T1 cell structure

Question 1

two types of cells

Answer 1

eukaryotic (plant and animal)

prokaryotic (bacteria)

Question 2

differences between eukaryotic and prokaryotic cells?

Answer 2

P - smaller

E - contain membrane bound-organelles and nucleus containing genetic material

Question 3

what is the prokaryotic cell wall composed of?

Answer 3

peptidoglycan

Question 4

how is genetic information stored in a prokaryotic cell?

Answer 4

found free within cytoplasm as:
chromosomal DNA (single large loop of circular DNA)
plasmid DNA

Question 5

what are plasmids?

Answer 5

small, circular loops of DNA found free in cytoplasm and separate from the main DNA

carry genes that provide genetic advantages

Question 6

order of magnitude?

Answer 6

power to the base 10 used to quantify and compare size.

Question 7

list the components of both plant and animal cells

Answer 7

nucleus
cytoplasm
cell membrane
mitochondria
ribosomes

Question 8

list additional cell components found in plant cells

Answer 8

chloroplasts
permanent vacuole
cell wall

Question 9

other than storing genetic information, what is the function of the nucleus?

Answer 9

controls cellular activities

Question 10

describe the structure of the cytoplasm

Answer 10

fluid component of the cell

contains organelles, enzymes and dissolved ions and nutrients.

Question 11

function of the cytoplasm

Answer 11

site of cellular reactions

transport medium

Question 12

function of the cell membrane

Answer 12

controls the entry and exit of materials into and out of the cell

Question 13

function of the mitochondria

Answer 13

site of later stages of aerobic respiration in which ATP is produced

Question 14

function of the ribosomes

Answer 14

joins amino acids in a specific order during translation for the synthesis of proteins.

Question 15

what is the plant cell wall made of

Answer 15

cellulose

Question 16

function of the plant cell wall

Answer 16

provides strength

prevents the cell bursting when water enters by osmosis

Question 17

what does the permanent vacuole contain?

Answer 17

cell sap (solution of salts, sugars and organic acids)

Question 18

function of the permanent vacuole

Answer 18

supports the cell, maintaining its turgidity.

Question 19

function of the chloroplasts

Answer 19

site of photosynthesis

Question 20

describe how sperm cells in animals are adapted to their function

Answer 20

haploid nucleus - contains genetic information

tail - enables movement

mitochondria - provides energy for tail movement

acrosome - contains enzymes that digest the egg cell membrane

Question 21

describe how nerve cells in are adapted to their function

Answer 21

long axon - allows electrical impulses to be transmitted all over the body from CNS

dendrites - from the cell body connect to and receive impulses from other nerve cells, muscles and glands

myelin sheath - insulates axon and speeds up the transmission of impulses along the nerve cell

Question 22

describe how muscle cells are adapted to their function

Answer 22

arrangement of protein filaments - allows them to slide over each other to produce muscle contraction

mitochondria - provides energy for muscle contraction

merged cells in skeletal muscle - allow muscle fibre contraction in unison.

Question 23

describe how root hair cells in plants are adapted to their function

Answer 23

large surface area - absorbs nutrients and water from surrounding soil

thin walls - don’t restrict water absorption.

Question 24

describe how xylem are adapted to their function

Answer 24

no upper or lower margins between cells - provide a continuous route for water to flow

thick, woody side walls - strengthen their structure and prevent collapse

Question 25

describe how phloem cells are adapted to their function

Answer 25

sieve plates - let dissolved amino acids and sugars be transported up and down the stem companion cells - provide energy needed for active transport of substances along the phloem

Question 26

what is cell differentation

Answer 26

process by which cells become specialised

Question 27

why is cell differentiation important

Answer 27

allows production of different tissues and organs that perform various vital function in the human body

Question 28

At what point in their life cycle do most animal cells | differentiate?

Answer 28

early in their life cycle

Question 29

how long do plant cells retain the ability to differentiate?

Answer 29

throughout their entire life cycle

Question 30

purpose of cell division in mature animals

Answer 30

repair and replacement of cells

Question 31

what changes does a cell go through as it differentiates

Answer 31

becomes specialised through acquisition of different sub-cellular structures to enable a specific function to be performed by the cell.

Question 32

how does a light microscope work

Answer 32

passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed

Question 33

advantages of light microscopes (4)

Answer 33

inexpensive easy to use portable observe both dead and living specimens

Question 34

disadvantage of light microscopes

Answer 34

limited resolution

Question 35

how does an electron microscope work

Answer 35

uses a beam of electrons which are focused using magnets. electrons hit a fluorescent screen which emits visible light, producing an image

Question 36

name the two types of electron microscope

Answer 36

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

Question 37

advantages of electron microscopes

Answer 37

greater magnification and resolution

Question 38

why do electron microscopes have a greater magnification and resolution?

Answer 38

use a beam of electrons which has a shorter wavelength than photons of light.

Question 39

how have electron microscopes enable scientists to develop their understanding of cells?

Answer 39

allow small sub-cellular structures to be observed in detail enable them to develop more accurate explanations about how cell structure relates to function

Question 40

disadvantages of electron microscopes (4)

Answer 40

expensive large so less portable require training to use only dead specimens can be observed

Question 41

magnification equation

Answer 41

mag= size of image/ size of real image

Question 42

how do bacteria multiply

Answer 42

binary fission (simple cell division)

Question 43

how often do bacteria multiply

Answer 43

once every 20 mins if enough nutrients are available and the temperature is suitable

Question 44

2 ways in which bacteria can be grown

Answer 44

nutrient broth solution colonies on an agar gel plate

Question 45

what nutrients make up a nutrient broth solution

Answer 45

all nutrients required for bacteria to grow including nitrogen for protein synthesis, carbohydrates for energy and other minerals.

Question 46

what are uncontaminated cultures of microorganisms needed for?

Answer 46

investigating disinfectant and antibiotic action

Question 47

describe the preparation of an uncontaminated culture using aseptic technique

Answer 47

1. use pre-sterilised plastic petri dishes or sterilise glass petri dishes and agar gel before using with an autoclave 2. pour the sterile agar gel into the petri dish and allow time to set 3. sterilise the inoculating loop by passing it through a Bunsen burner flame 4. dip the inoculating loop into the solution of microorganisms and make streaks with the loop on the surface of the agar 5. put the lid on the dish and secure with tape, label and store upside down 6. incubate at 25C in school labs

Question 48

why must petri dishes and culture media be sterilised before use

Answer 48

kill any bacteria already present

Question 49

why must inoculating loops be sterilised by passing them through Bunsen burner flame

Answer 49

kill any bacteria present already

Question 50

why must a Petri dish be secured with tape and stored upside down

Answer 50

stops bacteria in the air contaminating the culture lid is not fully sealed to prevent the growth of anaerobic bacteria in a lack of oxygen upside down to prevent condensation from forming and dripping down onto the colonies

Question 51

why are cultures incubated at 25C in school laboratories

Answer 51

harmful pathogens are less likely to grow at this temperature

Question 52

what is the formula used to calculate cross-sectional area of a bacteria colony or clear area around a bacterial colony

Answer 52

πr2 = 3.14 r = radius (diameter/2)

Question 53

how is the number of bacteria in a population after a certain time calculated from the mean division time

Answer 53

1. Calculate the number of times the bacteria will divide in the given time period from the mean division time. 2. Use the following equation to calculate the number of bacteria: Number of bacteria in population at end of time period = number of bacteria at the beginning of the time period x 2number of divisions in the time period Express the answer in standard form if possible.