Topic 2 -Cell structure

Question 1

What are eukaryotic cells ?

Cell Structure

Answer 1

Complex cells that contain a nucleus and other membrane-bound organelles. These are plant and animal cells. (agal cells and fungal cells)

Question 2

Describe agal cells.

Cell Structure

Answer 2

They are a lot like plant cells - they have the same organelles. they can be single celled or multicellular.

Question 3

Describe fungal cells.

Cell Structure

Answer 3

They’re like plant cells, however their cell walls are made from chitin not cellulose and they don’t have chloroplast because they don’t photosynthesise. This includes mushrooms and yeast.

Question 4

What is the function of cell surface membranes ?

Cell Structure

Answer 4

They regulate the movement of substances in and out of the cell. They also have receptor molecules on it which allow it to respond to chemicals like hormones. Act as a barrier between the cell and its environment.

Question 5

Describe the properties and functions of a nucleus.

Cell Structure

Answer 5

A large organelle surrounded by a nuclear envelope (double membrane) which contains pores. The nucleus contains chromosomes which are made from protein bound linear DNA, it also contains one or more nucleolus. The nucleus controls the cells activity’s by controlling the transcription of DNA. DNA contains instructions to make proteins. The pores allow substances (like RNA) to move between the nucleus and cytoplasm.The nucleus make ribosomes

Question 6

Describe the properties and functions of mitochondria.

Cell Structure

Answer 6

they’re usually oval shaped and have a double membrane, the inner folds to form a structure called cristae inside the matrix, which contains enzymes involved in respiration. The site of aerobic respiration, where ATP is produced. They’re found in large numbers in cells that are very active and need lots of energy.

Question 7

Describe the properties and functions of chloroplasts.

Cell Structure

Answer 7

A small, flattened structure found in plant and agal cells. It’s surrounded by a double membrane and also had membranes inside called thylakoid membranes, these are stacked in some parts of the chloroplast to form grana. Grana are linked together by lamellae - thin flat peices of thylakoid membrane). The site where photosynthesis occurs, some occurs in the grana and some in the stroma (thick fluid).

Question 8

Describe the properties and functions of golgi apparatus.

Cell Structure

Answer 8

A group of fluid-filled membrane-bound flattened sacs. Vesicles are often found at the edges of the sacs. It processes and packages new lipids and proteins. It also makes lysosomes.

Question 9

Describe the properties and functions of golgi vesicles.

Cell Structure

Answer 9

They’re small fluid filled sacs in the cytoplasm surrounded by a membrane and produced by the golgi apparatus.they store the lipids and proteins that are produced and packaged by the golgi apparatus, and transport them out of the cell.

Question 10

Describe the properties and functions of lysosomes.

Cell Structure

Answer 10

A round organelle surrounded by a membrane with no clear internal structure. it’s a type of golgi vesicle and contains digestive enzyme called lysozymes. These are separate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or break down worn out components of the cell.

Question 11

Describe the properties and functions of ribosomes.

Cell Structure

Answer 11

They’re a very small organelle that either floats free in the cytoplasm or are attached to the Rough endoplasmic reticulum. it’s made up of proteins and RNA. it’s not surrounded by a membrane. it’s the site of protein synthesis.

Question 12

Describe the properties and functions of rough endoplasmic reticulum.

Cell Structure

Answer 12

a system of membranes enclosing a fluid filled space. the surface is covered in ribosomes. it folds and processes proteins that have been made in the ribosomes.

Question 13

Describe the properties and functions of smooth endoplasmic reticulum.

Cell Structure

Answer 13

They’re a system of membranes enclosing a fluid filled space. synthesises and processes lipids.

Question 14

describe the properties and functions of a permanent cell vacuole.

Cell Structure

Answer 14

A membrane bound organelle found in the cytoplasm of plant cells. It contains cell sap, a weak solution of sugar and salts. The surrounding membrane is called the tonoplast. It helps maintain the pressure inside the cell and keeps it rigid shape. It prevents plants from wilting. involved in the isolation of unwanted chemicals in the cell.

Question 15

What are prokaryotic cells ?

Cell Structure

Answer 15

cells with no membrane bound organelles and no true nucleus.

Question 16

What size are the ribosomes in bacteria ?

Cell Structure

Answer 16

70s

Question 17

What’s the role of the slime capsule ?

Cell Structure

Answer 17

Helps to protect the bacteria from an attack by cells of the immune system.

Question 18

What’s the properties and function of the cell wall in bacteria ?

Cell Structure

Answer 18

supports the cell and prevents it from changing shape. made out of a polymer called murein, a glycoprotein.

Question 19

What’s the properties and functions of a plasma membrane in bacteria ?

Cell Structure

Answer 19

is made mainly of lipids and proteins. control the movement of substances in and out of cells.

Question 20

what’s the DNA in bacteria ?

