Intro To Biology And Cell Membrane

Question 1

Biology

Answer 1

Study of life

Question 2

Histology

Answer 2

-Science of microscopic organisms structure and function
-organization of tissues and organs

Question 3

Cytology

Answer 3

Study of cell structure and function

Question 4

What is the cell membrane/plasma membrane?

Answer 4

It is the outer boundary that envelopes all cells to limit the entrance of particles into the cell

Question 5

Can we view the cell membrane with the LM? why? how?

Answer 5

No, we can not we can not view it with a light microscope because it is very thin

Question 6

How does the cell membrane appear with an electron microscope?

Answer 6

It appears as 3 layers (trilaminar)
-outer electron layers appear dense (black)
-Central electron layer appears lucent (pale)

Question 7

What is a cell membrane formed of?

Answer 7

It is formed by two layers of lipids (bilayer) with proteins and carbohydrates

Question 8

What are the layers of bilayer lipids formed of?

Answer 8

Mainly of phospholipids and cholesterol

Question 9

What does each phospholipid molecule consist of?

Answer 9

Each consists of a peripheral hydrophilic end (head), and a hydrophobic end (tail)

Question 10

What does hydrophilic and hydrophobic mean?

Answer 10

1. water-loving
2. water-hating

Question 11

What are proteins in the cell membrane made of?

Answer 11

1. integral (intrinsic) protein
2. peripheral (extrinsic) protein

Question 12

Integral (intrinsic)

Answer 12

extends across the whole lipid bilayer (the protein is completely visible)

Question 13

Peripheral (extrinsic)

Answer 13

either on the inner or outer surface of the plasma membrane…due to cytoplasm (only tip inside cell membrane)

Question 14

Carbohydrates

Answer 14

carbs are combined with integral proteins to make glycoproteins or with lipids to make glycolipids

Question 15

What are the two main components that form the cell coat?

Answer 15

1. glycoproteins
2. glycolipids

Question 16

Cell coat

Answer 16

covers the outer surface of the cell membrane

Question 17

Why is there the trilaminar structure shown by EM with two different colours?

Answer 17

the dense black colour is due to the deposition of the stain on the hydrophilic layers of the lipid bilayer

Question 18

cell junctions

Answer 18

-contact points between neighbouring cells
-epithelium and basal lamina

to stick cells together

Question 19

where are cell junctions most abundant?

Answer 19

epithelium

Question 20

5 most common types of cell junctions?

Answer 20

1. Tight junctions
2. Adherent junctions
3. Desmosomes
4. Hemidesmosomes
5. Gap junctions

Question 21

Tight junction (zonula occuldens)

Answer 21

-Gap between cells are very narrow (nothing can pass through)
-creates a barrier that seals off the body cavities

Question 22

Example for gap junctions

Answer 22

endothelial cells lining the brain and spinal cord to separate blood from interstitial fluid

Question 23

Endothelial cells

Answer 23

single layer that lines all blood vessels
-regulates exchange with bloodstream and surrounding tissues

Question 24

Interstitial fluid

Answer 24

the fluid that fills spaces between cells

Question 25

Adherent junction (zonula adherens)

Answer 25

They hold cells
-form a continuous belt around the cell
- gap between cells in narrow but less than tight junction, some particles may pass through

Question 26

desmosomes (macula adherence)

Answer 26

-button-like structure between neighbouring cells
-found mainly in the skin, heart and muscles
-Prevent mechanical stress and support cells

Question 27

Hemiodesmosomes

Answer 27

connect the epithelial cell to the basal lamina

Question 28

Gap junctions

Answer 28

-communication channels between cell membrane and neighbouring cells
- allow rapid spread of impulses between cells
-present in cardiac and nervous cells

Question 29

what are the cell membarne

Question 30

Phagocytosis

Answer 30

ability of cell membrane to pass solid particles forming phagosome

Question 31

pinocytosis

Answer 31

ability to pass fluid droplets forming pinocytic vesicles

Question 32

exocytosis

Answer 32

to extrude secretory substances and waste outside the body

Question 33

cell coat (glycocalyx)

Answer 33

receptors for some hormones as insulin and helps in cell recognition

Question 34

cell junction

Answer 34

allow cell communication