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MPHARM > The Cell > Flashcards

The Cell Flashcards

1
Q

Cell Parts

A

Cells – the basic unit of life
Organelles - small structures inside a cell with specific functions.

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2
Q

Cell Membrane/Plasma Membrane

What is the function and structure of the cell membrane?

A

Function: Regulates materials entering and exiting the cell.

Structure: Two layers of phospholipids, proteins

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3
Q

Cytoplasm

What is the cytoplasm, where is it and what is its structure?
What is the cytosol?

A

All cell contents that lie between the cell membrane and the nucleus. (organelles + cytosol)

The cytoplasm is inside the membrane but outside the nucleus

Structure: made up of fluid and organelles except for nucleus

Cytosol = liquid portion/non-organelles.

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4
Q

Nucleus

What is the function and structure of the nucleus?

A

Function:
The Nucleus has many functions.
- “Control Centre.” Regulates DNA & RNA actions.
- It controls and regulates activities of the cell.
- It controls, genetic information, protein synthesis, cell division and cell growth.
- It stores DNA, RNA and ribosomes.
- It regulates transcription of the mRNA
- It produces ribosomes

Structure:
The Nucleus is a membrane bound organelle and it is the largest organelle in a cell. It consists of the nuclear envelope, nucleoli, chromatin, nuclear lamina and nucleoplasm.
Contains DNA

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5
Q

General nuclear morphology

Can Nuclei have variations in shape size and location?

What are their common features?

A

Nuclei have variation in shape, size and location
- can be oval, flattened, tiny, huge, single, many, lobed or position variable

They have some common features:
- Large, spherical organelle
- Near center of cell
- about 6 μm in diameter
- about 10 % of the cell volume

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6
Q

Do all eukaryotic cells have a nucleus?

A

Although most cells have a nucleus, there are exceptions. The best-known is the red blood cell, whose function is to carry oxygen from the lungs to the body’s tissues
They are called ‘anucleate cells’

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7
Q

Look at notes for diagram of nuclear structure

A
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8
Q

Nuclear Envelope

What is the function and structure of the nuclear envelope?

A

Function: Regulates what enters or exits the nucleus. - has nuclear pores for this

Structure: Surrounds the nucleus and has a double Layer of Lipids (inner and outer membrane)

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9
Q

Nucleolus

What is the function and structure of the nucleolus?

A

Function: Produces RNA, which are used to make all proteins. (produces ribosomes and rRNA)

Structure: Inside Nucleus, separate from DNA, spherical structure

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10
Q

Nuclear Lamina

What is the nuclear lamina?

A

Protein mesh which provides mechanical support to the nucleus

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11
Q

Nucleoplasm- What is it?

A

An amorphous fluid containing soluble components such as proteins, RNA, ribonucleoproteins and small molecules

It also contains the fibrous chromatin (50% protein and 50% DNA ) which occupies about 80- 90% of the nuclear volume

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12
Q

DNA – Deoxyribonucleic acid

What is the function and structure of DNA?

What is chromatin and what are chromosomes?

A

Function: Provides information on how to make proteins. (codes for protein synthesis)

Structure: Made up of nucleotides, locked in the nucleus. 2 strands of polynucleotides which form a double helix- held together by hydrogen bonds between bases. Two strands are antiparallel. 2 Sugar Phosphate backbones.

Chromatin – unorganized DNA (normal state)
A complex of DNA, and histone proteins which can condense to form visible chromosomes.

Chromosomes – organized DNA (present before cell division)

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13
Q

Endoplasmic Reticulum

What are the main functions of the endoplasmic reticulum

What is the structure of endoplasmic reticulum?

How much of the membrane in the cell does it comprise?

A

Function:
- Detoxification of drugs
- Translocation of proteins.
- Glycosylation of proteins - adding sugar to them
- Assembly of lipid bilayers

Structure: tubes and channels (they have cisternae), have a single membrane, often associated with vesicles - these bud off the ER to transport proteins to the Golgi body

Typically comprises more than 50% of membrane in the cell

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14
Q

What are the 2 main types of endoplasmic reticulum?

