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GCSE Biology Unit 1
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Structure of animal and plant cells:

Both animal and plant cells have: -

A nucleus

-

A cell membrane

-

A cytoplasm

-

Mitochondria (for respiration)

Differences between animal and plant cells: Animal cell
- Has not got chloroplasts
- Has not got a vacuole
- Has not got a cell wall

Plant cell
- Has got chloroplasts
- Has a vacuole
- Has a cell wall

Specialised cells: Specialised cell
Sperm cell

Adaptation
Tail to swim
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Many mitochondria to release energy
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Hair like structures call cilia beat to move mucus to the
back of the throat
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It allows certain substances to pass through the cell membrane
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g
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OSMOSIS:
This is the diffusion of water from a region of high water concentration (low solute) to a region of low water
concentration (high solute) across a selectively permeable membrane down a concentration gradient
...
The cell
membrane stretches and bursts
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Water moves from a high concentration of water
molecules to a low concentration of water molecules through a semi permeable membrane
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OSMOSIS IN A PLANT CELL:
Plant cell in water:
There is more water outside of the cell than inside
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The cell becomes Turgid
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The water moves down a concentration gradient
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The cell is Plasmolysed
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In other word’s they
must be moved from an area of low concentration to an area of high concentration
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Active transport examples:
-

Root hair cell
Kidney
Muscle cells

Diffusion
-

Osmosis

Active transport

Is how oxygen leaves a
cell
Is Passive

-

Involves water only

-

Requires energy (ATP)

-

-

High to low
concentration
Occurs in nature

-

How water keeps a
plants cells turgid
Is Passive

-

Movement of particles
Needs a semi
permeable membrane

-

High to low
concentration
Occurs in nature
Movement of particles

Is against a
concentration gradient
Involves transports of
solutes
How minerals get into
root hair cells
Movement of particles

-

-

-

SUMMARY:
Diffusion is a passive process
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Movement of particles down a concentration gradient
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It’s from a region of low solute to a region of high solute
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Active Transport Is movement of particles in/out the cytoplasm against the concentration gradient,
from an area of low concentration to an area of high concentration
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ENZYMES:
How they work: -

When an enzyme gains kinetic energy, it collides with a substrate to create a product in the active site
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Increasing the temperature
means there will be more
successful collisions
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Each enzyme is specific –
one enzyme catalyses one
reaction

ENZYMES
All enzymes start to
denature at 100 degrees
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They increase the rate of
chemical reactions in living
cells
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Table of digestive enzymes:

Part of gut

Enzyme

Substrate

Product

Mouth

Amylase

Starch

Sugar

Stomach

Protease

Protein

Amino acid

Small intestine

Protease

Protein

Amino acid

Carbohydrase

Starch

Sugar

Lipase

Fat

Fatty acids and
glycerol

LOCK AND KEY HYPOTHESISE:
This theory states that the substrate is like a key and the enzyme is like a lock and together they fit to make a
reaction
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SUMMARY:
Enzymes fold in a specific way and one enzyme catalyses one reaction
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When an enzyme gains kinetic energy, it collides with a substrate to make a product in the active site
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KEY WORDS:
Optimum – particular
Passive – No energy required
Semi permeable membrane – cell membrane
High concentration of water – Low solute
Low concentration of water – High solute



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