CELL STRUCTURE AND DIVISION

Topic 2A

What is the difference between prokaryotic cells and eukaryotic cells

• prokaryotic cells are smaller and simpler

  or

• eukaryotic cells are complex and larger

Give 4 examples of eukaryotic cells

• animal cells

• plant cells

• algal cells

• fungal cells

Give 1 example of a prokaryotic cell

• bacteria

Name the 3 extra organelles in a plant cell than in an animal cell

• cell wall

• chloroplast

• vacuole

In a plant cell, what is the cell wall made of

• cellulose

In an algal cell, what is the cell wall made of

• cellulose

In a fungal cell, what is the cell wall made of

• chitin

What is the structure of the cell-surface membrane

• found on the surface of animal cells

• found inside the cell wall of other cells

• mainly made of lipids and protein

What is the function of the cell-surface membrane

• regulates the movement of substances into and out of the cell

• has receptor molecules on it, this allows it to respond to chemicals like hormones

What is the structure of the nucleus

• A large organelle surrounded by the nuclear envelope (double membrane) which contains nuclear pores

• the nucleus contains chromosomes which are made from protein bound linear DNA

• contains nucleolus which floats in the nucleoplasm

What is the function of the nucleus

• controls the cells activities by controlling the transcription of DNA

• DNA contains instructions to make proteins

• the nuclear pores allow substance like RNA to move between the nucleus and the cytoplasm

• the nucleolus makes ribosomes

What is the structure of the mitochondrion

• oval shaped (usually)

• double membrane

• inner membrane is folded to form structures called cristae

• inside is the matrix which contains enzymes involved in respiration

What is the function of the mitochondrion

• the site of aerobic respiration

• where ATP is produced

What is the structure of the chloroplast

• A small, flattened structure in plant and algal cells

• surrounded by a double membrane

• contains membranes inside called thylakoid membranes which are stacked up in parts of the chloroplast to form grana

• grana are linked together by lamellae

• contains stroma in the middle (like a cytoplasm for the chloroplast)

What is the function of the chloroplast

• the site of photosynthesis

• some parts of photosynthesis occur in the grana and other parts happen in the stroma (a thick fluid)

What is the structure of the Golgi apparatus

• a group of fluid-filled, membrane bound flattened sacs

• vesicles are often seen at the edges of these sacs

What is the function of the Golgi apparatus

• processes and packages new lipids and proteins

• makes lysosomes

What is the structure of the Golgi vesicle

• a small fluid filled sac in the cytoplasm

• surrounded by a membrane

• produced by the Golgi apparatus

What is the function of the Golgi vesicle

• store lipids and proteins made by the Golgi apparatus

• transports these lipids and proteins out of the cell membrane

What is the structure of the lysosomes

• a round organelle

• surrounded by a membrane

• type of Golgi vesicle

What is the function of the lysosomes

• contains digestive enzymes called lysozymes

• these enzymes can be used to digest invading cells or break down worn out components of the cell

What type of cell is the 70S ribosome found in

• prokaryotic

What type of cell is the 80S ribosome found in

• eukaryotic

What is the structure of a ribosome

• a very small organelle that either floats freely in the cytoplasm or is attached to the RER

