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Biology Paper 1 > Cell Biology - Cell Structure > Flashcards

Cell Biology - Cell Structure Flashcards

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1
Q

What are the differences between eukaryotic and prokaryotic cells?

A

Eukaryotic cells are plant and animal cells and contain membrane bound-organelles and a nucleus containing genetic material.
Prokaryotic cells are bacterial cells and are much smaller and contain free floating DNA. They don’t contain mitochondria or chloroplasts.

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2
Q

What is the prokaryotic cell wall composed of ?

A

Peptidoglycan

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3
Q

How is genetic information stored in a prokaryotic cell ?

A

Found free within the cytoplasm as chromosomal DNA (single large loop of circular DNA) and plasmid DNA

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4
Q

What are plasmids

A
  • Small circular loops of DNA that are
    found free in the cytoplasm separate
    from the main DNA
  • carry genes that provide genetic advantages eg antibiotic resistance
  • can be transferred from one cell to another
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5
Q

What are the organelles only found in plants?

A

Chloroplasts
Permanent vacuole
Cell wall

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6
Q

What is the function of the nucleus?

A

Controls activities in the cells
Stores genetic information

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7
Q

What is the function of the cytoplasm?

A

-Liquid substance where chemical reactions occur
-Contains organelles, enzymes and dissolved ions and nutrients
-transport medium

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8
Q

What is the function of the cell membrane?

A

Controls movement of substances in and out of the cell

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9
Q

What is the function of mitochondria?

A

Site of aerobic respiration, providing energy

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10
Q

What is the function of ribosomes?

A

-Where protein synthesis occurs
-joins amino acids in a specific order during translation for the synthesis of proteins

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11
Q

What is the plant cell wall made of ?

A

Cellulose

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12
Q

What is the function of plant cell wall ?

A

Provides strength to cell
Prevents the cell from bursting when water enters by osmosis

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13
Q

What is the function of the permanent vacuole ?

A

Contains cell sap to support the cell, maintaining its turgidity (keeps it rigid)

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14
Q

What is the function of chloroplasts?

A

Where photosynthesis occurs as it contains chlorophyll which absorbs sunlight

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15
Q

What is cell differentiation?

A

The process by which cells become specialised to carry out a particular function

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16
Q

Why is cell differentiation important?

A

Allows production of different tissues and organs that perform vital functions in human body

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17
Q

Describe how sperm cells in animals are adapted to their function

A
  • specialised to carry the male’s DNA to egg cell for successful reproduction
  • many mitochondria which supply energy to allow cell to move
    -the acrosome (top of head) has digestive enzymes which break down outer layers of membrane of egg cell
  • streamlined head and long tail to aid swimming
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18
Q

Describe how nerve cells are adapted to their function

A
  • specialised to transmit electrical signals quickly from one place in body to another
  • long axon allowing impulses to be carried along long distances and all over the body from cns
    -dendrites (extensions from the cell body) means branched connections can form with other nerve cells
    -nerve endings have many mitochondria which supply the energy to make special transmitter chemicals (neurotransmitters). These allow impulses to be passed form one cell to another
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19
Q

Describe how muscle cells are adapted to their function

A
  • specialised to contract quickly to move bones causing movement
  • lots of mitochondria to provide energy for muscle contraction
    -arrangement of protein filaments (myosin and actin) allows them to slide over each other causing muscle to contract
  • can store a chemical ( glycogen) that is used in respiration by mitochondria
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20
Q

Describe how root hair cells are adapted to their function

A
  • specialised to absorb water by osmosis and mineral ions by active transport from the soil as they are found in the tips and roots
    -large surface area to absorb more water and nutrients from soil
    -have mitochondria to provide energy from respiration for the active transport of mineral ions
21
Q

Describe how xylem cells are adapted to the function

A

-specialised to transport water and mineral ions to the plant from the roots to the shoots
- lignin is deposited in spirals which helps the cells withstand the pressure from the movement of water
-hollow in centre so water can move through
-tubes are joined end to end forming a continuous tube

22
Q

Describe how phloem cells are adapted to their function

A
  • specialised to transport substances around plant
    -sieve plates let dissolved amino acids and sugars be transported up and down stem
  • pores allow cell sap to flow
  • companion cells provide energy needed for active transport of substances along the phloem
23
Q

At what point do most animal cells differentiate?

