2.1.1 CELL STRUCTURE

Question 1

what are the two main types of organism and what creates the distinction?

Answer 1

• Prokaryotic organisms made up of prokaryotic cells (single-cellled organisms, smaller and simpler e.g. bacteria)
• Eukaryotic organisms made up of eukaryotic cells (complex and include all animal and plant cells)

Question 2

Define cell ultrastructure?

Answer 2

a cells organelles and internal structure

Question 3

2 types of eukaryotic cells

Answer 3

• animal
• plant

Question 4

What organelles are found in Animal cells? (structure and ultrastructure)

Answer 4

• plasma/cell surface membrane
• rough endoplasmic reticulum
• smooth endoplasmic reticulum
• nucleolus
• nucleus
• nuclear envelope
• lysosome
• ribosome
• Golgi apparatus
• cytoplasm
• mitochondrion

Question 5

What organelles are found in Plant cells? (structure and ultrastructure)

Answer 5

• plasma/cell surface membrane
• rough endoplasmic reticulum
• smooth endoplasmic reticulum
• nucleolus
• nucleus
• nuclear envelope
• lysosome
• ribosome
• Golgi apparatus
• cytoplasm
• mitochondrion
• **cell wall with plasmodesmata **(‘channels’ for exchanging substances between adjacent cells)
• vacuole (compartment that contains cell sap)
• **choloroplasts **(involved with photosynthesis)

Question 6

Difference between plant and animal cells?

Answer 6

Plant cells have the same organelles as animal cells with a few added extras:
* **cell wall with plasmodesmata **(‘channels’ / gaps in cell wall for exchanging substances between adjacent cells)
* vacuole (compartment that contains cell sap)
* **choloroplasts **(involved with photosynthesis)

Question 7

Organelles of eukaryotic cells

Answer 7

inc description and function

Question 8

Plasma membrane (aka cell surface membrane)

Answer 8

Desc:
* membrane found on the surface of animal cells and just inside the cell wall of plant cells and prokarytic cells
* made mainly of lipids and proteins

Fun:
* regulates movement of substances into and out of the cell
* has receptor molecules on it, allowing it to resond to chemicals like hormones
* compartmentalisation

Question 9

cyoplasm

Answer 9

Desc:
* found in animal / plant cells
* jelly like substance

Fun:
* cell support / structure
* cite of chemical reactions
* cytoskeleton

Question 10

Cell wall

Answer 10

Desc:
* a rigid structure that surrounds plant cells
* made mainly of carbohydrate cellulose

Fun:
* supports plant cells

Question 11

Nucleus

Answer 11

Desc:
* large organelle surrounded by a nuclear envelope (double membrane)
* contains many pores
* contains chromatin (made from DNA and proteins)
* often contains a nucleolus (small, dense spherical structure present during interphase)

Fun:
* controls cells activities (by controlling transcription of DNA)
* DNA contains instructions too make proteins (translation)
* pores allow substances (e.g. RNA) to move between the nucleus and the cytoplasm
* nucleolus makes ribosomes

Question 12

Lysosome

Answer 12

Desc:
* round organelles surrounded by a membrane with no clear internal structure

Fun:
* contains digestive enzymes kept speerate from cytoplasm by surrounding membrane, can be used to digest invading cells or to break down obselete / worn out components of the cell

Question 13

Ribosome

Answer 13

Desc:
* very small organelle that either floats free in the cytoplasm or is atttatched to the RER
* made up of proteins and RNA
* not surrounded by a membrane

Fun:
* site where proteins are made

Question 14

Rough endoplasmic reticulum

Answer 14

Desc:
* system of membrames enclosing a fluid-filled space
* surface is covered with ribosomes
* Cisternae flat membrane bound compartments

Fun:
* Folds and processses proteins that have been made at the ribosomes

Question 15

Smooth endoplasmic reticulum

Answer 15

Desc:
* system of membrames enclosing a fluid-filled space
* no ribosomes
* Cisternae flat membrane bound compartments
* continuous three-dimensional network of tubules, vesicles, and lamellae.