• it is made up of proteins and RNA it is not surrounded by a membrane

• it is made of a small and large subunit

What is the function of the ribosome

• site where proteins are made

What does RER stand for

• rough endoplasmic reticulum

What does SER stand for

• smooth endoplasmic reticulum

What is the structure of the RER

• a system of membranes enclosing a fluid filled space

• the surface is covered with ribosomes

What is the function of the RER

• folds and processes proteins

What is the structure of the SER

• a system of membranes enclosing a fluid-filled space

• no ribosomes

What is the function of the SER

• synthesises and processes lipids

What is the structure of the cell wall

• a rigid structure that surrounds cells in plants, algae and fungi

• in plants and algae the cell wall is made of cellulose

• in fungi the cell wall is made of chitin

What is the function of the cell wall

• supports cells and prevents them from changing shape

What is the structure of the vacuole

• a membrane-bound organelle

• found in the cytoplasm

• contains cell sap- a weak solution of sugar and salts

• the surrounding membrane is called the tonoplast

What is the function of the vacuole

• helps to maintain pressure in the cell

• keeps the cell rigid

• stops plants wilting

• involved in the isolation of unwanted chemicals in the cell

What are epithelial cells in the small intestine specialised for

• food absorption

What is a tissue

• a group of cells working together to perform a specific function

What is an organ

A group of different tissues working together

Name the parts of an animal cell

• cell surface membrane

• nucleus

• nucleolus

• nuclear envelope

• nuclear pores

• nucleoplasm

• mitochondria

• cytoplasm

• Golgi apparatus

• Golgi vesicle

• lysosome

• RER

• SER

• ribosome

Name the parts of a plant cell

• cell surface membrane

• nucleus

• nucleolus

• nuclear envelope

• nuclear pores

• nucleoplasm

• mitochondria

• cytoplasm

• Golgi apparatus

• Golgi vesicle

• lysosome

• RER

• SER

• ribosome

• chloroplast

• vacuole

• cell wall

Name the parts of a bacterial cell

• slime capsule

• cell wall

• plasma membrane

• plasmids

• circular DNA

• flagellum

• cytoplasm

• ribosomes

In bacterial cells what is the cell membrane made of

• lipids

• proteins

In bacterial cells what is the cell wall made of

• murein - a glycoprotein

What is the function of the slime capsule in bacteria

• helps protect it from attack by the immune system

What are plasmids

• small loops of DNA

• contains genes for things like antibiotic resistance

Do prokaryotic cells contain membrane bound organelles

• no

What type of ribosomes do bacterial cells contain

• 70S

What is the job and structure of the flagellum

• rotates to make the prokaryotic cell move

• its a long hair-like structure

Name 3 parts of a virus

• core of genetic material (DNA or RNA)

• protein coat around the core called a capsid

• attachment proteins stick out from the edge of the capsid. These let the virus cling onto a suitable host cell

How do prokaryotic cells replicate

• binary fission

What are the 4 steps of binary fission

• circular DNA and plasmids replicate (plasmids can replicate more than once)

• cell grows and the DNA loops move to opposite poles of the cell

• cytoplasm begins to divide

• cell wall forms and two daughter cells are produced

Describe how viruses replicate

• they use their attachment proteins to bind to complimentary receptor proteins on the surface of host cells

• they inject their DNA/RNA into the host cell

• the host cell uses its machinery to replicate the parts of a virus

• the virus assembles and leaves the cell

Explain why some viruses can only infect one type of cell

• different viruses have different attachment proteins

• therefore they require different receptor proteins on the host cell so some viruses can only infect one type of cell

Define magnification

• how much bigger the image is than the specimen

Define resolution

• how well a microscope can distinguish between two points that are close together

What is the equation for working out magnification

• magnification= image size / actual size

What are the two types of microscope

• light

• electron

What is the maximum magnification on a light microscope

• X1500

What is the maximum resolution on a light microscope

• 0.2 micrometres

Name 2 types of electron microscope

• transmission electron microscope

• scanning electron microscope

How do TEMs work

• uses electromagnets to focus a beam of electrons which is transmitted through the specimen

• denser parts of the specimen absorb more electrons which makes them look darker on the final image

Give 1 advantage of TEMs (transmission electron microscopes)

• very high resolution so you can see the internal structure of organelles like chloroplasts

Give 1 disadvantage of TEMs (transmission electron microscopes)

• can only be used on thin specimens

How do SEMs work

• they scan a beam of electrons across the specimen. this knocks off electrons from the specimen which are gathered in a cathode ray tube to form an image

Give 2 advantages of SEM (scanning electron microscopes)

• images can be 3D

• can be used on thicker specimens

Give a disadvantage of the SEM (scanning electron microscope)

• it has a lower resolution than the TEM

What method is used to separate out different organelles in a cell

• cell fractionation

What are the 3 steps of cell fractionation

• homogenisation

• filtration

• ultracentrifugation

Within cell fractionation, describe homogenisation

• the process of breaking up the cells

• this can be done by vibrating them or by grinding them in a blender

• this breaks the plasma membrane and releases the organelles into solution

When breaking up the cells during homogenisation, the solution that the organelles fall into have to have 3 important conditions what are they

• cold - this is to reduce the activity of enzymes that break down organelles

• isotonic - this means it has the same concentration of chemicals and water as the cell being broken down to prevent damage to the cells through osmosis causing the cell to burst.

