Cells

Question 1

What is a cell?

Answer 1

The cell is the basic functional unit of all living things.

Question 2

What is the plasma membrane? (Cell membrane)

Answer 2

It’s the external part os the cell which enclosures the nucleus and cytoplasm.

Question 3

What is the cytoplasm?

Answer 3

It consists of specialized bodies called organelles suspended in a fluid matrix called cytosol.

Question 4

What is the cytosol made of?

Answer 4

Water and dissolved substances such as proteins and nutrients.

Question 5

What is the function of the plasma membrane?

Answer 5

Separate the internal metabolic events from the external environment and control the movement of materials into and out of the cell.

Question 6

What is the structure of the membrane?

Answer 6

The plasma membrane is a double phospholipid membrane (lipid bilayer) with the polar hydrophilic heads forming the two outer faces and the non-polar hydrophobic tails pointing toward the inside of the membrane.

See in folder: Class 1
File: Plasma Membrane - Structure - Hydrophobic and Hydrophilic.

Question 7

Where are the proteins scattered through?

Answer 7

The flexible phospholipid membrane.

Question 8

How is it called the proteins which attach loosely to the inner or out membrane surface?

Answer 8

Peripheral or extrinsic proteins.

Question 9

How is it called proteins which extend into the membrane?

Answer 9

Integral or intrinsic proteins.

Question 10

How is it called proteins which span the whole membrane?

Answer 10

Transmembrane proteins.

Question 11

What are the parts of a transmembrane protein?

Answer 11

Hydrophobic regions (alpha helical chains) and hydrophilic regions (beta sheets)

Question 12

What is the fluid mosaic model?

Answer 12

A model which explains the structure of functional cell membranes. Explanation: Phospholipid bilayer + proteins; Fluid: Phospholipid and proteins can move (sideways); Mosaic: pattern produced by the scattered protein molecules when the surface of the membrane is viewed from above.

Question 13

How does a cell rises?

Answer 13

From preexisting cells by cell division.

Question 14

How does it work a phospholipid bilayer?

Answer 14

Tails points inwards, facing each other and forming non-polar hydrophobic interior;

The phospholipids heads face the aqueous medium that surrounds the membranes;

Phospholipid tails: Saturated or unsaturated;

More unsaturated phospholipid tails more fluid membrane;

The longer the tails the less fluid membrane.

Question 15

What Hydrophobic tails are made of?

Answer 15

Fatty acids.

Question 16

What types of fatty acids are there?

Answer 16

Unsaturated: containing double bonds.
Saturated: contains only single bonds.

Question 17

What do the double bonded fatty acids (unsaturated) produces?

Answer 17

characteristic kinks (dobras) that make the membrane more fluid.

Question 18

What does the colesterol do?

Answer 18

Fills the kinks produced by unsaturated fatty acids, distributed throughout the phospholipid bilayer providing some rigidity to the plasma membranes of animal cells.

Question 19

What is a glycolipid?

Answer 19

lipid molecules on the outer surface of the cell surface membranes with short carbohydrate chains attached to them.

Question 20

What is a glycoprotein?

Answer 20

protein molecules with short carbohydrate chains attached to them.

Question 21

What is a glycocalyx?

Answer 21

A sugary coating to the cell made of carbohydrate chains. In animal cells it’s formed mainly from glycoproteins. In plants cells it mainly comprises of glycolipids.

Question 22

What is the function of the carbohydrate chains on the membrane structure?

Answer 22

They project itself like antennae into the watery fluids surrounding the cell, where they form hydrogen bonds with the water molecules and so help to stabilise the membrane structure. The carbohydrate chain form a sugary coating to the cell, known as glycocalyx.
They also help the glycoproteins and glycolipids to act as receptors molecules, chi bind with particular substances at the cell surfaces. Different cells has different receptors, depending on their function.

Question 23

What are the 3 major groups of receptors?

Answer 23

1) Signalling receptors: part of the signalling system that coordinates the activities of cells; The receptors recognise messenger molecules like hormones and neurotransmitter, which are chemicals that cross synapses allowing nerve impulses to pass from a cell to another. When the molecules binds to the receptor, series of chemical reactions triggered inside the cell.
2) Endocytosis receptors: They bind molecules that are part of structures to be engulfed by the cell surface membrane.
3) Binding receptors: Bind cells to other cells (cell adhesion) on tissues and organs of animals.

Question 24

What does a signalling receptor?

Answer 24

part of the signalling system that coordinates the activities of cells; The receptors recognise messenger molecules like hormones and neurotransmitter, which are chemicals that cross synapses allowing nerve impulses to pass from a cell to another. When the molecules binds to the receptor, series of chemical reactions triggered inside the cell.

Question 25

What does a endocytosis receptor?

Answer 25

They bind molecules that are part of structures to be engulfed by the cell surface membrane.

Question 26

What does a binding receptor?

Answer 26

Bind cells to other cells (cell adhesion) on tissues and organs of animals.