Fun:
* synthesises and processes lipids

Question 16

Vesicle

Answer 16

Desc:
* a smalll fluid-filled sac in the cytopalsm
* surrounded by a membrane
* formed by either the Golgi or SER/ RER or cell surface membrane

Fun:
* transports substances in and out of the celll (via the plasma membrane) and betweeen organelles

Question 17

Golgi appparatus

Answer 17

Desc:
* group of fluid-filled, membrane bound, flattend sacs where vesicles are often seen at the edges of the sace
* Cisternae flat membrane bound compartments

Fun:
* processes and packages new lipids and proteins
* makes lysosomes

Question 18

Mitochondrion

Answer 18

Desc:
* usually oval-shaped
* double membrane (inner folded to form structure called cristae)
* inner matrix containing enzymes involved in respiration
* Found in large numbers in cells that ar4e very activce and require a lot of energy

Fun:
* site of aerobic respiration where ATP is produced

Question 19

Chloroplast

Answer 19

Desc:
* smalll, flattend structure found in plant cells
* surrounded by double membrane
* membranes inside called thylakoid membranes which are stacked in some parts of the chloroplast to form Grana which are linked by lamellae which are thin flat pieces of thylakoid membrane
* stoma - thick fluid found in chloroplasts

Fun:
* site of photosynthesis (GRANA/STOMA)

Question 20

Centriole

Answer 20

Desc:
* small, hollow cylinders
* made of microtubules (tiny protein cylinders)
* found in alll animal cells but only some plant cells

Fun:
* involved with the seperation of chromsomes during celll division

Question 21

Cillium

Answer 21

Desc:
* smalll, hair like strcutures
* found on csm of some animal cells
* in cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside
* single pair of microtubules in the middle
* known as 9+2 formation becasue nine pairs surrounding two centeral mts

Fun:
* microtubules allow cillia to move
* used by cell to move substances along cs

Question 22

Flagellum

Answer 22

Desc:
* like cillia but longer
* stick out from cs surrounded by plasma membrane
* in cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside
* single pair of microtubules in the middle
* known as 9+2 formation becasue nine pairs surrounding two centeral mts

Fun:
* MTs contract to make flagellum move
* Flagella are used like outboard motors to propel cells forward (eg. when a sperm celll swims)

Question 23

organelles working together 2 main examples?

Answer 23

• Protein production
• The cytoskleton

Question 24

explain the process of protein production in eukaryotes

Answer 24

• proteins made at ribosomes
• ribosome at RER make proteins that are excretedor atttached to the cell membrane
• free ribosomes in cytoplasm make proteins that stay in the cytoplasm
• new proteins produced at RER are folded and processed (eg. sugar chains are added) in the RER
• transported from RER to Golgi in vesicles
• at Golgi proteins may undergo futher processing (eg. sugar chains are trtimmed or more are added)
• proteins enter more vesicles to be transported around the cell (eg. glycoproteins found in mucus move to the cell surface and are secreted

proteins may be stored at the RER until needed by the Golgi

Question 25

What is the cytoskeleton

Answer 25

• dynamic (constantly changing) allowing it to respond to changes in the cell and carrry out its functions
• a network of protein threads running through a solution of chemicals in the cytoplasm
• In euk cells protein threads are callled mfs (very thin protein strands) / mts (tiny protein cylinders)

Question 26

What are the four main functions of the cytoskeleton?

Answer 26

1. The microtubules and microfilaments support the cells organelled, keeping them in position
2. they also help to strengthen the cell and maintain its shape
3. Responsible for the transport of organelles and materia; within the cell (eg. movement of chromosomes when the seperate during cell divisiom depends on contraction of microtubules in the spindle, movement of vesicles around the cell relies on cytoskeletal proteins)
4. the proteins of the cytoskelton can also cause the cell to move (eg. movement of the cillia and flagella caused by cytoskeletal protein filaments that run through them so in the case of single cells that have a flagellum(eg. sperm cells), the cytoskeleton propels the whole cell)

Question 27

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