1
Q
Cell definition
A
a collection of living matter enclose by a membrane
2
Q
Types of cells
A
Prokaryotic cells
- a cell that lacks a nucleus (still has DNA)
Eukaryotic cells
- a cell that contains a membrane-bound nucleus and other membrane-bound organelles
3
Q
Cell Theory
A
- all organisms are composed of cells
- all cells arise from pre-existing cells
- The cell is the basic unit of life
4
Q
Organelles
A
structures suspended in the cytoplasm that carry out a particular function
5
Q
Cell membrane structure
A
- phospholipid bilayer -> a hydrophilic polar phosphate head and a hydrophobic non-polar lipid tail
6
Q
Cell membrane function
A
- separates intracellular fluid from extracellular fluid (protects the cell)
- regulates what enters and exits the cell (selectively permeable membrane)
- supports the cell and is sensitive to changes
7
Q
Homeostasis
A
maintaining a constant internal environment
achieved by:
- exchange of nutrients & waste
- maintaining a constant temperature
- blood glucose levels
- water
- concentration of fluids
- blood pressure
- heart rate
8
Q
Fluid mosaic model of the cell membrane
A
Fluid - phospholipids are constantly moving
Mosaic - made up of individual parts joined together
9
Q
Cytoplasm structure
A
- cytosol: thick watery fluid that is 70-90% water
- contains dissolved ions, salts & carbs
10
Q
Cytoplasm function
A
- supports floating organelles
- suspends non-water soluble proteins & lipids
11
Q
Nucleus structure
A
- largest organelle
- contains genetic material (DNA)
- contains chromatin (contains DNA & proteins called histones)
12
Q
Nucleus function
A
controls cell activity
13
Q
Nucleolus structure
A
- suspended in nucleoplasm
- contains RNA
14
Q
Nucleolus function
A
produces ribosomes -> role in protein synthesis
15
Q
Nuclear envelope structure
A
- dense spherical structure
- made of an inner & outer membrane (two phospholipid bilayers)
- nuclear pores -> allow movement of molecules
16
Q
Nuclear envelope function
A
seperate the cytoplasm from the contents of the nucleus
17
Q
Ribosomes structure
A
- Composed of RNA & protein
- Consists of a large subunit and a small subunit
- Make in nucleolus
18
Q
Ribosomes funtion
A
Site of protein synthesis - amino acids join to make proteins
19
Q
ER Structure
A
- parallel membranes
- a system of membrane channels and flattened sacs continous with the outer membrane of the nuclear envelope
20
Q
ER Function
A
- connects cell membrane with nuclear membrane
- Transports proteins around the cell and involved in the manufacture of lipids
21
Q
Rough ER
A
- ribosomes on the surface -> move proteins into Rough ER so it can be transported through in vesicles (sacs)
- provides a surface for chemical reactions involving protein synthesis
22
Q
Smooth ER
A
- no ribosomes
- synthesises lipids & steroids (e.g. cholesterol, estrogen)
23
Q
Golgi body structure
A
- 3-20 flattened, stacked curved sacs (vesicles that are received from ER are broken down to form Golgi vesicles at the other end)
24
Q
Golgi body function
A
- Modify & package proteins in vesicles for secretion
25
Golgi body location
- near nucleus
- surrounded by vesicles
26
Protein processing examples
- add sugars -> ***glycoproteins***
- remove 1st amino acid from new proteins -> ***functioning proteins***
27
Lysosome function
**breakdown** molecules and old organelles
28
Lysosome structure
- contains **enzymes (made in Rough ER)**
- ***made in Golgi body***
- spherical sacs surrounded by single membrane
- more common in **animal cells**
- *kind of like specialised vesicles*
29
Enzymes in lysosomes
- highly ***acidic*** - powerful digestive
function:
- digests large molecules
- recycle cellular resources (by ***apoptosis*** - programmed cell death of worn-out organelles)
30
Mitochondria structure
- contains **ribosomes** and **own DNA**
double membrane:
- inner: convoluted to form ***cristae*** and surrounds a liquid ***(matrix)*** and is coated in **enzymes**
- outer: contains ***transport protein*** and forms ***aqueous channels*** for molecules to enter
- intermembrane space: breaks down **carbs**
31
Mitochondria function
- release energy to the cell - ***cellular respiration***
32
ATP process
***adenine triphosphate***
- matrix **enzymes** supply hydrogen and electrons to reactions in cristae
- energy is released by breaking the molecule to **ADP - *adenine triphosphate***
- then recycles to conversion back to ATP during aerobic respiration
33
Endosymbiont theory
- some of the organelles in eukaryotic cells (***mitochondria & chloroplasts***) have evolved from organelles in prokaryotic cells
34
Centrioles structure
- pair of **hollow cylindrical** structures - make up of bundles ***microtubules***
-*** not found in plant cells***
35