A

Early in their life cycle

24
Q

For how long do plant cells retain the ability to differentiate?

A

Throughout their entire life cycle

25
Q

What is the purpose of cell division in mature animals?

A

Repost and replacement of cells

26
Q

What changes does a cell go through as it differentiates?

A

Becomes specialised through acquisition of different sub-cellular structures to enable a specific function to be preformed by the cell

27
Q

Define magnification

A

The number of times bigger an image appears compared to the actual size of the real object

28
Q

Define resolution

A

The smallest distance between 2 objects that can be distinguished

29
Q

How does a light microscope work ?

A

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

30
Q

What are the differences between light and electron microscopes

A

Light: - uses light - low resolution
- easy to use -cheap -live specimens
- focussed by glass lenses -true colour
- low magnification (max x1250) -portable
Electron: -uses electrons -high resolution - need specialist training -expensive -dead specimens - focussed by magnets -black and white/false colour - high mag( max x50,000) - large, can’t be moved

31
Q

How does an electron microscope work?

A

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

32
Q

Name the 2 types of electron microscopes

A

Transmission electron microscope
Scanning electron microscope

33
Q

Why do electron microscopes have a greater magnification and resolution?

A

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

34
Q

How have electron microscopes enabled scientists to develop their understanding of cells?

A

Allows smaller sub-cellular structures (mitochondria) to be observed in detail
Enables scientists it develop more accurate explanations about how cell structure relates to function

35
Q

How do bacteria multiply?

A

Binary fission - cell splits into 2

36
Q

Explain how to prepare a microscope slide

A
  • place slide on stage
  • use lowest x4 objective lens
  • adjust light source
  • move stage close to objective lens without lens touching slide
  • turn focus knob so slide moves away from lens
  • use fine focussing knob to get a clear image
  • change objective lens so eyepiece lens X objective lens= magnification
  • refocus
37
Q

How often do bacteria multiply?

A

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

38
Q

State 2 ways bacteria can be grown

A

Nutrient broth solution
Colonies on an agar gel plate

39
Q

What nutrients make up a nutrient broth solution?

A

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

40
Q

What are uncontaminated cultures of microorganisms needed for?

A

Investigating disinfectant and antibiotic action

41
Q

Why can’t viruses be grown on agar?

A

Because they need living cells to reproduce
They have to be grown inside suitable host cells

42
Q

Describe the preparation of an uncontaminated culture using aseptic technique

A
  • use pre-sterilised plastic patio dishes or sterilise glass petri dishes and agar gel before use to kill unwanted microorganisms
  • pour the sterile agar gel into Petri dish and allow time to set
  • sterilise the inoculating loop by passing it through a Bunsen burner flame
    Dip the inoculating loop into the solution of microorganisms and make streaks with the loop on surface of the agar
  • put the lid on the petri dish and secure it with tape. Label and then turn and store it upside down
  • incubate the culture at 25 degrees in school laboratories
43
Q

Why must Petri dishes and culture media (agar) be sterilised before use?

A

To kill any bacteria already present

44
Q

Why must inoculating loop be sterilised by passing it through Bunsen burner flame?

A

To Kill any bacteria present on the inoculating loop

45
Q

Why must Petri dish lid be secured with tape and the whole dish stored upside down?

A

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

46
Q

Why are cultures incubated at 25 degrees in school lavatories?

A

Harmful pathogens are less likely to grow at this temperature

47
Q

What is the formula to calculate the area of a bacterial colony?

A

Pi radius squared

48
Q

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

A
  • calculate the number of times the bacteria will divide in the given time period from mean division time
  • use equation: number of bacteria in population at end of time period= number of bacteria at beginning of time period X 2 to the power of numbers of divisions in time period
49
Q

Calculate conversions

A

nm —/1000–micrometers—/1000–mm—/1000–m

Biology Paper 1 (7 decks)

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