Module 2- Foundations in Biology

What images do light microscopes produce?

Semi- detailed, magnified 2D images of specimens using light

Do light microscopes require specimens to be dead?

No

What images do TEM microscopes produce?
3D or 2D?

- Detailed images of dead specimens.
- 2D

What images do SEM microscopes produce?
3D or 2D?

- Detailed image of specimens surface
- 3D

What microscope has produced this image ?

TEM

What microscope has produced this image ?

SEM

What microscope has produced this image?

Light Microscope

Do electron microscopes require specimens to be dead?

Yes

Microscopy:
Why are stains used on specimens?

To highlight specific components or structures.

Microscopy:
Why would a wet mount be used for a specimen?

To prevent the specimen from drying out.

What is the difference between magnification and resolution?

Magnification increases the size of the image, resolution is the ability to tell 2 close objects apart.

Define resolution

The ability to distinguish two close together but separate objects

Name 12 Animal cell components.

- plasma membrane
- Cell wall
- Nucleus
- Nucleolus
- Nuclear envelope
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum
- Golgi apparatus
- Ribosomes
- Mitochondria
- lysosomes
- centrioles

What is the function of the plasma membrane?

Controls the movement of substances into and out of the cell

What is the function of the Cell wall?

Provides structure and support, prevents cells from bursting

What is the function of the nucleus?

Contains DNA, controls metabolic processes inside cell

Name a cellular activity the nucleus controls

Cell division

What is the nuclear envelope?

double membrane with pores surrounding the nucleus.

What is the function of the rough ER?

Responsible for synthesis and transport of protein.

What is the function of the smooth ER?

Produces and stores lipids and carbohydrates.

what is the structural difference between SER and RER?

RER has ribosomes on surface, SER does not

What is the function of the Golgi apparatus?

modifies proteins and packages them into vesicles.

What is the function of mitochondria?

Site of aerobic respiration and production of ATP.

What is the function of ribosomes?

Site of protein synthesis

What is the function of lysosomes?

Contains hydrolytic enzymes for the breakdown of waste materials in cells.

Which system do lysosomes play an important role in?

Immune system.

What is the role of lysosomes in the immune system?

Break down pathogens ingested by phagocytic cells.

What is apoptosis?

programmed cell death

Give 2 examples of what lysosomes break down:

Old organelles, pathogens

What are centrioles?

- Part of the cytoskeleton, made of microtubules
- involved in the organisation of spindle fibres during cell division

Name 2 components in plant cells and not in animal cells

- Vacuole
- Chloroplasts

What is the cell cycle?

an ordered sequence of events taht take place in a cell resulting in division of a cell forming 2 identical daughter cells

What is the interphase?

The longest stage of the cell cycle, where the cell works normally but prepares for cell division.

Are cells dividing during the Illnterpahse?

No

What is the longest phase in cell division?

Interphase

What happens during interphase?

5 points

* DNA replicates and is checked for errors
* Protein synthesis occurs in the cytoplasm
* Mitochondria- grows and divides, increases in number
* In plant cells - grow and divides, increases in number
* Normal metabolic processes carry on occurring

List the three stages of interphase

G1

S

G2

In the interphase what does S mean

Synthesis phase

What is the G1 phase during interphase?

first growth phase

What happens during G1 in interphase?

4 things

Preparation for DNA replication

Cell grows in size

Organelles are replicated

Protein synthesis

What happens during the S phase of interphase?

DNA is replicated in the nucleus

What is the G2 phase in Interphase?

Second growth phase

What happens during G2 ?

3 things

Cell size increases

Energy stores increase

Duplicated DNA checked for errors

What is the M stage?

Mitotic stage

What two stages does the mitotic phase consist of?

Mitosis

Cytokinesis

What happens during Mitosis?

Cell division

What happens during mitosis?

The nucleus divides

What happens during cytokinesis?

The cytoplasm divides and 2 cells are produced

What is the G0 pahse?

the phase when the cell leaves the cycle either temporarily or permenantly

3 brief reasons why a cell may enter the G0 phase

Cell is already specialised

DNA of the cell may be damaged

Senescent cells

\

Why must the cell cycle be controlled?

(4points)

To ensure that the cell has:

\- grown to the correct size

\- that replicated DNA is error free,

\- chromosomes are in their correct positions during mitosis

\- to ensure that 2 identical daughter cells are created from the parent cell

What are checkpoints ?

checkpoints are the control mechanisms of the cell cycle

What do checkpoints do?

