Module 2-Cells

Question 1

Eukaryotic cell basic features

Answer 1

~Make up complex eukaryotic organisms
~Larger than prokaryotes
~Cells arise by mitosis or meiosis
~Cell surface membrane is made up of a phospholipid bilayer

Question 2

Prokaryotic cell features

Answer 2

~Make up single celled prokaryotic organisms
~Cells arise from other cells by binary fission
~Do not have membrane bound organelles

Question 3

What are the sub-cellular structures in animal cells?

Answer 3

Mitochondria, ribosomes, ER, golgi, lysosomes, nucleus, cell membrane, centrioles

Question 4

What are the sub-cellular structures in plant cells?

Answer 4

Mitochondria, ribosomes, ER, golgi, nucleus, cell membrane, vacuole, chloroplasts, cell wall made of cellulose

Question 5

What is the nucleus?

Answer 5

Contains the cells DNA and is surrounded by a nuclear envelope

Question 6

What is the nuclear envelope?

Answer 6

Double membrane structure that has a number of pores. Both membranes are phospholipid bilayers. The pores control the passage of ions, molecules and RNA between the nucleoplasm and cytoplasm.

Question 7

What is the nucleolus?

Answer 7

Made of proteins, RNA and DNA. Ribosomal RNA is joined together with associated proteins in the nucleolus to assemble the ribosomal subunits. Secondary roles include immobilising proteins and forming signal recognition particles.

Question 8

What is the mitochondria?

Answer 8

The mitochondria makes ATP via aerobic respiration.

Question 9

Describe the structure of the mitochondria

Answer 9

Oval shaped, double mebraned organelle that have their own ribosomes and DNA. Each membrane is a phospholipid membrane embedded with proteins. The inner layer of the membrane has folds called cristae, the area surrounded by the folds is called the mitochondrial matrix which contains membranes used for respiration.

Question 10

What is the golgi apparatus?

Answer 10

series of flattened membranous sacs that release golgi vesicles. They also transport, package and modify proteins and lipids into vesicles for delivery to targeted destinations.

Question 11

What are the golgi vesicles?

Answer 11

Membrane bound, fluid filled vesicles located in the cytoplasm. They are small, round and are seen in a high density near the edges of the golgi sacs.

Question 12

What are lysosomes and lysozymes?

Answer 12

Lysosomes are a type of golgi vesicles which store and transport modified proteins and lipids from the golgi apparatus to target cells. Lysozymes are enzymes in the lysosomes which aid the breakdown of proteins, polysaccharides, lipids, nucleic acids and old organelles.

Question 13

What are the ribosomes?

Answer 13

Can be free floating in the cytoplasm or attached to the cytoplasmic side of the ER. They are very small and made of protein sub units. They aren’t covered by a membrane and are in charge of protein synthesis.

Question 14

What is the ER in general?

Answer 14

a series of interconnected membranous sacs and tubules responsible for modifying proteins and synthesising lipids. Membrane is a phospholipid bilayer embedded with proteins.

Question 15

What is the RER?

Answer 15

RER has ribosomes on its surfaces and is responsible for processing and folding proteins.

Question 16

What is the SER?

Answer 16

SER has no ribosomes on its surface and is responsible for making and processing lipids.

Question 17

What is the plasma membrane?

Answer 17

The fluid mosaic model says that it is made up of a variety of components that are continuously moving around. they are partially permeable and the attachment point for some extracellular and intracellular structures.

Question 18

What is the cell wall?

Answer 18

Rigid covering that protects the cell. Plant and agal cell walls are made of cellulose, fungal cell walls are made of chitin. Provide structural support and provides shape for the cell.

Question 19

What are centrioles?

Answer 19

have a cylindrical shape and are made up of parallel micro tubules that surround a central cavity. Mostly found in pairs that are arranged at right angles to each other. Are a key component of centrosomes which are crucial for organising micro tubules in the cell and help organise the mitotic spindle during cell division.

Question 20

What are flagella?

