Cell Biology

Question 1

What is a eukaryotic cell and give 2 examples

Answer 1

Eukaryotes are often multicellular (made up of many cells) such as plant and animal cells

They contain a nucleus

Question 2

What are prokaryotic cells and provide an example

Answer 2

Prokaryotes are single celled (only one cell) -Bacteria cells

They do not contain a nucleus

Question 3

What is found inside an animal cell and what do each subcelluar structure do?

Answer 3

Mitochindria : contain enzymes needed for respiration, for the cell to use

Ribosomes : where protein synthesis take splace

Nucleus: contains genetic material (including DNA) and controls cell activity

Cytoplasm: jelly like substance where chemical reaction takes place

Cell membrane: controls what enters and exits the cell

Question 4

What sub cellular structures are only found inside the plant cell and what do they do?

Answer 4

Cell wall: made of cellulose that provides structure and protection to the cell

Vacuole: holds cell sap that keeps the cell swollen

Chloroplast: This is where photosynthesis takes place chlorophyll absorbs light for food to be produced

Question 5

What subcellular structures are found inside a bacterial cell

Answer 5

Circular stand of DNA
Plasmid
Cytoplasm
Cell wall
Cell membrane

(Flagella a hair like structures is also found on bacterial cells)

Question 6

What is differentiation

Answer 6

Process by which different type of cells develop specific cell ctructure to become specialised for its job

Question 7

Provide an example of cells which undifferntiate and what do they do

Answer 7

Stem cells are undifferentiated cells which means they have the ability to differentiate into any type of cell

Question 8

How are sperm cells specialised and what do they do

Answer 8

Role: transpoet male DNA to the female DNA for sexual reproduction

Design: The head contains all genetic information ready for fertilisation

Acrosome contains enzymes that are able to digest the egg cell membrane

Lots of mitochodnria to provide energy for movement

Streamlined body and tail

Question 9

How are nerve cells specialised and what do they do

Answer 9

Role: rapidly carry electrical impulses around the body

Design: long axon to carry impulses over long distances

Dendrites both ends to enable connections with multiple other nerve cells

Insulated fatty sheath which helps impulses move along the nerve quickly

Releases neurotransmitter which transports electrical impulses across a synapse

Question 10

How are muscle cells specialised and what do they do

Answer 10

Role: They are responsible for movement bg contracting and or moving bones

Design: contains lots of mitochondria to provide energy for contraction

Protein filaments that slide over to cause the muscle to contract

Question 11

How are root hair cells specialised and thier function

Answer 11

Role: They are an exchange surface, specialised for absorbing water and nutrients from the soil

Deisgn: root hair cells have a large surface area for efficient absorption.

They have a vacuole of cell sap that is more concentrated than soil water which creates a water potential gradient for efficient water

Lots of mitochondria to provide energy for active transport of mineral ions from the soil

Question 12

How are xylem cells specialised and their function

Answer 12

Role: transports water and dissolved ions in a plant.

Design: xylem cells are dead and hollow and do not have no have any cell walls allows water to travel freely

Deposited spiralised lignin gives cell wall strength

Question 13

How are phloem cells specialised and role:

Answer 13

Responsible for transport of sugar and amino acids around the plant

Design: Cells joined end to end with sieve plates to allow passage for substances

companion cell which contains mitochondria providing energy for transportation of substances

Pores in wall for cellsap to flow through

Question 14

How do light microscopes work

Answer 14

Uses light and lenses to create a magnified image of a specimen which enables scientists to view their individual cells and their large subcellular structure

Question 15

How do electron microscopes work

Answer 15

They have a great magnification and resolving power because they use electron beams

This allows for more detail to be seen such as mitochondria, chloroplast and nuclei and subcellular structures such as ribosomes and plasmids

Question 16

What is the magnification calculation

And answer the question

Example: A student measures an image of a cell usinga ruler. It is 55 mm wide and the image has been magnified by factor of x 5000. What is the actual width of the cell in μm?

Answer 16

Size of the image
___________________= actual size
Magnification

0.011mm or 11 μm

Question 17

Req prac:

1)How to prepare the slide

2) How to view slide under microscope

3)Check your findings

Answer 17

1) Add water to the clean slide then carefully extract the cells and place them ontop the slide in the water with tweasers.

Highlight the cells using iodine solution with a pipette and then place the coverslip over the top of the specimen ( use a tissue if there is any excess solution)
by carefully tilting and lowering it ontop

2) clip the slide on the stage and select the objective lens with the lowest magnification. Look through the lens and adjust the coarse adjustment knob until the image is focused and the fine-adjustment knob.

