CELL STRUCTURE FLASHCARDS

Define organelles

Components of cells which perform a specific function

Define ultrastructure

The internal structure of a cell

Whats the largest organelle in the cell

The nucleus

What organelle stores DNA

Nucleus

What are the three main functions of the nucleus

Store and transmit genetic info. Provide mRNA for protein synthesis. Act as the control centre of the cell

How is the nucleus separated from the rest of the cell

Presence of the nuclear envelope

What is the nuclear envelope composed of

A double membrane containing nuclear pores

What do the nuclear pores allow

Allow substances to pass through, like mRNA, ribosomes and some hormones like steroid

Whats contained in the nucleoli

Densley packed DNA and protein

Where is ribosomal RNA made

Nucleolus

Where are ribosomes assembled

Nucleolus

How is chromatin formed

DNA being tightly packaged through association with histone proteins

What is chromatin and where is it found

Nucleus. It's genetic material and condenses into tightly coiled chromosomes

How does the nucleus control all the cells activities

By controlling the transcription of DNA

Whats the cytoplasm in the nucleus called

Nucleoplasm

How big are ribosomes

20nm wide

Do ribosomes contain a membrane

No

What are the two subunits that make up ribosomes

40s (smaller) and 60s (bigger) subunits

What is each subunit of ribosomes made out of

Ribosomal RNA and protein

Where can ribosomes be found

On the R.E.R or free floating in cytoplasm

Whats the function of the ribosomes bound to the rough endoplasmic reticulum

Synthesise proteins to be exported out of the cell

Whats the function of free floating ribosomes

Synthesise proteins that will be used inside the cell

Whats the function of the mitochondria

Carry out aerobic stages of respiration to produce ATP

Whats the function of the membrane of the mitochondria

Controls what enters and exits the mitochondrion

Whats the purpose of the cristae

Increase SA for attachment of proteins involved in aerobic respiration

What does the matrix contain

Enzymes for aerobic respiration, lipids, ribsomones and DNA

Whats the function of mitochondrial ribosomes and mitochondrial DNA

Allow the mitochondria to self replicate in response to increased energy demand

What is the cell surface membrane composed of

Two layers of phospholipids (phospholipid bilayer)

Whats the essential role of the cell surface membrane

Controls what enters and exits the cell

What does the cell surface membrane have on it

Receptors to interact with other proteins and respond to chemicals like hormones

What does the cytoplasm contain

Dissolved molecules that take part in metabolic reactions

What is the cytoskeleton

Complex network of proteins in the cytoplasm

Whats the function of the cytoskeleton

Give the cell mechanical strength and involved with movement of organelles in the cell

What are the three components of the cytoskeleton

Microfilaments, intermediate filaments and microtubules

Whats the smallest component of the cytoskeleton

Microfilaments

How big are microfilaments

7nm

What are microfilaments made of

Actin

What is actin

A polypeptide that makes up microfilaments

Whats the functions of the microfilaments

The mesh in cytoplasm is important for maintaining shape and mechanical strength and important for cell movement in cells like amoebas and lymphocytes

Whats the second smallest component of the cytoskeleton

Intermediate filaments

How big are intermediate filaments

10nm in diameter

What are intermediate filaments made out of

Interlocking protein fibres

Whats the functions of the intermediate filaments

Anchor the nucleus within the cytoplasm and are able to extend outside the cell, allowing cells to stick together and communicate

What are the largest type of cytoskeleton filament

Microtubules

How big are microtubules

18-30nm in diameter

What are microtubules made out of

Tubulin

What are microtubules important for

Movement of substances and organelles in cytoplasm

How do microtubules carry out their function

Help of dynein and kinesin which walk along the microtubules and carry organelle with them.

