Cells in the Human Body

Question 1

What are the 4 parts of the cell theory?

Answer 1

1. A cell is the basic structural and functional unit of living organisms.
2. The activity of an organism depends on both the individuals and collective activities of its cells.
3. The biochemical activities of cells are dictated by the relative number of their specific subcellular structures.
4. Continuity of life from one generation.

Question 2

What are the 3 main parts of a human cell.

Answer 2

Plasma membrane
The cytoplasm
The nucleus

Question 3

What is the plasma membrane?

Answer 3

A fragile outside boundary of the cell.

The intracellular fluid is packed with organelles.

Question 4

What is the nucleus?

Answer 4

Controls cellular activities and typically lies near the cell centre.

Question 5

What is the nucleolus?

Answer 5

Round body located inside the nucleus.

Makes ribosomal sub-units from proteins and ribosomal RNA, sending these sub-units to the rest of the cell where they combine into complete ribosomes.

Question 6

What are ribosomes?

Answer 6

Functions as a micro-machine for making proteins.

Question 7

What are the functions of ribosomes?

Answer 7

1. Translate encoded information from cell nucleus provided by mRNA
2. Link amino acids together
3. Export the polypeptide produced to the cytoplasm where it forms a functional protein

Question 8

What is the rough endoplasmic reticulum?

Answer 8

Involved in some protein production, protein folding, quality control and despatch.

Studded with ribosomes

Question 9

What is the smooth endoplasmic reticulum?

Answer 9

Associated with the production and metabolism of fats and steroid hormones.

It is a ‘smooth’ because it is not studded with ribosomes and associated with smooth, slippery fats.

Question 10

What is the chromatin?

Answer 10

A complex of nucleic acids (DNA or RNA) and proteins (histones).

Question 11

What is the golgi apparatus?

Answer 11

consists of stacked and flattened membranous sacs. Known as the principle ‘traffic director’ for cellular proteins.

Functions to modify, concentrate and package the proteins and lipids made at the RER

Question 12

What are lysosomes?

Answer 12

Spherical membranous organelles containing activated digestive enzymes.

Lysosome enzymes can digest almost all kinds of biological molecules.

Question 13

What is the cytosol?

Answer 13

The viscous, semi transparent fluid in which other cytoplasmic elements are suspended.

Question 14

What are the mitochondria?

Answer 14

Power plants of a cell, providing most of its ATP supply.

The density of mitochondria reflects the cell’s energy requirements, generally clustered where the action is.

Question 15

What are centrosomes?

Answer 15

Acts as a microtubule organizing centre.

Contains centrioles.

Question 16

What are centrioles?

Answer 16

Form the basis of cilia and flagella

Question 17

What is the nuclear envelope?

Answer 17

Binds the nucleus. Double membrane layer.

Maintains the shape of the nucleus and acts as a scaffold to organise DNA in the nucleus

Question 18

What are microtubules?

Answer 18

Hollow tubes made of spherical protein sub-units called tubulins.

Stiff but bendable, they determine the overall shape of the cell.

Question 19

What are the intermediate filaments?

Answer 19

Tough, insoluble protein fibres.

Attach to desmosomes and act as the ‘internal guy’ - wires to resist pulling forces exerted on the cell

Question 20

What is the plasma membrane?

Answer 20

interstitial fluid that is developed from the blood. Selectively permeable barrier.

Contains thousands of ingredients including amino acids, sugars, fatty acids, vitamins.

Question 21

What are 5 membrane transport mechanisms?

Answer 21

1. Diffusion
2. Osmosis
3. Facilitate diffusion
4. Active transport
5. Cytosis (vesicular transport)

Question 22

Define diffusion.

Answer 22

Diffusion is the tendency of molecules or ions to move from an area where they are in higher concentration to an are where they are in lower concentration, that is, down or along their concentration gradient until they reach their equilibrium.

Question 23

What factors affect the rate of diffusion?

Answer 23

Molecular size (the smaller, the faster due to less collisions)

Temperature (the warmer, the faster)

Question 24

Define osmosis.

Answer 24

Osmosis is the diffusion of a solvent, such as water, through a selectively permeable membrane.

Occurs whenever water concentration differs on the two sides of a membrane.

Question 25

Describe the process of osmosis.

Answer 25

Even though water is highly polar, it passes via osmosis through the lipid bilayer, passing through the hydrophobic lipid tails.

Question 26

What does it mean if a red blood cell is hypotonic?

Answer 26

Water is taken on by osmosis until they become bloated and burst

Question 27

What does it mean if a red blood cell is isotonic?

Answer 27

Cells remain their normal size and shape

Question 28

What does it mean if a red blood cell is hypertonic?

Answer 28

Cells lose water by osmosis and shrink

Question 29

What is facilitated diffusion?

Answer 29

Certain molecules, notably glucose and other sugars, some amino acids are transported passively even though they are unable to pass through the lipid bilayer.

Instead they move through the membrane by a passive transport process called facilitated diffusion.

Question 30

Describe the process of facilitated diffusion.

Answer 30

Molecules are either bound to protein carriers and carried across or they move through a water-filled protein channel.

Question 31

What is active transport?

Answer 31

Active transport moved solutes (i.e. Na+ and K+) against a concentration gradient.

To do this, cells must expend the energy of ATP

Question 32

What is cytosis/vesicular transport?

Answer 32

The transportation of fluids across cellular membranes inside membranous sacs called vesicles.