a capsule in bacteria?

Answer 39

The capsule is a slimy layer made of protein that prevents desiccation and helps hide the bacteria from the host's immune system by covering antigens.

Question 40

What is the role of the flagellum in bacteria?

Answer 40

The flagellum is a rotating structure used for bacterial movement. Some bacteria have one or multiple flagella, while others may have none.