Centrioles function
- help organise ***cell division*** - produces **spindle** to seperate cells
- aren't always needed in the process
36
Vesicles structure
**membrane-bound** sac
37
Vesicles function
**stores** materials for ***transport***
38
Microtubules function
rods that keep **organelles in place** or **move them** in and out of cell
39
Cilia structure
- hair like projections
- on outside of cell
40
Cilia function
**beat to move** cell or materials across the cell surface
41
Microvilli
- finger-like extensions of the cell surface membrane
- in epithelial cells
- increase **surface area**
42
Endomembrane system
**restrict enzymatic reactions** to **specific compartments** within the cell
consists of:
**- nuclear envelope**
- ER membranes
- golgi apparatus
**- vesicles**
43
Cholesterol function
keeps the **structure** of cell membrane
44
Peripheral proteins
***Glycoprotein*** - *(a.k.a **recognition** protein)* cell **signalling** through **antigens**
45
Transmembrane proteins
*span the entire membrane*
*a.k.a. **integral** proteins*
- **channel proteins**: forms a channel through the membrane for ***smaller molecules*** to pass
- **carrier proteins**: binds to ***larger molecules*** and helps them move across the membrane (*they are **specific***)
- **receptor proteins**: binds with molecule out of cell to ***make a change*** inside cell (*they are **specific***)
46
Cell transport
the movement of molecules **across** the membrane
- passive - doesn't require energy
- active - requires energy
47
Simple diffusion
movement of lipid-soluble substances **that can diffuse** between the phospholipids of the membrane
48
Molecules that can undergo simple diffusion
***lipid-soluble molecules:***
- oxygen
- carbon dioxide
- fatty acids
- alcohol
- steroids
49
Diffusion
the **net** movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient as a result of their random movement until they reach an equilibrium (equal)
*most efficient way to get particles in and out of cell*
50
Concentration gradient
**difference** in concentrations on either side of the membrane
- **greater** concentration gradient = **steeper** gradient on graph = ***faster reaction***
51
Factors affecting the rate of diffusion
- **distance** particles travel
- **concentration gradient**
- **surface** area
52
Osmosis
diffusion of **water** across a semi-permeable membrane from an area of ***high water concentration to an area of low***
water is small enough to fit between the phospholipids without touching *(but can also go through **channel proteins**)*
53
Osmotic pressure
- ***concentration of water*** depends on how much **solute** is dissolved
- low pressure = dilute solution
- high pressure = concentrated solution
54
Tonicity
a measure to ***compare water concentration*** in 2 diff solutions by comparing the ***concentration of solutes*** that can't cross the cell membrane
55
Isotonic cell
concentration of solute is the **same** inside and outside of cell
water will move in and out of cell ***at equal rate***
56
Hypertonic cell
concentration of solute is ***more outside cell***
water moves **out** of cell
cell ***shrinks***
57
Hypotonic cell
concentration of solute is ***less outside cell***
water moves **into** cell
cell ***bursts***
58
Facilitated Transport
the use of ***channel or carrier proteins*** to move across the membrane
59
Facilitated **Diffusion**
***water-soluble molecules*** must pass through channel proteins
**e.g. water & ions (calcium, sodium)**
60
Carrier-mediated Transport
***used for larger molecules** (e.g. glucose, amino acids)*
- carrier proteins open on ***one side*** on cell membrane
- binds to molecules, changes shape to release it to other side
- can become **saturated** when all the carriers are **occupied** - *concentration will not increase the rate of movement*
61
Carrier-mediated transport types
- facilitated diffusion -> **with** the concentration gradient ***through a protein carrier***- no energy required
- ***active transport*** -> **against** the concentration gradient - energy required
62
Vesicular transport
movement of substances in and out of cell **enclosed in vesicles**
- vesicles can ***fuse*** with cell membrane or ***form from*** membrane
- a.k.a. ***bulk transport*** - transports large amounts of materials
63
Endocytosis
type of vesicular transports that brings material **into** the cell
*- membrane surrounds & encloses extracellular material
- vesicle then **pinches off** and is suspended in cytoplasm*
- phagocytosis *(cell-eating)*
- pinocytosis *(cell-drinking)*
64
Exocytosis
contents of a vesicle are pushed **out** of cell
*- vesicle forms inside cell, migrates to membrane & fuses with it, contents are pushed out*
65
Why are cells so small?