3) Place your data down by drawing and labelling clearly and in proportion and mention the magnifcation and title of the microscope.

Question 18

Why is replication important

Answer 18

new cells are produced for growth and to replace old cells

Question 19

How do eukaryotic and prokaryotic cells divide

Answer 19

Eukaryotic organisms divide by mitosis

Prokaryotic organisms divide by binary fission

Question 20

Chromsomes: what do they do, location and number

Answer 20

Found inside the nucleus which contain genetic material called DNA

Each chromosomes contains a large number of genes which are sections of DNA that controls the development of specific characteristics. Before cells divide DNA is replicated so new cells have their own copies

There are a total of 23 pair of chromsomes (46 total)

Question 21

Eukaryotic cells divide in a process called mitosis. Explain the stages of it

Answer 21

1) Interphase: cells grow, and prepare for mitosis by replicating all subcellular structures (mitochondria and ribosomes). DNA is duplicated so each new cell has a copy of it. Additionalky, an x-shaped chromosome is formed with both sides of the cross containing the same DNA

2) Mitosis: nuclear membrane breaks doen and chromsomes line up at the centre of the cell. Spindle fibres pull the arms of the chromsomes to opposite ends of the cell by contracting. Then membranes form around the chromosome which creates nuclei for the new cell.

3) Cytokinesis: cytoplasm and cell membrane divide in a process called cytokinesis, producing 2 identical daughter cells that contain the same DNA as each other and the parent

Question 22

Importance of mitosis

Answer 22

It is an essential process to grow and replace damaged cells

Zygotes undergo mitosi-embros undergo mitosis and differentiation to become a foetus

Asexual reproduction divide by mitosis so strong genes can be spread throughout nature (resistant against pests)

Question 23

What are stem cells and what can they do

Answer 23

They can differentiate into many different type of cells and produce more undifferentiated cells

Used to cure diseases

Used for research

Used for cloning

Question 24

Where are plant stem cells found and what can they be used for

Answer 24

Found in the meristems

They are used to differentiate into any type of plant cell all throughout the life of the plant

These cells can be used to produce to clone plants to prevent extinction or clone crops with advantageous features (herb/pest resistance)

Question 25

Where are adult stem cells found and what do they do

Answer 25

Found in bone marrow and other adult tissue (liver cells)

Can only differentiate into other adult stem cells

Question 26

Uses of embryonic stem cells

Answer 26

Differentiate into any human body cell, research or to cure diseases.

Question 27

Embryonic stem cells can be used to treat diseases such as and how

Answer 27

Diabetes (type 1)
Patients do not produce enough insulin to regulate blood sugar levels resulting in embryonic stem cells to be trasplanted in the patient as insulin producing pancreatic cells will be produced to do the function

Paralysis
Paralysis caused by damaged nerve cells can be created to replaced thr nerve cells in the spinal cord

Question 28

What is therapeutic cloning

Answer 28

It is when stem cells are made with the same genetic informatin as the patient. Cells produced by the stem cell will contain the same genetic information as the patient and will not be rejected

Question 29

Why do people object against stem cell use

Answer 29

Stem cells can become contaminated with viruses which are passed to patients making them more sick

Morality and religious views: human embryos are potential human lives and should not be used to create treatments

Question 30

Support for stem cell treatment

Answer 30

Curing ill people is more important then the rights of embryos and therfore should be used where possible. Most embryos are unwanted and will be destroyed

Question 31

What is diffusion

Answer 31

The net random movement of particles from an area of high concentration to an area of low concentration.

Question 32

What can diffuse across a partially permeable membrane

Answer 32

Oxygen and carbon dioxide diffuse in and out of cell during gas exchange

Waste products such as urea diffuse out of cells

Some proteins and big carbohydrates from food are too large to diffuse across a membrane so they get digested into amino acids and glucose which are small enough to cross

Question 33

What is rate of diffusion affected by

Answer 33

Temperature- high temp=more kinetic energy=moving faster

Concentration gradient- larger the difference=faster the rate of diffusion

Surface area of the membrane- larger the SA=faster the rate of diffusion=more particles pass through the membrane

Question 34

What is SA:V

Answer 34

Used to measure how easily substances can move in and out of an organism

Question 35

SA:V in single celled and multicellular organisms

Answer 35

Single celled organism have large SA:V. Substances do not travel far to get to where it needs to be within the cell through simple methods.( Diffusion,osmosis,active transport)

Multicellular:

Small SA:V Substances do travel far to get where they need to be within the cell which means they require highly adapted exchange surfaces and transpor sustems to provide for the cells