Cell Structure

Answer 20

a single circular loop of dna floating in the cytoplasm. not attached to any histone proteins

Question 21

What are plasmids.

Cell Structure

Answer 21

Small loops of DNA they contain the genes for antibiotic resistance and can be passed between prokaryotes. they’re not always present.

Question 22

What’s a flagellum?

Cell Structure

Answer 22

a long hair like structure that rotates to make the bacteria cell move. not all cells have them

Question 23

Are viruses alive cells ?

Cell Structure

Answer 23

No, they’re particles.

Question 24

in a virus what does the core of genetic material contain ?

Cell Structure

Answer 24

DNA or RNA

Question 25

What’s the capsid of a virus ?

Cell Structure

Answer 25

The protein coat around the core of genetic material.

Question 26

what are attachment proteins in a virus ?

Cell Structure

Answer 26

they stick out from the edge of the capsid and bind to receptors on the suitable host cell

Question 27

Describe the processing and secretion of hormones in a eukaryotic cell

Cell Structure

Answer 27

The rough endoplasmic reticulum transports proteins that have been made in the ribosomes to the golgi apparatus. at the golgi apparatus the proteins are processed and packaged and then sent in the golgi vesicles to be secreted at the cell surface membrane.

Question 28

what’s the protein coat around the core of the virus called ?

Cell Structure

Answer 28

capsid

Question 29

How does the capsid help the viruses.

Cell Structure

Answer 29

protects it from attack from immune system cells of the person it’s infecting.

Question 30

Describe the role of one named organelle in digesting bacteria.

Cell structure

Answer 30

lysosomes fuse with vesicles and release hydrolytic enzymes

Question 31

Suggest one explanation for the faster rate of plasmid replication in cells
growing in a culture with a high amino acid concentration.

Cell structure

Answer 31

More amido acids an be used in protein synthesis so enzymes such as DNA polyermase can be made which are used in DNA replication.
Amino acids are used in respiration so more energy for DNA replication to occur

Question 32

What’s the equation for magnification ?

Microscopy

Answer 32

magnification = image size / real size

Question 33

What’s the definition of magnification ?

Microscopy

Answer 33

how many times bigger the image is than the real size of the specimen

Question 34

What’s the definition of resolution ?

Microscopy

Answer 34

How well a microscope can distinguish between two points that are close together.

Question 35

name the conversions for mm um and nm

Microscopy

Answer 35

mm x 1000 um x1000 nm
nm /1000 um /1000 mm

Question 36

How does an optical microscope work ?

Microscopy

Answer 36

It uses light to form and image

Question 37

give the advantages and disadvantages of optical microscopes

Microscopy

Answer 37

They have a lower resolution of 0.2 nanometres, meaning smaller organelles cannot be seen such as ribosomes. they have a lower maximum magnification of x1500.
Preparation is simple and quick. natural colour of the specimen can be seen. living and dead tissues can be seen.

Question 38

how do electron microscopes work ?

Microscopy

Answer 38

they use electrons to form an image

Question 39

Give the advantages and disadvantages of electron microscopes.

Microscopy

Answer 39

they have a higher resolution of 0.0002 nanometres meaning images can be seen in more detail and smaller organelles can be seen. They have a higher maximum magnification of X500000.
preparation is lengthy and complex. can only view dead specimen as in vacuum. artefacts are more likely to occur. image occurs in black and white. more expensive

Question 40

how do transmission electron microscopes work ?

Microscopy

Answer 40

They use electromagnets to focus a beam of electrons on the specimen and transmit through the specimen. the denser area of the specimen absorbs more electrons causing it to appear darker on the image.

Question 41

Give the advantages and disadvantages of the TEM.

Microscopy

Answer 41

They have a high resolution so you can see internal structure of the organelles like chloroplast.
they can only be used on thin specimen and create a 2D image.

Question 42

How do scanning electron microscopes work ?

Microscopy

Answer 42

They scan a beam of electrons across the specimen. this knocks off electrons from the specimen which are gathered in a cathode ray tube to form an a image.

Question 43

How would you prepare a specimen ?

Microscopy

Answer 43

Add a drop of water to a slide.
Use tweezers to add a thin layer of the specimen to the slide on top of the water drop.
Add a drop of stain to the slide to highlight the structures of the specimen.
Add the cover slip by standing it upright on the slide then carefully tilting and lowering it so it covers the specimen, trying not to get any air bubbles.

Question 44

How would you use an optical microscope?

Microscopy

Answer 44

clip the prepared slide onto the stage.
select the lowest powered objective lens.
use the coarse adjustment knob to move the stage just below the objective lens. then use it to lower the stage downwards until the image is roughly focused
use the fine adjustment knob until you get a clear image.
if a higher magnification is needed select a higher powered objective lens and refocus the image.

Question 45

What are artefacts ?

Microscopy

Answer 45

Things that you can see down the microscope that aren’t apart of the specimen. eg. air bubbles dust and fingerprints. they’re more common in electron microscopes due to the lengthily and complex preparation.