Cells must be small enough so they can have a ***higher/larger surface area to volume ratio*** in order to exchange materials efficiently
**otherwise requirements cannot be met**
66
Structural levels of the body
cells -> tissues -> organs -> systems -> organisms
67
Types of tissues
- epithelial tissue
- connective tissue
- muscle tissue
- nervous tissue
68
Epithelial tissue function
**covers/lines** organs & all body surfaces - ***protective barrier***
69
Connective tissue function
- connects or separates, and **supports** all other types of tissue in the body
- *stores nutrients*
- *cushions organs*
70
Non-cellular material
material not made of cells
71
Muscle tissue structure
- contains **muscle fibers** - contract to become shorter
- elastic
- excitable - respond to nerve impluses
72
Types of muscle tissue
***Skeletal muscle***
- attached to skeleton
- **striated** *(striped appearance)*
- **voluntary** control
***Smooth muscle***
- makes up **organs**
- ***no striation***
- cannot be controlled voluntarily
***Cardiac muscle***
- heart muscle
- **faint** striations
- cannot be controlled voluntarily
73
Nervous Tissue
***Function:***
receives & transmits messages as **electrical impulses**
***Structure:***
- made up of **neurons**
- *brain, spinal chord, nerves*
74
Epithelial tissue structure
- cells are very close together with ***little intERcellular fluid*** between them
- vary in shape depending on tissue:
- smooth -> for things to get in and out *(secretion)*
- striated -> many layers *(protection)*
- cubodial
- columned
- squamous (squashed flat)
75
Epithelial examples
- layer of the skin
- lining of the intestines, heart, kidney, liver & lungs
76
Muscular tissues are responsible for
- **movement**
- **process of digestion**
- waste elimination
- **breathing**
- speech
- blood circulation
77
Connective tissue structure
- not as close together as epithelium - seperated by ***large*** amounts of **non-cellular material** (a.k.a. matrix)
78
Connective tissue types/examples
**Proper:**
- loose tissue *(adipose)*
- dense tissue *(tendons)*
**Specialised:**
- bone
- cartilage
- blood
79
Extracellular fluid
Fluid that is surrounding the cell
*e.g. **tissue fluid** or **blood plasma***
80
Nutrients that cells need to take in
- water
- oxygen
- **glucose** for cell respiration
81
Tissue definition
A group of **similar** cells in the same **place** with the same **function**
82
Active Transport examples
- uptake of glucose in intestines
- sodium-potassium pump (sodium goes out of cell and potassium goes into cell)
83
How do Rough ER and Golgi work together to create lysosomes
- Lysosomes are found in the Golgi Body
- Enzymes are formed in Rough ER
84
Explain why an abnormal inner membrane of mitochondria can lead to symptoms of fatigue
- that's the site of **electron transport chain**
- which produces most ATP
- therefore, less ATP is produced
- cell function is reduced
- body functions slow down, causing fatigue
85
During exercise, chronic fatigue patients often experience a burning sensation in their muscles along with lack of strength. Explain why this happens
- limited O2 supply in excercise
- anaeorbic respiration takes place
- lactic acid produced
- less ATP is produced
86
Function of mucscle fibres in small intestine vs stomach
**small intestine:**
- contracts causes **segmentation**
- keeps contents **moving**
**stomach:**
- oblique muscle layer is an extra layer for **churning**
87
Smooth muscle function
movement of internal organs
88
Cardiac muscle function
contracts to pump heart
89
Skeletal muscle function
Movement of skeleton
90
what can't cells without nucleus' do
| 2
- nucleus can't control cell function
- no cell division, growth or repair
91
Discuss how nervous tissue differs from other types of tissue
| 2 marks
-** carry nerve impulses**
- **produce neurotransmitters **to produce impulses of other cells
92
What helps maintain shape of human cell (bc no cell wall)
| 2
microfilaments and microtubules
93
similarity between types of muscle
- many mitochondria