• A buffer solution added - to maintain the pH

Within cell fractionation, describe filtration

• the solution is filtered through a gauze to separate any large cell debris or tissue debris

Within cell fractionation, describe ultracentrifugation

• you have a solution containing organelles

• to separate a particular organelle from the others, you use ultracentrifugation

• the cell fragments are poured into a tube

• the tube is put in a centrifuge and is spun at a low speed

• the heaviest organelles collect at the bottom of the tube forming a thick sediment called the pellet

• the rest of the organelles are suspended above the sediment - supernatant

• supernatant is drained off

• centrifuge is spun faster and the next heaviest organelle collects

• this is repeated at higher and higher speeds

After being in the centrifuge, a thick sediment forms at the bottom of the tube. What is this called

• the pellet

After being in the centrifuge, a thick sediment forms at the bottom of the tube and there is a solution containing the rest of the organelles on top. What is this called

• supernatant

During ultracentrifugation, in what order do the organelles get separated

• nuclei

• chloroplast

• mitochondria

• lysosome

• ER

• ribosomes

What are the 2 types of cell division

• mitosis

• meiosis

What is mitosis needed for

• growth

• repair

The cell cycle consists of a period of growth and DNA replication. what is this called

• interphase

Interphase is separated into 3 stages. what are these called

• G1 or gap phase 1

• synthesis

• G2 or gap phase 2

What happens during gap phase 1

• cell grows

• new organelles and proteins are made

What happens during the synthesis stage of interphase

• cell replicates its DNA

What happens during gap phase 2

• cell grows

• proteins needed for cell division are made

What are the 4 stages of mitosis

• prophase

• metaphase

• anaphase

• telophase

What joins two chromatids

• centromere

What is one strand of a chromosome called

chromatid

Describe prophase

• chromosomes condense getting shorter and fatter

• tiny bundles of protein called centrioles start moving to opposite ends of the cell forming a network of protein fibres across it called the spindle

• the nuclear envelope breaks down and the chromosomes lie free in the cytoplasm

Describe metaphase

• the chromosomes line up down the middle of the cell and attach to the spindle fibres by their centromere

Describe anaphase

• the centromeres divide separating each chromatid

• spindles contract

• this pulls the chromatids to opposite poles of the spindle

• this makes chromatids appear to be V shaped

Describe telophase

• the chromatids reach opposite poles on the spindle

• they uncoil and become long and thin again

• they are now called chromosomes again

• nuclear envelope forms

• this forms 2 nuclei

• division of the cytoplasm (cytokinesis) occurs

• this results in 2 genetically identical daughter cells

What is cytokinesis

• division of the cytoplasm

What stage of the cell cycle is this

• anaphase

What stage of the cell cycle is this

• telophase

What stage of the cell cycle is this

• prophase

What stage of the cell cycle is this

• metaphase

Explain what is cancer the result of

• uncontrolled cell division

• due to a mutation in a gene that controls cell division

• this causes cells to keep dividing which causes a tumour

• cancer is the result of a tumour that invades surrounding tissue

What controls mitosis and the cell cycle

• genes

What part of the cell cycle does chemotherapy disrupt and how

• G1

• this prevents the synthesis of enzymes needed for DNA replication

• this disruption to the cell cycle forces it to kill its self

What part of the cell cycle does radiation disrupt and how

• Synthesis

• radiation damages DNA at several points in the cell cycle (before and during S phase) the DNA in the cell is checked for damage

• if there is damage, the cell will kill itself

what is the advantage of light microscopes

• cheap

What is the advantage of electron microscopes

• high resolution and magnification