They monitor and check that processes of the cell cycle have been accurately completed

When does the G1 checkpoint happen?

At the end of the G1 phase just before the cell enters G2

What does the G1 checkpoint check for?

3 points

\- cell size

\- nutrients

\- growth factors

\- DNA damage

What will happen if an error in DNA of the cell is found at the G1 at the G0 checkpoint?

The cell will enter G0 and will not go back into the cell cycle- this period is called permanent cell arrest

When does the G2 checkpoint occur?

end of G2 phase before the start of the mitotic phase

What does the G2 checkpoint check for?

\- DNA replication

\- Cell size

\- DNA damage

What is the metaphase checkpoint also called?

Spindle assembly checkpoint

What does the Metaphase checkpoint check for?

correct attachment of chromosomes to spindle fibres

When does the Metaphase checkpoint occur?

After the metaphase before the anaphase

What are enzymes?

Biological catalysts

What type of proteins are enzymes, globular or fibrous?

Globular

What is an anabolic reaction?

Metabolic reactions that construct molecules from smaller units

Which type of reaction requires energy from ATP hydrolysis?

Anabolic reactions

What is a catabolic reaction?

Metabolic reactions that break molecules down into smaller units

Which type of reaction releases energy

Catabolic or anabolic?

Catabolic

Which reaction builds molecules and requires energy?

Anabolic reaction

Which reaction breaks up molecules and releases energy?

Catabolic

Define metabolism

The sum of all of the different chemical reactions that take place in living cells

What is the name which describes

“Enzymes can only increase the rate of a reaction up to a certain point”?

Vmax

What does Vmax mean in enzyme action?

The maximum initial rate of the enzyme catalysed reaction

What must happen in order for an enzyme controlled reaction to happen?

Substrate and enzyme molecules must collide

What is meant by specificity of enzymes?

Enzymes are specific to particular substrates, and have specific active sites complementary to the substance they catalyse the breakdown of

What is activation energy?

The energy required to begin a reaction

What do enzymes do?

Reduce the activation energy required

What are the two models of enzyme action?

• lock and key model

• Induced fit hypothesis

What forms when the substrate is bound to the enzyme?

An enzyme substrate complex

Summarise the lock and key model (3 points)

• Enzyme and substrate are complementary

• Specific enzyme ‘fits’ into the active site of the enzyme

• Products released leaving the enzyme unchanged

What is the induced fit hypothesis?

A modified lock and key explanation for enzyme action where the enzyme becomes slightly modified in shape when binding to the substrate

What an intracellular enzyme?

An enzyme that acts within the cell

Give an example of an intracellular enzyme…

Catalase

What is catalase an example of?

An intracellular enzyme

What does catalase do?

Breaks down hydrogen peroxide into oxygen and water

Which enzyme breaks down hydrogen peroxide?

Catalase

True/False ?

“ Catalase is an extracellular enzyme”

False, intracellular

Why is catalase important? (2)

• Because it breaks down hydrogen peroxide in plant and animal tissues

• Hydrogen peroxide is toxic

What is an extracellular enzyme?

Enzymes that work outside the cell that made them

Usually extracellular enzymes work outside the cell that made them, how does this differ in fungi? (3 steps)

• In fungi the enzyme is secreted outside of the body

• Organic matter is broken down

• Then it is absorbed and used by the fungi for growth

Give 2 examples of extracellular enzymes involved in digestion .

Amylase, trypsin

Why are extracellular enzymes necessary?

Because large molecules that cannot enter cells directly through the cell surface membrane need to be broken down into smaller components first

State 2 types of organisms that rely on extracellular enzymes to gain nutrition

Single celled, multicellular

Why is starch digested in 2 steps?

Because two enzymes are needed, each enzyme catalyses 1 reaction

In the first step of digestion of starch what are starch polymers broken into?

A disaccharide; maltose

Which enzyme is involved in the breakdown of starch into maltose?

Amylase

Where is amylase secreted? (2)

• Saliva in the mouth

• pancreatic juice in the small intestine

After starch is broken down into maltose by amylase; what happens next?

Maltose is broken down into glucose by maltase

What does maltase break maltose down into?

Glucose

True or false

“Maltose is a monosaccharide”

If false, give the correct answer

False, disaccharide

Where can maltase be found?

In the small intestine