Cell Structure And Function

Question 1

In microscopy sections of tissue must be

Answer 1

Thin enough for light to pass through, preferably single layers of cells

Question 2

Staining for microscopy involves

Answer 2

Adding coloured dyes to slides to make biological specimens visible under the microscope, staining is necessary because most biological cell structures are colourless and otherwise invisible the stains bind to chemicals in specimens to give contrast so you can distinguish between different parts of the cell

Question 3

Compare the resolution of a light microscope and an electron microscope

Answer 3

LM: Low as light has long wavelength so cannot distinguish objects close together.
EM: High as electron beam has short wavelength so can distinguish objects close together.

Question 4

Compare the magnification of a LM and EM

Answer 4

LM: Low (X1500) so small objects can’t be seen.
EM:High (X1500000) so small objects can be seen.

Question 5

Compare staining images in LM and EM

Answer 5

LM: Coloured dyes are used to give a coloured image.
EM: Heavy metals, denser objects absorb more electrons so appear darker, image is not coloured

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Question 6

Describe the specimens used in LM and EM

Answer 6

LM can see living cells and can be used to follow some processes in living cells.
EM cannot look at living cells as the vacuum kills them.

Question 7

Compare artefacts in LM and EM

Answer 7

LM: Not a problem
EM: Sample preparation complicated, and produces artefacts

Question 8

Compare Scanning EM and Transmission EM

Answer 8

1. In SEM electron beam bounces off surface of sample to produce a 3D image of surface, in TEM an electron beam penetrates the sample to show internal strictures of organelles.
2. In SEM the specimen doesn’t need to be thin, in TEM Specimen must be very thin
3. In SEM magnification and resolution is low compared to TEM, in TEM it is very high.

Question 9

What is the formula for magnification

Answer 9

M=I/A

Question 10

If a question gives you a photo with a scale bar drawn on it how do you work out the actual size of the object

Answer 10

Actual size = Length of object / Length of scale bar x Measurement of scale bar

Question 11

What’s ultrastructure

Answer 11

The detailed structure of the internal components of cells as revealed by an EM

Question 12

Describe the structure and function of the smooth ER

Answer 12

Single membrane cells which makes lots of lipids have lots of smooth ER, for example liver cells and fat cells

Function: makes and processes lipids

Question 13

Describe function and structure of rough ER

Answer 13

Has a single membrane, the outer surface is covered in ribosome cells who itch make lots of proteins.

Function: Makes and processes proteins

Question 14

Describe the structure and function of ribosomes

Answer 14

Structure: have no membrane and are found on rough ER or free in the cytoplasm and are made of RNA

Function: invited in translation of mRNA into protein.

Question 15

Describe structure and function of a cell membrane

Answer 15

Structure: has a bylayer of phosphor lipids and is folded in some animal cells to form microvilli

Function: regulates movement of substances in and out of the cell

Question 16

Describe the structure and function of mitochondria

Answer 16

Has a double membrane, the inner membrane is folded to form cristae

Function: aerobic respiration produces ATP

Question 17

What is the structure and function of the nucleus

Answer 17

S: double membrane called nuclear envelope which has pores in it to let mRNA out.

F: controls activities of the cell and stores/protects the DNA

Question 18

What is the structure and function of lysosomes

Answer 18

S: Has a single membrane which helps contain enzymes which would otherwise digest the whole cell.

F: contains digestive enzymes for destroying worn out organelles

Question 19

What is the structure and function of Golgi apparatus

Answer 19

S: Has a single membrane and a stack of flattened sacks. Golgi vesicles transport protiens and lipids from the Golgi to the cell surface membrane for secretion.