What are dynein and kinesin

Cytoskeletal motor proteins

What do motor proteins need to carry out their function

Energy from ATP hydrolysis

What do microtubules compose and why

The spindle for cell division, it enables chromosomes to be moved within the cell

What are centrioles made up of

Microtubules

How is the spindle formed

Long microtubules extend from the centrioles

What are centrioles and microtubules also important for (excl. cell division)

Formation of cilia and undulipodia

What are cilia and undulipodia

Protrusions from cells which are surrounded by a cell membrane

How are cilia and undulipodia formed

Centrioles divide and line up at cell membrane. The microtubules grow outwards which deform the membrane and form protrusions

Whats the difference between cilia and undulipodia

Cilia are shorter

Give and example of cells that have many cilia and why

Epithelial cells lining airways to help mucus move along airways

Why do most cells have at least one cilium

They contain receptors allow the cell to detect signals in environment

Whats the only human cell that contain undulipodia and why

Sperm cells to enable them to move

What type of cells are lysosomes highly abundant in

Secretory cells

Why type of bilayer surrounds lysosomes

Lipid bilayer

Give an example of a lysosome

Vesicles

Where are vesicles formed

Golgi apparatus

What do vesicles contain

Digestive enzymes like proteases, lipases and lysozymes

What is the function of lysozymes

Hydrolyse specific bacterial cell walls

Where are vesicles abundant in

Phagocytic cells

Whats the function of the vesicle

Keep the hydrolytic enzymes in separate compartments

Name some roles of lysosomes

Hydrolysis of material ingested by phagocytic cells. Digestion of old or damaged organelles to recycle useful components. Complete breakdown of cells when they have died. Release of enzymes to digest material outside of cells.

Whats the fluid in the E.R called

Cisternae

Whats the main function of the R.E.R

Provide a large surface area for protein synthesis

Whats the main function of the S.E.R

Synthesise, store and transport lipids and carbohydrates

What does the S.E.R contain many of and why

Enzymes to aid lipid metabolism incl. synthesis of cholesterol and steroid hormones

Whats the function of the golgi

Modifies and repackages proteins, lipids and carbohydrates

How are proteins modified in the Golgi Apparatus

By joining them with other molecules

Give examples of how proteins can be modified

Lipids added to make lipoproteins, sugars added to make glycoproteins and polypeptides can be joined together to make the full protein

What come off the Golgi to form a vesicle

Proteins, carbohydrates and lipids

Where do the vesicles get sent to after budding off the Golgi

Cell surface and other places within the cell for storage

What happens to the vesicles once they reach the cell surface

Used for incorporation into the plasma membrane and secretion or to be exported outside the cell

What is the first stage of protein synthesis

Gene coding for insulin in transcribed into mRNA in the nucleus

What happens after the mRNA is transcribed into the nucleus

It leaves the nucleus through the pores and travels to the ribosomes on the R.E.R

What happens when mRNA reaches the R.E.R

The ribosomes translate the mRNA and assemble insulin molecules, then pass into the cisternae of the R.E.R

What happens when mRNA goes reaches the cisternae of the R.E.R

The vesicles with the insulin are pinched off the R.E.R and travel to the Golgi Apparatus

What helps the vesicles get to the Golgi

Microtubules and motor proteins

What happens when the vesicles get to the Golgi

They fuse together

What happens when the vesicle fuses with the Golgi

The insulin molecule is processed and packaged

What happens when the insulin is packaged and processed

The modified molecules bud off from the Golgi in vesicles

What happens when the vesicles bud off the Golgi

The vesicles travel towards and fuse with the plasma membrane

What happens when the vesicles fuse with the plasma membrane

The plasma membrane opens to release the molecules outside (exocytosis)

How big are chloroplasts

4-10µm

Whats the function of the chloroplast

Site of photosynthesis

Whats the function of the double membrane of the chloroplast

Controls what enters and leaves the chloroplast

What is a granum

A stack of thylakoids

What do thylakoids contain

Chlorophyll

Where does the first stage of photosynthesis take place?

In the chlorophyll

How are the grana linked together

By intergranal lamellae

What is the stroma

Fluid filled chamber surrounding the grana.

Where does the second stage of photosynthesis take place

Stroma

What does the stroma contain and why

Enzymes, starch grains, DNA and ribosomes, allowing chloroplasts to quickly and easily manufacture proteins for photosynthesis

What do plant vacuoles contain

Dissolved solutes