Question 46

Give the advantages and disadvantages of SEM

Microscopy

Answer 46

the image can be 3D. thicker specimen can be used but they give lower resolution then TEM.

Question 47

Why can an optical microscope not view internal details of cells ?

Microscopy

Answer 47

The resolution is too low because he wavelength of light is too long.

Question 48

How does cell fractionation work ?

Studying cells

Answer 48

1.Homogenisation: Breaking up the cell can be down by grinding the cells up in a blender. This breaks up the plasma membrane and releases the organelles into a solution. The solution is kept ice cols to reduce enzyme activity that would break down the cell. The solution also must be isotonic - meaning that it should have the same amount of concentration of chemicals as the cell being broken down, this means water potential isn’t affected so the cell doesn’t burst or shrivel by osmosis. A buffer solution is used to maintain pH.
2.Filtration: removing large debris: the homogenate is filtered through a gauze to separate any large cell/tissue debris. The organelles are much smaller so they pass though.
3.Ultracentrifugation:serparating the organelles: The cell fragments are poured in a test tube and put in a centrifuge which spins at a low speed. The heaviest organelle, like nuclei, form a pellet at the bottom. The supernatant is drained off and placed in another tube, then placed in a centrifuge that spins at a higher speed. This continues.

Question 49

What’s the order of organelle separation during cell fractionation ?

Studying cells

Answer 49

nuclei
mitochondria
chloroplast
lysosomes
endoplasmic reticulum
ribosomes

Question 50

what’s mitosis ?

Cell division

Answer 50

the process of a parent cell dividing to produce two genetically identical daughter cells.

Question 51

What’s mitosis needed for ?

Cell division

Answer 51

the growth of multicellular organisms and the repair of damaged tissue

Question 52

What are the stages of the cell cycle ?

Cell division

Answer 52

INTERPHASE:
gap phase 1: cell grows and new organelles and proteins are made
synthesis: cell replicates it’s DNA ready to divide by mitosis.
gap phase 2: cell keeps growing and proteins needed for cell division are made.
the cell cycle begins and ends with mitosis.

Question 53

What happens during interphase ?

Cell division

Answer 53

The cell carries out normal functions but also prepares to divide. the cells DNA is unravelled and replicated to double its genetic content. the organelles are also replicated and it’s ATP contents is increased (ATP provided the energy for cell division).

Question 54

Describe prophase

Cell division

Answer 54

The chromosomes condense getting shorter and fatter. Tiny bundles of proteins called centrioles start moving to opposite ends of the cell forming a network of fibres called spindle fibres. the nuclear envelope disintegrated and the nucleolus disappears.

Question 55

Describe metaphase

Cell division

Answer 55

The chromosomes line up alone the equator of the cell and become attached to the spindle fibres by their centromere.

Question 56

Describe anaphase

Cell division

Answer 56

The centromeres divide, separating each pair of sister chromatids. The spindles contract pulling chromatids to opposite ends of the cell. this makes the chromatids appear in a v shape.

Question 57

Describe telophase.

Cell division

Answer 57

The chromatids reach the opposite ends of the on the spindle fibres. they uncoil and become long and thin again. they’re now chromosomes. A nuclear envelope forms around each group of chromosomes and there is now 2 nuclei.

Question 58

describe cytokinesis.

Cell division

Answer 58

The cytoplasm divides. forming 2 daughter cells that are genetically identical to the original cell and each other.

Question 59

how would you work out the time taken for cells to divide ?

Cell division

Answer 59

number of cells in the phase / number of cells X100

Question 60

what is cancer caused by ?

Cell division

Answer 60

uncontrolled cell division. Mitosis and cell cycle are controlled by genes, if there are mutations in these genes the cells will grow out of control. the cells keep dividing and a tumour forms which invades surrounding tissues.

Question 61

Why are cancer treatments more likely to kill cancer cells than normal body cells ?

Cell division

Answer 61

cancer cells divide more frequently.

Question 62

Describe how the Gap phase 1 can be targeted by drugs to treat cancer

Cell division

Answer 62

Some chemical drugs (chemotherapy) prevent the synthesis of enzymes that are needed for DNA replication. this means the cell is unable to enter the synthesis stage and the cell is forced to kill itself, preventing the growth of a tumour

Question 63

Describe how the synthesis phase can be targeted by drugs to treat cancer

Cell division

Answer 63

radiation and some drugs cause damage to DNA at several points in the cell cycle the DNA is checked for damage, if severe damage is detected then the cell will kill itself - preventing the growth of tumour.

Question 64

how do you work out mitotic index

Cell division

Answer 64

number of cells with visible chromosomes / total number of cells observed

Question 65

What’s the main difference between DNA in prokaryotes and eukaryotes?

Cell structure

Answer 65

Eukaryote is linear
Prokaryote is circular.