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GCSE BIOLOGY PAPER 1 > B1 > Flashcards

B1 Flashcards

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1
Q

What are the three subcellular structures only found in plant cells? (with their functions)

A
  1. Cell wall- made of cellulose and provides the cell with structural support and strength
  2. Vacuole- contains a cell sap, which is a weak solution of sugar and salts
  3. Chloroplast- contain chlorophyll, which absorbs the light needed for photosynthesis, site of photosynthesis
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2
Q

What are the subcellular structures that are present in both plant and animal cells?

A
  • Cell membrane- controls which substances enter and leave the cell
  • Cytoplasm- a gel-like substance, where most of the chemical reactions happen
  • Ribosomes- where protein synthesis occurs
  • Mitochondria- site of respiration
  • Nucleus- contains the cell’s genetic material(DNA), controls the activity of the cell
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3
Q

What are the differences between prokaryotic and eukaryotic cells? (give an example of each)

A
  • Eukaryotes- organisms made out of eukaryotic cells, eukaryotic cells are complex. example: animal cell
  • Prokaryotes- organisms made of a prokaryotic cell- a single-celled organism. example: bacterial cell
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4
Q

What do bacterial cells have instead of a nucleus?

A

circular strand of DNA- floats freely in the cytoplasm and has no membrane

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5
Q

Name any other structures only present in bacterial cells and their functions

A
  1. Flagellum- used for locomotion
  2. Plasmids- small closed circles of DNA
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6
Q

How have electron microscopes helped our understanding of subcellular structures?

A

They allow us to see smaller things in more detail, such as the internal structure of mitochondria etc…

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7
Q

Magnification equation

A

Magnification= image size / size of real
object

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8
Q

Function of cytoplasm?

A

Jelly-like substance where most chemical reactions for life take place

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9
Q

Function of ribosomes?

A

Protein synthesis takes place, making all
proteins for the cell

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10
Q

Function of mitochondria?

A

Aerobic respiration - releasing energy for the cell

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11
Q

What are plasmids?

A

Small rings of DNA that code for specific
features such as antibiotic resistances

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12
Q

Examples of specialised cells?

A

Nerve cells, muscle cells, sperm cells

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13
Q

How are nerve cells specialised?

A
  1. a long axon to cover more distance
  2. branched connections at the ends which allow the nerve cells to connect and form a network through the body
  3. covered with a fatty sheath which insulates the cell and speeds up the nerve impulse
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14
Q

How are muscle cells specialised?

A
  1. Contain proteins that slide over each other and make the fibres contract
  2. Contain many mitochondria to transfer energy needed for chemical reactions to take place
  3. Store glycogen, which can be broken down and used in cellular respiration by the mitochondria to provide energy needed for the fibres to contract.
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15
Q

How are sperm cells specialised?

A

1.Long tail helps it to move
2. Middle section is full of mitochondria,
which provide energy for the tail
3. Large nucleus contains genetic information to be passed on
4. Acrosome stores digestive enzymes to
break down the outer layers of the egg

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16
Q

How are root hair cells specialised?

A
  1. Increased surface area for water to move into the cell
  2. Permanent vacuole that speeds up
    movement of water by osmosis from the soil across the root hair cell
    3.Many mitochondria to transfer energy
    needed for active transport
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17
Q

What is osmosis?

A

The movement of water through a semi-permeable membrane down the conc gradient

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18
Q

What effects the rate of diffusion?

A

Difference in conc, temp, surface area

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19
Q

Active transport?

A

The movement of substances from a dilute solution to a more concentrated solution against the conc gradient

20
Q

Give 2 differences between electron
and light microscopes

A

Electron= higher magnification and resolution

21
Q

How are xylem cells specialised?

A
  1. They are dead cells with holes at the top and bottom to allow water and mineral ions to flow through
  2. they are strengthened by lignin( gives strength and support to the plant)
22
Q

How are phloem cells specialised?

