A2.2 cell structure

Question 1

magnification
resolution

Answer 1

how many times a specimen has been enlarged
how clean specimen is shown

Question 2

what is magnification

Answer 2

increase of an objects image size compares to its actual size
equation= magnification= measures image size/ actual specimen size

Question 3

light microscope

Answer 3

visible light passing through living or dead specimens
can be stained or tagged

Question 4

electron microscope

Answer 4

use electrons passing through a specimen to form an image

Question 5

differences between light and electron microscope

Answer 5

LIGHT ELECTRON
cheap expensive
easy specimen preparation complex specimen preparation
lower resolution and enlargement much higher resolution and enlargement
specimens may be living or dead specimens are dead in fixed material
can be stained, tagged has two types; SEM, TEM

Question 6

how electron microscopes work

Answer 6

electrons have a shorter wavelength than light
-electrons absorbed by denser parts of sample
and when picked up by electron detector, forms an image
-only dead specimens and only produced in black and white

Question 7

SEM and TEM microscopes

Answer 7

SEM (scanning( TEM (transmission)
-beam of electrons beams of electrons through thin sections
scanning surface of specimen view of inner structure
-3D -2D
-higher resolution

Question 8

techniques used in electron microscopy

Answer 8

1) Freeze fracture microscopy
= freezing sample, using specialized tool to break sample into smaller pieces, which are observed under microscope to see internal structure. It it used to visualize structures like internal plasma membranes

2)cryogenic electron microscopy
= freezing specimen in ice, to stabilize molecules and uses computer enhancement

Question 9

techniques used in light microscopy

Answer 9

1) immunofluorescence
=involves antibodies that have dyes already combined with them and these specific antibodies combine with specific antigens on a structure being used. When antibody bring antigen, structure is ‘tagged,’ with immunofluorescence, and will emit light when irradiated, making bright colours

2) fluorescent dyes/stains
=dyes that combine with specific cellular components, when irradiated the parts that accept the dye will fluoresce. colors produce more visibility

Question 10

structures common to all cells

Answer 10

1) DNA as genetic material
-includes genes that code for proteins

2) cytoplasm- water based suspension where metabolic reactions occur

3) a plasma membrane, composed of phospholipid bilayer

Question 11

prokaryotic cells

Answer 11

-smaller and simpler than eukaryotic cells
-lack nucleus
-non-compartmentalized
-70s ribosomes
-naked DNA in a loop
-lack membrane bound organelles

Question 12

list of features of a prokaryotic cell

Answer 12

-cell wall
-plasma membrane
-flagella
-pili
-ribosomes
-the nucleiod

Question 13

cell wall and plasma membrane in prokaryotic cells

Answer 13

cell wall:
structure= carb-protein
function=
-protects and maintains shape
-keeps cell from rupturing

plasma membrane:
-found just inside cell wall
-controls movement of materials in and out of cell, and plays a role in binary fission

Question 14

gram positive and gram negative

Answer 14

• a way to classify bacteria is their ability to retail a crystal violet dye
  gram positive= bacteria that have cell walls that have a violet appearance when exposed to crystal violet. E.G: bacillus and staphylococcus

gram negative= bacteria do not retain this dye and do not appeal violet

Question 15

Pilli and flagella in prokaryotic cells

Answer 15

Pilli=
-hair-like growths on the outside of the cell wall.
-used for attachment and joining bacterial cells in preparation for sexual reproductions

Flagella=
-longer than pilli
-allow cell to move and are anchored to cell wall and plasma membrane

Question 16

ribosomes in prokaryotic cells

Answer 16

-small structures and occur in large numbers
-site of protein synthesis
-70s

Question 17

the nucleoid region in prokaryotic cells

Answer 17

-non compartmentalized and contains long, continuous thread of DNA.