Answer 20

hair like structures
eukaryotic flagella have a 9+2 arrangement, bacterial flagella are helical and are mainly made up of protein flagellin.
are used by some organisms for locomotion
eukaryotic flagella generate propulsion using a whipping motion whereas bacterial flagella move in a propeller way.

Question 21

What are cilia?

Answer 21

have a central core called axoneme. primary cilia have a 9+0 arrangement whereas motile cilia have a 9+2 arrangement. Help to move substances internally by synchronising their beating.

Question 22

What are the jobs of the cytoskeleton?

Answer 22

-maintains cell shape
-secures some organelles in specific positions
-allows cytoplasm and vesicles to move within the cell
-enables cells with multicellular organisms to move

Question 23

What are the 3 types of protein fibre within the cytoskeleton?

Answer 23

-microfilaments
-intermediate filaments
-microtubules

Question 24

What is the role and structure of the microfilaments?

Answer 24

-thicken the cortex within the inner edge of a cell and resist tension
-made of 2 intertwined strand of globular proteins (called actin) which works with a motor protein (called myosin) to help cellular events requiring motion
-can disassemble and reform quickly allowing the cell to change its shape and move. White blood cells make use of this ability as they can move to the site of infection and phagocytose the pathogen.

Question 25

What is the role and structure of the intermediate filaments?

Answer 25

-found throughout the cell and hold organelles in place
-are made of several strands of fibrous proteins that are wound together and able to bear tension, maintaining the shape of the cell and anchoring the nucleus and other organelles in place.

Question 26

What is the role and structure of microtubules?

Answer 26

-found in the interior of the cell where they maintain cell shape by resisting compressive forces
-widest components of the cytoskeleton (diameter of around 25 nm)
-walls made of polymerised dimers of 2 globulised proteins (alpha and beta tubulin)
-can disassemble and reform quickly
-provide a track in which vesicles move through the cell
-pull replicated chromosomes to opposite ends of a dividing cell
-are structural elements of flagella, cilia and centrioles

Question 27

Definition of magnification

Answer 27

Process of enlarging an object in appearance

Question 28

Definition of resolution

Answer 28

The ability of a microscope to distinguish between 2 adjacent points on an object. The higher the resolution the better the detail of an image.

Question 29

Features of a light microscope

Answer 29

-visible light passes and is bent through the lens system to enable the user to view the specimen
-specimen can be alive
-individual cells are usually transparent and their components are not distinguishable unless stained however this usually kills the cells.
-maximum resolution is 0.2 micrometers
-maximum magnification is x 1500
-nucleus and mitochondria can be seen

Question 30

Features of a scanning electron microscope

Answer 30

-beam of electrons moves backwards and forwards across a cells surface creating details of the cells surface characteristics
-knocks electrons off the specimen and these come back together to form an image
-can be 3D
-do not have to be thin specimens like in a TEM
-resolution is lower than that of a TEM

Question 31

Features of transmission electron microscope?

Answer 31

-electron beam penetrates the cell and provides details of a cells internal structures
-in thin specimens you can see the internal structures of organelles such as chloroplast
-uses electromagnets to focus the electron beam
-maximum resolution of 0.0002 micrometres
maximum magnification is around x 1,500,000

Question 32

Dry mount

Answer 32

-solid specimens are viewed whole or sectioning is used where the sample is cut into very thin slices
-specimen is placed on the centre of the slide and a cover slip is placed over the sample
-e.g hair or pollen

Question 33

Wet mount

Answer 33

specimens are suspended in a liquid such as water or oil
cover slip is placed on at an angle
e.g aquatic samples

Question 34

Squash slides

Answer 34

a wet mount is prepared and then a lens tissue is used to gently press down the cover slip
e.g soft sample, root tip

Question 35

Smear slides

Answer 35

the edge of a slide is used to smear the sample creating a thin and even coating on another slide. a cover slip is then placed over the sample.
e.g blood

Question 36

Why is crystal or methylene blue used as a stain?

Answer 36

as they are positively charged dyes they are attracted to negatively charged materials in the cytoplasm leading to staining of cell components.