Chapter 2 Basic Components of Living Systems

Question 1

Function of the Nucleus

Answer 1

The nucleus contains DNA which is formed of chromosomes that are visible during cell division. The chromosomes are formed of a protein called histones which forms a complex called chromatin which coils around to form chromosomes. The DNA is in charge of protein synthesis although it happens in the ribosomes, it uses the DNA in the form of RNA to carry out protein synthesis. The DNA is not able to leave the nucleus because of the small pores in the nuclear envelope so RNA is used. The nucleus is in charge of metabolic activity since it produces the proteins used for metabolism.

The Nucleolus is in charge of producing ribosomes which are formed of proteins and RNA which are combined to form ribosomes for protein synthesis.

Question 2

Function of the Mitochondria

Answer 2

Mitochondria is where the final stages of respiration take place also producing energy which is then turned into ATP. The number of mitochondria in a cell reflect its activity. The mitochondria has two membranes, the inner and outer membrane. The inner membrane is called cristae which is highly folded and contains enzymes used in respiration. The fluid inside the mitochondria is called the matrix. Mitochondria contain there mt(DNA) which can produce its own enzymes and reproduce. Mitochondria also have ribosomes.

Question 3

Function of the Vesicles and Lysosomes.

Answer 3

Vesicles are sacs with a membrane that have the role of transporting materials around the cell. The lysosomes are specialised forms of vesicles because they contain hydrolytic enzymes. The lysosomes are responsible for breaking down waste material in the cells. They play an important role in the immune system of the cells. The play a role in programmed cell death or apoptosis.

Question 4

Functions and Structure of the cytoskeleton

Answer 4

The cytoskeleton is a network of fibres and tubes that are used for the shape and stability of the cell. It control cell movement and organelle movement.
The microfilaments contain fibres formed of protein actin which is responsible for cell movement. The microtubules are formed of gobular tubulin proteins that polymerise to form tubes that form a scaffold-like structure which act like tracks for vesicles around the cell. Spindle fibres are also formed of microtubules. There are also intermediate fibres which give mechanical strength and maintain there integrity.

Question 5

Function of the centrioles

Answer 5

They are a part of the cytoskeleton and they are in charge of producing the spindal fibres for cell division. They are also in charge of the positioning of cilia and flagella

Question 6

Function of Flagella and Cilia

Answer 6

Flagella are whip like and they are used to detect the chemical changes in the cells environment.
The re are two types of cilia mobile and stationary. The mobile cilia move around in a rhythmic manner, which create a current around the cell causing objects near the cell to move. The stationary cilia are used as sensory organs. Every cilia has two centroal microtubules surrounded by nine pairs of microtubules arranged like a wheel. Pairs of microtubules slide over each other causing a beating motion.

Question 7

Functions of Smooth Endoplasmic Reticulum

Answer 7

Has a similar structure to rough endoplasmic reticulum but it doesn’t have any ribosomes. It has the function of synthesising, storing and transporting lipids and carbohydrates - for example cholesterol and steroid hormones.

Question 8

functions of the Golgi Apparatus

Answer 8

Structure:
Contain fluid-filled, membrane-bound sacs known as cisternae.
Contain smaller vesicles.

Functions:
Process and package lipids and proteins - Carried out by the cisternae.
Store and transport lipids and proteins - Carried out by the vesicles.
Synthesise lysosomes - Specialised vesicles.

Question 9

Protein Production

Answer 9

(1) Proteins are synthesised at the ribosomes bound to the endoplasmic rectilum.
(2) They then travel in transport vesicles to the cis face of the Golgi apparatus. The vesicles fuse onto the Golgi apparatus and the proteins enter.
(3) In the cisternea the proteins are structurally modified before leaving the Golgi apparatus from its trans face.
(4) The vesicles travel and fuse with the cell surface membrane and release their contents by exocytosis. Some vesicles form lysosomes which contain enzymes for use in the cell.

Question 10

Functions of cellulose cell wall

Answer 10

Structure:
Made up of cellulose.
Contains channels (gaps) known as plasmodesmata (or plasmodesma if just one).

Functions:
Supports the cell - Contents of the cell press against the cell wall to make it rigid.
Prevents the cell from bursting - The cell wall can withstand high osmotic pressure.
Allows exchange of substances between cells - Plasmodesmata connects neighbouring cells.

Question 11

Functions of the Large Permanent vacuole

Answer 11

Structure:
Contains cell sap (solution of sugar and sugars).
Surrounded by a selectively permeable membrane known as a tonoplast.

Function:
Helps to maintain pressure within the cell, which keeps the cell rigid and stops the plant from wilting.

Question 12

Function of the Chloroplast

Answer 12

Structure:
Contain fluid-filled sacs known as thylakoids which are stacked up to form grana.
Surrounded by a double membrane, enclosing a fluid known as stroma.
Contain their own DNA and ribosomes.

Function:
Site of photosynthesis - These reactions take place in the grana and stroma.

Question 13

Differences with Prokaryotic cells

Answer 13

DNA - one molecule of DNA which is a chromosome which is super coiled without a membrane.
Ribosomes - Most prokaryotes have 70S ribosomes however these aren’t as good at producing more complex proteins.
Cell Wall - prokaryotes have a cell wall made of peptidoglycan AKA murein. It is a complex polymer formed from amino acids and sugars.
Flagella - Is thinner than the equivalent structure of eukaryotes and does not have the 9 + 2 arrangement. Energy to rotate the flagellum is supplied from a process called chemiosmosis, not from ATP as in eukaryotes. In this flagella a basal body attaches the flagella to the cell membrane. A molecular motor causes the hook to rotate giving the flagella a whip like movement which propells the cell.

Question 14

What was the first microscope to be developed and when

Answer 14

Light Microscopes in the 16th and 17th century.

Question 15

How a light microscope works

Answer 15

Has two lenses - the objective which is placed near the specimen and the eyepiece lens through which you view the specimen.
Illumination is provided by a light underneath the sample.

Question 16

Staining

Answer 16

Stains inrease contrast as different componenets within a cell take up stains to different degrees. The increase in contrast allows componenets to become visible so they can be identified.

Question 17

Magnification definition

Answer 17

How many times large the image is than the actual size of the object being viewed.

Question 18

Resolution definition

Answer 18

Is the ability to see individual objects as separate entities. Resolution is limited by the diffracction of light.

Question 19

Calculation for magnification

Answer 19

Magnification = size of image/ actual size of object

Question 20

Transmission electron Microscope

Answer 20

Similar to light microscope but here a beam of electrons is shined through and focused to produce an image.
This has the best resolution with a resolving power of 0.5nm.

Question 21

Scanning electron microscope

Answer 21

a beam of electrons is sent across the surface of a specimen and the reflected electrons are collected. The resolving power is from 3-10nm, so the resolution is not as good as the transmission microscope. It produces 3d images of the surfaces giving us information on the appearance of different organisms.

Question 22

Laser scanning confocal microscope.

Answer 22

Laser scanning confocal microscope moves a single spot of focused light across a specimen. This causes fluorescence from the components labelled with a dye. Light is then filtered through a pinhole aperture to only allow light radiated from very close to the focal plane to be detected.