Question 18

plasmids in prokaryotic cells

Answer 18

bacteria may also contain plasmids
-small, circular DNA molecules not connected to main bacterial chromosome
-replicate independently
-can help bacteria adapt to unusual circumstances

Question 19

what is binary fission and steps

Answer 19

simple way that prokaryotic cells divide. During this process, DNA is copied resulting in two daughters chromosomes, that attach to different regions of the plasma membranes. The cell elongates using specialized fibers and divides to form two genetically identical daughter cells.

Question 20

features of eukaryotic cells

Answer 20

common to all:
-nucleus-double membrane with pores
-80s ribosomes
-mitochondria

(non membrane bound=)
cytoskeleton= fibers that support organelles
ribosomes=makes proteins, can be free or attached to ER

(membrane bound=)
-nucleus (with nucleoid)
-endoplasmic reticulum(rough and smooth)
-golgi apparatus
-mitochondria
-chloroplast
-vacuole
-lysosomes
-centrosomes

Question 21

differences in organelles in eukaryotic cells

Answer 21

ONLY IN ANIMALS: -lysosomes, centrosomes, cilia, flagella
ONLY IN PLANTS: -chloroplast, cell wall, central vacuole

Question 22

cytoplasm

Answer 22

-region all organelles are found
-made from cytosol
-contain cytoskeleton

Question 23

cytoskeleton

Answer 23

are fibers made of proteins that provide functions like:
1) maintaining cell shape
2) anchors some organelles
3)helps cellular movement

it contains three types:
1) acting filament- functions in cell division and cell movement
2) intermediate filament- reinforces cell shape and anchors some organelles
3) microtubules- shape and supporting cell

Question 24

endoplasmic reticulum

Answer 24

-extensive channel of networks extending all over cell
-participants in protein and lipid synthesis
-processes and transports molecules for cell
-can be found free or on ER

rough=protein producing and transporting, sends them in vesicles
smooth= had additional roles like; -detoxification
-lipid synthesis

Question 25

ribosomes

Answer 25

-dont have exterior membrane
-conduct protein synthesis in a cell
-can be found free or attached to ER
-composed of a type of RNA + protein
-larger and denser than in prokaryotic
-80S in eukaryotic

Question 26

golgi apparatus

Answer 26

flattened sacs called cisternae, stacked on one another
-processes and packages protein and lipid molecules
-sends around or out of cell.

-one side of the apparatus is near the rough ER called the CIS side , it receives the products from ER, then they move into the apparatus
-they move to the opposing side called the TRANS side

Question 27

mitochondria

Answer 27

-they have their own DNA, allowing independence in the cell
-reactions of aerobic respiration take place
-had folded inner membrane
-cristae provides larger surface area of chem reactions
-‘‘powerhouse of cell’

Question 28

nucleus

Answer 28

-bordered by a double membrane (envelope) which allows compartmentalization
- contains nuclear pores
-DNA in form of chromosomes in eukaryotic
NUCLEIOI= where ribosome molecules are manufactured here and pass through nuclear envelop before assembling ribosomes

Question 29

chloroplast

Answer 29

-only found in plants and algae
-contains a double membrane
-contains DNA (in form of rings) and 70s ribosomes
-the interior contains granum, thylakoids and stroma

Question 30

centrosomes

Answer 30

only found in animal cells
-consist of pair of centrioles and right angles
-involved in assembly of microtubes which are important for providing structure and cell division
-located at one end of nucleus

Question 31

lysosomes

Answer 31

only found in animal cells
-are digestive centers that arise from Golgi apparatus
-does not have internal structures
-contains lots of enzymes
-‘‘recycling components’

Question 32

vacuoles

Answer 32

-usually formed in Golgi apparatus
-membrane bound
-in plants occupies large space
-in animals there are many small ones

Question 33

simple summary of functions of each organelle

Answer 33

nucleus= contains the DNA
nucleolus= makes ribosome molecules
mitochondria=releases the energy
chloroplast= convert sunlight to sugar
ribosomes= makes proteins
ER= carries proteins/lipids/minerals in pathway
golgi apparatus= packages and ships proteins
lysosomes= breaks stuff down
cell wall= protects/supports cell
cell membrane= controls what enters/ exits
vacuole= storage
cytoplasm=fluid holding organelles
flagella= movement