A

Rough Endoplasmic Reticulum:
- Covered with ribosomes
- Lots of them in cells carrying out extensive protein synthesis
- synthesises and transports proteins

Smooth Endoplasmic Reticulum:
- Has no ribosomes
- synthesises and transports lipids
- Lots of them in cells with lipid and drug metabolism

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15
Q

Ribosomes

What is the function and structure of ribosomes?

A

Function:
Synthesises proteins.

Structure:
small circular organelles
Complex of ribosomal proteins and ribosomal RNA
Consists of both a smaller subunit and a larger subunit which each contain protein and RNA molecules
Found free in the cytoplasm or attached to RER

Lots of drugs work on 70s ribosomes of prokaryotes (targeted). They are different from our 80s ribosomes

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16
Q

Vacuoles and vesicles

What is the function and structure of vacuoles and vesicles?

A

Function: Storage for water, nutrients or waste.

Structure: small membrane-bound organelle

(won’t find it in prokaryotes)

17
Q

Lysosomes

What is the function and structure of lysosomes?

A

Function: contain enzymes that break down materials in a cell.
- Digest macromolecules
- Cleans up broken down organelles

Structure: Small membrane-bound organelles/ vesicles containing digestive enzymes

White blood cells attack and destroy invaders - they digest them in lysosomes.

18
Q

Lysosomal enzymes

What pH do lysosomal enzymes work best at?

How do lysosomes create this pH environment?

Why is it important to create this pH environment?

Why evolve digestive enzymes which function at a pH different from cytosol?

A

Lysosomal enzymes work best at pH 5

There are proteins in the lysosomal membrane which pump H+ ions from cytosol into lysosome

It is important because enzymes are proteins, so they are very sensitive to pH as it affects their structure

Evolved this way as a safety measure - digestive enzymes won’t function well if some leak into the cytosol due to it not being the right pH, so self-digestion won’t occur (autolysis)

19
Q

Lysosomal storage disease (very rare)

(information- no need to memorise)

A

Lipids
- Gaucher’s disease
- Niemann-Pick disease
- Tay Sachs

Glycogen & other polysaccharides
- Farber disease
- Krabbe disease

Proteins
- Schindler’s disease

20
Q

Lysosomes can be used to kill cells when they are supposed to be destroyed

Why do some cells have to die?
What is this process called?
Describe the process.

A

Some cells have to die for proper development in an organism

process - apoptosis
- “auto-destruct” process
- lysosomes break open & kill cell

Examples
ex: tadpole tail gets re-absorbed when it turns into a frog
ex: loss of webbing between your fingers during foetal development

21
Q

Cellular digestion (process involving lysosomes)

A

Lysosomes fuse with food vacuoles

Polymers digested into monomers (by digestive enzymes)

Monomers pass to cytosol to become nutrients of the cell

22
Q

Mitochondria

What are the functions and structure of mitochondria?

What the mechanism mentioned involves?

Are mitochondria present in all eukaryotic cells?

How big are mitochondria?

A

Function: Produce energy for the cell – site of cellular respiration. “The Powerhouse”
Major function is energy conversion and ATP generation
Convert food energy (carbs and fatty acids) to ATP- Oxidative phosphorylation
Mechanism involves electron transport chain, proton gradients and coupled ATP synthesis

Structure: Double membrane-bound (envelope), intermembrane space between 2 membranes, kidney/bean shaped, Inner membrane is highly folded, extensions from inner membrane called cristae, has a matrix space, has ribosomes, has chromosomes (5-10 copies)

Present in all eukaryotic cells
Fairly large organelles (approximately 1μm diameter)
(only get mitochondrial DNA from mother)

23
Q

Mitochondrial Function = Oxidative metabolism
The conversion of food energy into chemical (ATP) energy can be divided into 3 stages:

A

1 - Large molecules broken down into smaller subunits
2 - Numerous small molecules converted to a few key molecules which play a central role in metabolism
3 - Oxidation to produce ATP

(Look at notes for a diagram)

24
Q

ATP

What is ATP?