A
  1. Sieve tubes have no nuclei and each sieve tube has a perforated end so its cytoplasm connects one cell to the next
  2. Companion cells, adjacent to the sieve cells provide the energy needed to transport substances in the phloem
23
Q

What is a stem cell and where are they usually found in humans and plants?

A

Stem cells are undifferentiated cells.

  1. usually found in early human embryos (embryonic stem cells)
  2. Adult stem cells can be found in bone marrow
  3. In plants, stem cells are found in meristems
24
Q

How can stem cells be used to cure diseases? Give at least two different ways.

A
  1. can be transferred from the bone marrow of a healthy person to replace faulty blood cells of the patient
  2. embryonic stem cells can also be used to replace faulty cells in sick people e.g. insulin- producing cells for people with diabetes.
  3. can be used for therapeutic cloning, where an embryo is made to have the same genetic information as the patient, reduces risks of rejection
25
Q

Give a possible risk for using stem cells

A

stem cells that are grown may become contaminated with a virus and this would be passed on to the patient

26
Q

Why are some people opposed to the use of human embryos?

A

each embryo is seen as a potential human life

27
Q

Give two arguments to support the use of embryonic stem cells

A
  1. the embryos used in research are usually unwanted and would have been destroyed
  2. curing the lives of patients alive and suffering takes priority over the rights of embryos
28
Q

What is a diploid cell?

A

a cell that contains two complete sets of chromosomes

29
Q

What is a gamete?

A

a reproductive cell

30
Q

What is mitosis used for by multicellular organisms?

A
  1. growth
  2. repair/replacement
  3. development
31
Q

What are the stages of the cell cycle (bold are the stages of mitosis)?

A

Interphase- The DNA in chromosomes copies itself ready for mitosis.

Prophase- The DNA in chromosomes and their copies condense to become more visible. The membrane around the nucleus disappears.

Metaphase- Chromosomes and their copies line up in the middle of the cell.

Anaphase- Chromosomes and their copies are opposite poles of the cell.

Telophase- New membranes form around the chromosomes at each end of the cell.

Cytokinesis- The cell membrane pinches in and eventually divides into two daughter cells which are identical

32
Q

Describe the three stages of the cell cycle

A

stage 1: growth of cell and replication of DNA and sub cellular structures (mitochondria, ribosomes)

stage 2: mitosis: the nucleus divides and the chromosomes separate

stage 3: cytokinesis: the cell membrane divides forming two genetically identical daughter cells

33
Q

Explain the process of binary fission

A
  • The circular DNA and plasmids replicate
  • The cell gets bigger and the circular DNA strands move to opposite poles of the cell (sides)
  • Plasmids are randomly distributed
  • Cytoplasm begins to divide and new cell membrane and cell wall form around the new cells
  • Cytoplasm divides and two daughter cells are produced. Each daughter cell has one copy of circular DNA but can have a variable number of plasmids
34
Q

What are some ways to prevent contamination when using a culture of microorganisms? Give at least three different ways

A
  1. Petri dish and culture medium need to be sterilised before use e.g. by heating to a high temperature
  2. The inoculating loop can be sterilised by passing it through a hot flame
  3. The lid of the Petri dish should be lightly taped on to prevent any air entering
  4. The Petri dish should be stored upside down so drops of condensation do not fall on the agar surface
35
Q

What is the maximum temperature at which microorganisms in a school lab should be grown and why?

A

25°C because harmful pathogens are more likely to grow in conditions which are above 25 degrees

36
Q

Give three substances that can diffuse through cell membranes

A
  1. amino acids
  2. glucose
  3. water
  4. oxygen
37
Q

Give the two main differences between active transport and diffusion

A
  1. Active transport uses energy whilst diffusion is a passive process
  2. Active transport absorbs substances against a concentration gradient
38
Q

How are alveoli adapted for gas exchange?

A
  1. thin walls which allows a short diffusion pathway
  2. a large surface area
  3. a good supply of blood
  4. a moist lining for dissolving gases
39
Q

How are the villi in the small intestine adapted for absorbing digested food?

