Cell structure

What 2 things should be described, for a 2 mark graph question, on describing relationships?

The general trend and an observation and description of a specific point on the graph

How much of the cell cycle is the interphase?

90%

What is stage 1 of the interphase?

Growth 1

What is used to macerate the root tip in the mitosis practical?

A mounted needle

Why is the coverslip lowered at an angle, onto the sample, in the mitosis practical?

to prevent air bubbles

What direction does the cover slide need to be pressed down onto the sample, in the required practical for mitosis?

down vertically

What is used to see the cells in the sample in the mitosis practical?

A light microscope

Why are random fields of view used in the mitosis practical?

To remove bias

What is being counted in the mitosis practical?

dividing and non dividing cells, seperately

Why do HCl and acetic orcein both require safety goggles and spill management?

they are corrosive irritants

How are the risks of cutting oneself with a scalpel or mounted needle reduced in the mitosis practical?

Used pointing away from the body

Why must sideways movement of rhe coverslip be avoided in the mitosis practical?

it rolls the cells, destroying the delicate chromosome structures

Why are the root tips (end 1-2mm) used in the mitosis practical?

They contain meristem, which is where cells are rapidly dividing

Why is HCl used to

It stops mitosis happening and hydrolyses the cell wall and middle lamella

Why is the cell macerated in the mitosis practical?

To seperate cells and help the stain access the cells

How is mitotic index calculated?

Number of cells with visible chromosomes/Total number of visible cells

What happens in G1 of the interphase?

The cell grows physically larger. Organelles replicate, and the cell builds up a large reserve of proteins and ATP.

What is the 2nd phase in the interphase?

S

What happens in the S phase of the interphase?

DNA replication occurs. Every chromosome in the nucleus creates an exact copy of itself. The quantity of DNA inside the cell exactly doubles, though the total number of chromosomes remains the same.

What is the 3rd stage of the interphase?

Growth 2

What happens in G2 of the interphase?

The cell grows a bit more and synthesises the proteins needed for mitosis

What is the first stage of mitosis?

prophase

What is the prophase of mitosis?

hromosomes condense becoming visible under a light microscope. They appear as two sister chromatids joined at a centromere. The nuclear envelope breaks down and disappears, exposing the chromosomes to the cytoplasm. The centrioles migrate to opposite poles of the cell.The centrioles begin developing protein spindle fibres, which form the spindle apparatus.

What is the 2nd stage of mitosis?

Metaphase

What happens in the metaphase of mitosis?

Chromosomes line up perfectly along the equator of the cell. The spindle fibres attach directly to the centromere of each chromosome.

What is the 3rd stage of mitosis?

anaphase

What happens in the anaphase of mitosis?

he centromeres divide in two, releasing the sister chromatids from each other. The spindle fibres contract and shorten. This pulls the individual chromatids (now called chromosomes again) rapidly to opposite poles of the cell.

What is the final (4th) stage of mitosis?

telophase

What happens in the telophase of mitosis?

The chromosomes reach the opposite poles of the cell and begin to decondense , becoming long, thin, and invisible. A new nuclear envelope reforms around each separate group of chromosomes, creating two distinct nuclei. The spindle apparatus disintegrates and breaks down.

What is the final stage of the cell cycle?

cytokinesis

What happens in cytokinesis?

the cytoplasm divides forming 2 genetically identical daughter cells.

What is cancer caused by?

a genetic mutation in the genes that regulate the cell cycle

What does the mutation in a cancer cell cause?

uncontrolled cell division, resulting in the growth of an abnormal mass of cells called a tumour.

How do most cancer treatments work?

They disrupt the cell cycle, to stop rapid cell division

What cell division stage does cisplatin disrupt?

Interphase S phase

How does cisplatin treat cancer?

binds to DNA and prevent it from replicating. If DNA replication fails, the cell cycle stops, triggering apoptosis (cell death).

What part of the cell replication do drugs like vincristine or taxol disrupt?

The metaphase and anaphase of mitosis

How do drugs like vincristine or taxol disrupt mitosis and treat cancer?

inhibit the formation or contraction of spindle fibres. Without functional spindles, the chromosomes cannot line up or separate correctly, halting mitosis completely.

Why do cancer treatments cause immune supression and hair loss?

they are not highly specific to cancer cells so they target all rapidly dividing cells

Where does plant growth occur?

Meristems

Why is the absolute tip of a plant root used in the practical on mitosis?

it contains rapidly dividing cells

Why are meristem tissues stained in the mitosis required practical?

to make the naturally colorless chromosomes visible under a light microscope.

why is the sample squashed in the required practical for mitosis?

squashing the sample creates a single, thin layer of cells so light can pass through the specimen clearly.