What happens when ATP energy is hydrolysed?

A

ATP is considered the molecular unit of intracellular energy currency.

When ATP energy is hydrolysed, it generates energy for all cellular processes

25
Q

Totally quantity of ATP in an adult is approximately 0.10 mol/L.

But…..approximately 100 to 150 mol/L of ATP are required daily so we only have enough for around 2 minutes

Solution: each ATP molecule is recycled 1000 to 1500 times a day

Thus, the human body turns over its weight in ATP daily. 65 kg ATP recycled per day in a normal resting adult (Figure 74-5).

A
26
Q

Mitochondrial ATP synthesis

Describe the process

A

The energy from the high energy electrons is used to pump protons (H+) across the inner mitochondrial membrane from the matrix and into the inter-membrane space

The protons then flow back down the concentration/ proton gradient and this energy drives coupled ATP synthesis (flow of H+ ions provides sufficient energy to produce ATP)

(Look at notes for a diagram)

27
Q

Pharmaceutical example- Mitochondrial diseases

Mitochondrial inheritance behaves differently to nuclear inheritance
When a mitochondrion divides, the 5-10 copies of DNA are divided randomly between the two new mitochondria

Why do mutations to mitochondrial DNA occur frequently?

So what does this tell you about the frequency of mitochondrial disorders?

A

Mutations to mitochondrial DNA occur frequently, due to error-prone DNA replication (unlike nuclear DNA)

This means mitochondrial disorders occur spontaneously and relatively often

About 1 in 4,000 children will develop mitochondrial disease by the age of 10 years

28
Q

Golgi apparatus
(also known as Golgi complex, Golgi Apparatus, Dictyosome(plants))

What is the function of the Golgi apparatus?

A

Transport, modification and packaging of proteins.
Also protein processing- Cleavage of peptides to produce activated proteins
And protein sorting and localisation

29
Q

What is the structure of the Golgi body

A
  • consists of a series of cisternae (around 4 - 8) which are flattened, stacked pouches -has associated vesicles.
  • It has a slightly concave, polarised structure. Matrix proteins aid in holding this structure together. This structure is further supported by cytoplasmic microtubules.
  • There are 3 primary compartments of the Golgi apparatus, these include cis, medial and trans. Cis is the compartment which is closest to the endoplasmic reticulum. The middle layers of the cisternae make up the central compartment. Trans is the compartment furthest away from the endoplasmic reticulum.

There’s variability in size and number of compartments

30
Q

Protein modifications

A

Addition of sugars (glycosylation to give proteoglycans)

Addition of fatty acids (production of lipoproteins)

Addition of phosphate groups (phosphorylation)

31
Q

Cytoskeleton

The cytoskeleton is an essential component of all eukaryotic cells and extends throughout the entire cytoplasm

What is the function and structure of the cytoskeleton?

A

Function:
Provide support and structure for the cell.
(Provides a supporting framework for the cell and gives the cell its particular shape)
Actin filaments anchored just underneath the plasma membrane are responsible for changing the shape of the cell

Structure: Tubules
It includes microfilaments and microtubules

Analogy – Wood, cement, steel beams
(Look at notes for a diagram)

32
Q

What does the cytoskeleton and its associated motor proteins do? Give 2 examples

A

Cytoskeleton and its associated motor proteins organises and moves the cytoplasmic contents
- Movement of organelles (microtubules)
- Movement of vesicles (microtubules)

Whole cell movement is polarised and directional
Movement of cells is important in developmental processes

33
Q

Centrioles

What is the function and structure of the centrioles?

A

Function: microtubules that help divide the cell during cell division.
(spindle fibres form from them)

Structure: Tubules

(Look at notes for a diagram)

34
Q

Cilia and Flagella
What is the function and structure of the cilia and flagella?

A

Function:
Provides movement for the cell or objects moving by the cell.

Structure:
Flagella – 1 long fibre
Cilia – many short fibres

MPHARM (13 decks)

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