Question 36

How to calculate total SA to V ratio

Answer 36

Calculate SA each side of the shape Length X width and adding them all together

Volume is calculated by doing Length X width X height

Question 37

Answer the SA:V question

Horse:

4cm by 4cm cube

Rat:
1cm by 1cm cube

Answer 37

Horse:
Total SA= 4^2 x6=96cm^2

Volume=4x4x4=64cm^3

SA:V=96:64=1.5:1

Rat:
Total SA=1^2 x 6=6cm^2

Volume=1x1x1=1cm^3

SA:V=6:1

The SA:V of the small rate is a much greater than the SA:V of the horse

Question 38

How are small intestines adapted for exchange

Answer 38

Lined with lots of villi which increase the surface area of the small intestines and therfore provide a quick absorption

Each villus has a single layer of surface cells and has a vast network of capillaries = short diffusion oatheay to the bloodstream and the concentration gradient is maintained

Question 39

How are lungs adapted for exchange

Answer 39

Contains lots of tiny air sacs called alveoli allowing for gas exchange:

They provide a massive surface area for exchange of gases

They have a moist lining for dissolved gases

They have very thin walls so a short diffusion distance

They have a good blood supply form capillaries to maintain the concentration gradient

Question 40

How are fish gills efficient for gas exchange

Answer 40

Each gill has many gill filaments which in turn are covered in lamellae which provides a massive surface area for oxygen

Lamellae have excellent blood supply (capillary network) and a thin layer of surface cells to provide short diffusion distance

Blood flows in the opposite direction to the water so a large concentration gradient is maintained and oxygen is absorbed from the water

Question 41

How are leaves adapted for gas exchange

Answer 41

Underside of the leaf is covered with tiny holes called stomata which allow CO2 to enter and oxygen and water vapour to leave, down concentration gradient.

Stomata are controlled by guard cells that close or open the stomata depending on water levels

Cell wall of the cell inside the leaf are the second exchange surface. Co2 diffuses into the cells for phtosynthesis and oxygen snd nd water vapour diffuse out.

Air spaces within the leave increase the area where gas exchange can take place

Question 42

How are roots adapated for exchange

Answer 42

Root hair structure provide a large surface area to collect water and mineral ions

Vacuole full of concentrated cell sap creates a steep potential gradient

Lots of mitochodnria for the active transport of mineral ions

Question 43

What is osmosis

Answer 43

Osmosis is the movement of water particles from area of high concentration to low concentration across a partially permeable membrane. (No cellular energy required)

Question 44

Required practical:

Effect of different salt/sugar concentrations on the mass of plant tissue.

Explain how to conduct the experiment

How to analyse the resukt

Answer 44

1) set up test tubes containing 10cm^3 of different sugar solutions. All solutions should vary from pure water to (1mol/dm^3) concentrated solution

Cut the potato into cylinders with equal size using a cork borer. Then measure the mass in grams using a balance

Place the each potato in a different beaker with different solution for 24 hours

Take the potatoes out, dry with a paper towel and measure their mass again with a balance

2) Record the mass of the potatoes with a balance before and after the experiment with the results calculate

Water uptake/loss is found by: rate of change(g/hr)=
Change in mass
————————
24(hr)

If finding percent change mass=

Final mass- original mass
———————————— x100
Original

Question 45

What is the independent, control and dependant variable of the potato required practical:

Answer 45

Independent variable is the concentration of sucrose solutions

Control variable include the volume of sucrose solutiom, time, temp and type of sugar used

Dependant variable is the mass of the potato

Question 46

What is active transport

Answer 46

Active transport allow substances to move form an area of low concentration to high concentration against the concentration gradient

Atp energy from respiration and a carrier protein on the cell membrane is required

Question 47

Example of active transport

Answer 47

Root hair cells are specialised cells which transporr substances such as water and mineral from the soil to the plant. Ions are moved from the soil and into the cell through active transport

The small intestines uses active transport to absorb nutrients (calcium and amino acids). Active transport allows nutrients to be absorbed into the wall of the intestines against the concentration gradient so they can enter the blood and be used for respiration

Question 48

Explain all transport process

Direction of flow

Requires energy?

Examples

Answer 48

Diffusion: high to low (down the conc)- passive- CO2 and oxygen exchange in lungs, fish and cells, nutrients entering the bloodstream from the intetsines, transport of waste products

Osmosis: high to low (down the conc), passive, water in and out of cells

Active tarnsport: low to high conc (against the gradient)-yes- mineral ions into plant root hair cells,food particles from the small intetsines to the cells