F:modifies and packages proteins and lipids and also makes Golgi vesicles and lysosomes

Question 20

What is the structure and function of peroxisomes

Answer 20

S: has a single membrane with a crystal core and is known as a micro body

F: involved in catabolism of lipids and reactive oxygen species. Also has a role in sugar metabolism and lipid biosynthesis

Question 21

What is the structure and function of centrosome

Answer 21

S: composed of centrioles and microtubules which can be used as highways for vesicle transport or spindle fibres for centromere attachment during mitosis

Question 22

What do mitochondria produce

Answer 22

ATP by aerobic respiration for processes such as active transport and protein synthesis

Question 23

Mitochondria have a large surface area to volume ratio meaning

Answer 23

Oxygen can be absorbed for aerobic respiration by a short diffusing path to the centre

Question 24

What are 2 important properties of stem cells

Answer 24

1. They replace themselves by dividing by mitosis
2. They are undifferentiated

Question 25

What happens during differentiation

Answer 25

Some genes are expressed whereas other genes are not, the genes that are expressed are transcribed unto mRNA which is then translated into proteins, these proteins modify the cell so it becomes specialised

Question 26

Name 4 different types of stem cells

Answer 26

Totipotent, pluripotent, multipotent, unipotent

Question 27

Where is totipotent stem cells found and what are their properties

Answer 27

In the embryo during the first few divisions. Can produce any type of body cell, can even give rise to a whole other new organism

Question 28

Where are pluripotent stem cells found and what are their properties

Answer 28

In the embryo after the first few divisions. Can mature into any type of body cell except the cells that form the placenta.

Question 29

Where are multipotent stem cells found and what are their properties

Answer 29

Found in mature mammals. Can mature into a li,tied number of cell types (blood stem cells can make red blood cells)

Question 30

where are unipotent stem cells found and what are their properties

Answer 30

Found in mature mammals. Can only mature into one type of cell

Question 31

How is an epithelial cell specialised to carry out particular functions

Answer 31

1. It has lots of microvilli which have large surface areas for diffusion and active transport of molecules into the cell.
2. It has lots of Golgi vesicles, which transport proteins to cell surface membrane for active transport and facilitated diffusion.
3. It has lots of mitochondria which produce ATP to supply energy to support active transport of molecules into cell.

Question 32

What is the function and specialised features of a sperm cell

Answer 32

F: sex cell/gamete/haploid cell involved in sexual reproduction/fusion with egg cell

SF: has flagella tail to swim up the uterus. Has mitochondria to supply energy to swim and lysosomes for penetrating the egg cell.

Question 33

What is the function and specialised features of a squamous epithelial cell

Answer 33

F: makes up alveoli walls and capillary vessel walls
SF: thin to allow exchange of substances over a short diffusion pathway. Has large surface area for efficient diffusion

Question 34

What is the function and specialised features of an intestinal epithelial cell

Answer 34

F: lines the intestine to promote absorption of digested food products.
SF: Has a folded cell surface membrane to create microvilli which increases surface area to promote diffusion of substances. Has lots of mitochondria and Golgi for supplying ATP for active transport and vesicles for tracking absorbed products.

Question 35

What is the function and specialised features of an erythrocyte

Answer 35

F: transports oxygen around the body in the bloodstream
SF: contains haemoglobin for binding to oxygen for transport in the bloodstream. Has a bi-concave shave and nucleated cells which increase the volume in the cytoplasm for more haemoglobin storage.

Question 36

What is the function and specialised features of a leukocyte

Answer 36

F: protects body from foreign pathogenic invaders
SF: contains a dense lysosome content for digested engulfed pathogens. Capable of ruffling the cell membrane to bind to pathogenic antigens and trigger phagocytosis

Question 37

What is the function and specialised features of a muscle cell

Answer 37

F: involved in contractile processes to move a body part or content
SF: actin and myosin contractile protiens are contained in the cytoplasm. Contains dense mitochondria for ATP and ER for calcium which is needed for muscle contraction.

Question 38

What is the function and specialised features of a secretory gland cell

Answer 38

F: involved in synthesis and release of a product into a cavity or duct or into the blood stream
SF: contains dense ER for protein synthesis. Dense Golgi apparatus for vesicle information and secretion via exocytosis

Question 39

What is the function and specialised features of a nerve cell

Answer 39

F: involved in the transmission of electrochemical action potentials for communications in the body
SF: contains mitochondria for ATP to maintain ion gradients across the axon and dendrite membranes. Has dense ER and Golgi apparatus to supply calcium and vesicles for exocytosis of vesicles containing neurotransmitters and synapses.