How big of a sample is cut from the very tip of the squash using a sharp scalpel in the mitosis practical?

5-10mm

Why is the squash root tip placed in HCl for 15 minutes?

To break down the middle lamella and soften cell walls

How is the squash sample incubated in the mitosis practical?

15 minutes in a beaker with HCl

What is done to the squash sample, after being incubated, in the mitosis practical?

Rinse the tissue thoroughly in cold distilled water and place it onto a clean microscope slide

What is used to stain the squash sample?

acetic orcein stain

How long should the squash sample be left for, after having acetic orcein stain applied to it, in the practical for mitosis?

2 minutes

What is the nuclear envelope?

a double membrane with nuclear pores to allow movement of mRNA and ribosomal subunits move between the nucleus and the cytoplasm

What is the nucleoplasm full of?

chromatin, consisting of DNA associated with histone proteins.

What is the role of nucleolus?

assembles ribosomal subunits and produces RNA

How many nucleoli are there in a nucleus?

1 or more

What is the function of the nucleus?

to store genetic information of the cell and is the site of transcription and DNA replication

What is the mitochondria surrounded by?

A double membrane

What is the function of the mitochondria?

To produce ATP via aerobic respiration

What are the folds in the inner membrane of the mitochondria called?

Cristae

What is the advantage of having folded cristae?

Increased surafce area for electron carriers and ATP synthase

What is the matrix in the mitochondria?

The fluid filled centre which contains enzymes for the link reaction and the krebs cycle

Why does mitochondria contain its own circular DNA?

To code for specific mitochondrial proteins

Which ribosomes do mitochondria contain?

70s

What is the function of smooth endoplasmic reticulum?

To synthesise, store, and transport both lipids and carbohydrates

What is the structure of smooth endoplasmic reticulum?

made of a network of membrane-bound tubules

Describe the structure of rough endoplasmic reticulum

made of a network of flattened membrane-bound sacs called cisternae, with ribosomes attached to its surface.

What is the function of the rough endoplasmic reticulum?

The ribosomes synthesise proteins, and the endoplasmic reticulum is involved in the processing and folding of the proteins.

Describe the structure of the golgi apparatus

made of a stack of flattened membrane-bound sacs called cisternae.

What is the function of the golgi apparatus?

Receives proteins and lipids and modifies and packages them.

Where would a secretory enzyme be made?

Golgi apparatus

What is a fungal cell wall made of?

Chitin

What is a bacterial cell wall made of?

Murein

What is a plant cell wall made of?

Cellulose

Is the cell wall permeable?

Yes

how are adjacent cell walls held together?

By a layer called the middle lamella and are connected by plasmodesmata, which are microscopic channels of cytoplasm that pass through the cell walls.

How do the modified molecules bud off?

In vesicles

Where do vesicles transport processed molecules?

Through the cytoplasm to other parts of the cell. Vesicles can fuse with the cell-surface membrane, releasing their contents outside the cell by exocytosis.

What are vesicles involved in the formation of?

Lysosomes

What is a triplet of bases called?

A codon

What is the function of a ribosome?

Site of DNA translation and protein synthesis

Where are 80s ribosomes found?

In the cytoplasm of eukaryotic cells, and on the rough endoplasmic reticulum

Where are 70s ribosomes found?

In prokaryotes, mitochondria and chloroplasts

What is a ribosome made of?

A large subunit and a small subunit, which come together when when they bind to a mRNA molecule

Where are centrioles found?

In animal cells

What is the function of centrioles?

To Organise the spindle fibres during cell division.

What is the function of spindle fibres?

to attach to chromosomes and help separate the chromosomes during cell division.

What ribosomes are found in Prokaryotes ?

70s

What is the function of plasmids in a prokaryote?

To carry non-essential DNA, which can be shared to other prokaryotes

How is essential DNA stored in prokaryotes?

in a singular DNA strand found in the cytoplasm

What is the function of a glycoprotein capsule on a prokaryote?

To prevent dessication and evade phaocytosis

What is the function of a flagellum?

Locomotion

How many flagella do prokaryotes have?

0,1 or many

What are pili on some prokayotes?

fine protein strands used to attach to surfaces or to transfer Plasmids during conjugation

Describe the structure of centrioles

A pair of cylindrical structures made of microtubules.

What are lysosomes enclosed by?

a single membrane

What is the function of the lysosomal membrane?

To prevent hydrolytic enzymes entering the cytoplasm and digesting the cell

What is found in the inner lumen/matrix of a lysosome?

a high concentration of hydrolytic enzymes

What is the optimal pH for hydrolase enzymes?

4.5-5

Why do Transmission electron microscopes have the highest resolution?

The electron beam used has a short wavelength

Why may a TEM be used specifically?

So internal structures can be seen, as they have the highest resolution