A
  1. have a single layer of surface cells
  2. have a good supply of blood which assist with quick diffusion/absorption (capillaries inside them)
40
Q

How are leaves adapted to maximise the amount of carbon dioxide that gets to their cells?

A
  • the underneath of the leaf is covered with little holes called the stomata
  • the size of the stomata is controlled by the guard cells
  • the flattened shape of the leaf increases the area of the exchange surface
  • the air spaces inside the leaf increase of the area of the exchange surface( walls of cells) so there is more chance for carbon dioxide to get into the cells.
41
Q

Growing bacteria
(Required practical)

A

Petri dish and agar jelly must be sterilised by being heated before use
Reason – this will kill any bacteria that are present in the solution or on the Petri dishes.

Pour the sterile agar jelly in sterile pétri dish and allow to set fully.
Reason – this provides the selected bacterium with all the nutrients needed to grow.

Sterilise the inoculating loop, by heating it in the Bunsen burner flame.
Reason - kills any bacteria that are present on the loop.

Dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate.
Reason – this allows the bacteria to spread out and to grow in individual colonies on the agar plate.

Replace the lid as soon as possible, secure with tape and stored upside down.
Reason -this stops additional unwanted bacteria in the air contaminating the plate and drops of condensation falling on agar jelly

Incubate at a maximum temperature of 25°C in schools and colleges.
Reason – this reduces the chance of growing harmful pathogens.

42
Q

Zone of inhibition test

A

Soak filter paper disks in a variety of solutions, use either different concentrations of the same solution, or a variety of different solutions.

Pour the sterile agar plates and allow to set fully.
Reason – the effectiveness of the solutions at killing the bacteria can be tested.

Measure the clear area around the soaked filter paper disks. A control disk must be also included.
Reason - size of zone of inhibition indicates the effect of the substance tested on the growth of the specific bacterium.

43
Q

Pond weed
(Required practical)

A

Set up a boiling tube containing 45cm3 of sodium hydrogencarbonate solution (1%). Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form.

Cut a piece of the pondweed, Cabomba. The pondweed should be 8 cm long.

Use forcepts to place the pondweed in the boiling tube carefully. Make sure that you don’t damage the pondweed, or cause the liquid to overflow.

Position the boiling tube so that the pondweed is 10 cm away from the light source.

Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute.

Repeat the count five times and record your results.

Calculate the average number of bubbles produced per minute.

Repeat the experiment at different distances away from the light source.

IV – distance from the light source/light intensity.
DV – the number of bubbles produced per minute.
CV – concentration of sodium hydrogencarbonate solution, temperature, using the same piece of pondweed each time.

44
Q

Using a light microscope
(Required practical)

A

Equipment:
• specimen (Onion) - epidermal tissue
• tweezer
• water (pippet)
• glass side
• iodine
• cover slip
• light microscope

-take the epidermal tissue with some tweezers

-add a drop of water to a clean slide w/ pippet

  • then place the epidermal tissue on the slide

-add a drop of iodine to stain the cell so the structure can be observed

-Place cover slip on top of specimen
(care must be taken to avoid smudging &
trapping air bubbles)

-clip slide on stage

  • esure lowest-powered objective lens is over slide

-use coarse adjustment to bring stage just below lens

look in eyepiece and gradually move stage down w/ coarse knob (stop when image is in focus)

-adjust fine adjustment known entail clear image is obtained

-to observe image at higher magnification, change the objective lens and adjust FA knob

45
Q

Mitosis vs Meiosis

A

mitosis
•Results in 2 identical daughter cells
•1 cell division
•results in diploid daugher cells
•Chromosome number = same as parent cell
•daughter cells genetically identical
•occur in all organisms except viruses
•Creates all cells (somatic) apart from germ cells.

Meiosis
-Results in 4 sex cells
-2 successive cell divisions
-results in 4 haploid daughter cells
-half number of chromosomes of parent cells
-daughter cells genetically different
-only in animal, plants & fungi
-Production of gametes for sexual reproduction

GCSE BIOLOGY PAPER 1 (4 decks)

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