Question 34

differences in prokaryotic and eukaryotic cells

Answer 34

PROKARYOTIC:
-DNA in forms of rings with no proteins
-DNA free in cytoplasm
-no mitochondria
-70s ribosomes
-no internal compartmentalization
-smaller
EUKARYOTIC:
-DNA with proteins as chromosomes
-DNA is enclosed within nuclear envelope
-mitochondria present
-80s ribosomes
-internal compartmentalization
-larger

Question 35

processes of life

Answer 35

ALL ORGANISMS ( MULTI OR UNI ) CARRY OUT THESE FUNCTIONS OF LIFE:

1) metabolism- sum of all chem reactions occurring within an organism
2)growth- development of an organism
3)-reproduction- ability to produce offspring
4)responding to stimuli- as environment changes, so does organism
5)homeostasis- maintenance of internal conditions
6) nutrition- ability to aquire energy/materials needed for life
7)excretion- releasing materials not needed/harmful into environment
8)movement-ability to move/change positions

Question 36

ways that unicellular organisms carry out life functions

Answer 36

homeostasis= cell membrane controls movement of what comes in and out
excretion= vacuoles store waste
response to stimuli= cilia, flagella allow movement
nutrition= vacuoles carry out digestion
growth= ribosomes provide building blocks for growth

Question 37

differences in structure of animals, plant and fungal cells

Answer 37

CELL WALLS
Animal cell do not have a cell wall
Plant cell walls are composed of the polysaccharide cellulose
Fungal cell walls are made up mainly of glucans, chitin and glycoproteins

VACUOLES
present in animal cells but they tend to be small, numerous
Plant cells have large permanent vacuoles used for the storage
Like animal cells, fungal cells can contain vacuoles but they are small and non-permanent

CHLOROPLASTS
Animal cells do not have chloroplasts
Plant cells possess many chloroplasts
Fungal cells do not have chloroplasts

CENTROILES
Animal cells contain centrioles used in the role of microtubule organisation during cell division
Plant cells do not possess centrioles
Fungal cells do not possess centrioles

CILIA/FLAGELLA
Animal cells can have cilia and flagella, associated with a basal body (a protein structure from which the cilia are assembled),
Plant cells do not contain cilia or flagella
fungi do not contain cilia or flagella

Question 38

Atypical cell structures

Answer 38

exception of cells theory:

1)skeletal muscle fibers- groups of cells fuse together to form fibres that are multinucleate with limited nuclear membrane resulting in multiple nuclei

2) phloem tissue- transporting dissolved substances around plant and has no nuclei or mitochondria and supported by companion cell

3) fungal hyphae- Fungi have many long, narrow branches called hyphae. cells are multinucleated with continuous cytoplasm ad cell divides nucleus but doesn’t undergo cytokinesis. No end cell wall makes it appear as one

4) red blood cells- no nucleus=larger volume for oxygen binding

Question 39

theory of endosymbiosis

Answer 39

theory that all eukaryotic cells evolved from a common unicellular ancestor that had a nucleus and reproduced sexually and engulfed the smaller prokaryotes (mitochondria and chloroplast) that could create energy via endocytosis
EVIDENCE:
-same size as most bacterial cells
-can divide by simple binary fission
-has their own DNA which is naked and circular and produce their own ribosomes
-has a double membrane
-has their own transcription and translation

Question 40

differentiation of cells

Answer 40

Every nucleus within the cells of a multicellular organism contains the same genes. because of this, they have a diverse range of functions because during differentiation certain genes are expressed (‘switched’ on)
Whether a gene is expressed or not is triggered by changes in the environment

Question 41

atypical definition

Answer 41

cells that have an abnormal feature not found in usual cells